4.0 ohv compression ratio

[dahunter_2007]

I plan on swapping the heads from a 95-97 4.0 onto my 94 4.0 to make it a little higher compression. I was wondering if anyone could tell me approx. what compression ratio I would have? Any input is greatly appreciated. Thanks!

 

[Yellowsplash]

Close to a 10:1 ratio...if you plan on "turbocharging" it as your info states you might wanna rethink that unless you have access to some real high octane gas and a good dyno tuner.

 

[dahunter_2007]

Close to a 10:1 ratio...if you plan on "turbocharging" it as your info states you might wanna rethink that unless you have access to some real high octane gas and a good dyno tuner.

No the one I plan on turbo charging I have done the opposit to. lol I put the 95-97 pistons in it with the stock heads to lower the compression a lil to make it a little safeer as a DD with a turbo. Tha one I plan on making high compression is my dads. But thanks for the advise!

 

[OdinAF]

How do people always get this backwards?...
The 95TM heads are (i think 14-16cc)smaller in the compression that your heads thus less space means your compression ration should be like 8.6-1

Less space lower number, more volume higher number.

 

[UrbanRedneckKid]

So if I cram the same amount of air (bore x stroke), into a smaller hole (combustion chamber)... Your saying I'll have a lower compression ratio....

You might rethink who's backwards...

 

[RonD]

Yes, if you have a total cylinder displacement of 1000cc with piston at BDC and 100cc(combustion chamber) at TDC then compression ratio would be 1000:100, 1000cc compressed into 100cc or 10:1

If you decrease the size of the combustion chamber(100cc down to 90cc) then compression ratio goes up

 

[adsm08]

Swept volume divided by combustion chamber size is the compression ratio. If you do anything to reduce the chamber size, flat pistons, smaller head chambers, stuff a dead cat in the cylinder, you increase compression.

 

[shane96ranger]

How do people always get this backwards?...
The 95TM heads are (i think 14-16cc)smaller in the compression that your heads thus less space means your compression ration should be like 8.6-1

Less space lower number, more volume higher number.

You, Sir, are the one that has it backwards.

Sent from the can

 

[adsm08]

He isn't completely wrong. Just mostly. If you increase the size of the chamber, either by dishing the piston or opening up the head you reduce combustion while allowing more volume. On the other hand, increasing swept volume of the cylinder will increase compression. That's how a stroker kit works. It alters the throw of the piston to allow more volume in.

 

[shane96ranger]

He isn't completely wrong. Just mostly. If you increase the size of the chamber, either by dishing the piston or opening up the head you reduce combustion while allowing more volume. On the other hand, increasing swept volume of the cylinder will increase compression. That's how a stroker kit works. It alters the throw of the piston to allow more volume in.

Understood. I agree.

He only mentions a head swap with a smaller combustion chamber. He is dead wrong if that is the only change.

Sent from the can