Brand new head gasket leaking

[morehops]

So I tore down an old 360 and had it machined 0.030 over, crank 10/10 , new camshaft and lifters, new springs, heads done completely.

Got it running for about 20 minutes to break it in and seemed to be running well. Fast forward to starting it up again a week later, and I see there is coolant in the oil. No visible leaks, spark plugs look fine. Just coolant in the oil, and fresh coolant on the valve springs and rockers.

I end up pulling the intake manifold and reseat it with valley pan and fresh RTV. All good? Nope.

Next day I'm prepping to restart it, and I see that there is coolant on the oil pan, starter, coming from the passenger side head on the corner.

I assume its the head gasket, so I loosed the head bolts and retorque them all 35-65-95-110 ft lbs. Should be good?

I run the engine briefly, and I can see the coolant start to drip strongly on the ground. Cut it off quick. Looks like half way down the passenger side head to the back corner of the head, under the head gasket is leaking coolant.

So where I am now, engine refresh with all new seals, leaking coolant on the middle to back of the passenger side head gasket. What could cause this so quickly? Why would it leak more after retorqueing the head bolts? I thought that would help.

Any suggestions welcome, Thanks in advance.

Shawn

[tufcj]

Hate to say it, but it's pretty common for AMC heads to crack at the bottom corners. There was a sharp corner left in the casting and they stress crack. Chances are that it cracked when you torqued it down with a new head gasket. That's why it's very important to follow the factory sequence, and tighten in 3-4 steps. The only way to tell is pull the head and take it back to the shop for a magnaflux.

What brand head gasket? Is it composite? I usually use Fel-Pro, head side dry, block side coated with spray copper. It's important if the block wasn't decked. The solid metal side goes toward the block, be sure you didn't install them upside down.

Bob
tufcj

[morehops]

Thanks Bob. I did tighten in factory order and with progressive torques, and the heads were checked at the machine shop. Nonetheless, sounds to be a common problem that matches my symptoms. Only other thought I had was the head bolts being old are not working well. But they seem to be holding 110 ft/lbs. I considered replacing those as a minimum easy fix before going the whole way down. Anything else I could test?

[tufcj]

If you could find someone with a coolant system pressure tester I suppose you could attach that and pressurize the coolant system and look for leaks. It may only leak when the engine is warm though. Usually when the heads crack at the corners they only leak to the outside. My first guess with coolant in the oil would have been the intake, but you covered that. I know it's a lot of re-work, but I'd pull the leaking head and have it checked for cracks.

Bob
tufcj

[morehops]

That's the plan, I'll be pulling the head tonight. Clearly fresh coolant leaking pretty good between head gasket and block on bottom side. Will get head to machine shop tomorrow.

Should I be worried about the block? Anything else to change? One local guy said I should change the pickup since coolant was running shortly in the engine.

[morehops]

Bob, quick update, got new head bolts from this great engine shop in Belmont. $15. The 14 bolt had a good amount of white coolant on it when I took it out.

Installed and retorqued in order in 4 stages (35, 65, 95, 110), and without starting it looks like the 13 bolt is leaking coolant out very bottom left of head. But I haven't done full compression yet to see if other places are leaking.

Does this still sound like a head thats cracked, or could it be a head gasket only? (praying this one!) Thanks, Shawn

[tufcj]

That's where the heads usually crack, either 12 or 13 (the end short bolts). There shouldn't be coolant on any of the bolts, all should be blind holes. I would check that #14 bolt hole to be sure it hasn't cracked into the water jacket. It's just really hard to tell without pulling the head.

Bob
tufcj

[morehops]

Ok, will be pulling the head today and checking all of the above. Plan to get the head back to the machine shop to check it fully tomorrow.

[morehops]

531532533534535536537538

Jim, I got the head off, but don't see anything out of the ordinary. I looked for cracks, but don't see any to the naked eye. Is there an exact spot to look?

I'll be hitting the machine shop in the morning to magnaflux and test.

[jeepsr4ever]

What is the casting number? If it is a 291 then your almost guaranteed a crack in the corner. They cut the head at a strait 90 degrees which leads to cracks right there. Not much pops out in the pictures except that lousy mark in your piston.

[tufcj]

I'm not seeing anything that looks like the head gasket failed. There may be a crack by the lower bolt hole in the last couple of pictures. It doesn't look like it made it to the water jacket though. Might be worth knocking a freeze plug out and looking inside with a bore scope. Have your machine shop magnaflux it.

Bob
tufcj

[morehops]

I thought the same thing. Heads are 3220502-2

[morehops]

539

Can you see this crack? Running 45°

[tufcj]

Yep. Right down from that nice square edge in the casting. Typical.

Bob
tufcj

[morehops]

540

Now to find a 502 head! Thanks for the help guys

[morehops]

Do you guys know if I need to match the 502-2 heads? Or will other heads match up ok with my other head?

Shawn

[morehops]

Guy in town will only sell me a pair, wants $225. Surely I've got to find a better price?

[jeepsr4ever]

Small price to pay

[tufcj]

It doesn't need to be a 502. All of the bridged rocker heads back to about 1974 are basically the same. 73 and earlier heads used individual rockers and screw in studs like a Chevy. My guess is that your machine shop missed that crack. Maybe you can get some relief from them on the work on the replacement.

Bob
tufcj