Morris Minor Owners Club

Evenin' all, this topic will probably have been discussed many times but I can't seem to find the posts. Basically, I bought an 850 engine two years ago that had been fully restored.............34 years before! The chap who had it was driving back from London when his engine let go so the car was towed in to a garage near Luton and the engine replaced. Two weeks later, the MOT was up and the car failed so badly that he scrapped it and kept the engine in his garage until I came along. Well, that's the story. Any hoo, it has been a great little engine most of the time but on three occasions it has blown the head gasket, Once between 1 and 2 and twice between 3 and 4. This has happened on the way home from work again tonight so I've just ordered another gasket set. I can't understand why it will behave properly for several months over a couple of thousand miles, then let go, at slow speed, pulling away from traffic lights. Could the head be warped? It's iron and there are no obvious defects. Are modern gaskets not up to the job? Am i not torquing the head down properly? Are 850 engines known for this? Any advice will be gratefully received. Rob.

Sorry to hear about your troubles.

Copper head gaskets are generally considered to be the best. The one sold by Minispares feels more solid and seems better made to me than the one from ESM but it is more expensive. https://www.minispares.com/gug702506hg- ... minispares

You need to make sure as you mention, that the neither the head or block are warped. You can do this with a straight edge. Obviously cast iron does not warp anything like as easily as alloy but it can warp if seriously overheated or torqued down incorrectly.

When I did my head gasket I was advised to check the face of the block (by Phil on this forum) for "pulled-up" threads. This is where the thread in the block has become raised above the surface of the block. You can detect this issue by removing all of the studs and then testing with a blade such as a Stanley knife blade or even better a Stanley knife blade window scraper (for removing paint from glass). This is good for cleaning up the face of the block but it will catch on pulled up threads. You can sort these out by lightly countersinking.

The mating surfaces of head and block must be spotless. A green plastic pot scourer and WD40 works well. The scraper mentioned above helps with bits of old gasket. No sealant is used but the head gasket is lightly greased. Ensure it is the correct way up. Copper colour side UP.

Obviously you need to follow the correct sequence for tightening up the head nuts and use a torque wrench. You also need to re-check the torques and re-tighten after one heating/cooling cycle and again I would suggest after a good run out. I check the torques whenever I do the rocker clearances.

Stephen

A couple of other things....
Firstly, although the Minor W/S Manual says 40 lb.ft for all engine sizes, it's generally accepted that over the years for various reasons (anything from BMC's later experience to the quality of modern gasket material) it should be a little more, around 45-48 lb ft.

Also, the sequence for tightening A Series heads changed; see here: viewtopic.php?p=705741#p705741

Thanks Guys, I have just had a copper head gasket delivered and will start the process tomorrow. Last time. a couple of the studs came out with the bolts seized on to them. I didn't try to get the bolts off but put the studs back in and torqued the whole lot down. Was that a mistake?

1958trebor wrote: ↑Sat Aug 23, 2025 1:37 pm Thanks Guys, I have just had a copper head gasket delivered and will start the process tomorrow. Last time. a couple of the studs came out with the bolts seized on to them. I didn't try to get the bolts off but put the studs back in and torqued the whole lot down. Was that a mistake?

Yes that was a mistake and probably why your head gasket keeps falling. If the nut is totally seized on the stud you could have been measuring the torque just of the stud bottoming out in the block rather than the nut and washer actually clamping down on the cylinder head. Free off the nut or buy new studs, nuts and washers.

Stephen

Doh!

The threads in the block must be clean and free of crud.. A old head stud with a flat filed to just below the 3/8" UNC thread root screwed into the block with grease applied to the threads it is a good way of cleaning up the threads.
The head nuts must be free on the studs.
I would suggest that the stud holes in the block are slightly countersunk to remove any pull up of the block top..
The studs should be screwed hand tight into the block.
A slight smear of grease can be applied to both sides of the head gasket. There is no need for goo of any sort.
The head gasket fitted and the cleaned up head placed over the studs.
Fit the rocker gear and head washers & nuts. Do not apply oil or lubricant to the head nuts or to nuts that have to be torqued.
Tighten and torque the head nuts as per the workshop manual. The later BL tightening sequence is preferred.
Retorque after the first heat cycle.
The use of the later studs and flanged nuts is encouraged as the head nuts can be torqued to 50lbf ft which gives a much better clamping force to the head and gasket..