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MG MGA - Should I replace my cylinder head gasket?

At the end of last fall I had blown a head gasket on my 1500 MGA. I decided at that time to make a few changes including:
1) Sent head to machine shop to check for cracks and install Stellite exhaust valves and overhaul as necessary.
2) New ARP racing studs with their moly-lube
3) Replacing the head gasket to Payen type
When I put it back together I torqued the head to 40 ft/lbs and lubed per instructions. It took quite a while (10min or so) for the white smoke to clear on the first startup. After that I was left with a puff of smoke upon accerlation in first gear after stop. This smoke appeared at times white and other times grey. I thought I could smell the sweet smell of antifreeze. Also it was a beast to start cold. I drove it 500 miles like this (hey the weather was nice...) Then I looked at the exhaust as it was idling. I saw what looked like water droplets and smelled like antifreeze. Also to note the oil looked normal and I noticed no loss of antifreeze (my new aluminum radiator allows me to see this...)
Since it was time I retorqued the head and found that 4 of the 11 nuts needed to be tightened to 40 ft/lbs. I put everything back together and fired it right up. No more smoke, no more hesitance to start. Everything seems to have cleared up. Sorry for the long story here, but my concerns are these...

Am I courting disaster if I don't replace the head gasket? Is it safe to assume that it was not properly sealed and that retorquing the head solved my problems? Or should I anticipate failure of the head gasket in the near future due to some crack already in it that I just figuratively put a band-aid on?
Thanks in advance for your help,
James
James Hurm

James, the WS manual recommends 50 ft lb for head nuts. I would torque to that, and provided smoke / smell has gone, leave well alone.
Art Pearse

Sounds like it's fine now. I would be reluctant to torque the head studs any more than the recommendations. I would enjoy driving it again!
Neil McGurk

The Workshop Manual specifies 50-lb/ft torque for head bolts. I certainly would NOT stop at 40-lb-ft unless you have a very good reason (like maybe an allow cylinder head with manufacturer's special requirements).

Also re-torque it when the engine is warm (for original iron head), and do it again after 300-500 miles of running. I know there are head gaskets that may claim not to need re-torque (not sure if I believe it or not), but better safe than sorry, and it certainly won't hurt anything.

If it was only a tiny coolant leak, and it is not leaking after the re-torque it should be good to go (and go fast if you like). Those Payen gaskets are good stuff, never had a problem with one.
Barney Gaylord

ARP torque specs are significantly lower than the original specs for the same fastner. I think the reason is the harder ARP bolts/studs do not have to be overtorqued to accomodate stretch to the same extent as the milder steel OEM-type units. Having said that, in the case of a head gasket, the designed-in compression of the head gasket also has to be factored into the torque. It's not clear (at least to me) what the optimum torque would be given both considerations. Any professional mechanical engineers or race mechanics out there?

Steve
Steve Brandt

Thanks for the advice and reassurance. Barney and Art, do you think I should torque to 50 ft/lbs, even though the instruction sheet for the ARP studs says to torque to 40 ft/lbs? Would there be any harm in that?
And Barney - I think I am going to go fast!
Thanks,
James
James Hurm

Stud ultimate strength and hardness is mostly not related to stretch or thermal expansion. All steel parts have pretty much the same thermal expansion rate and modulous of elasticity, meaning a grade 8 bolt will expand or stretch the same amount as a grade 2 or 5, until it reaches the elastic limit (where it will ultimately stretch thinner and break). So changing the studs to a different material strength should not affect the working characteristics at all.

When the book calls for 50, I'd use 50, at least for an iron head. I have seen too many head gaskets fail when not properly tightened. The only time I have seen lower torque specs was for an alloy head, and I wouldn't have enough guts to violate the alloy head manufacturer's spec's on that issue.

If you had time to fiddle you might try contacting ARP to ask why they recommend only 40 when the original application obviously calls for 50.
Barney Gaylord

The reason for the lower torque may be due to the "moly lube" you mention. If the friction is reduced the same clamping force will be achieved with a lower torque.
Neil McGurk

Clamping force is what it's all about. I'm surprised the ARP only recommend 40, aren't they supposed to be higher tensile strength?
I agree with both Barney and Neil if you are using a super lubricant.
Art Pearse

This thread was discussed between 30/04/2009 and 01/05/2009

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This thread is from the archive. The Live MG MGA BBS is active now.