[Wyldweazel]

greetings and salutations. I searched thru the vast collection of forums, reviewing various post about Cam Specs. I have been struggling with my new build as I was hoping to get some information.

So last year I had my engine rebuild. 68 400. It started out being stock, with the hi compression 2 bbr heads. It ran very solid, and if you opened up the "mighty rochester", it would smoke the 1 tire. (hahaha)

The engine was bored .030. New Keith Black pistons with new stock length connecting rods. stock crank. Kauffman 62 cc heads, MSD distributor, and box. Comp Roller Cam with 1.5 roller rockers, and a Sniper on a edelbrock RPM perfomer to feed it. Custom 2.5 dual exhaust with H pipe and Super 44 Flowmaster mufflers. The garage said the engine would be 11.5-1 compression and at one point, bragged that the engine would be doing over 500 hp. At the end of the build... I was unable to have it dyno'd to review the actual results.

The engine runs very smooth. I was hoping for a bit more lope to the idle, but it does run nice. It glides down the highway, effortlessly. However, after all I have put into this engine... I am surprised about one thing. It won't smoke that one tire, anymore. I was at a car show, talking to a very nice gentleman, about my build. He made the observation that... "my heads might be so big, they are swallowing my cam." It made me wonder. Especially since this cam was "specially chosen for my build combination."

So, after way to much talk.... Can anyone tell me what I should expect from this Comp Cam? I am wondering if I shouldn't increase the lifter ration to 1.65 to maximize my cam... or maybe my cam rpm ratio, doesn't like my stock torque converter. All thoughts are welcomed.

So what cam do I have?

51-000-11 (which means custom grind I found out)
Camshaft 3014B/3035B HR 112.0 + 4.0
Cam Spec... INT EXH
Adv Dur: 268 276
Dur @ .050 218 224 Lobe Sep 112
Valve Lift .535 .531

[tom s]

Not sure what you mean?Its a custom cam.If you get a Comp lobe book you can order a cam with virtually any lobes.The cam is not very big for a HiPo build.Tom

[Steve C.]

The specific information regarding the numbers you posted are within here:


http://www.compcams.com/Technical/Ca...terCatalog.pdf

51 is the engine prefix code for Pontiac

000 is the part number for a custom grind

11 is for a steel billet roller

The lobe numbers are listed on pages 23 & 24 ( the "B" listed after them is suffix code for a roller cam journal )


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[Cliff R]

"The garage said the engine would be 11.5-1 compression and at one point, bragged that the engine would be doing over 500 hp."

Not sure where they came up with "500 hp", but the cam used is pretty small for the CID and static compression ratio. Being a HR cam doesn't make a nickels worth of difference. Moving up to KRE heads with close to 260cfm intake flow, then throwing in a cam that woln't make power much past 4500rpm's certainly isn't the "recipe" for 500 hp out of a 400CID engine build.

I've witnessed dyno runs with those exact same heads bolted to a well prepared 406 and even with a larger 221/229/112 and 228/235/112 cams and it didn't make 500hp, down around 450-470hp.........Cliff

[steve25]

KRE does not offer a off the shelf 62 Cc head, only a 65, and with using either of the two common KB .030" over 400 Pistons your compression would be 10.7 or 9.5 with a 65 CC head.
If your looking to nail or exceed a true 500 hp out of a .030" 400 motor with 260 cfm heads then its bigger Cam time and up the compression time to over 11 to 1!

[dmac]

Do a compression check. A quick look at the Wallace site shows that with the 260 cfm heads, your max HP would occur at about 6000 rpm. Maybe if your cam was selected to operate at that rpm range, you would reach the 500 HP, assuming the block and heads were built to handle that rpm.

It may be that the builder was saying that the block could handle that much HP.

[Lee]

Stock Chevy 5.3 liter truck motors have heads that flow at least as good as your heads, with a smaller cam - so we can totally dismiss the "swallowing the cam" theory.

I suspect the engine needs some serious tuning. Find somebody local that knows how to tune your Sniper system, check the timing, etc.

