I value the opinion of most of you guys and gals here. (Notice I said MOST!!) Seriously, I need to improve my bottom end torque...street car only..I may have some other issues to attend to, but the one Im concerned with here is my cam...currently a solid flat tappet, 286/292 adv., 250/256 at .050, .595/.605 lift, 110 lsa...would going to a duration , at .050, of 245/250 and lift .580/.580 make a noticable difference in bottom end?? It comes on hard now at about 3000, but feels soft at lower RPM's...10.6 CR, oval port heads with big valves, 3000 stall w/ 3:73's.. The same cam company will do this one, a custom grind, but Im wondering if that much, or little, of a change in duration will do what Im expecting. Has anyone here had any experience with a cam change alone making a big difference in performance? Another cam company said I should leave the one I have in it, should be making tons of torque graemlins/clonk.gif ...Help anyone?? John

John, open the separation up to 112 on that smaller grind and you should be OK, but how can we know? Using 243/251@.050 and it seems to have enough bottom. So much so , the lash is set tight.

You degree the current cam? Make sure it's in advanced? If you do a custom cam, you might want to open it to 112 to aide the low end smoothness and to keep your DCR the same.

OR put some big port heads on there and spin the snot out of it! tongue.gif ( just in case you were actually valuing my opinion ;) )

Thanks Gene....No, this time I just installed it dot to dot..I degreed the last two, and thought I could get away without it this time..maybe that's my problem. The other cam company that I mentioned felt that was the problem, that it had to be running retarded...he also told me to ditch the gear drive and go with a good double roller chain... Im not fond of the gears anyhow, so they're going this time.

Well, at least spin the motor over and check your #1 valves using Harold's method. And if you find them even, or the exhaust still closer to the head, well, that's the first thing before you swap cams. Set the cam so the exhaust just passes the intake on the way up and goes around .050 higher. Oh, you can check it with a degree wheel too!

Can you change phasing easily with a gear drive?

And BTW, I think you'd have an octane problem with the small cam and 10.6. You'd need to go to 112lsa I bet.

John,

What is your entire setup?

I have not run one but the UD/Lunati that Gene (and a few others run) looks like it would be a real nice cam. Fairly aggressive lobes (duration @.200) which translate into torque. IMO, have it ground on a 110 deg lobe sep and play with the lash to tune it abit.

The only thing that would worry me about this cam is with duration of 276/284 and 10.6 cr, you may have problems running pump gas.

What converter are you running? My cam is similar in size to yours (in a 350) and bottom end is very strong. The car has pulled a 1.70 60'.

Darren, Im going to look into the Lunati cam.. Combo is 454 +30, 049 heads w/ 219/188 valves, Team G intake w/ 850DP, Howards cam mentioned above, TH400 w/ 3k stall, 3.73 gears w/ 28" tire. I dont know if the pump gas would be a problem, as the heads I had on before were closed chamber, with the same pistons I have now...I was at about 11.3/1, and had no problems running 93 or 94 octane...These current heads were 119cc, but I had them milled to give me the CR I have now.

Well, I DO think it's the best street/strip BBC cam out there! smile.gif

Check your cam phasing first John. Think you'll have issues with pump gas and that cam. I calc'd 10.51:1 compression, and a DCR just under 8.6 with the cam in +7. you'll be close, and I wouldn't advance it as much.

But I think the solution to your issue is a new timing set!

I would think a 3k stall car would feel soft below 3k. Unless you have a hi $$ converter.
But I drive a stick car.
You might try a different intake/carb to get the low end cleaned up some. Lots of people post that the RPM cleaned up the bottom and have similar top to a
TG. With the 290ish cams.
I've ridden in cars with a UD288/296,RPM & the 950hp that were fine on the bottom end.

I put in comp xe274 in my bbc dual plane and mighty demon. Ive got so much bottom end torque that i just cruise in drive starts making power at 2000 pulls to 6000.

--------------------------------------------------------------------------------
Darren, Im going to look into the Lunati cam.. Combo is 454 +30, 049 heads w/ 219/188 valves, Team G intake w/ 850DP, Howards cam mentioned above, TH400 w/ 3k stall, 3.73 gears w/ 28" tire. I dont know if the pump gas would be a problem, as the heads I had on before were closed chamber, with the same pistons I have now...I was at about 11.3/1, and had no problems running 93 or 94 octane...These current heads were 119cc, but I had them milled to give me the CR I have now.
John,

I think if you are going to be changing cams, I would also change the intake. An RPM or Stealth would be a much better choice.

