Leathl_WS6

I am looking at a boat that has 2 502/502 gm crate motors. They hae 1471 blowers, super chillers, and 4 holley 800cfm marine carbs.

He is way overpowering these things in it's current configuration. My question is can these gm 502's safely make 600 or 650 hp with the chillers and 1471 blowers. Naturally I know there will most likely have to be a cam change.

Thanks Rob

KNOT-RIGHT

Bigger blower equates to less heat.
Not knowing cam and heads. makes it tough.
Making 650hp on a 502 with that hardware is
a walk in the park.

Pure Energy

How much boost ? I had Procharged 502 crates @ 5.5 lbs and never a problem.

The bigger the blower, the cooler the charge @ same boost.

The only thing I would be concerned about is how hard he ran the boat. Do a compression and leak down.

Leathl_WS6

I checked into this further These are bone stock ZZ502 crate motors. Right down to the cams.

CR 9.6 JE Forged Pistons

aluminum large oval port 110cc combustion chambered heads. Intake runner volume is 290cc installed are stainless steel valves 2.25 in. intake side and 1.88 in. on the exhaust side. Valve springs are rated at 140 lbs. closed and 368 lbs. open, good for up to .680 in. lift. Roller cams and lifters

527 in. intake lift, .544 in. exhaust lift, and the duration at .050 in. for intake is 224 and 234 for exhaust with a 110-degree lope centerline.

Can I leave these cams in there? I would think reversion would be a big issue with these cams. What cam should I run to get most econimical package top speed is not a huge concern. I am more intrested in crusing speeds say at 3500 to 4000

Also the carbs are 850cfm holley's four of them. Are these going to be too big?

Thanks Rob

Leathl_WS6

Motors were fresh over the winter both of them. I will still do a leak down and compression but lets say they are fresh.

He claims 7psi now. According to him reversing the pullies will net 3psi. Which is where I think I want to be.

zahndok

7lbs doesn't sound that aggressive to me. Maybe just drive the boat easy and stay out of the sticks. Yeah right

44MTI

The short blocks will be fine. I have had several friends run 750-800 hp with stock gm stuff with no problem at all. However I would not run that much boost without lowering the compression ratio. Merc runs 7.5-8# with an 8:1 compression ratio. I would also change the valves to Inconel.

Pure Energy

Some good reading on zz502

http://www.offshoreonly.com/forums/s...ighlight=zz502

jeff32

is this a 94 Lear boat, 38 foot?

Leathl_WS6

Jeff yes I found out last night it was a lear. I was under the impression it was actually a cig. I am going to pass on it. The guy lives just a few miles from me he really needs to sell it bad now. If I didn't still have my boat I would make him an offer. The boat need some TLC a new cuddy and new exhaust for sure. But the motors have all the right stuff. He blew them up a few times. Probably just poor tuning. He has since added the new carbs retard boxes and MSD's.