Valve to Piston Clearance

[lars49]

Does anyone know offhand what the valve to piston clearance is on a '02 GM 3400 V6 engine? I am considering milling the heads to increase the CR.

I could do it with clay but I was hoping that I could find a quick answer instead of trying to track down where to buy modeling clay locally.

Cross posted to MGE

[MGBV8]

Larry,

Spend some more time mulling this over.  There are other places to get more bang for your buck.  Your engine is already rated at 9:1. This is an all iron engine. It's not going to tolerate as much compression as an all aluminum engine. A wee bit more compression is not going to do much, especially for the money & effort involved.

If ya really want to wake up this engine, swap over the late aluminum heads & intake from a FWD engine. This requires a piston change, though. Add a bigger cam, too.  

[Moderator]

If you're swapping heads and/or doing a valve job anyhow, milling heads is actually pretty cheap. But how much bang do you get? Bruce Bowling (of the "Bowling and Grippo" who originated MegaSquirt") has a handy little online calculator for estimating the horsepower benefit of boosting compression ratio. It's an extremely simplified estimator, but it'll give you a ballpark figure. Link: http://www.bgsoflex.com/crchange.html

[MGBV8]

Bowling's Compression Ratio -> HP Calculator
Computation Results:
Engine Horsepower (peak) is 160
Old Compression Ratio is 9.0
New Compression Ratio is 10.0
Computation Results:
Computed New Engine HP is 165, a 3 percent change

[lars49]

It is an aluminum head engine with a current CR of 9.6:1  But looking a the numbers and after talking with my machinist, I've come to the conclusion it is not worth it.  New pistons would do it but I am not willing to fork out another $1K on parts and $600 to balance the engine.  .I'm hoping that a 25% increase on the input flow volume will do something worthwhile.

[MGBV8]

Is this a FWD engine?

Bowling's Compression Ratio -> HP Calculator
Computation Results:
Engine Horsepower (peak) is 185
Old Compression Ratio is 9.5
New Compression Ratio is 11.0
Computation Results:
Computed New Engine HP is 192, a 4 percent change

[lars49]

Yes it is a FWD.  Not much bang for the buck by increasing CR, is there?

[Moderator]

More than fancy valvecovers... and over the whole RPM range too.

[BlownMGB-V8]

Also increases gas mileage.

Jim