340 compression ratio

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Barracuda Freak
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Ok, next question from the newbie,

My 64 Barracuda has a 340 that began life in a 1970 Duster. I've been trying to figger out just what to do with this engine(it runs, little blue smoke on startup, runs decent though, but haven't had it on the road at all(no plates).

Now, I've read that these 340's in 1970 were ~10.5-1 compression ratio. pretty stout for a stock engine. Although, there were one or to web locations that stated 9.2-1 or thereabouts. The stock manifold is the 4bbl. Right now, it has an Edelbrock RPM Airgap with a Holley 650.

How do I find out for sure what the compression ratio is as it sits?? While looking for cams, many state compression ratio in the 9's, how do I decide on which cam?? I plan on ending up with ~3.55 gears in the back, the stock j-heads, stock 833? tranny.

Any help is deeply appreciated

FF
 
The 340`s made from 68-71 had the 10.5-1 compression as well as larger valves, in `72 the compression dropped and the valves got smaller with the advent of more strict emission controls. You can do a compression check and (granted the valves are in decent shape) get an idea of what compression the engine has. My stock `68- 340 with original pistons runs in the upper 170`s.
 
Longgone said:
The 340`s made from 68-71 had the 10.5-1 compression as well as larger valves, in `72 the compression dropped and the valves got smaller with the advent of more strict emission controls. You can do a compression check and (granted the valves are in decent shape) get an idea of what compression the engine has. My stock `68- 340 with original pistons runs in the upper 170`s.
Click to expand...
yep, anything over 150 psi is- 10.25 compression, what the pre 72 had.
 
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