Fairly basic pump gas oval port 454 with 10.5 compression and large valves.

Installed cam is solid roller 262/272 0.050 duration with 0.670/0.670 lift.

Have 5000+ converter in turbo 400.

Car weighs 3480 with me in it.

Track altitude 2600 feet.


Or do I need to do something major like changing, heads, pistons and cam?

Would like to achieve mid ten second performance with pump gas and small motor (ie 454 plus overbore). Is this realistic?

Im gonna have to say no. I assume your talkin bout the malibu here cause its fairly close to the tens......but even stil, just to sneak into the tens...you are three tenths away. Three tenths might not sound like much, but its a whole lot to ask when your already low elevens(read lots of power) and you wanna go that much faster(read lots more power hehe) on just a cam swap.

Do you have numbers on your heads(what cast and what about flow numbers)? Track incrementals? What about dyno tuning(has that ever been done)? Your definitely goin fast enough for the mph though, so Im sure it hooks nice and does everything right in that area(but post them incrementals anyway if you got em).

But either way....Im just gonna go out on a limb and guess that the right set of heads have the most potential in this situation to make better things happen. The cam definitely is NOT childs play. I dont know if its right, but its definitely big. But youd be hard pressed to go that much faster with just a bigger/better cam. The right heads would probably make the current cam do a lot more work as well as unlock the potential for other cams to do more. So far though, these are just guestimations though. Post up some more info about the combo and the track times cause it might make this easier to see what goin on hehe.

Greg, thanks for your comments.

The heads are gm oval port "049" casting with large valves and port cleanup.

The track incrementals are:

60 ft 1.60 - 1.63 (footbraking no tire spin with 10.5x28 slicks)
330 ft 4.65
660 ft 7.21 at 95.5 mph
990 ft 9.36
1320 ft 11.3 at 119+

I am sure that the timing (36-37) and jetting is not totally optimized but it is not real far out either. My converter is perhaps a bit too loose and will flash to over 5500 on the return road in high gear and slips about 12-13 percent in the traps.

I have a tranny brake but did not play with it much. Tried it once with 4500 rpm on the two step and it went 1.59 on the sixty foot. Otherwise just launching from about 2000 on the footbrake. The 11.29 was with tranny brake. Footbraking still went 11.32.

Shifting around 6300 and 6600 through the traps.

Right now I'd wonder if the cam isn't too big for the compression you have. And second if it wouldn't hurt to run the motor higher. When I had my 427 with 11-1 compression the car weighed 3588 with a 260/268 .628/.648 flat tappet cam I shifted it at 7200 and went 11.20's at 118. This motor was dynoed and peak power showed up at 7250 with that cam. I don't know if your cam is bleeding off so much compression, what is the LSA of this cam.

The 60ft seems light for the e.t., I was in the mid 1.6x's running high 11's, low 12's. How do you leave the line? I flash mine from 12-1500 rpms. I think suspension work might get you close to 10's. I was in the 10's with a smaller cam, the XR286R on a 107lsa (.656/.661 248/254) in my 10.5-1, 505, 781's now Brodix RR ovals. What intake are you using?

are you in a dead hook deal? Seems like you can get at least another tenth out of the 60 ft time. I'd guess that without going bonkers on some 600" bullet it not going to be any one thing. Just a bunch of small things here and there. Track altitude isn't going to help any either. Ever had a A/F meter or wideband O2 hooked up?

Maybe a pair of RR Ovals?

Ray, I have run this engine on an engine dyno and the horsepower did not change much between 5800-6200. It did not exhibit the horsepower increase that you would expect in the over 6000 rpm range. Because the results were not great did not persue a more lengthy dyno session or try to run the motor much higher. It starts and runs excellent (sounds great too) but is not making power above 6000 like you would expect with this much cam duration. 110 degree centerline

Bob, the car has a 9 inch ford with ladder bar and coil over shock setup. With 10.50x28 MT slicks it does not spin according to witnesses. Running Team G manifold and Holley 850.

The fact that the engine and solid roller cam does not seem to want to run up to the 7000 rpm range with good power leaves me wondering where the problem is.

The question is where to go next with this setup?

There is definitely a problem. You are right that the motor should make 7000 rpm with that cam. Are you sure the motor really has 10.5-1 compression? And second if the motor only goes to 6000 in it's powerband that converter isn't helping any. The only thing I can come up with is maybe the oval port just isn't flowing enough. It's definitely not the car if you say it did it on the dyno too, so that rules out ignition and fuel.

I see several problems with the combination, none are an easy fix and no one change will solve your troubles.

