Thread: Please analyze this engine setup!

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My son bougth a rebuilt 396 that has been stored for 10-15 years.
Block casting number: 3916323, 060 bore
Heads: 3964291 108cc?
Cam: Comp Cam 11-430-8 (10) Grid number 280HR
Pistons: TRW L-2287
Rods: Manley 14060

It seems that it has prox 11,88 comp ratio but the cam specs says it for 9,5:1 ratio.

The engine has not been started.

What do you guys think?

Chevy BB is all new to us..

Thanks!

what is the octane rating of fuels in your area.?

Originally Posted by HOSS429

what is the octane rating of fuels in your area.?

98 octane..

It's definitely NOT 9.5 compression, your pretty vlose with your 11.5 + guess.

If you have 100 octane gas, your OK, but not good for daily driver with low octane fuel.

if after you run it you find your compression a bit high retard the timing a bit or even use two head gaskets . ( double stack ) . i`ve done that without problems .. and even the factory once did it .. wish i could get 98

Originally Posted by Geezer2

It's definitely NOT 9.5 compression, your pretty vlose with your 11.5 + guess.

If you have 100 octane gas, your OK, but not good for daily driver with low octane fuel.

CC recomends 9,5:1 for the cam.
How will it work with 11,8?

It's not a daily driver.
Weekends only

With a good intake and headers you'll be fine. Most likely CC reccomendation is for 9.5 and higher compression. That much cam in an 8-1 engine would be terrible on the low end.

the problem with running too small of a cam in an engine with alot of compression is detonation. After searching for this piston I came up with a 47.1 cc dome or a 43.1 cc dome. Not sure which one you have but they are both under the same general part number. With the 43 cc, zero deck, and .040 gasket, I came up with 11.89 CR , and with the 47cc dome I came up with 12.49CR!! I think with 11.8 CR you are right on the verge of needing to run race gas, 98 is awesome but 110 sounds better. I would be weary of running a cam with only 224 degrees @ .050 lift. Sounds very small for a 12 to 1 engine. If you are dead set on using this motor I would use 110 octane, and retard the timing alot. If you hear detonation I would get off the gas real quick, cause it don't take long for a piston to melt under these conditions. What will the motor be used for? I would at least shoot for 240 degrees @ .050 on the cam duration. Plus those old magnum cams are outdated, much more potential with an Extreme Energy cam!!

Run a bigger cam!!