Another option (if you have the $$$) is replace the 850 with a 950HP. I did this about about a year and a half ago and the low speed throttle response was greatly improved. This was the main reason I purchased this carb. I felt my low speed was a little "flat". The HP carb really helped that out. graemlins/thumbsup.gif

Could you please give me a little info on your cylinder head swap. What casting heads were you using? What about now? What is the PN# of your pistons? Why did you switch? The reason I'm asking is I have a set of '063 closed chamber heads sitting on the garage floor and was thinking about installing larger valves, doing some port work and installing them to bump the CR from 10:1 to about 10.6-10.7 cr. I am running a ported set of 049's now and was wondering if it is worth the effort. I have seen posted on this board flow numbers on heads and the open chamber and closed chamber (on average) seem to flow very similar.

Thanks for your input.

Get a Performer RPM intake to improve your bottom end/throttle response..I'd rather change an intake over a cam any day...whats the timing curve look like?

Thanks guys, this is the input I needed. I had a long talk with a cam grinder today about this problem, and we talked about a custom grind. I dont really want to change again, but on the other hand, Im pulling the intake, radiator, water pump, etc. to degree and change the timing set, so how much effort is it to pull out the cam and put in another one. He suggested one that would get the torque curve down where I need it, and it would also not bleed off as much compression, which would also help. I might as well do it, and this will be the last time!! (I think I said that before ;) ) And I am also putting my RPM back on, and a different carb...hopefully I'll happy with this. I asked the cam guy if there is anything else I need to do, and he said invest in another set of back tires! :D This is a good thing, right??

Darren, the rect. port heads I took off were 3964291, LS6 replacement heads..they are closed chamber, about 106cc. I changed mainly because the intake port is huge, and I felt a smaller runner would help with street performance. I went with 049's, had them milled to get me my 10.6 CR, and had the bigger valves installed and machine work done. Pistons are TRW L2349F30. Honestly, no seat of the pants difference, but again, I made other changes at the same time. Hope this helps your decision a little. John

A cam ground on a wider LSA will NOT help the bottom end power.

A tighter LSA will, but the car will have a more radical idle.

You have a high performance motor, NEVER rely on the DOT to Dot method, always, and i mean ALWAYS degree in the ICL.

I ran exactly the same cam in the old Super Street car. It worked great with 4.88s and a 5000 convertor. I would consider it streetable with a 4spd or more convertor than you have. I would think your cam idea is a step in the right direction but have you tried other changes?

I see some problems, the car needs more gearing, a looser converter, and an RPM manifold.

You might want to change carbs to a 950HP also, but thats not an immediate problem.

Well, lets see how that cam is installed,, and a dual plane would really help. ( I remember the huge change when I put a divided plenum back in the L88 mani)

Brian, if you've ever driven a stick car with a hot 110 lsa cam vs a wide 114 lsa cam you'd KNOW that wide lsa's , all else being equal, help low speed torque, I really mean driveability. Dont know what a dyno would say, but clearly easier to drive. We might be disagreeing on semantics.

Here are a few points to note about tighter LSA's:

-more agressive idle
-In the mid range the tighter LSA tricks the engine into having better flow, by helping purge the cylinder of exhuast gasses and helps pull in the intake charge.
-helping fill the cylinder with more air/fuel and therefore creating more cylinder pressure.

-A tighter LSA will make more average torque, and typically less peak torque.

The LSA tips were proven to me by an experienced racer, and backed up by not only his conclusive back-to-back comparison testing....but also a stock eliminator racer in our group of racers.

*Note* this is NOT my testing, but being that it has been done by two close friends of mine, and fellow racers. I dont believe it should be ommited from the discussion.

Brian, every one will be degreed in the future. The one I will get will be a 108 lsa, vs. 110 now...also less duration by 6 degrees or so. The cam designer said the tighter lsa will build more cyl.pressure, which I want. He also said he doubted the advance or retard question was an issue, that if it ran anywhere near OK, it cant be that far off that it would affect performance that much. Gene, I dont doubt at all what you're telling me, but I dont have any experience with lsa's and driveability...let's hope that it's not a problem. He said that 2 degrees tighter will not cause a problem with tuning, as in rough idle..at least not any worse than I have already.

In my opinion i would speak with Charlie Plott at ATI about possibly having a converter built that will work better for the combo, and make the switch to an RPM manifold.

i think a smaller cam will help bottom end power, but since this is a street ride, i would keep the 110 LSA for idle quality.

I also think you may be risking problems with detonation since you have alot of compression for pump gas.

John, you are in NY, you might want to make the trip out to englishtown on March 28th, and speak to the real expert on BBC street power. I race with him....you wont be disappointed.