My combination last season was very close to yours with a 461 bbc with 781 heads and a solid roller cam, 262/272 @ .050, .697" lift, 110 lsa, 108 icl. The difference being I had 13 to 1 compression to your pump gas.

You really need to do a static compression test to see what kind of cylinder pressure it's building. Mine made 230 psi, I bet yours iss much less than 200 psi.

Your biggest issue is that the car isn't running strong on the first half of the track. That kills ET big time, not lack of rpm.

Too big of a cam for compression will kill torque which also kills the cars ability to 60' well and recover after each shift.

Also, a converter that flashes to 5000+ with your low torque and suspected excessive slippage is making this problem much worse.

The fact that the engine won't pull beyond 6200 on the dyno tells me you have issues like valve control, etc. What kind of valve springs, what kind of open/seat pressures, what kind of pushrods (diameter and wall thickness)???

The cam Bob listed is a very good grind for pump gas bbc's. Ran the same one myself with a 107 lsa and it ran quite well. Your cam is just shy of 20 degrees at .050" too larger.

Couple ideas I can suggest.

- smaller cam to build more cylinder pressure which will build stronger torque. Cam Bob listed is a good choice.

- keep your current cam and put larger dome pistons, mill the decks of the block and heads to achieve 13 to 1 or more compression.

- purchase a top quality converter like an ATI, Coan or PTC. You need optimal flash stall (5000+ if good), but you also need good efficiency and lockup at the stripe.

- take a good look at the valvetrain and figure out why the engine won't rev past 6200. While it was on the dyno would have been a good time to search that out. With pump gas and Bob's cam, I'd expect peak power to be at 6200-6500ish rpm and shifts to be made at 6800ish. Finish line rpm of 6800-7200 rpm.

I can believe the car is dead hooking as it isn't building strong torque and working the suspension/tire hard. Get some of the issues I brought up and I'll bet the 60's and 330's improve dramatically as well as the rest of the incrementals.

With the basic parts you have, I'd exect the car to be running 10.50's to 10.70's at your track elevation. Probably quicker than that depending on the given Density Altitude.

You have some classic mismatch stuff going on. But the good news is it's all fixable with a few dollars. :thumbsup: :D

Todd

BTW, I've said this before and still feel it holds true.

When trying to dial a combination in like this hard data can make a world of difference.

Last season I installed a $550 basic data logger which reall opens your eyes to what's going on with your combination on track. In my case, it could have saved me thousands of dollars had I installed one years ago. Wide band O2 really helps dial in not only th jetting, but also seeing where the fuel curve is and if there are any rich or lean spots rigth off the line that need attention. Even the smallest thing will show up on WBO2 and in my case, the simplest fix from this data made very large improvements on track.

with the converter flashing that high your already out of your peak power band, making your 60's slower! a tighter converter will work better especially with the heads you have, cam is not way out there, EX .700+ lift with 10.5:1 compression.

with the converter flashing that high your already out of your peak power band, making your 60's slower! a tighter converter will work better especially with the heads you have, cam is not way out there, EX .700+ lift with 10.5:1 compression.

The combination I ran last season had the current 8" ATI converter flashing to 5300 rpm.

A tighter converter will not fix the whole mismatch of issues going on.

I don't agree with your comment on the heads vs the converter flash stall. There are several of us who have run oval heads, with most of us having converters flashing to 5000+ rpm. But the converter needs to be a quality effiecient piece.

The oval heads have NO problem maintaining power to 7000 rpm!

The combination I ran last season had the current 8" ATI converter flashing to 5300 rpm.

A tighter converter will not fix the whole mismatch of issues going on.

I don't agree with your comment on the heads vs the converter flash stall. There are several of us who have run oval heads, with most of us having converters flashing to 5000+ rpm. But the converter needs to be a quality effiecient piece.

The oval heads have NO problem maintaining power to 7000 rpm!

well i think he also said he dynoed it and there was no change in power past 6000?.......................

well i think he also said he dynoed it and there was no change in power past 6000?.......................

Did you read my previous reply? (the long one. lol)

That engine has an issue in why it will not pull past 6200 rpm. I ran very similar spec cam and it pulled strong to 7000 rpm, no problem. heck, my heads weren't even ported, just bowl blended and it still pulled to 7000 rpm. The heads aren't the problem.

Did you read my previous reply? (the long one. lol)

That engine has an issue in why it will not pull past 6200 rpm. I ran very similar spec cam and it pulled strong to 7000 rpm, no problem. heck, my heads weren't even ported, just bowl blended and it still pulled to 7000 rpm. The heads aren't the problem.

ok i'm not bashing your oval port cast iron heads!!, it's was only a suggestion as to the problem to maybe get more people to think, now that you have answered it THANKS HAVE A NICE DAY.

