? about displacement

[joker]

Is there any "easy" way to find out what displacement and compression ratio an engine is without physically removing the heads? My cousin was wondering if in fact his engine was a 306, or really just a stock 302 bottom end and what the compression ratio is on the engine. I know you could take the heads off and measure piston size and the dish/dome and calculate it from there, but is there any easier way?

[Craig K.]

You can "pump" the cylinders to get cubic inches, not sure about compression ratio.

Racing groups did this at one time to verify the engine size for the group that you were racing in. Not too many do it anymore, as now they usually just tear doen the engines instead.

[EZ SPEED]

Originally Posted by Craig K.

You can "pump" the cylinders to get cubic inches, not sure about compression ratio.

Racing groups did this at one time to verify the engine size for the group that you were racing in. Not too many do it anymore, as now they usually just tear doen the engines instead.

They still do that at certain racing events Craig, I know they used to do this at the Talledega Shortrack years ago.

[Wicked]

I would say you could not know compression ratio or displacement unless you know combustion chamber size, bore, stroke, and a few others small details like head gasket thickness, piston valve relief volume etc.

You can not tell static compression from a compression check due to temp change of the air when compressing, ring seal, cam timing, etc as well as inaccuracy of the gage.

A compression check and knowing the mileage might help you determine whether if has been rebuilt or not(i.e. 302->306). Nothing absolutely definite though.

Craig, what fluid do they use for "Pumping"? Just air? What about leaks past rings? Explain the process, I am not familiar.

[Craig K.]

Brad,

I am not sure how they "pump" the cylinders,but I do know at one tie it was done in many amature racing groups. The group I use to race with up north had one of these gages, but while I was racing with them, they had never used it.

[Italian LX]

Originally Posted by KB ZILLA

They still do that at certain racing events Craig, I know they used to do this at the Talledega Shortrack years ago.

Yeah, I've heard of FFW pumping motors if it is contested.

[Italian LX]

Originally Posted by joker

Is there any "easy" way to find out what displacement and compression ratio an engine is without physically removing the heads?

It requires specialized equipment, but it can be done. As mentioned previously, you can pump the motor to determine displacement and then use a whistler device to measure the combustion chamber volume. Then it's just a mater of a simple calculation.