Blown up Procharged 6.2

[Craig]

OK, little help here :) A friend has a 29' Powerquest vee hull. He had twin 6.2 motors with Prochargers set up for 5# boost. He was coming home from the sandbar running hard for about 5 minutes. One motor started losing rpm's. Bottom line, he took it to the shop and it busted some ring lands off two pistons and tuliped a valve. So, to me this seems to me to be a fuel delivery issue, maybe leaned out during the hard run. Any thoughts on this and a cause??? I think think the motors are basically stock besides the Prochargers. I know this motor has hypereutectic pistons as opposed to forged. Anyone, anyone.......
http://www.justanothertoy.com/photogallery/powerquest/russengine.jpg
http://www.justanothertoy.com/photogallery/powerquest/russengine1.jpg
http://www.justanothertoy.com/photogallery/powerquest/russhead.jpg

[1BIGJIM]

Ok I will go out on the line. I think you answered your own question. "hypereutectic pistons as opposed to forged"
Is going to part of the problem.
Buy a Whipple Charger :D

[HP350SC]

6.2 is MPI correct? How does Procharger control the fuel and timing curves? Just bumping fuel pressure is a band aid approach. Do they rely on the stock knock sensor? Don't think those pistons would have made it 5 minutes @5lbs. WOT with any s/c.

[Craig]

Yeah, I was wondering about the pistons. The 6.2 is MPI. I was thinking about calling ProCharger and getting some info on how they compensate. I had heard that the boosted fuel pressure is a band aid.

[1BIGJIM]

I have seen pistons with holes clean through them. Remember hypereutectic pistons are a fancy name for cast piston. Cross my fingers, I just installed a set of K.B. in my new engine :rolleyes: I have one hour and no problems but I have no plans for nitrous or super charger. If I had to do it all over again I would of spent the extra $200 and put in forged. I am already over budget:frown:
Good luck on your project..

[Quality Time]

I read on another board about a whippled 6.2 coming a part as well. 26 Daytona with twin 6.2's.

[Craig]

Luckily, my boats still running, this boat is a friends, sorry Russ :p I spoke with Procharger today and they said their suggestion would be to put in forged pistons, go figure. What are they selling a kit for if they know it needs forged slugs :confused:
BTW, QT, a 26 Daytona with twins?????

[HP350SC]

I got away with cast pistons in my old 350 w/7lbs. boost, but I never held WOT for more than 30 seconds. Also, that is keeping a close eye on timing and fuel delivery.
I think I remember reading somewhere the hypereutectic piston material was "brittle" for lack of a better term. I know of some off road guys that have broken ring lands on the hyper. pistons with N/A motors.

[powerplay230]

Here's a question after looking at pictures. Look at color of the one cylinder that broke- is it different because just that one ran lean or did that cylinder get cleaned up from water getting in it. If fuel delivery don't MPIs run more evenly cylinder to cylinder.
I know I'm paranoid about getting water in motor after having it happen twice in two seasons...

[CARLSON-JET]

Not an expert on supercharge engines, although I have one. I would check the rod bearings. if they look hammered, I would guess something to do with pre-ignition or detonation . whether due to low octane gas, lean out or a half dozen other culprits. there are alot of symptoms not shown in the pics that would leed one to a better conclusion. Or, the easy way is to just say .. crap pistons, forged will cure all. If your friend has really deep pockets, buy bore and reassemble to play the scenario over again .. I personally would look at every aspect I could. Looking is free and has to be done anyways. I too would really like to know why this happened. Please post the final results. OPM (other poeples mistakes) can save others countless time effort and money not to mention a fun summer of boating. R.B.

[Chadzilla4ever]

running hard for 5 minutes and cast pistons is a death sentence. When merc designed this engine they didn't design it for use with a supercharger. If your friend wants to continue to run it hard he should have both engines gone through. Put forged pistons, inconel exhaust valves and all the rest of the good stuff in them. Also, after he has them rebuilt, have someone tune the engines on the water with a laptop and an air/fuel ratio meter. This is very important as there will probably be some lean spots in the fuel curve. One company that does alot of efi tuning isGT PERFORMANCE in Montclair Ca. Their # is909-982-8391. Ask for Gary. He has been doing efi longer than most.

[Craig]

I appreciate all the input. I'll see Russ tomorrow at the lake. I think the forged pistons are the first step and checking the fuel delivery seems to be next!

[565edge]

My old 383" chevy with a whipple tuleped the valves from the knock sensor backing timing out of it and heating the exhaust up.

[Wetter the Better]

i had a 383 with the same problem on a NOS .ring ends butted together and pops the top off the pistons and the pistons were forged,run a larger ring gap and never look back.has nothing to to with cast.hyper or forged pistons i had 350hp shot on cast pistons for 2 years and never hurt a piston in a stock rebuilt 350 with cheap rings
later