Todd

Thanks so much for your very comprehensive response.

You are exactly right about my compression. My cranking compression ranges between 150 and 160 psi on all cylinders. A leakdown test revealed 7 cylinders at 19% and one at 37% (leaking through exhaust valve but not enough to affect compression test).

I agree with you that the lack of torque caused by too much cam for the compression and loose converter are contributing to the car feeling lazy off the line and in the first part of the track.

I am running a Comp Cams solid roller (grind CB 295D-R10 marine solid roller), but the heads do not have the recommended Comp springs. The Comp recommended valve springs are 944-16. According to Comp these springs have 195 pounds at 1.95 installed height and 750 pounds at 1.200 compressed. I removed two springs last spring and tested them. Don't have my sheet handy but if I remember correctly the installed height was near spec and the open pressure was around 550 pounds (approx .65 actual lift). This may be just a bit on the low side of where you want to be. Is it possible that 100 pounds of spring deficit could cause a problem? Again going from memory pushrods are also Comp 7/16 dia with 0.280 wall thickness. I remember the .280 is "etched" on the pushrod.

I calculate dynamic compression to be in the 7.5 range.

If I make the change to a smaller cam like Bob's to boost compression pressure, will it still work on pump gas?

I have plans to get a quality "tight" 5000 converter.

My goal is still to get into the 10's with pump gas and "small" 454 normally aspirated motor.

Anyway here is the additional info that may help you to further analyze the problems with my engine combo.

When the engine was dynoed did the hp fall off drastically or just stop climbing at 6300? If it was valve float you would start to see a drop once the valves were uncontrolled. You say you checked them at .650 lift. The rating is given at .750 lift so you may not be far off. The pushrods I believe you mean .080 wall thickness. .280 is a 1/4 inch wall pushrod, if you have them that would definitely cause a problem:D Don't worry about exact stall numbers for the converter. When you tell the converter builder what you have, he will build it around your car.

Comp #7954 3/8 diameter standard length and 0.080 wall thickness

it did not fall off drastically, maybe very slight downward trend.

Basically showing:

5000 rpm 415 hp
5500 rpm 450 hp
5800 rpm 450 hp
6000 rpm 440 hp
6200 rpm 450 hp

I don't think these are altitude corrected numbers and are a bit of a summary of some scattered readings testing timing and jetting, but I think are pretty representative of what I am feeling which is the lack of over 6000 rpm engine performance.

those must not be corrected numbers, otherwise somebody left the barn door open and about 100 of the little ponies got away.


does your engine stutter or break up at all on top end?

You do have a good fuel pressure gauge you can see from the seat?

Seems like an experienced dyno guy would have picked up the valve float if it was in float on the dyno. I'm half deaf and I can hear the tone of the engine change when it goes into valve float. Also seems like you'd have had collateral damage by now.

i would say no on another cam.

if it was my engine i would be on a budget and looking for cheap hp and finding more thru the chassis, so i would get another convertor for sure first thing.

then i would remove my heads and mill some off and then i would run steel shim gaskets. shim gaskets are good for .5 in compression over the normal .040" and double check the springs for proper pressure to allow the cam to run up the rpm range. even though you might not be making more hp your engine should still rev up and sound good.


you still will be able to run pump gas and i would work on the timming ( might even lock it out and set it at 36 or so were ever you make the best trap speed at)and carb jetting that alone timming and jetting will make big different. forget about e.t. and tune for mph. and i would be looking to make sure i em crossing the finsh line at peak rpm of your power. might have to readjust tire height some or change gears.

i sure would think about fluids i run, go synthetic and look at everything that turns.......can i lighten it up some........ what ever rotates make it lighter.

take control of your engine as far as heat is concerned. header wrap, insulate fuel lines and do what you can to keep carb cool. get cooler air to the engine. and make sure at least an air cleaner base plate is used. seen to many people run with no air cleaner at all.taking control of the heat under the hood has two bennifits, more power and more consistant e.t.'s,

water pump? go electrical, or use small motor to spin the stock pump, power steering remove it,use headers to help the engines low end torque, use a small tubed header with maybe an extension.

you have the parts to run mid tens its time to fine tune your combo. in my eyes i see no reason to tear the engine down and buy new heads or pistons. the art of fine tunning is where your numbers are at not more internal parts.

im a budget kinda guy and i have learned to find hp and lower e.ts thru fine tunning and chassis that would cost very little.


my opinion so dont bash on me to hard for what i believe. thanks

If I make the change to a smaller cam like Bob's to boost compression pressure, will it still work on pump gas?

