jsmith929

I'm looking at putting some afr 195 on the car. Is the stock compression on my gonna be enough to take advantage of the added air flow. I have a lingenfelter 219 can and I'm looking at a first intake to go with it . Just wondering if the factory 9.3 comp. is enough to take advantage of it.

GeneralDisorder

iTrader: (1)

Compression, while it does make a difference, doesn't make *that* much of a difference. 9:1 vs. 10:1, other factors being fairly even, is only going to change the power by 10-20 HP. Depending on fuel quality and how much timing it will allow.... maybe not even that much. And dynamic compression means much more. A camshaft with more overlap is going to have lower dynamic compression and is going to handle higher static compression better before detonation. The way it's usually quoted is 9.5 ish for iron heads, and 10.0 ish for aluminum heads. But there's a ton of factors.

GD

skinny z

You say factory 9.3. If that much is true, you'll need to determine if the replacement heads have the same chamber volume as the stockers. If not then work out your actual compression ratio from there.
As GD pointed out, the next step is to determine if your Lingenfelter cam will give a reasonable dynamic CR.
Calculations are easy but there is considerable info needed: Head cc, piston dish/valve relief volume, bore and stroke, rod length as well as all of the specs for the cam in question. Advertised duration and LSA in particular.

jsmith929

I'm looking at AFR 195 in a 65cc chamber with l98 plug design . It's a stock 88 350 short block with low miles on it .I thought the stock short block had a 9.3 comp ration with factory Iron heads?

skinny z

Using 12cc piston dish volume as a guide along with a typical .025" piston below deck height and a .040" head gasket, a 64 cc chamber volume will yield just under 9:1. Bump that chamber volume up to 65 cc and the compression falls in at 8.8:1. Substitute an .026" gasket and that rises to 9.16.
If you can dig up the specs on the Lingenfelter cam, the dynamic compression ratio can be worked out. That's generally a pretty good indicator of how an engine will perform.