Head bolts loosening
 

I have a freshly rebuilt 455 mostly stock except .030 over and a new melling spc7 in it. Its not broken in yet only a little time idling and the 20 minutes cam breakin. Problem is it burns coolant and oil quite bad. Block and head are flat, replaced gaskets multiple times, torqued bolts to spec etc...
When I torque head bolts it works perfect, no smoke, no steam out of exhaust.
After 1-2 heat cycle, head bolts get loose and its back. Replaced bolts with new set from ames, did not help. What should I try?

did you have block decked to make sure it was flat

Check for crap in the bottom of the bolt holes in the block for the head bolts.

Also, have the heads been milled a good bit?

been decked at machine shop but will double check.

Yes heads been milled, not sure how much machine shop removed.
Will double-check bolt holes anyway I need to pull heads off.

What heads are you running?

I can see issues that can lead to burning coolant, but the oil is another story.

Have the heads been rebuilt with new valves and valve seals?

Has the torque wrench been calibrated?

Did you mistakenly get head bolt set N521AF ( for round port heads ) or maybe yours are packaged wrong?
The round port heads take longer bolts in many locations.
The longest bolt for D port heads should be 4”.

If one or more head bolts are tool long and the end of the bolt is bottoming out in the hole even though torqued properly actual clamping force might not be correct.

This weekend I pull the head off and planning these:
Compare bolts one by one to the factory ones. Head is also factory.
Make sure the holes are clean.
Measure deck and head for flatness... did already but doesnt hurt
Order gaskets. So far I used only FEL-PRO 8518PT do you think i should try another brand?

Beforehand all above, compression and leak-down test just to see where we are.

Am i missing something?

Sam Agnew had a major issue with Fel-Pro 1018 gaskets, there's an oblong hole in them that was allowing an oil path on his home-ported Edelbrock heads. He replaced the oblong-hole Fel-Pros with Mahle gaskets that have a smaller, round hole.

https://forums.maxperformanceinc.com...=866228&page=3
starting about Post 116, and onward.

https://forums.maxperformanceinc.com...1&d=1705877446

Each head bolt when loaded thru the head should stick out no more then 3/4" with a unmilled head.

The Fel Pro 1016 gaskets have that same oblong hole and I have never had a issue with them when running iron heads.

Head bolts need to be retorqued after initial startup, don't care if they are 'no retorque' gaskets or not, have to at least check them.

Did you do an after-start retorque on any of the re-attempts?

I've had Cometics require 2 or more retorques after heat cycles.

If you don't retorque, and a leak occurs, the gasket is done. There again, don't care what type of gasket it is.

When you disassembled after the last go-around, did you inspect the gasket, and/or see where it was leaking?

Maybe post some pics of a gasket that leaked or was replaced, both sides.



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1016 gaskets are a standard go-to, and reliable. They work. But they do require retorque.

Chase the threads in the block.

OE type bolts should be installed with engine oil on the threads, other hardware usually has a torque value and lube values specified by the bolt/stud manufacturer. If they are not OE type, follow the hardware manufacturer's recommendations for install, torque value, and lube.

The surfaces should be clean, no remaining material from previous gasket, and wiped down with a solvent such as acetone, before assembly. No sealants etc should be used, unless specified by the gasket manufacturer. Fel-Pro I'm pretty sure says dry, at least for the 1016s anyway. Follow the manufacturer's recommendations regardless of what anyone else tells you.

Proper use of a torque wrench is key as well. 'Creep' up to the value with steady, even psi, and do NOT yank to get the click. I usually find the spot where it clicks, reduce psi slightly and creep up to the value slowly, holding it there until it doesn't move anymore.

What torque value/setting are you using? And what heads?



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Also, use the recommended torque value steps and pattern when torquing.


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Pontiac torque sequence and increments:

https://www.tinindianperformance.com...rque-sequence/

Again, use the recommended lube the manufacturer specifies.



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I don't agree on the re-torque.

I've always practiced one-and-done.

I always stayed away from copper head gaskets for this exact reason.

I am not saying checking torque is a bad thing, surely it cannot hurt - but if done properly with conventional head gaskets it should not be required.

For curiosity's sake, why not go out there and put a torque wrench on a bolt now, see what you get?

IMO, copper head gaskets are for race vehicles, ones that you remove heads for inspections regularly. Those usually get a coat of spray too, like copper gasket spray.

Once I've done a complete pass on torque, I do one more pass to make sure all are the same/done. On a head, by the time you get to the last bolt, it may have shifted.

And as you stated, it can't hurt. But just to say, I've seen no-retorque head gaskets get up to another 1/4 turn after initial start. (ARP studs)


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Agree. Never have run copper gaskets on my engines over the years,
Multi-layer the only way to go for a street engine.

Tom V.

Yes, Cometic MLS' are the way to go, and have used them on at least my last 5 engines.

Every time I go back over them, they all get at min 1/16 - 1/8 of a turn.

If you don't believe me that's fine, but go do a pull on a head bolt and see what you get.

As for the OP, since there's already been issues, then making multiple passes makes sense. I would watch that thing like a hawk.



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