What is the maximum you can bore 604 and be fastrack legal?

[car23]

Looking at buying another 604 but weighing all the facts of buying one that has been freshened vs one that has never been into.

[Egoracing]

None, it is not legal to bore a crate.

[car23]

I thought i read somewhere you can go .005 over thats it. i know i have seen pistons in .001 i saw some on chevy website. u wouldnt need to bore just hone.

[dirttrackrocker]

I thought the whole idea of Crate Racing was, you weren't allowed to do ANYTHING to them.

[car23]

Just trying to get mine freshened and looking at buying a spare. You use them until they need to be bored and throw them away. i guess?

[Egoracing]

Use them up, then bore it and sell the short block to another class and keep the intake and heads or sell them to someone that needs them. I have seen the intakes sell for $200 on E bay and the cam/lifters sold for $150 and the oil pan with valve covers and timing chain cover sold for over $300.

[1cln_sdime]

Also thought it was .005

[Steve_Hendren]

Maximum legal bore size for a 604 is 4.008". However the maximum piston diameter is 3.999", which eliminates the use of oversize pistons. Also....unless you run the NeSmith series which allows aftermarket oversize piston rings which can be gapped, the ring end gap on the GM ring would increase by pi for every .001" of bore size.

Steve Hendren
Hendren Racing Engines
(828)-286-0780
Certified Engine Builder for: FASTRAK, NeSmith, NDRA

[car23]

thanks steve