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alligator 09-17-2002 07:44 AM

GMPP CRATE MOTOR Intake Manifold Vacuum
Guys, I have a 1968 Camaro Sport Coupe.
It has a 327 2V, Powerglide tranny, 8.2" 10Bolt Diff, 4-wheel manual drums, PS, and AC.
I want to do a modified restoration of the car to include a 12 bolt diff, 4 wheel power disc brakes, 5 speed, GMPP CRATE MOTOR, modern AC, stereo, etc...
Not Pro-Street, not Pro Touring, but a stock looking vintage car with all the muscle and some comfort.
My question is what GMPP CRATE MOTOR to pick.
I want at least 400HP.
I want to run power disc brakes.
I want to have AC.
I want to drive it 5-8000 miles a year.
With that in mind, I need a certain amount of Intake Manifold Vacuum to power the disc brakes.
Now I know that you can get aftermarket electric pumps to assist a power booster, but I have read that these things are not really reliable from other news groups.
Also, an overcammed engine typically does not react well to an AC compressor turning on.
So my question to the group is: How much Intake Manifold Vacuum do the following GMPP CRATE MOTORS have at a given idle and what is the groups experience with idle quality?

330HP / 350 Engine
ZZ4 / 350 Engine
Ram Jet 350 PFI Engine
Fast Burn 385 Crate Engine
HT 383 Truck Engine
425HP/454 H0 Engine
450 HP/502 H0 Engine
502/502 ZZ Engine


4 Jaw Chuck 09-17-2002 07:52 AM

Where the hell did I leave that crystal ball...I know it's around here somewhere? Anyone see it?

MHenricks 09-17-2002 08:32 AM

Go to each engine has a brief description of the motor and some of the qualities. It also list some idle features as well as average vacuum readings.

Remember the more duration the less vacuum. Anything above 225 dgree will have poor vacuum and rough idle.

[ September 17, 2002: Message edited by: MHenricks ]</p>

alligator 09-17-2002 12:25 PM

Thanks MHenricks.
So if I stick with the GMPP small blocks or the 454HO, then I should get decent vacuum and idle?
I really have my heart set on the 502/502ZZ.

MHenricks 09-18-2002 11:23 AM

What is the duration of the cam

41willys 09-18-2002 11:27 AM

I have the ZZ502, with a few extra mods, but the cam is at .050 224/234, .527"I/.544"E.

johnsongrass1 09-18-2002 07:02 PM

12-14 in. Should be enough to operate power brake booster.

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