Fastbird

iTrader: (5)

OK, here is the deal. I have a new motor. Deck was just done and is straight, heads were just milled and are straight. The problem is when I pressurize the system to test for leaks, I get a small leak on the rear of the driver side and the front of the passenger side at the junction of the head to the block. It is not the intake manifold because it is not wet, only a little drop or two at the bottom by the lower head bolts. This is a Bow Tie block so the holes are blind and coolant cannot come through there.

The motor was assembled in the winter, heads torqued to 75 ft/lbs. top row and 70 on the bottom. This is with studs and moly. The torque settings are what the block was honed with. The torque sequence was correct and the nuts were tightened in three sucessive rounds.

Thanks for reading this far.

The question is does a motor that is built in the winter leak a little until it is started for the first time? I figured the heat would seal any imperfections, then I would retorque the heads. I was also considering using a GM product called COOLING SYSTEM SEAL TABS. GM recommends putting them in new motors. Has anyone heard of this?

Any help would be greatly appreciated.

Thanks

Steve

ede

are you using a shim type gasket? if so the finish on the heads and deck have to be pretty smooth for it to seal. did you use any sealer? i always use k&w copper sealer in a spray can and have never had a leak, and when i've took engines back down with it the head gaskets delaminate instead of coming off in one piece, good stuff.

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Fastbird

iTrader: (5)

Ede, thanks for the quick reply.

I did not use any type of sealer on the head gaskets, I did not think you needed it. The surface on the heads and the block was very smooth and the head gasket was a FelPro 1044, regular gasket.

Fastbird

iTrader: (5)

ttt

MrMike99

What did you put on the studs prior to installing in the block? I used some "NEW" latest and greatest sealer and on first startup I had several leaks coming from the head studs, I pulled each stud one at a time cleaned the hole and stud and put good ol' permatex#2 on the threads and NO leaks.
Just a thought! Mike

RB83L69

I agree with Mike, it's the studs where they go into the block. The threads go directly into the water jacket. For some reason studs are more difficult to get a good seal with than bolts.

My favorite stuff on the threads is Permatex 300, the brown gooey stuff. You should use something that doesn't harden because there's so much motion there from thermal exansion. Silicone for instance will eventually fail because it tears.

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"So many Mustangs, so little time..."

Fastbird

iTrader: (5)

I did not put anything on the studs because they do NOT go into the water passages on a Bow Tie Block. They are blind holes.

Any other suggestions?

RB83L69

Duh! I knew that. Says so right in your posting.

Oh well, no further ideas... gotta be the gasket.

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"So many Mustangs, so little time..."
ICON Motorsports

ede

rb i'm so glad someone besides me over looked what was there in front of their eyes. i'm tired of always being the dumbass here.

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Red Devil

How much were the heads milled?

Vader

RD,

Are you thinking what I'm thinking? Casting porosity? A direct leak through the castings from thin sections left after milling? This is what the GM seal tabs are supposed to fix. They impregnate the castings to prevent porosity. It's not as good as a commercial impregnation treatment before assembly, but it can help. Just a thought.

BTW - The ECM is now at 6MHz and doing well...no flames yet!

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Later,
Vader
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RB83L69

Some people will hot rod anything.... that's as bad as I used to be with stereo equipment

Good question about the milling, I've seen heads where the places where the only metal that was left afterwards didn't align with any gasket material. Late model "light" castings are especially bad about that.

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[This message has been edited by RB83L69 (edited January 19, 2001).]

Fastbird

iTrader: (5)

The heads are Wold Products Sportsman II's. I had them milled 11 thousanths and then used a 12 thousanths thicker gasket to compensate. I had to take Loc-Wire rings off the surface of them that was 8 thousanths deep.

One observation I have made since this thread started. They leak under 7 psi of pressure but not at 0 psi. and it is very concentrated. Like only spot, about as wide as a dime. in the back corner. Do you really think those GM tablets would help? What about the dowels bottoming out in the head? Is that possible?

ede

i think the dowel holes in the block go to a water jacket, so if they did bottom out in the head they would just press in to a water jacket. at this point the gm seal tabs wouldn't hurt. if you still have a leak you know as much as you hate to the head will need to come back off so you can take a look.

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