apitts73

got the head off!!
seems the head bolts were tightened to 70...none loose.

nothing stands out except for the scratch i put in #1 from a screw driver(oops)....its not bad.
i took some pictures but i cant seem to figure out how to upload or post them.....it was getting dark out so they arent the best...not bad though.
anyone know how to do pictures?
thanks,
adam

Tom M'Guinn

Hit "post reply" in the bottom right (rather than just filling in the box at the bottom of the thread) and then click manage attachments to add a picture or five.

Do you have a precision straight edge? You should check the deck and head with one to make sure everything is flat. What head gasket were you using and can you post a picture of it? Look for signs were coolant got into the cylinder (on the gasket, head and deck)...

apitts73

thanks tom
heres the pics....ill take better ones tomorrow if needed

apitts73

looking closer at the pistons i just noticed exhaust valve marks on all 4 pistons where they contacted!!
what the f**k?

carlege

was the head trued or re decked or the block? with that many HG jobs i would think someone would have done that trying to fix the problem

Tom M'Guinn

Post a picture of the contact. Did you check the timing belt alignment before removing the head? Did you retension it since the motor was built?

apitts73

not sure about the head..but i think it was resurfaced once, twice at the most.

no i didnt retention the the belt...its got the spring tensioner on it.
no i didnt check the timing before removing the belt...but it makes sense i should have!

im thinking that the contact is from when the cam seized at the first start up...i know they contacted then....but when the cam was replaced the valves were not bent(they were checked)....today my mechanic friend said that it looks fresh..not 2100miles ago!
i hope he is wrong and it is from before
sorry...bad pic from phone camera

apitts73

also looking at the valves there are no marks or any evidence of contact!

Tom M'Guinn

Not sure where to start, but will jump in....

The spring tensioner just helps you set the tension, but once you set the tension and tighten the bolts, the spring tensioner does not move and does not dynamically maintain tension as the belt breaks in. In other words, you need to retension the belt, even with a spring tensioner. If memory serves, the retension is recommended at 2000, so you were slightly overdue.

What caused the cam to seize when you first started it? Did you re-use the same belt after that?

Was this an MLS gasket? What studs? Those aren't o-rings are they - picture too small to tell?

Was the coolant level going down before this happened and/or were you having any trouble keeping the cooling system vented?

What octane were you running and for which VR map?

With all due respect to our friends at Lindsey Racing, I have to doubt a properly functioning 3" exhaust by itself is ever the root cause of a blown head gasket, let alone one with the colorful "back story" emerging in this thread.

apitts73

thanks for that info on the belt tensioner!

-the reason the cam blew was the only thing not new on the motor was oil pressure relief valve in the head....starved the cam of oil.

-did not reuse the belt(Kevlar belt)

-cometic HG/ stock studs/ no o-ring

-coolant was always fine....didnt even go down when it blew, if it did it was a small amount

-chevron 94 gas
Here is where i think the problem is:
vitesse chip board was set to default mode...not image #4 like it should have been set to.
the race fuel switch/plug was plugged in...which means it was set to race fuel mode!
the FQS was set at #2 or #3....not sure what it should be set at
All these things should have been taken care of at the shop, before they gave it back!
ive been reading the vitesse manual to learn as much of it as i can understand...but extremely intimidated and unsure of most of it!

also there was a lot of carbon on the pistons for only 2100miles. and there is no sign anywhere of where the HG let go.....checked the deck and the head and also the gasket really carefully.

im going to put it back together next week...add the back pressure kit and find out how bad/not bad it really is.....before i go to the bigger exhaust and downpipe.

thanks again Tom(and everyone else) for the help and interest

Tom M'Guinn

I also see some scoring in your cylinder, which might suggest things were getting hot in there or you had air pockets. Race gas maps with the most aggressive VR maps, on pump gas, could very well explain it though...

Duke

Any pics of the headgasket? Did you find where it let go?

Chris White

So far nobody has mentioned the probable cause…

Ignition timing. Our engines can stand a lot of variation in mixture for short term – but they will fail with just a few events of ‘bad’ ignition timing. Too much advance will create serious cylinder pressures – well over what the studs and gasket can support. 3.0 liters have very different ignition timing requirements (John is on top of this) but the intermittent chip issue could have caused all sorts of timing issues. The race gas switch would also (I am assuming here) called up a more aggressive timing curve.

So – this one fits all the prerequisites of an ignition timing related failure.

I am always slightly amused that many folks always zero in on AFR whenever they see a 951 failure. As long as you take care of all the heat issues you can run a 951 engine on boost at 13:1 or leaner for a while. If you try 30 degrees of timing on street gas at over 1 bar of pressure you have mere seconds before serious physical failure.

The ‘seized’ cam is a whole other can of worms. What is meant by the cam ‘blew’? did you wipe a lobe or did it start to seize to the cam tower journals?

BTW – the valve marks do look like they are very recent – any chance you rotated the cam or engine after taking the belt off? Sometimes the cam will rotate by itself due to valve spring pressures after the belt is removed.

BTW2 – take a good look at the head gasket for any evidence of the failure (and post some good pics).

Chris White

Check this thread for a similar problem – repeated head gasket failure, new engine and another head gasket failure….sounds similar!

https://rennlist.com/forums/showthre...eferrerid=1956

Duke

I assume ignition timing was the point when compression ratio was brought up earlier in this thread as well as running VR race gas maps.

BTW, how does the cylinder walls feel, looks like scoring?