Head lifting off block under boost . .

[GLHS422]

I was wondering how to tell if a cylinder head is being lifted off of the block under high boost. I'm assuming the car will lose a lot of power - will you still get the "coolant in the oil" syndrome like when a headgasket is blown?

I only remember this being mentioned a few times - I believe one of the occasions was Ken talking about a car on the dyno.

Can this happen without blowing the headgasket?

[glhsken]

It WILL pressurize the coolant passages... Means coolant will POUR out the overflow.

It takes BIG boost (+25psi) or or a bad job on the head to cause it to happen any lower.

Can't imagine it sealing too wel after that. The car on the dyno DID drive home.. Took loots of water for that trip

[GLHS422]

Thanks for the help! As usual, your knowledge has greatly helped out a fellow TD'er!! heh. Anyway, I'm just trying to eliminate possible problems.

My car went 102 mph at 16-17 psi and mid 1500 EGT's at a 2700 ft track, then the next week with no changes, it only went 98 mph at 20 psi and wouldn't even break 1400 EGT at a sea level track. At the high elevation track, I turned fuel pressure up to 60 psi static to be safe, and at the sea level track, I turned it back down to 55 psi and it still ran rich - totally backwards because it should be running richer at a high altitude track. I didn't want to turn fuel pressure down any further because I'm pretty sure something else is causing the problem.

Compression still checks out good - 130 130 125 125

The other weird thing happening is that when coasting to a stop on the street, the RPM's will bounce up and down between 1100 and 1600 or so - pretty annoying but it didn't used to do that.

Also, when fully cold, when engine starts up, it will fire and die immediately - you have to hold the throttle to get it to "warm up" - you'd think I had a chokeless 800 cfm double pumper on the thing!! LOL

The car ran great and all of a sudden started acting up like this, so I'm thinking it's a sensor or connections somewhere, but so far it hasn't thrown any codes except the usual 33 - A/C.

[Shelby VNT]

You may have a bad vehicle speed sensor connection or a speed sensor on it's way out. The erratic idle while you are coasting with the car in neutral is one of the tell tale signs.

[GLHS422]

Quote:

Originally posted by Shelby VNT You may have a bad vehicle speed sensor connection or a speed sensor on it's way out. The erratic idle while you are coasting with the car in neutral is one of the tell tale signs.

That's a good point . .I'll have to check that out. Can you get speed sensors at the local Autozone/Kragen, or should I get one from the dealer??

[supercrackerbox]

Seems like that's another one of those parts people only go to their dealer for. Part #4740088 if you have a speedo cable.

[CSX321]

Could also be the AIS motor and/or wiring for same. Very like the symptoms I had with a flaky AIS wire connection at the LM.