I ran mine on 91 octane, thats all we can get, would occasionally throw 5 gallons of 110 in the tank, about every other week at the track. I dont use header wrap, fuel line wrap, electric fans, or a water pump drive. I have a 14x5 K&N filter on mine, might pick up .02 if I remove it. I do have a plastic carb spacer and a lifter valley tray (last year I did not) The cam I used was recommended to me by Ed Bigley, worked great, car ran good, but it was originally purchased to do a 468 and I was talked into the 505 by the builder, yet still that cam did a fine job for being somewhat on the small side. I cant remember off the top of my head but I'm thinking I had between 170-180 cranking compression. The year before last I tried a Vic Jr twice and both times I lost 60ft with no improvement in e.t., gained a little mph was all.

My opinion is this, if you just install a "tighter" converter, it could be even worse in the first half of the run. With as little TQ as you probably have, the higher stall at launch will help "crutch" that a bit. But, not all 5500 converters are the same! I've seen as much as .3-.4 in the 1/8th between two converters that stalled about the same. Name brands like ATI, Hughes and others are well worth the money!

Unless someone really screwed up the heads when they installed the bigger valves and did the port work, it's not the heads either.

Listen to Todd and ddeennis! I believe they hit the nail on the head! With that much cam, you can easily run enough compression to get your cranking pressures up around 185-200 and still run pump gas.

First thing you need to figure out is why it won't rev. My ovals were still pulling hard at 7k+, with only slightly more cam than you have.

I think a few guys have proven that the RPM Air Gap is a great choice on these heavier cars and with ovals, even with a decent size cam. The team G is not one I would run.

Look closely at some combinations that are running well like Bob's. Bob has a great working suspension, a very good name brand converter, and a cam, intake, and compression ratio that match the RPM range he want's to run. It's all about the combination!

Valve control issues tend to make the engine run like it's on a rev limiter when severe.
You should be able to view the tops of the valve stem and see if there is an issue.
Look for a star type pattern.. Especially on the intakes as they are heavier.

I'm running a roller with 200 on the seat and 550 over the nose and because this thing just flat wants to go to 7000, I do see the beginnings of a star pattern on the intakes. Cam is 260/266 .670/.680.

I need more spring and lighter retainers to solve the problem.....or to switch cams. Comp street rollers are very agressive.

Ron

Ron,

The tops of the valve stems look just fine. Partly because the person that built the engine used lash caps........BUT the lash caps were resting on the valve retainer locks! NOT on the top of the valve stem. I knew that this was not a good setup so I removed the lash caps.

Before I ran the engine this summer I checked basic stuff like spring pressure (but on only one cylinder), piston valve clearance and adjusted valve lash. For the 3/8 valve stem I could not find a suitable lash cap that would sit clear of the retainer locks. So I just removed the lash caps and run without them. The rocker geometry is still just about perfect going from open to closed.

I hope I am not misleading anyone when I say it won't rev, it will rev but not with the kind of "pull" or charge that you want or should have. The engine does not make any increase in power above 6000.

It picks up about 25 mph on the second half of the track which I understand to be fairly normal, so it isn't like it is a real dog.

But there may be another half second with this engine if I can do the correct diagnosis and make the right changes. We did run it up to 6600 on the dyno but it was not making power like it should.

A change to a slightly smaller cam would be the easiest way to get a bit more compression pressure. Decking and milling the heads of course requires a lot of work. The pistons have got a 0.340 dome which I think is 33 cc volume.

Just ran the DCR calculator again and static compression is 10.5 with a dynamic compression of only 7.5. Think the 7.5 is pretty low. Tried using a cam with 280 advertised duration in the calculator and that raises the dynamic compression to 8.0

I really appreciate all the good comments.

Well at least you have a place to start from. Like I said before at least for now you can rule out the car since it did the same on the dyno. That motor should easily be a 550hp+ motor when you get it straightened out.

Was the cam degreed? If so where was it set? I picked up 20 psi of cranking compression by advancing the cam 4* on my old engine. It brought the 60ft down from a 1.68 to a 1.53 best and picked up 1 to 1.5 mph at the big end. Its really cheap fairly easy and probably worth a try. Just be sure to recheck the piston to valve clearance. Mine was getting pretty tight to the intake valve.

Just a thought, mech or vac carb?

Hey Sandy,

I never ran my combo through the DCR calculator....nor do I wish to. I'm sure it would reveal that I'm way off base......

