For you folks running 'midrange torque peak' engine design, have you ever gone to a single pattern cam? It would seem, from what theory I know, that a single pattern would more emphasize the mid torque peak and should affect launch /60' favorably. Just curious. The notes on the Isky site which said that single pattern designs ALWAYS give more torque intrugues me.

Then Harold had designed a single pattern solid 248@.050 cam for those midrange peak 496s.

Seems like only us "HP motor" 7000 rpm folks should be running split pattern for the upper rpm pumping efficiency gain.

Unfortunately there likely isn't any good back-to-back testing other than maybe dyno results. But likely no 'real world'.

My hypothesis is that for early torque peak motors, a single pattern cam will give you more right in the middle. Trouble is, its a hypothesis. And a big port 7000 rpm 427 is not the correct testbed.

Thnx for any insights/experiences.

I've wondered this too.

I think the relationship between head/intake/exhaust flow capability and valve events cannot be overlooked. What I mean is that you cannot make a "broad brush" statement about single pattern cams always being better. When you look at the whole system (c.i., heads, intake, headers), some engines will like a single pattern, and some will like a dual pattern.

Anyone else have better insight?

I use a single pattern in BigRed.
I also put a single pattern cam in the 534" we run in a 69 camaro for the torque increase in the mids.

I figured the same thing after reading more years ago then I care to remember where Ed Isky said that the correct single pattern cam will almost always out torque a dual pattern cam..

I can not verify it one way or another, but platying around with D2K lead me to install a good old CC 282S in my 496 for max. midrange grunt per it's sim. program and my particular combination..

I honestly think it can't be all that far off.

And that is why I keep asking Harold about a street friendly 288 solid street roller cam b/c it is a single plane cam too. That way, I can step up for the power I have left on the table IF I ever figure the solid roller life issue is resolved to my satisfaction..

pdq67

Factory BB heads have exhaust port problems. They used to make single pattern cams for mild oval port motors that worked fine. When you get a Big Port motor the exhaust is so poor compared to the intake the standard became 10deg more duration. The modern aftermarket heads throw the old concept out especially the Oval port ones. Small Blocks don't have this problem that is why you have always had single pattern cams.

Serious question here, I'm not flaming anyone.

Mike F. If what you say is true, howcome all the newer stuff, even the SB stuff is dual patterned? The whole XE line of cams from CC is dual pattern, I think.

Slowpoke, Most of the newer aftermarket heads, both small and big block, also have much better intake ports than exhaust ports. Same reasoning.

Just curious..where does "bse" :rolleyes: factor into this question btw?

I'm runnin a 286 Comp single pattern hyrdraulic flat tappet. Since I ported the exhaust on my heads well, and have a nice free flowing exaust with an x-pipe, I don't think I need any more help getting rid of exhaust gas's with a dual pattern. Besides the exhaust isnt what "really" makes the power anyways. So I was able to choose the biggest cam for my application and still have some torque.

I think he was just wondering if us torque guys ala BSE had tried a single pattern cam vs. the dual pattern. My Lunati has just like Mike says 10* more duration adv. 300/310 on the exhaust side. I've heard the same, exhaust doesnt flow nearly as well as the intake side. The machinist has reshaped the exhaust ports on my 781's, more rounded and opened up slightly, we'll see what happens come spring with the 505.

Intake to exhaust flow % is important but somehow I'm not sure it's as cut and dried as that.If you had a B,O,P or some Fords I think it's more of a factor.... But even with some early BBC heads that had poor exhausts they still run suprisingly strong with single pattern cams.I'm not at all saying that
you wont or cant make the same power with a dual pattern...not saying that at all...

But if you were to call Ron and ask him how many cars there are out there with Iskys " OLD " style single pattern cams , running in the 10's...I'd bet he would laugh and say it's a whole bunch of them... Let alone any of his " Newer " faster acting lobes.....

I still think that for up to 6500 RPM most Chevy engines simply dont need a dual pattern cam and past that then " Maybe ".... But for most Chevys
it takes a fair amount of RPM ( and RPM per second) to get to the point where exhaust is haveing trouble exiting the chamber gets to be a problem... especially with headers.I
am refering to N/A non N2O engines.

Where I work we sell ( well I wont say how many ) but easily over 1000 cams a year.... and honestly single pattern cams out sell dual patterns 4 to 1 here.