"the real expert on BBC street power"

graemlins/boring.gif

I dont appreciate that at all Gene, i'm doing my best to direct John here to a source that will give him very good, very useful information that will help him acheive what he wants.

While i am i student to this Particular racer, its best to go directly to the source.

I say the real expert, in the context that i am NOT the real expert, instead i am a student to him.

I should probably just stay quiet but just for the heck of it I'll say what my overall impressions of LSA are... I've run them 108,109,110,112 and 114 LSA in various cams and various engines.

To me the tigher the LSA the rougher the idle.The wider the LSA the less rough the idle.

With say a 108 - 109 type LSA the right off idle to say 2000 RPM is a bit worse than say a 110-112 type cam...right there in the just let the clutch out area... Talking part throttle street driving here.If you roll into the throttle with a close ratio 4 speed and some decient gears and maybe just screwing around and not really getting after it and short shift at say 5500 the tigher LSA's feel like the car is driving through your back as that famous mid range torque plants you in the seat.If you full throttle it the tighter LSA's really slam you hard and pull and the tach needle flies...

The wider 110-114 type stuff seems to idle abit better and the part throttle in the off idle to say 2500 range seems smoother and cleaner ..but not as fun in the mid range ..say from 2500 -5500 RPM...smoother but not as much of the slam you back in your seat like the tigher LSA stuff.Full throttle from say 2000 up they dont seem to respond quiet as well and then from say 4500 on up they kinda explode and go nuts and then fall off.

So it depends on how you define part throttle off idle.... roll into the thottle or really getting after it.....or launching your car or downshift and hit it or whatever..... Your both right.

Originally posted by Motor Martyr:
Here are a few points to note about tighter LSA's:

-more agressive idle
-In the mid range the tighter LSA tricks the engine into having better flow, by helping purge the cylinder of exhuast gasses and helps pull in the intake charge.
-helping fill the cylinder with more air/fuel and therefore creating more cylinder pressure.

-A tighter LSA will make more average torque, and typically less peak torque.

The LSA tips were proven to me by an experienced racer, and backed up by not only his conclusive back-to-back comparison testing....but also a stock eliminator racer in our group of racers.

*Note* this is NOT my testing, but being that it has been done by two close friends of mine, and fellow racers. I dont believe it should be ommited from the discussion. Ok,,,here's my half cents worth :rolleyes:
Brian,
While I agree that with the same cam you will build more torque sooner with tighter lobes I believe you have part of your answer backwards.
Widening the lobes, again all else being equal will widen & flatten the torque curve with less peak torque & typically more top end HP.
Bringing them closer together will give you higher peak torque in a smaller RPM range.
It will also build torque sooner as what you are doing is advancing the intake lobe & retarding the exhaust lobe.
But the reason for building cylinder pressure sooner has more to do with where the intake valve closes than with cylinder filling because of scavenging.
At idle and off idle the wider lsa will clean up the engine because of less overlap & reversion.
Air is never "pulled" into the cylinder except during that time when the exhaust system is at a lower pressure than the cylinder because of exhaust gas velocity & even then air is still not pulled in, it is pushed in because of the difference in pressure between what is above the carb or whatever opening you have & the lower pressure in the cylinder & again the lower pressure in the exhaust than the cylinder at certain higher RPMs. Air or fluid always moves from hi to low pressure areas,,, it's one of old ma natures laws ;)

BTW, don't know if anyone else has mentioned it but I think you deserve an "atta boy" for your complete change in the tone of your posts & helpful replies graemlins/thumbsup.gif

..some good info on this thread graemlins/thumbsup.gif
..and yes,talking to that BBC guy from NJ is always a worth while experience..he'll never steer you wrong and is more than useful and willing to help.

Brian,whens that small block going in?

Again, thanks...lots of info for sure. Brian, as it happens, I will be going down to E'town in a few weeks. As far as the 108 vs. 110 or more, I have to think more on it..I dont want to be fighting the roughness at lower R's all the time Im driving around town...On the hiway, at say 65 or so, Im spinning roughly 3k, maybe little more, so it shouldnt be a problem there. I notice that a lot of the UD cams that have been so popular here over the last couple years are on a 107 lsa, even tighter than what Im thinking. Im wondering how they have been to drive, or are these basically in a strip car.

They don't 'clean up' until 2000 rpms or so. John, you building a 1/4mile car , somethng you drive, or what combination of the two?

