95gmc

I have a 1995 GMC Sierra k1500 z71 5.7tbi.
Just a little background info, I started this "project" with a 120,000 mile great running 1996 5.7 vortex I had in the corner of my shop. I removed the intake and heads, and installed a freshly rebuilt(professionally) set of TBI heads completely stock along with the stock TBI intake and throttle body ect. So basically I have a 350 TBI with a roller cam and roller lifters, steering away from the flat tappet setup.
The problem I'm having is I can't for the life of me get more than 1000 miles out of a set of head gaskets (fel-pro) before It starts blowing antifreeze out the tailpipe!! This is the third time it's happend and I don't know where I've gone wrong.

Yesterday I performed a compression test and cylinder's 1,2,7,8 tested fine but cylinder's 3,4,5,6 failed. Test results read as follows; 1=165, 2=164, 3=128 and falling, 4=0, 5=136 and falling, 6=0, 7=164, 8=163. I'm sure it never overheated and I was at home when it started missing and shut it off immediately when it started spewing antifreeze out the tailpipe.
I have done quite a few hg jobs on numerous vehicles in the past without a hitch.
Any advice or suggestions would be greatly appreciated because I'm stumped and don't want to install new gaskets, again, only to blow another one! Where have I gone wrong??

GeneralDisorder

iTrader: (1)

What gasket part number are you using? Some of the newer MLS style gaskets require a very fine surface finish on both th head and the block to seal properly.

GD

95gmc

Fel-pro part number 7733PT2

Schurkey

Did you drill the block face for a coolant bypass that the TBI water pump needs, but the Vortec block probably doesn't have? (Some Vortec blocks are drilled already. Many are not.)

Are the block decks warped/scored?

Are the heads warped/scored?

Is the intake manifold-to-cylinder head gasket surfaces flat 'n' true? Are you using the correct, "special" TBI intake gaskets?

Is the exhaust restricted on one bank, so that there's excessive exhaust gas overheating the heads and intake manifold via the intake manifold exhaust crossover?

Proper torque on the head bolts? WHAT head bolts are you using?

WHAT on the gasket is failing? Fire ring? Photos (in focus, well-lit, properly cropped) would be helpful.

A .039 gasket on an engine that probably has .025--.030 piston-to-deck clearance results in WAY too large a quench distance. "I" would want thinner gaskets, or mill the deck surfaces, or get taller pistons, or some combination.

WHAT does the data stream show for fuel trim, spark advance, etc? You may not get valid readings now that the engine has popped, but when you start it again, be sure to scan the data.