I know that in my example a couple years ago when I took out the XE dual pattern and replaced it with a single pattern .... Well I was very pleased. :D .... Granted mines a low speed engine
but it certinally helped...have 12 deg longer ex
was simply not needed.

Not to get off the subject but a mutual friend of
mine and Mike Lewis ran a 53 Stude at Bonniville
with a stout SBC with VERY GOOD heads and he ran a custom Crane Roller with I " Think " it was 4 deg LESS exh than intake duration in this 9000 RPM engine..
Breaking his old Bonniville Record in the process.
He has since switched over to an SB2 and broke his records again.

Anyhoo.... you can spend thousands of dollars swapping cams until you find the perfect one...There is always some cam out there that may work " Better " than what you have.... Kinda hard to pick the perfect one in the 1st place... graemlins/beers.gif

The biggest deal, imho, about Ed's "BSE" combination is that it makes great grunt with the more common, cheaper parts is all..

But you do have to get the combination close to right-on to get out of it what a BSE motor can do.. But again that is a given with any good running motor...

Bttt, I have been dreaming about a 588" standard deck height motor for quite a while and when I got to looking at BIG heads I found some that had large to huge intakes, but rather small exhausts so figure that the piston helps push the crap out regardless unless I am missing something which I generally am??? (2.35"/1.88" sorta deal)... And even Chevy ran 2.19"/1.72" jobbers...

pdq67

PDQ,

I cant say for sure as I have never messed with engine that big but when you start messing with huge valves , they have to be moved over to fit them and I would think that going that large with an intake sort of put's the ex too close to a wall....and in those applications a dual pattern is probably near manditory....

Ya ever notice that through out the decades everyone keeps trying to stuff larger and larger intake valves and really dont go crazy with exh valves ? ... Perhaps the exh system and cam timing does alot more to evacuate air than the piston actually does in pushing it out .... perhaps it's when you get to the point where the piston is doing alot of the work to evacuate the cylinders that everything really needs more help.... I could be wrong but in my mind by the time the exh valve has reached max lift.. most of the air and pressure is out of the cyl.... if not maybe it needs more cam timing or exh changes.

Look at all the late design heads - the exhaust are all D port and relatively small. But they all flow extremely well. Port velocity is playing into the equation now more than ever. When you think about it, you can blow a 50ci cylinder down with the 5/8 spark plug opening. The key comes down to how efficient the whole package is. Small block Ford's are notorious for weak exhaust. I have seen some special grinds for these with 20* more exhaust timing. I would be more inclined to want to blow down a cylinder through a weak port by using earlier exhausts openings when the cylinder pressure is higher.

And that brings us to the topic of " TIME "...At low to mid engine speeds or lower RPM per second use there is plenty of " Time " for blowdown/ evacuation vs High RPM that has much less " Time " and therefore may need the extra help of a longer exh timing.... I really gotta think also that once you get into the 500 plus CID... things change and help is needed.... same with say 383 and above with SBC's
...

From my discussions with Harold, he said that he normally recommends a single pattern up to 5500rpm.

My machinist does a lot of the low end circle track motors. He said that a dual pattern was always quicker in these. Since these motors spend more time at 5k than a drag car....

I think that's only .005 cents worth.

Scott,

Excellent point. In fact, you have detailed what most of us are missing or have forgot to bring into the equation - how high will this motor spin? I know for a fact that the 454 I am putting together is destined to run 5500 - 5700 max. THe 408 motor I now have has been ran to 6100 - 6200, but thruthfully is only cam'd to an effective 5500-5700. Those of us that were playing around 30 years ago looked at a street strip perf engine as having to run 6500. A 5000 rpm motor was a truck motor. Just shows how things have changed.

Joe, I'm living in the past with a 7000 rpm street performance motor. Right or wrong - I LIKE IT!

"bse" for an easy descriptive term, as Bob points out, nothing more, nothing less.

Unless someone can demonstrably prove why, I can;t see why you would not use a single in the rpm range Joe mentions.

Little more..
Chris_69_SS says his 288/296F10 468 dynod 620 @ 6200rpm. May be a nice dyno, but still only 6200.
Even with my limited experience, it seems to take a large cam to get a 454 to peak up in the 6500+ range.
I guess Sq ports help.
Lots o variables...