Brian, my intent wasn't to upset you. Just a friendly reminder to ease up on the hero worship stuff. No one has a monopoly on knowledge. Secondly , I dont ususally ask guys that spend their time running 1320s what I'd do for a street ride, I'd ask them what to do in the 1320. When is the last time Ed got in the car and took the family for a nice long four hour cruise? Point taken. Understand you resepct the guy and look up to him. And it's wonderful that you have such a good professor at such an early age, but....ease up. I promise not to mention it again.

John , as has been pointed by two real experts (i.e. auto machine professionals), its the "off stoplight" smoothness you gain by going wider in lsa. That isnt the same as an early torque peak. Again, check the cam phasing, but a dual plane on ( and scrounge up that 850 , again), and you should feel as much low end as possible with that cam.

Oh, I always thought tighter LSAs give higher peak torque but very unlinearly, wider = lower peak but much more linear.

John, one last point. WHile the 850 was much too big for the single plane intake, I believe you'll find that on a dual plane it might be just right. Single planes are extremely sensitive to size, easy to overcarb. DUal plane take cfm better. The 750 might not be enough carb for a dual plane. In fact, I'll almost guarantee that. Not with a solid cam like that.

830 annular booster would be ideal for the street. Set it up a bit rich (especially in the secondary side) as you'll be giving it one helluva fuel signal through a dual plane rather than the single planes they ususally perch on.

Gene, street car only...we all want to say we drive a race car on the street, and OK, some actually do...but we also know it's not practical...No, I want a street ride. I'll look into the lsa more before I buy anything. It's too late for the 850 carb, its gone already..but that's not to say I wont be willing to get something else if needed..maybe that 830?? When you say "With a dual plane, you should feel as much low end as possible with that cam", which cam do you mean?? The one I have now, or the one Im thinking about, and at what lsa?? Now even Im getting confused graemlins/clonk.gif And when referring to smoothing out at about 2000 RPM's, do you mean the tighter lsa cams?

I'm reading right along.

Please keep up the good thread!!

pdq67

From what i've read I beleive he wanted you to check the cam you have now.To give more bottom end this cam would need to be installed advanced,the quickest way to do that would be to pull drivers side valve cover and bring #1 cylinder up on top dead center,either both valves will be on the seat,if they are you'll need to turn the engine over 180* to TDC again this time one of the valves should be off the seat and one on.You can check from the top of the retainer to the spring seat with a machinist ruler.The intake valve should be about .025" to .045" closer to the head than the exhuast valve if not the cam is either staight up or retarded.Good luck!

Mike,
Thanks for the compliments.
From what i understand about LSA, a tighter LSA will make more torque in the mid-range, and typically less peak, I've asked very reliable sources, and this is the answer i've recieved as to Why a Tighter LSA will make for quicker ET's in a typical low compression street/strip ride. (Low compression is relative that that of a typical race motor).

I'm no expert on this, and maybe you've done testing that you would like to share with us.

I would like to hear about anything you have to say on the subject. I'm always looking to learn more about these complex engine systems.

Excuse my laymans terms like "pulling" in the intake charge. From what i understand, a good scavenging exhuast system, complimented by a tight LSA will create a vacuum of sorts to bring in the Intake charge in the mid rpm range, creating higher cylinder pressures.

Is this correct?

Chris,
Soon enough, probably getting started next month.
Just got my trans back from STR :D

John,
I'm pretty easy to find, i fallow the summit bracket racing schedual (on sundays, its posted on etowns site). Ed races on the same days, and is also easy to find.

Think about what you're looking for in the car, and in the mean time, you can make other changes, such as the manifold.

Gene,
Drop it, my post had nothing to do with "hero worship", instead i'm refering someone to a racer who can help him more then myself.

While we're on the subject of carbs, the street/strip car test bed slowed down .06 with annular boosters on a Pro Systems built 1000HP.

Originally posted by Motor Martyr:
Mike,
Thanks for the compliments.
From what i understand about LSA, a tighter LSA will make more torque in the mid-range, and typically less peak,


Excuse my laymans terms like "pulling" in the intake charge. From what i understand, a good scavenging exhuast system, complimented by a tight LSA will create a vacuum of sorts to bring in the Intake charge in the mid rpm range, creating higher cylinder pressures.

Is this correct?


==
Brian,

On the first one you are correct , all else being equal tighter lsa will build more peak torque & do it sooner but what you posted was,

-" A tighter LSA will make more average torque, and typically less peak torque "
which is backwards I believe.

