502 hole in piston, oil everywhere
 

Long story short, I have a 502 MPI stock lower with Edelbrock aluminum heads and a side mount whipple charger. Last weekend it blew oil out the dip stick tube. We pulled the motor and have a hole in a piston. So I need to find a replacement set of pistons. Not sure if it needs bored yet, but wondering what brand and PN of piston I should order? JE, SRP, others; so I can get them ordered and start the rebuild process.
Thanks for any help you can provide me.

I obviously have developed a fuel delivery problem, and will be researching-posting for recommendations to replace the 2 merc pumps (lift & efi), whipple pump and filter seperator.

CP, or JE is the best choice !!
problem u had, is either running lean or to much timing or not enough octane fuel !!:eek:
Been there ..mhhh:party-smiley-004:

yea, it has not had any problems like this before. Fresh tank of fuel, but how do you know you are getting 93 octain when you fill up, just because the pump says so. Also with 3 fuel pumps, and 3/8 fuel lines, it is marginal in size.
I have seen others here eliminating the VST system and changing everything to 1/2 lines, so I plan on replacing all of this to eliminate those possible causes.

which hole went away?

Number 6, and 4 wasn't far behind as it was deformed also.

put in a blower pistons now..KB mast nice ones

28,
Depending on which pistons are in the engine now, you may want to satay with the same thing. One thing you need to pay attention to is the weight of the replacement pistons compared to the originals. If they are mor than a few grams different, you will need to rebalance the crankshaft.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

They are stock JE flat top pistons and I don't think they are available anymore. PN:J2700 is stamped on the bottom.
I have the parts in my suburban and will take it into the machine shop to see if it needs bored or just honed. I don't see any real scratches, but there is melted piston on the top of 2 of the cylinders.
BillK, good point on the balancing. I guess if I have to replace them then that will have to be done also. Not really sure how you would be able to find one about the same weight if it was a different piston.
ezstriper, are those Kieth Black pistons you are refering to? Are they blower pistons?

I used J&E blower pistons in my 502 blower motor with very good results. And yes you should re-balance the rotating parts.

I had previously melted the # 8 stock piston with the # 6 starting to go. Mine was BAD GAS. You are correct, you think you are buying 93 octane, but how do you really know?

Did you notice any difference after installing them? It looks like the JE-257956 is 8.4cr with my 118cc heads and I think stock was 9.1cr.

Too much boost which will cause melt down in #6 and #4 to follow. Will happen everytime..

I understand, but I am at 6psi and I have changed nothing. This was a 30 sec full throttle run and the temp was at 130 degrees. I have had this same setup for 7 years now and all of the problems I have had were due to the stock cast heads. Why all of a sudden is this a problem, that is the $10,000 question. I have ran full throttle at LOTO racing for miles on end without any problem.

yes, the KB are blower pistons about 8-1 but the tops are thicker to stand up under boost and the rings are moved down in most cases, you will need to balance the engine at this point don't skimp there or bad thing may just happen again...

Nothing lasts forever.......maybe it was time.

after that much time on the engine the ring seal may have went away letting oil into the cumbustion chamber which could cause preignition/detonation. that being said it would up the octane requirement. safe bet would to be upgrade the fuel system also a drop in compression and total timing would give a little edge for the variation of fuel quality available. definately go forged as supercharged engines are always on the edge of detonation/preignition at higher rpm

I have a nice set of gently used 509 pistons JE

Back about 4 or 5 years ago I blew a hole in a piston. I was using a flat tappet cam and a few of the lobes went down. That caused a piston to go lean and boom!! The root cause of the problem was the oiling system. I had upgraded to about 450HP and I had the stock 330 cooler and lines.

I know, there are many possible reasons. So I plan on upgrading the fuel system.
JCPERF, what is the pn: of those pistons, and what exactly does (gently used) mean? How many hours are on them. My instinct is to start with new though.