Replacing Blown Head Gasket

[Paul Mascuch]

I have been dealing with overheating on my 1948 MGTC. I’ve reset the mixture, the timing, had the radiator flow tested, installed an MGB 7 blade fan, and replaced the water pump. I pulled the head and found evidence of a blown head gasket between cylinders 2 and 3.

My question is when I replace the head gasket should I use a copper gasket dressing or install the new gasket dry? Also after installing the new gasket and torquing the head, how much time should I run the engine before retorquing? When retorquing should I just check the torque on the head nuts, or should they be slightly loosened and then retorqed?

Thank you,

Paul Mascuch

[Steve Simmons]

There will likely be varying responses on this but here's my preference...

I use the standard County gaskets (original style) as sold by most suppliers and I do not use any dressing. They have some kind of coating on them already. I try to not touch the coating with my hands. The head and block are scrupulously cleaned with brake cleaner before installation.

I normally go about 200 miles before re-torquing. When I do, I loosen the nut about 1/8 turn and then take it up to spec. Then I move to the next nut.

Others have their own preferred methods but this has worked for me. So far I've never blown a gasket on my TC. Compression is about 9.1:1.

I hope this fixes your overheating issue. I would definitely think about having the head checked for flatness since it blew, especially if it blew because of overheating.

[Duncan M]

WKF Wood says nothing is needed on the gasket. Top of page II-11 or page 17. http://www.ttalk.info/WKF-Wood-XPAG-Engine-Book.pdf
I recently used nothing. You definitely do need to check your head for flatness. The reason the gasket often blows between 2 and 3 is because on these engines the head wants to deform upwards towards the middle.

[Tom Lange, MGT Repair]

Almost ANY technique is better than the usual torque-and-you're-done method. First, consider possible causes: the wrong torque is used, the block is not flat, the head is not flat, the head studs are stretched.

First, remove the head studs and check their condition - most are stretched or gouged. Screw on a head nut, and if you feel resistance, the stud is stretched - you can often see a waist in the threads. If the stud is stretched you will NEVER get accurate torque, and the studs must be replaced. I then run a small circular whetstone all around the deck surface to remove the high-spots where the threads have pulled up slightly. Checking the block flatness in situ is done with a really straight straight-edge and a .001 feeler gauge. Put the feeler gauge under the straight-edge and see if you can pull it out; check all over the head, and if you can easily pull it out the engine needs to come out and be re-surfaced. Do the same with the head, which is more likely to warp.

If I use an NOS gasket I lightly use Copper Coat seal on both sides; as Steve says above, new gaskets already have some coating. I put it all together and torque the head cold to 30, 40 and then 50 foot pounds with the original studs, or 60 with my replacement studs. I then put the rocker gear back on, and adjust the valves slightly loose, say .015". I then start the engine and make sure all is well, blipping the throttle a few times. I cool it all the way down and then use a 19/32" socket to loosen the nuts 1/4 turn in sequence, and then re-torque to spec, one at a time. (The 19/32" socket allows you to re-toraue without removing the rocker gear each time - just remove the clips for the end nuts.) I then take the car out for a test run, let cool and toraue again. After 50, 100, and 500 miles I do it again - always cold - and have, like Steve, never blown a head gasket.

Stretched head studs are the most common cause of blown head gaskets - see mgtrepair.net for my improved head studs.

Tom Lange
MGT Repair

[Steve Simmons]

I'm curious why I sometimes see people mention the difficulty of getting to the head nuts. Is it because of the replacement 12-point nuts? I've never had an issue. I use a 3" extension and a regular socket and it fits right onto all of them.

I also agree with Tom about torquing in several steps. I feel this is critical to success.

[Tom Lange, MGT Repair]

Steve - my "regular" Whit sockets are too tall, and I found a 19/32" socket at the Tool Barn to cut down, for $1. It's now a dedicated socket!

Tom Lange
MGT Repair