G. McDonald

I ordered replacement gaskets from summit and that's what they sent me. The package says it is for 350 (5.7L) OHV VIN P Engine (1992 - 1997). Is that a stock replacement for the LT1? I see everyone using the Fel-pro 1074 but I never hear of anyone using this Fel-pro head gasket. Needless to say, I have coolant leak into cylinder no. 7 and am trying to figure out what caused it so I fix it once and for all. All reassembly was very much by the book (The LT1 gospel according to Shoebox) so I cannot think where I might have F'ed up. Dissassembly is currntly underway.

Thanks for the input.

raroz28

I used the 9966PT's.

If you just replaced the gasket and it's leaking, then you probably have another problem.

Did you have the heads inspected? It's important to take aluminum heads to a machine shop for inspection and maybe some milling if they're warped at all. If you did not do this, I'd imagine the head is warped or possibly has a crack in it.

G. McDonald

The heads were milled and presumably thoroughly inspected as part of the LE2 rebuild that was done on them. I have to assume they were perfectly flat. ARP head bolts with plenty of GM teflon thread sealer were used (maybe I'll use ARP teflon thread sealer next time?) - I have to assume that the GM stuff was not the source of my problems.

I put dye in the coolant and ran the car then started disassembly and saw clear fluorescent coolant on the roof of the no. 7 exhaust port, coolant may also be getting into no. 8 cyl. Bolts were carefully torqued in steps to 60 ft-lbs (as per ARP's instructions for aluminum heads) - and double checked. I will have to see what I get once the heads are off.

I don't think it's very likely but I have read some posts about the locator pins being slightly too long after heads have been milled and the locator pin hole in the head is too shallow to allow the head to seat properly against the head gasket (sounds very far-fetched to me). I will check out the pins, but I don't think the problem is going to be that easily remedied.

Which head gasket is best for sealing? I don't really care too much about gaining an extra bit of compression with a thin gasket - sealing is what matters to me right now.

Thanks

kline454

Well i had the same problem on my 383, with the 9966pt head gaskets, small leak to 7-8 i went with the 1074 problem gone!

G. McDonald

Kline 454,

When you originally did the head gaskets and they leaked, did you use any of that spray-on "copper coat" gasket adhesive or anything like that? Did you use it with the 1074 gaskets? Were you able to identify any problem with the original 9966PT gasket that leaked, i.e was there a slight water passage misalignment that I did not notice when I compared my gasket to the original GM unit?

It seems odd to me that the 1074 would seal better than the stock replacement given that I believe the 1074 is thinner than the 9966PT, correct?

I also used a very small dab or ultra grey RTV around the four head gasket bolt holes that correspond to the four mid-length head bolts (the ones at either end of the heads) because it appeared that they were prone to leaking oil down the bolt shaft from the upper portion of the head. I believe this is becaus those are the only four bolts that have a pool of oil sitting around their bolt head. I hope placing this small amount of RTV on the head gasket was not in some way responsible for my problem - from what I have read, I doubt it.

Did you check the pin locator length on your engine - sounds unlikely but worth a look. If that was your problem, going to the 1047 would not have solved the problem since that gasket is apparently thinner than the 9966PT.

Thanks for the responses.

shoebox

I used the 9966PTs almost 4 years ago. No problems so far. I installd them dry, IIRC. I would not use RTV on a head gasket. In the old days, I always used the spray copper coat and I think it would be ok on todays head gaskets. You do need to use thread sealant on the bolts.

kline454

everything was done the same with both head gaskets if you look at them next to each other the 9966pt has a larger coolant hole next to cyl.7-8 and thats where mine was leaking to. my head and block checked out replaced gaskets and been spraying it with a 200shot ever since.

G. McDonald

Has anyone else used the Fel-Pro 9966 PT head gasket? Results/problems?

I have to assume there are a few people out there who have used them since Summit is recommending them as the stock replacement head gasket for the LT1 (that's why I ended up buying them).

I hope my solution is as simple as replacing them with the 1074 gaskets.

THX

G. McDonald

Kline454 (and others) - a few other questions,

Did you pressure test your cooling system at some point during the install of the 1074 head gaskets?

I was thinking it might be useful to try that as soon as I have the heads back on in order to make sure the cooling system (and head gaskets) are sealing up as they should - before putting all the rest of the crap back on (i.e. intake, etc.). Can anyone confirm that this would work?

Would I need to even fill the cooling system with coolant to do a pressure test? I'm geussing I wouldn't have to refill it.

Does anyone know to what pressure I should pump up the cooling system to test - and how slowly should that pressure drop in a system that is sealing correctly?

Much thanks for the input.

kline454

Check your block and head for warp and pin lenght if its with in spec put the 1074s on and call it done!!! Unless it a large leak you really are not going to be able to see it with a pressure test like that.

1racerdude

The 1074 will work with NO leaks. It is .049 compressed.

G. McDonald

So last night I removed the intake manifold and found something odd.

Inside the no. 7 intake port there looked to be more than an ounce of coolant sitting on top of the intake valve (it was closed obviously).

Is this possible as a result of a leaking head gasket? I would have thought the only way to get this would be to have a crack in the head that allowed coolant to get directly into the intake port.

There were also clear signs of coolant in the intake ports for cylinders 8 and 6 and to a lesser extent in intake port no. 5.

I should have the heads off within the week so hopefully I will know more then.

Any experience with this before? Aside from a visual inspection of the heads and a check to confirm block and heads are flat, I suppose I should have the heads pressure checked but I'm pretty sure Lloyd E. does that before shipping them out.

Thanks for the input.

seawolf06

He may or may not have pressure checked them. I would assume he did, though, like you said. I don't know how coolant would get into the ports like that other than a cracked head. I would think any coolant in the cylinder would get pushed out of the exhaust valve or just cause hydrolock.