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Discussion Starter · #1 ·
2 cam choices for mild 396. Disregarding roller vs....,feel
free to predict performance
characteristics of each. Max HP, idle vacuum etc. And why ?

Is the Elgin an exact GM 502 copy ?

How much will extra Comp lift affect HP ?

Lobe separation ?

Duration ?

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Best place for BBC cam questions is over on Team Chevelle - you might try posting there.
 

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The bigger cam won't be mild at all in a 396. You'll have vacuum problems (less than 10").
The smaller ZZ502 cam will probably make 10" to 12" idle vacuum.
Why are they building a 396 ? Pistons are expensive. It's cheaper to build a 454+
I'm using the ZZ cam in my 489. I expect about 14" vacuum at idle.
 

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Discussion Starter · #4 ·
What determines the bigger cam ?

What is considered expensive pistons,
street motor ?

How does one estimate vacuum ?
Is vacuum dependent on idle speed ?
 

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What determines the bigger cam ?

What is considered expensive pistons,
street motor ?

How does one estimate vacuum ?
Is vacuum dependent on idle speed ?
I'll respond to a couple of your questions. There are too many variables to be able to answer the other questions.
Intake duration determines which cam is bigger.
Vacuum is dependent on idle speed. You need to determine the optimum idle RPM for the engine and camshaft. A cam with 230 @ 0.050" duration in a 302 will have much lower vacuum than it would in a 400. Also, the idle speed would need to be higher with the smaller engine.
 

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Personally, the ZZ cam is a great choice for street applications. Makes good power, sounds good and is easy to tune, while being good on parts.
 

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What heads will you be using? That will determine if your comp cam will be worth while in the lift category.

As for the duration, I have a similar cam in my 489 that makes 11 inches of vacuum(237/243 on a 109). I would expect that to make around 10 or so even with the 112.

Larger cam is determined by over lap which is determined by valve timing and duration(generally)

Personally? I would use the zz502 cam in a 396, unless you're wanting to spin to higher RPM. But for a street cam, that 502 cam will be much more fun to drive since it makes better lower to mid range power.

I am going to be building a 454 or 489 for my 68(and upgrade the trans/rear when they break) and I will be using something similar to the 502 cam or anything with the durations in the 220s on a 112.
 

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Discussion Starter · #9 ·
My 396 is a street car with (don’t laugh)
063 heads and blended bowls. Steel shim head gaskets and decked. I estimate 10-10.5 compression w/21 cc domes, Sealed Power Forged.

Air gap aluminum intake, MSD 8360, Hedman Headers and Pypes.

Comp roller rockers. I used Elgin cam which I believe is a GMPP 502 cam. Rollers are Howard’s #1020 Hyd Rlr, Race. They are actually made by Gatormon. I buy from Star Performance, great price and service.
Cost in January cam and lifters, $ 659
to me.

Of course, there’s a 750 DP w/HP Holley upgrade on top.

I’ve been up and down w/air bag pressures, lead over right rear tire etc
and cannot control wheel hop. Very disappointing. M 21 and 3:73, 14” stock wheels.

My only other option is to remove Holley and install an Eddiebrook carb, which should choke off enough HP to reduce wheelspin 😁

About 2500 miles on rebuild, 20-50 Schaefer oil. Lifters are quiet. Plenty of PB vacuum at 900-1000 idle, plenty of torque.

email me your email and I’ll send you
a short video of engine running

[email protected]

???.... I estimate 400-425 HP or about the same as original 396 375 (450) cars in ‘69. Were they also plagued w/wheel hop ?

Font Screenshot Parallel Number Rectangle


Elgin Pro Stock E-1235-P
 
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