On the "pushin/pullin" deal, I see it in the rags all the time & it's one of those little misconceptions I like to correct as I was corrected years ago by some folks a hell of a lot smarter than me :D

And you are correct, a good exhaust system can actually "over scavenge the cylinder under certain conditions & "pull" the fuel right out the exhaust. It can do it with tight or wide lsa depending on where the exhaust valve closes in relation to how well the cylinder is being filled at the time of exhaust valve closes.
At least this is my limited understanding of a very small part of what goes on inside these things we like to think we understand :confused:

If Harold would jump in here he could explain this much better as he has probably "forgotten" more about cam timing in relation to air flow & piston position than most of us will ever know ;)

Johnny,
Sorry about rambling on your post :(
I agree with the consensus here that the first things you need to do is change the intake & be sure the cam you have is advanced at least 4 degrees.
It is a bit "lumpy" but should have plenty of low end.
I am not a huge fan of Howard's shelf cams along with a few other "brand name" shelf stuff but that's another story ;)
If you decide to change cams before settling at least have a talk with our resident "cam guru"
Even if you don't buy his product you will come away with a much better understanding of what you should have.

Heck, let's use the term's suck and blow!!

A piston going down on the intake cycle suck's the charge in due to creating a slight vacuum above it's top whereas one going up on the exhaust cycle creates pressure b/c it's pushing on the charge and that helps blow it out!!

How's that??

And remember "poked, stroked and blown, AND if that isn't enough try a little gas"....

Again, great thread!! AND I even wish Ed could pop in here AND be CIVIL too......

pdq67

My personal favorite cam company is Crower, just simply becuase they've bent over backwards to help me out.

Comp, Crane, crower, LSM and others are good companies.

Mike,
I understand that a correctly set up exhuast system combined with a tight LSA will help fill the cylinder with its scavenging effects.

Thanks guys, I'll check before I go pulling anything out. Im curious to see where it's at anyway. Brian and Mike, I'll take that all into account, very helpful...and Mike, I have tried no less than 3 times over a 9 day period to contact our resident cam expert, and have received no response. Happened last year too, that's why Im not running that cam now.

I just want to thank you guys for such a "spirited" thread. Best reading I've done in a long while. I learned more from this one "conversation" than I have from all the other cam discussions combined. graemlins/beers.gif

Yes, of course, with the cam that's already in there. I'm not a frivolous cam swap advocate, unless you're swapping roller grinds. Because a new flat tappet cam is always a odds maker in a rat.

John, kinda hope you find the cam out of phase. That change and a dual plane will make it feel like a new mill.

Brian, I havent known anyone to run one on the street yet, although Pat Kelley runs/ran on his strip ride. Recommended by my tripwoer 'guru'.

830 annular seems to the 'theoretically ideal' carburetor for a 430-460 street rat. Good fuel atomization at mid-range speeds for some efficiency and great throttle response.

Again, something for the street ride which isn't a strict ET improvement. The fact that there was a .06 change wouldn't be as relevant. You should have crisper throttle response for everyday mid-throttle driving. John might not ever ET it, but that would allow him to use a carb large enough to cover the upper rpm band well. BTW, did they jet the heck out of that ProSystems carb? Seems you might have to.

The short point is, its likely that an 850 is the best ET'ing carb for a setup like John's. But they're such awful pigs on the street, gas wise. 750 cfm would be better that way, but leaves something missing north of 5000+.

I'll help you stay 'easy' on that new motor John!

The Best ETing carb in John's application, would (in my opinion) be a 950HP series carb.

back to Back the Annular booster went .06 slower, that's pretty significant if you are searching for ET.

Patrick James at Pro Systems considers Racer's testing to be top notch, and the results to be accurate.

Originally posted by Motor Martyr:
back to Back the Annular booster went .06 slower, that's pretty significant if you are searching for ET.

Oh, absolutley a big time no-go. That's a huge number at that level.

I actually asked another fellow NJ racer his opinion on the Annular boosters a while back. He considers them suitable for a truck, or something where the only concern is off idle performance.

He runs a 3300lb camaro, with a 468" motor, solif f/t cam, 12.5:1, aluminum heads, 4150 single carb, backed by a glide. his best ET is 9.80 @136....so having said that, i take his advice, knowing its coming from a knowledgable source.

This is just My opinion, based on the testing of my friends car, and the honest advice from a fellow racer.
If someone wants to try otherwise, feel free, just let us know how the testing turns out.

Originally posted by Johnny O:
Thanks guys, I'll check before I go pulling anything out. Im curious to see where it's at anyway. Brian and Mike, I'll take that all into account, very helpful...and Mike, I have tried no less than 3 times over a 9 day period to contact our resident cam expert, and have received no response. Happened last year too, that's why Im not running that cam now. =
John,

I know Harold can be a bitch to get ahold of sometimes but the fact remains the information you will come away with is worth your time.

