29scarab

Finally got my engine apart from Memeorial weekend. All the oil from the engine was all over the engine compartment. At the time couldn't figure out where it was coming from.

My mechanic got the engine apart and informed the #4 piston was cracked or broken. Haven't seen it yet. He said the crankcase was pressurized from the broken piston and blew all the oil out of the engine. He said when he pulled the head off the pistons on the same side as number 4 looked like the engine had been burning a little rich, but not lean as to melt or crack a piston. He is suppose to take the engine the rest of the way apart.

This engine does have a Whipple supercharger on it. I did not just slap the supercharger on it when I bought it. I had the engine gone through with good parts. Crane HP gold roller rockers, good head gaskets, rings etc....

My mechanic is going to take the engine down to a short block so I can take it down to my race engine shop.

What do you think the cause of the piston failure would be? Should I just replace the one piston and put it back together? Should I tare the engine the rest of the way apart and inspect the rest of the engine? The engine has about 200 hours on it since it was rebuilt with the Whipple on it.

When I do put it back together I heard there was a cam upgrade with engines with Whipples on them. Would it be to my advantage to install one of these cams and what would the HP increase be from a stock cam? The heads are stock with a mild porting job done on them less than 50 hours ago.


Anyone out there with some info would be greatly appreciated on helping me make the decision of which avenue I might want to take on this one.

Thanks,
Shawn

articfriends

iTrader: (1)

Was the piston forged or hyperuetectic? I have had hyperuetectisc pistons crack and break before in motors(pure and simple they are not as strong as forged). If you think its a fatigue problem have the others checked by machine shop for cracks,its possible another one isn't far behind. Which piston is it,certain ones inherently run leaner than others,maybe it got hot at one point? Bob Madera(aka RM BUILDER) is a cam guru,he eats and sleeps camshaft technology,he can profile you a cam that will optimize your combination and he sells custom otdered cams for same price you'd pay for a off the shelf cam out of most magazines,Smitty

Smitty

iTrader: (1)

Definitely make sure to put a good set of forged pistons in the motor. Also while you are there change the cam for more power. I have 2 509's with crane 731 cams and edelbrock heads with only port work on the exhaust side and at 8 lbs boost I am making 775 hp and at 3800 rpm 850 ft lbs torque with a Whipple.

29scarab

Appreciate the input guys. Not sure what kind of pistons they are. It was the number 4 piston that cracked. When I get some more info I will post it on here. My lil' crystal ball sees a rebuild coming soon>>>

Thanks

Turbojack

Good Forged pistons don't crack. You may break a ring land, burn a hole thru the top, or destroy it by a valve dropping, or spark plug breaking.

Tear it all the way down. You are close now & the extra cost would be way less then starting back again teariing it down when it lets go because you did not catch the other possilbe problem.

What were you doing when motor went south?

29scarab

Turbojack...

Think I saw your boat at lil' Bills shop one time. He had just got through doing some touch up paint on your outdrive.

I was cruising on Lake Travis at 50mph. My friends saw smoke pouring out of the vents on the side of the boat. Thats the only indication I got other than losing some throttle. Someone told me the computer on a 502mpi has a sensor that starts shutting the engine down on loss of oil pressure. Not sure on that one.

What was so wierd about the whole thing is...I got it home and put it on the hose and put oil back in it and the lifters tapped for a minute till it pumped back up and I couldn't hear anything different other than a little miss in the engine. I was still thinking I had a high pressure oil line blow or something.Thats what I was looking for.I don't think I spun any bearings or anything.

First time I had an engine do that to me. I'm keeping my fingers crossed I didn't mess too much up on the bottom of the engine.

Turbojack

Get a picture of the piston & let us see it. Are/were you in boost at that speed? Don't yet rule out being too lean.

29scarab

[QUOTE=Turbojack] Don't yet rule out being too lean.[/QUOTE

Thats a good point. The short block and heads are headed to Owens Racing in Pearland on wednesday. We'll see what Joe thinks about it.