For about the last 6 months I have been working on a friends 383 LT1 with a procharger at 13 PSI.

A little history on the engine. My friend got it last winter from an engine builder that specializes in LT1's. It is a 383 with a fully forged lower end(built for 16 PSI), a custom ground supercharger camshaft(I think the cam card was showing .565+ lift on the exh a little less on the int). The last engine he ran had LT4 heads so he sent those to the engine builder to check over and use on this engine. Once he got the engine he had a local shop install it. Less then 500 miles after he got the car back he calls me because 4 of the rocker studs have loosened up. I tightened all of the studs and readjusted the rockers and sent him on his way. A month later a rocker start ticking again and we found a broken rocker, We just thought that it was because of the crappy Crane gold rockers that he was running so he upgraded to the Comp cams pro magnum Rockers. After that he took the car in to get dynoed(It dynoed at 542 RWHP at 13 PSI) and on the trip back to his house a valve retainer broke dropping a valve. Well come to find out the engine builder used the stock LT4 hot cam springs that where binding especially on the exh side. All the springs where binding though. We sent the engine to the machine shop who ended up replacing 2 pistons and while it was apart my friend decided to upgrade to some TFS CNC ported heads with proper valvesprings and also decided to use his very high flow oval blade throttle body. I then got to reinstall the engine and on our first test drive, right after my friend did a short 3/4 throttle burst in 2nd gear it started pouring smoke out the exhaust and the crankcase was full of coolant. Back to the machine shop and this is what we found on cylinder 4 and 6.


A little more info on the car. It has a single walbro 255 pump and 60 lb injectors. It did go slightly lean at 6500 RPM on the Dyno with the LT4 heads. I think these new heads and throttle body are flowing so well that even at part throttle and relativly low RPM the engine went lean, detonated and caused what you see above. Just wondering what others think.

 

Overheating or incorrect torque of the head bolts is generally the cause of a head gasket failure.

Was that on boost? That looks like a standard type head gasket. At the boost levels you are saying he is running you definiitely need a Fel Pro MLS or Cometic head gasket.

 

Not overheated, allthough it did get a little warm during the bleeding procedure. Even if it did overheat, it wouldn't have caused the gasket to crinkle like it did. The machine shop checked the torque before they took it apart and it was fine. Both the head and deck surfaces are as flat as flat can be. I wasen't driving so I couldn't see the boost gauge, My friend said he was at 3/4 throttle and just ran it from 3000 up to about 5500 RPM but with the pulleys he has the boost has never gone over 13 PSI. The head gaskets are Felpro part # 1074 and are what the engine builder uses for all of his engines including the top of the line 700 HP 383 blower motor he offers. This is what they should look like. http://www.jegs.com/webapp/wcs/store...-1&showValue=3

We did talk to one of the local drag racers that has a lot of experience with supercharged engines and as soon as he looked at the pictures all he said was detonation. I am thinking it detonated because it was running lean. The fuel system was just barely supporting the power he had with the stock LT4 heads.

 

Yea that is a standard Fel Pro Permatorque gasket. I would definitely be stepping that up to a MLS type gasket.