As for cam companies I use about 80% Isky & their roller lifters exclusivly, some cams from Comp but custom grinds only, I do not use their shelf grinds anymore & Harolds when he was still Ultradyne.
I have talked with Harold a few times since he moved to Lunati when I could get to him & spent about an hour with him at the PRI show but haven't gone back to using the cams yet.
I still feel he is the best at what he does though ;)

Mike, I agree, its nothing personal here, just kinda aggrevating when you want help, or an answer, or worse yet when you actually want to buy something. Anyhow, I still think he's one of the best. And Gene, Im going to try really hard to get to the garage later today and check the phasing...I hope I see a major problem, actually..at least that way I'll know what the problem is. And I know you'll help me stay "easy" on the motor...If I get it running right, Im not sure how easy I'll be with it, have a lot of making up to do!!

Good thread,
Johnny O, did you do a compression check on the current combo? The cam that's in there doesn't seem that big in my opinion unless I'm not getting a correct picture from the numbers posted. Is the timing curve and fuel curve dialed in for the current combo? What exhaust system are you using? 2 1/2"? 3"? tailpipes? mufflers? Exhaust pressure has about the biggest influence on performance cams and magnifies as the LSA narrows. Just some more things to think about before slapping more parts on. smile.gif Bob

Originally posted by Johnny O:
Anyhow, I still think he's one of the best. And Gene, Im going to try really hard to get to the garage later today and check the phasing...I hope I see a major problem, actually..at least that way I'll know what the problem is. And I know you'll help me stay "easy" on the motor...If I get it running right, Im not sure how easy I'll be with it, have a lot of making up to do!! Easy, you're kidding right? Hehehe, a solid-cammed rat graemlins/hurray.gif And yea, I HOPE YOU SEE A MAJOR PROBLEM, since it's isnt major at all. Just an adjustment. BTDT with my pro-assembled shortblock. Phasing was backwards. No biggie. Better if a one-piece pan gasket was used. Plus you could get rid of the 'whiner' if you wanted.

John, if wasn;t so paranoid about flat tappet cam break-in, and had an extra $250, I'd want to try the 112 LSA version of the Lunati A3 276/84 cam., just to see. Comparing it to a 114lsa cam with a completely different lobe profile is fuzzy. Of course, the rollerized version comes stock on a 112! But that wouldn't be fair either. anyway, with my 'small' 112.5 cc chambers, I could use to lose a bit of cyl pressure.

Trouble is, I **think** the tighter LSA helps intake charge velocity, as told me by Harold. An issue with rect ports. But if using smaller inlet ports, maybe a schooch wider is fine. Less 'give up' vs large port heads.

All speculation I'm afraid.... After going from 114lsa to 110, I'd never go back. But I'm wonder ing is 112 isn't a choice compromise. You do lose streetability with cams in excess of 250@.050 duration when you tighten the lobes. Guarantee you that.

Just ramblin' John, curious to hear which #1 valve is closer to the head on #6TDC.

On the annular booster issue, since my name came up. That carb is off the car right now. I trying a downleg 750. So far my mph went about one mph in the furlong (1/8 mile). However, the air was much better than when I had the annular carb on. The end of April is the next daytime race so I'll see what happens then when conditions are closer to what I ran the annular booster carb in. When I first replaced the 700 downleg carb with the annular the car slowed down. Eventually, car ran faster but it may have done that with the 700. Anyway, I suspect that downleg boosters are better for drag racing. As for street use, annulars really come off the line well, almost like FI.

On the tighter LSA issue, I have to go with Wolfplace. A higher peak but narrower torque band. This concentrates the torque in a relatively narrow band which works well for racing, particularly with a high stall converter. A wider LSA broaden the torque band producing more HP at the very bottom and top of the rpm range. Wide LSA have a higher average torque with a lower peak making them better suited for use in car needed to operate over a wider rpm range. Drag race cars tend to operate over a much narrowed rpm range and can better utilize a narrow LSA. This said, a cam with very short duration can make an excellent RV type cam with a narrow LSA. Crane (I believe it is) makes a RV cam, with about 250º (maybe less) adv on a 105º (or 106º) LSA. The reason being, that with such a short duration even with a tight LSA excessive overlap is not an issue. This takes advantage of the higher peak torque (at a lower rpm due to the short duration) but sacrifices top end power. The cam builds torque very fast at a relatively low rpm. It's pretty much all through by 4000 rpm.

