My 502 started losing oil psi and i found some metal in the oil filter when i cut it open so i feared the inevitable and pulled the motor. I will start by claiming i am NOT. A mechanic but i know a little and try to do what i can. I dropped the motor off to the builder and here is what i know so far. He hasnt gotten it torn down all the way yet but gave me a quick update

Gen 4 bowtie block
Eagle crank
Merlin heads ( said it looked like some port work had been done he was guessing 120cc but hadnt really got into yet)
Dish pistons (motor had a blower at one time) again he was guessing 8.5:1 compression?
Lunati rocker arms
Roller cam (doesnt have it out yet but will put it on the cam dr and find out what it is)
Dart intake
Holley carb ( not sure on specs yet)
Msd ign

He said he found a trail of rusty colored crap from 1 head bolt. That it possibly might be getting water in? The oil looks fine. Also the tray under the intake had some weird rusty looking crap. Other then that he thought the motor looked really good. Also said he saw some odd wearing at the top of the cyclinder walls didnt know if a normal hone would get it out?

He is suggesting rings/bearings and valve job at a minimum. Obviously i wanna keep it as cheap as possible but while its open if there is anything i can do to increase power without. Taking out a loan im all ears

I will know more next week after he gets it all tore down.


Just curious if you guys have any suggestions?

what's your end game? Same performance? Boost it? First you need to find out why it failed but it sounds like your mech is on top of it.

Ideally id like to make a little more but id be happy with the same i suspose. I want reliability more then anything. No blower for me. Would like to be in The 475-525 hp range without changing pistons (assuming old ones are fine)

Im guessing bearings are worn from the little ive done to it. (Lost oil psi at hot idle, bronze colored metal flakes in filter)

Builder said i saved myself some $ by pulling it when i did. Was still running great but i figured it was on borrowed time.

I'm no builder, but if the Pistons are good to go then new rings, bearings, rebuild and shave the heads a smidge, use the thinnest head gaskets available, find a better cam, and enjoy another thousand hours out of it.

If it has "dished" pistons in it, you're alot lower than 8.5:1. A merc 502 with a small "DOME" piston, is around 8.75:1.

Crane 731 (low to mid 500hp) -741 (mid - semi upper 500hp) with Lightning exhaust.

You may be correct. I thought he said dish but maybe it was dome. He did say it was somewhere around 8.5:1 compression just from looking at it. He said it had the stock rods as well which he thought was odd considering what else he had found but said it was ok for what we were doing. Again this all assuming everything is in good shape.

Ive got stainless marine exhaust. A new set of lightings isnt in the cards. I had them on my last velocity and they are pretty bad ass.

So one of my heads is cracked and isnt worth it to be fixed. Basically looking for a new set of heads. End result is im looking for about 600hp now. Cam isnt ordered as were waiting to decide on which way to go with heads

Any thoughts on a set of heads that wont break the bank?

Its no joke when someone tells you what what ever budget is to double it!

Set of EQ's and a Crane 741 will get you 600.