Oh, that cam IS a really poor selection for your combination. I suggest NOT using the shop that

Do you have headers, RA manifolds or what?

Here is a video of a friend's car. He has nearly the same cam (his is 218/226, 110 lsa on a 107 ICL) in his 400. Unported "62" heads, and dished pistons giving him about 9.2:1 compression. This motor has been running trouble free for nearly 12 years now. https://youtu.be/d-f8yvRbBX4

[Steve C.]

I agree that 500 hp is optimistic. As an example here a 4.250 stroke combo with 260 cfm KRE heads, Performer RPM intake w/ worked Q-jet, 231 degree HFT cam and headers. Here 502 horsepower, more cubic inches and more cam.


http://www.pontiacstreetperformance....455MikeG2.html


.

[Cliff R]

Steve, that dyno run looks familiar, like one I did a LONG time ago when the KRE heads first came out. Look at the torque production, over 500 ft lbs clear out past 5200rpm's and 536ft lbs average torque for that pull. That'll get one of these big-heavy Pontiac's moving in a hurry!........Cliff

[ta man]

Originally Posted by Cliff R

Steve, that dyno run looks familiar, like one I did a LONG time ago when the KRE heads first came out. Look at the torque production, over 500 ft lbs clear out past 5200rpm's and 536ft lbs average torque for that pull. That'll get one of these big-heavy Pontiac's moving in a hurry!........Cliff

Those 2 articles in HPP would be good reading for anyone not familiar with the KRE head swap on your car.
I wonder how many KRE heads were sold because of those articles.

[Cliff R]

Not sure but I got a free set out of the deal. Thinking now I would have rather had $1 for every head sold!.....LOL.....Cliff

[Will]

That cam is tiny. There is no way you are anywhere close to 500hp with that in a 400.

The fact your engine can't turn the tire over, setup as it is, tells me you have tuning issues. It should have plenty of low end torque with that cam unless the compression ended up way lower than stated.

Time to get a handle on your timing curve and get that FI System dialed in.

Oh, and do you have headers or manifolds?

[steve25]

Let's nail down another fact here once and for all about Cam spec's before we head more in that direction!
Any given motors idle quality is determined by the Cams overlap duration , NOT IT'S LCA!

[1968GTO421]

Originally Posted by Will

That cam is tiny. There is no way you are anywhere close to 500hp with that in a 400.

The fact your engine can't turn the tire over, setup as it is, tells me you have tuning issues. It should have plenty of low end torque with that cam unless the compression ended up way lower than stated.

Time to get a handle on your timing curve and get that FI System dialed in.

Oh, and do you have headers or manifolds?

Agree totally with Will. And I don't think your "builder" is the guy to do the tuning.

[Will]

Do you have receipts with part numbers?

I think it would be good to verify the actual parts used so we can be sure your compression ratio is where it's supposed to be.

Do kre heads have part numbers stamped on them anywhere?

Also, I don't see any mention of timing have you put a timing light on this thing yet? You can figure out both initial and total timing with a dial back light. Make sure the vacuum advance is disconnected when you take the readings.

[Stan Weiss]

Can you do a cranking compression test and post the results?

Stan

["QUICK-SILVER"]

Originally Posted by steve25

Let's nail down another fact here once and for all about Cam spec's before we head more in that direction!
Any given motors idle quality is determined by the Cams overlap duration , NOT IT'S LCA!

Originally 68 Cat, 10.5 CR 400 2bbl, stock converter, and we'll assume it's still got highway gears in the back.

Smooth idle: 254 advertised cam specs are really close to the new roller cam. 269/277/113 vs. 268/276/112. Close enuff that the new engine should have about the same idle quality as it did stock.

Loss of off idle power: IMO the bigger intake and heads has reduced port velocity and hurt low RPM torque.

Cammed for stock converter low RPM operation. Heads and intake for higher than stock RPM operation. Heads and intake just ain't right for the app.

Clay