Here's more on LSA to help out those that are looking for a better understanding of Lobe Seperation, and its effects on the powerband

MAT posted on DRR:

If the ILC (intake lobe centerline) kept the same, increasing the lobe sep will:

1) move the exhaust opening point further into the power stroke - losing cylinder pressure (torque) at lower rpm in exchange for decreased pumping losses and cylinder charge contamination at higher rpm.

2) decrease overlap period, making the engine less prone to reversion-type power loss at lower rpm in exchange for poorer utilization of resonance tuning at the times it present.


In a well matched system - a system where the resonant lengths of the intake track / exhaust track are well coordinated to each other and the intended operating range of the application - the decrease in the overlap period created by the increased LSA will result in a NET LOSS of power within that operating range - given that the effects of pumping loss and combustion charge dilution are small in comparison to the increase in system volumetric efficiency from resonant effects.

The nature of resonant tuning is such that is a positive influence over a narrow rpm range, and has negative effects outside that range. This infers that an engine reliant on resonant tuning will also have a narrow effective power range

Drag applications have a narrow rpm band – less than 2000 rpm in most cases:

1) choose a matched intake/exhaust system such that their resonant signatures positively influence each other and the required rpm range in use
2) use as much overlap as possible – too much will make the power band too narrow to cover the operating range – too little will be wasting positive resonance tuning.


As the overall duration of the lobes increase – the lobe separation will increase to keep the overlap period from becoming excessive. That’s just math.

Summary – tight lobe sep cam is peaky with great mid-range power – overlap reversion kills the bottom end – pumping loss kills the top end. No problem – these things happen either below the converter and recovery rpm, or above the shift point / trap rpm.

Again – IMO – and set me straight if you think I’m out to lunch.

This stuff really comes into it’s own when making changes to 2 stroke engines.

MAT
Here is another source, that is very good reading.

Lobe Seperation and Its effects explained (http://drr.infopop.cc/eve/ubb.x?a=tpc&s=3476075&f=80760912&m=216601026&r=896601026#896601026)

Here is part of a discprition that I found in an old 1973 Sig Erson catalog that I have... This was back in the day when Sig Erson owned his own company.

.... " Contrary to what some cam manufactures say , very minor changes in lobe centers can alter the power range of an engine sufficiently to make a winner out of an also ran and subtle changes in lobe centers (LSA) are one of the top secrets of the successfull cam designer.

To decrease the lobe centers of a given camshaft the exhaust lobe would be retarted and the intake lobe advanced.This would cause the exhaust to open later and close later and the intake to open earlier and close earlier.

A camshaft with closer lobe centers will have more overlap ( valves open @ TDC at the start of the intake stroke ) and higher cylinder pressure due primarily to the earlier intake closeing. The camshaft with closer lobe centers will always produce more power in the midrange than a cam useing the same profile with wide lobe centers, and in many applications produce more power all through the range depending on variables such as induction system , rod angularity and the flow capacity of the ports.

The full potential of lobe center changes can onlt be appreciated by someone who has had the opportunity to work with an engine that is equipped with a seperate cam for intake and exhaust such as the Offy, Jag , Four Cam Ford , Triumph Motorcycle ect. Until a person has been able to change lobe centers at will , he cannot fully appreciate the affects on performance."


Please note that back when this was written alot of the information we take for granted simply wasnt available to the average person.Very few cam companies back the neven published dur @ .050 numbers and most didnt list thier LSA'a in their catalogs either.

Well, I did the measurements you guys told me about...at TDC, the intake and exhaust are both open a bit, I measured from top of retainer to the flattest part of head right next to the seat...Exhaust is 1.750, and intake is 1.690, so .060 difference...remember, this was done with a machinist's rule, so there is definitely room for error, but I was careful to get them both measured in the same place. I did it twice, got the same reading both times. So is that what I should find?? And here is something that may be a problem...I had a breaker bar on the crank bolt, and I had pulled out all the plugs to make it easier to turn over. As I passed TDC the first time, I had to back up a little..when I turned counterclockwise, there was a little gap, like 20 crankshaft degrees, where it felt like nothing happened...there was no resistance like there was when I was going forward...I got thinking, is the crank gear bad, or loose in some way, or is there an internal problem?? So I put a screwdriver in the #1 cylinder and touched the top of the piston, then moved the crank...the piston moves up or down during that 20 degrees of movement, so that's good....Now I turned it over till the exhaust pushrod was in the middle of its movement (so I could feel it moving the most) I put my fingers on the pushrod, just touching the head..I moved the crank, and I dont THINK the pushrod moved...Its hard to tell, if the crank is only moving abaout 20 deg, the cam is moving 1/2 of that...but I tried it in both directions, and I dont believe I felt it move at all. Should there be any play at all in the timing gears?? Its gear drive. I would think no, but Im not an expert. I guess if you set everything up while turning in the right direction, and didnt back up at all, it should be all right, but common sense tells me there shouldnt be any play or lash in those gears...is there any with a chain?? I dont think so. So if there isnt supposed to be, I think I have a problem. Either way, I have to pull off the front cover and see whats up, as I said the gear drive is coming off anyway, I hate the whining... Oh, and I found the cam card, for you numbers guys. Lash is .025, I and E...lift .599/.618, Adv. 286/292, 248/258 at .050, 110 lsa. Someone asked me what the intake centerline is, I dont see where it says that on the card..am I missing something? And I had written 4 degrees down on the card, but cant remember now if it was ground 4 d. advanced, or if they told me to install it 4 d. advanced. I'll have to call tomorrow and ask about that. OK, so what do you guys think? John