Static CR with the 496 is 9.4:1....so the DCR would be way bad. Especially since we RETARDED the cam to kill low end power......sugested was 106 we installed at 109.

Still, the results were good. I'd still like to advance back to 106 and see what happens....although my builder says it won't be much if any. In fact, he says don't bother.

Since you run very well on the second half, might I suggest that you make sure the fuel system is up to snuff. The fuel system has the hardest time in first/second gear due to the g-forces in low....which is over quick but makes things bad in second then can recover in high gear. Your back half mph is excellent. (I go 108 followed by 133 and if my math is correct, that's 25mph same as you.)

As others have said...I think a high quality (read high dollar) converter will help.

Still disturbing are the dyno results.....maybe too small a carb, maybe valvetrain issues, maybe ???? I'm no expert.

Shift points can effect ET a lot with rats......try lower 1-2! Even mine likes 6000.....picks up a tenth...even though it loves to rev. As good as it feels at near 7000 1-2, it slows a tenth......every time! 2-3.....6800.

So I'm rambling just a bit.

My Nova with the 468 went 11.0s @ 119 all the time, and would sneak into the high tens on cool days. 3550 with me in it. Pump gas deal with a 255/263 less than .600 lift ultradyne solid and edel ovals. So I think you should be there as well. However, I live at or near sea level.....which you have to compensate for. 950 Holley and Dart oval intake btw......9:1 CR.

I never thought the 496 with only 140 more hp would pick up 1 second and 13-14 mph.......

Ron

No idea how the cam was installed.

Holley 850 DP with choke horn milled off.

81 jets in front and 88 in back (no power valve)

no jet extensions other other mods, basically stock carb.

Going to run a fuel pressure gage that I can see actual fuel pressure during a run when we get going again sometime in late May.

Around here the altitude correction for the dyno horsepower is 1.18 so the 450 hp corrected would be about 530.

My 11.3 at this altitude probably works out to 11.0 at sea level.

This is probably a good lesson for anyone contemplating buying a used motor that does not have very good documentation (or history of good performance) about how it was assembled and even some of the assembly practise (lash cap interference for example). It had not run well in a different car, so I took a chance for a good price and I got over 1 second better than it had ever run before.

I'm guessing the cam was installed too advanced. I've seen the exact same thing with a cam installed 4 degrees too far advanced. Makes great lowend but doesn't want to make any power past 6K

The engine has one of those aluminum timing covers with the inspection plate so does that mean I can change the cam timing from there?

(grind CB 295D-R10 marine solid roller)

Could it have something to do with the cam being a marine grind? I know most marine engines are built to have a broad flat tq curve and not too much RPM. Just a thought.

The engine has one of those aluminum timing covers with the inspection plate so does that mean I can change the cam timing from there?

You can check it for sure, but it depends on what timing set you have to know if you can actually adjust it with that cover. IT could be the marine cam like mentioned though. But its easy enough to check to see what the cam timing is at

Well here we are three weeks before the first test and tune weekend and the motor is out and the heads are off, and it is going back in a 500 pound lighter car!

The valve springs check out good at 540 pounds at 1.26 inches. However this is 170 pounds less than the Comp spec for the marine solid roller cam.

Going to pull the pan and timing cover and check the cam degree installation.

Looks like best option is to switch to a similar duration/lift Magnum (308AR) or XTreme Energy (XR292R) solid roller because both these cams will work with lighter valve springs than what I already have.

Just don't understand what it is about the Marine Roller (295DR-10) that requires 710 pounds at 1.26 and titanium retainers for similar duration/lift specs as the two cams listed above.

Cody, you might be right on about the cam timing. Checked cam timing this afternoon and it was at 107.5 degrees compared to the cam spec 110 degree intake centerline.

Nice to have the heads off, easy to find tdc. The timing pointer was off 3 degrees so what I thought was 38 total advance was actually 35!

Fixed the leaking exhaust valve (just had to lap it) and checked all valve springs. Heads are back together clean and ready to bolt on.

So next step is to pull the harmonic balancer and front cover and put an adjustable timing gear/chain set. Going to try and set the cam around 111 - 112 degrees to get some more top end charge.

Have also decided to stick with the billet solid roller with the 540 pound open springs. Although I don't believe the valve springs to be a problem in the drag race application, a rev kit might not be too bad an addition to gain just a bit of effective closing pressure.

Sounds like you are making some good progress Sandy, I can hardly wait to see the car. I know what you mean about 3 weeks away from the first test and tune, My car is all tore down as well, new trany with brake, new tq converter, new gears with strange axles, and all sorts of suspension and chassies parts ect, ect. it should be a good year.
Cheers
Bear