Keep blowing head gaskets - why?!?!? LONG - Ford Mustang Forums : Mustang Forum
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post #1 of 5 Old 07-25-2002, 03:27 PM Thread Starter
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Keep blowing head gaskets - why?!?!? LONG

This is kinda long but here goes

339 CID A4 block
Canfield custom ported heads
Victor 5.0 intake
ATI D-1 supercharger
HUGE front mount intercooler
don't know exact specs on cam, but considering where power peaks, I think its kinda small - solid roller tho

Heres the problem. Car made 550 RWHP with stock ecu and FMU. Took it to the track and a jackass played with the fmu and blew head gaskets. Replaced and changed to standalone FAST system. Got the FAST system installed by Bennett Racing and custom tuned at their shop. Took the car home, drove off the trailer and boom, blown again. Checked and looked like the local shop that did the gaskets last used the wrong ones (stock). Replaced with fel-pro 1046s myself and car made 590 RWHP, but also gained 50 RWHP throughout powerband. Makes 14 lbs. of boost at 6000 rpms. Power peaks at 5850 or so. Ran fine on the dyno with race gas, no problems. Ran fine for another 2 weeks or so on pump gas, then boom, blew the head gaskets. The second time the gaskets blew it was bad, they actually blew apart. This time it they were just kind of egg shaped, or oblong. Every cylinder. CR is now at 8:1, and the car is only running about 22 degrees of timing at WOT. A/F stays at 12:1 above 3000 rpms, as there isn't more than a pound or two of boost below 3000. Could I be running too much timing? Too little? Why does it peak so early? I figure it should at least rev to 6500 or maybe even 7000. That is minor compared to the head gasket issue right now though. When the gaskets blew the first two times, I had an 18lb cap on the radiator. The 3rd time, I had switched to a 7lb cap that bennet recommended. Anyone have any clues or where to look?

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post #2 of 5 Old 07-25-2002, 04:05 PM
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There are a few reasons why headgaskets blow.

1. The heads aren't flat.
2. The block isn't flat.
3. Low quality headbolts (doubtful with an R302)
4.Too lean a mixture (12.1 is pretty lean on pump gas)
5.Too much timing (22 sounds a little high on pump gas and 14#)

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post #3 of 5 Old 07-25-2002, 09:53 PM
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Is your fuel system up to the power you are making through out your rpm range? When I was running a blower before I only blew the head gaskets once - too much boost for the head bolts, but the gaskets were not burned. The bolts literally stretched, floating both heads. I was running an oversize fuel system for that particular setup with a custom burned dyno'd chip - thus no burned blown head gasket. I really like the FMU'less fuel system with a custom chip - had no problems with that setup.
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post #4 of 5 Old 07-25-2002, 11:47 PM Thread Starter
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Heads were straight, they were milled. Block I'm not sure, but it is being checked now. It has head studs, so that shouldn't be a problem. (I hope). 12:1 is too lean? Too me that sounds somewhat rich, but ok for safety. What should I aim for? 11.5, 11? Boy does power go down when its that rich. Also, I have heard that not enough timing will blow headgaskets as well as too much? Anyone else with similar setup? Looking for timing at WOT. 22 seems like too little to me. I can run almost 30 degrees on a turbo honda, but I know all motors are different.
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post #5 of 5 Old 07-25-2002, 11:57 PM
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Here are my .02. If you ran it on a dynojet dyno then there was no load on car, you also said you used race gas on dyno and pump gas on street. This is not good. If tuned for race gas and with no load and you put in pump gas and add a load then most likely you will detonate. If tuneing on dyno with race gas then use only race gas with that tune, you need a different set up with pump gas. Two different animals, also when you add a load to car it needs more fuel then for a pull on the dyno.
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