John, You can somewhat measure the slack in your timing set by watching the rotor on your distributor while turning the crank. Turn it clockwise then counterclockwise noting your timing marks untill the rotor starts turning in reverse, how many degrees? I hope it's not 20. A severely retarded cam will have a soggy lowend. The specs on your cam should make very livable power down low I would think.

Remember all those nylon coated timing sets on the old smallblocks in the 70's, I remember one engine I had that had lost all the nylon and the timing chain was so stretched that it rubbed the inside of the timing cover. The engine was gutless down low but actually spun up and ran decent to about 6000-this was a stock low compression engine with a severely retarded cam.

On average I think a good used timing set should only have 2-4 degrees of play, but I may be wrong.

It looks like it is in advanced as it should be. Shoot. Thought there migth be an easy answer. Now onward to the dual plane.

I contacted Erson way back before I bought their BB Hi-Flow AH hy- cam, (for my proposed 475" motor at that time), that is spec'ed at that time as follows.

284/218, 111/111, .542".

(I think it is now a 284/220, 110/? cam now??)

And I asked them why it was like that, (111/111), and the answer was that it was a good compromise between idle and grunt...

Good enough answer for me..

pdq67

PS., then the dreaded "more power, Scotty" bug bit and I ended up with a 496 and a good old CC 282S solid cam..

Well i'm glad i'm not a betting man I would have lost my shirt! smile.gif I hope the dual plane manifold solves the problem.I know I don't have the same cam I have 288/296f10 255/263@50 612/630 lift 10.7comp, performer rpm manifold,750DP and torque that you wouldn't believe.Just seems there shouldn't be that much of a difference down low! :(

Yeah, me too, and I would have gladly donated an old T shirt to John, for a simple tweak of the cam.

Well, thank you all for the help, ideas and knowledge..this has truly been an interesting thread. I checked w/ cam mfgr. today, its ground on 106CL, with 4 deg. advance..he told me I should install it straight up, but when I told him of the problems, or perceived problems, he said it certainly wouldnt hurt to go another 2 degrees. So maybe that's what I'll do. I going to degree the cam, a new timing chain is going back on, along w/ RPM intake and a little smaller carb. Im going with the cam I have, the custom grind was only a little smaller, and I dont think from what I might gain, it would be worth the money..Everyone tells me this one should be great, so Im just gonna find the combo to make it that way :D . Thanks again to all. graemlins/waving.gif I might get it done this weekend, or next for sure. I'll post an update. John

make sure you Check the Valve to piston clearance at whatever ICL you degree it in on.

Did you find out if the cam has any advance built into it? Be aware that the +4 and -4 marks on the timing set are in addition to any advance already in the cam. For example, to install a cam with 4º built into it "straight up" (a 106 LSA installed at 106º ICL), use the -4 mark on the timing set (+4 + -4 = 0). To install a cam with 4º in it at +4 ICL, use the "0" timing set marks (+4 + 0 = +4).

Brian, I will check to be sure. Pat, 4Deg. built in...he said OK to install another 2 deg. additional.

That'll work. The reason I mentioned the timing set is because so many people get confused about advance in the cam and setting up the timing set. Sounds like you got it right. graemlins/thumbsup.gif

Maybe with a little luck (trying to find the gaskets on a Sunday!! Yeah, right!) I'll get this done tomorrow. Before I pulled it all apart I did a compression test, just to see where I stand now.
#1 195 #2 195
#3 190 #4 200
#5 195 #6 200
#7 195 #8 195

Im assuming this sounds OK so far?? I did a leakdown test last summer on this same setup, and it was well within range. Gene?? Anyone?

Looks OK to me. A little more variance than ideal, but OK.