*604 upgrades-open motor rule*

Hey guys, can anyone chime in on what the best bang for the buck would be to increase the horsepower of a 604? I run in an open motor class, so rules are not an issue. I just happen to run a 604 and would like to just build on that as opposed to starting from scratch, but it does not have to be a sealed/legal 604 by any means. I understand there is a 383 kit for the 604. Does anyone have any experience with that? I’d love to get another 100 hp or so out of it if possible, and still maintain good reliability. Any info would be greatly appreciated.

Heads and cam will give you the best bang for the buck. Ask the question at www.speedtalk.com ... lots of experienced engine builders there.

For a TRUE LM open motor, you would be better off selling the 604 and using the money to start again.
For a 100 hp increase, you should be able to do that with heads, cam, bump up the compression with new pistons and better flowing intake and carb. I would also change the rods if it was mine.

He doesn't want an open motor...likely doesn't have the $$$$ for one either.

There are endless combinations that will take his 604 to 500hp....

I don't have any information that will help on modifying the engine but if you are anywhere close to the power curve needed to compete ---maybe just try switching to methanol fuel
the actual HP is not a significant gain but the torque is impressive and truthfully that is what you feel

Brad
www.race-1.com

how much difference between methanol and e-85 for hp and torque

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Originally Posted by Krooser

He doesn't want an open motor...likely doesn't have the $$$$ for one either.

There are endless combinations that will take his 604 to 500hp....

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You are right Krooser.
If you keep the heads and work them over, even the intake can make
500 hp even 550 hp no questions. But by the time you pay for this, change the rods and pistons to some that will hold up to this level,( balance, machine work, camshaft, lifters, bearings, oil pump, timing chain, carb and everything else going into to it), you are looking at 5 K minimum depending on who you get to do the work.
Granted you can do it cheaper but how long will it last ? If you are on a budget ( and who isnt ) and every dollar counts, just make it dependable and make it last so you dont do it twice.
Just trying to give the guy food for thought. I learned a long time ago, every time I skimped to try to save $1, it ended up costing me $10 in the long run. Just my 2 cents. Best of luck whatever you decide.

Keep that motor at 6500 rpms and it will last. The bottom end will handle 550 hp. Those GM rods are pretty good.

I know ive tossed good money after bad plenty of times but it doesnt sound like the OP is looking for a permanent solution... just trying to see if he can make it work.

Sounds like a cool thing to try... but i come from a time when most guys built their own stuff.

Its all good.... if you knew what i was building for power you'd really shake your head.

Head flow ~X2 is usually the HP you can make Methanol for sure. Stronger valve spring rate, cam upgrade, cubic inches(stroke and bore) in that order cost wise, fuel system could be a big variable depending on what you have and and have cheap access to.