Oh, I remembered a little more of my discussion with UDH. The extra exh duration cuts down on pumping losses but increases reversion. High rpm minimizes the time for reversion. I think UDH has a reversion soapbox....

The UD master list I printed prior to the fall doesn't list the 278/278Fxx. I might have tried it. Especially since I think my cam is a little big for what I want. My old Erson Hiflow II 288/288 solid only pulled to about 5800.
Not that I didn't go to 7k with it.

I hear you Gene - loud and clear. And to reiterate what I said in another thread the other day. There are few things "mechanical in nature" quite like hitting a solid cam 427 motor at 5000RPM and still have an RPM range left to allow you to run it out.

Ditto, Gene!! Love the high rpm's!!

I just put my foot in my old junk 301 until the points bounced, and then grabbed another gear and repeated!!

pdq67

Rapid Robert, The BB Chevy exhaust port is very lazy on the bottom of the floor where it exits going into the header. Filling the center of the port with material on the bottom will pick up the port flow dramatically. The iron head, with the dead spot in the exhaust port filled in some, can be made to flow about 275 CFM if the material is placed properly. There is a product that was made for a while called "I love my port plates" that showed the principle but i don't know if its still available.

Gene , pdq...

You guys might get a kick out of this one....


http://drr.infopop.cc/eve/ubb.x?a=tpc&s=3476075&f=75460652&m=39660872&r=11760872#11760872


Pull down and read the post from 743SGVEGA.

I'm not at all suggesting useing this cam as it's
way too big for a mid range grunt cam but somehow
I have to think he spun his 427 just abit faster than 5500 RPM.... :D

BTW the oldest Isky catalog I have is a 1977 and
the cam he used was available as a catalog item
back then in the 1977 catalog and maybe earlier.
Old school piece.. ( Did Harold design this one?)

.665 lift w/1.75RR , 320 @ .020 ,274 @ .050 108
single pattern.... Mechanical Flat Tappet Z95

Again I'm not saying he couldnt have gone quicker
with a dual pattern but this ancient single pattern cam didnt do too badly .

That's why I'm scared ta run a solid roller...

pdq67

?? You mean flat tappet?
Or did you mean the 200+ lbs seat pressure for the roller ?

Anyway, the motor I'm thinking of isnt anykind of 'bse' , just a stump puller. Ovals, 10:1, 20degree valve angles, Qjet, mid lift (550), and it seems like 233-7@.050, 270-273 seat, 111 lsa, single pattern.( 496c.i.) I'd run a solid if it was as quiet as my Crane was, which was quieter than Comp's hyd cams. But otherwise it needs to be very quiet, i.e. hyd. Its a 1972 crate L88 block, so I prefer to stick with non-roller hyds. If it was an GenVI block, I'd prefer a hyd roller in this case. 5500 rpm peak. Very little lope at idle, but max midrange peak tq. No stall either. Clutch, hence the slightly wider lsa (111-112).

Gene,

It's hard to believe that you would go with anything other than a solid. ;)

You really don't want one of those "squishy lifter" cams do you? :D

i believe that the exhaust port plates are made by MPG head servive. they are primarily a ford performance company but have the plates. if my memory serves me right I think the chevelle in the article picked up a tenth and was running low 13's. mike

Gene,

My link was simply to show an example of someone useing a single pattern flat tappet in a high RPM raceing application.

I dont know the person who wrote that reply .I wouldnt know him if I tripped over him. But if he was useing Isky springs then they were most likely
Isky 8005A springs....The suggested ones for the Z95
cam.... dual with dampner , 1.530 OD , 135 LBS @ 1.875 and 395 lbs @ 1.225 coil bind @ 1.160 with a max lift of .650.

I think his point was people getting in trouble with flat tappets and useing 200lbs on the seat Roller springs on flat tappet cam...instead of the correct 135-140 lb flat tappet springs.
That he uses the correctly matched flat tappet cam and springs... goes fast with old tech stuff that doesnt kill parts.

BTW my current BBC Isky flat tappet is a tad bit quieter than my old SBC Crane was....IE barely detectable by ear.....and I used cast iron exh manifolds on both this BBC and my last 327 with the Crane solid in it... so there is no header noise to confuse with the tappet noise.... They were both quiet .... and neither of them lopes. :D

Naw, Naw!!

Can't have a "NO-LOPING" cam!!

He, He!!

pdq67