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MG Midget and Sprite Technical - Recessed head gasket fail

As yall know I have a 1500 which is fairly standard and so has a recessed head.

The standard gasket on the car failed (it had stood for nearly 10 years) which I changed for another standard gasket a few weeks ago. This has now failed for a different reason. This time it failed in the recess between 3 and 4. I intend getting a Payen gasket asap as people have said they are far superior so hopefully it will be OK after that.

However, some on here have said to have the head skimmed and the recess removed. Just wondering if the failure in the recess is the reason? Is this a common problem? Is mine likely to do it again? I have an unknown spare engine, would you recommend having the recess removed and why?

As well as all this I have cleaned the head and top engine surfaces and checked etc flatness. This is all good and last time I must have done a good job as the gasket did not fail where in contact with my workmanship on the flat surfaces. However cleaning the recess is very difficult if not impossible compared to the flat surfaces of the top of the engine and the cyly had. Anyone got any advice on cleaning the recess? Or should I just leave it alone?
Dave Squire (1500)

there's a JT vid I seem to remember that included the recess and gasket on a 1500 - no doubt other vids are available on the subject too
Nigel Atkins

Dave,

Deb Evans who used to frequent this forum, and an expert on 1500 engines, used to recommend decking the block flat and using the earlier no-recessed 1300 gasket. You would have to take a bit off the pistons too.

I will find the link to the article. Very interesting read for any 1500 owner.

Cheers,
Malcolm
Malcolm Le Chevalier

Here you go...

http://www.british-cars.net/mg-midget-sprite-technical-bbs/the-bad-historyof-the-1500-crankshaft-2010011622103913152.htm

Malcolm.
Malcolm Le Chevalier

and another thought, I think the head bolts on the engine are a bit shoddy, upgraded heat bolts might help out but I don't know where you might get them from.

Malc.
Malcolm Le Chevalier

I blew two gaskets between 3 & 4 but my problem turned out to be a bad torque wrench. I used a properly calibrated engineers wrench and it wasn't a problem again. How accurate is yours?

Payen gaskets seem to help most people too!
Bob T

Don't be tempted to overtorque head bolts. The gasket seal is provided by those rings. If you over compress them, then the clamping pressure is spread over the whole gasket surface so the pressure is reduced.
Guy W

If you need to buy a Payen gasket, I think that James Paddock has the best deal, they even do a Payen gasket set.

http://www.jamespaddock.co.uk/parts.aspx?categoryID=5&vehicleId=2

-- Josh
Josh L

Thanks everyone,

Hopefully the Payen will do it for now.

I have another unused 1500 engine that is rusted up so when I have this going I will probably get it out and decide whether to refurbish it. Decide what to do about decking then.

Torque wrench is just a few weeks old from Machine Mart so hopefully it is just the operator with a problem or maybe as a mate says I could have just been unlucky with the HG itself and had a bad one.

Will be re-torqueing as per advice and last time.

Anyway as good as lunch time so off to get a gasket for an evening out (with the car in the workshop) of course.
Dave Squire (1500)

Got one from Rimmers and they price matched as per web site promise.
Materials look superior in all ways so hopefully a success this time.
Dave Squire (1500)

Dave,

Just thought that I would check to make sure that you know to torque a head down in several stages. That is, all bolts to maybe 1/3 final value, then 2/3, then 3/3, then go over again to see that it has stabilized. If it hasn't, then go over again till it does stabilize.

Charley
C R Huff

Hi Charley; I hadn't gone at it that well then but I see the reason. So no. My brain tells me I should know that but ...... I definitely will benefit from that timely advice. I sort of did it but not that accurately.

So its do the 1/3, 2/3 and final. Then run for about 300 miles then mark the nut positions, back off 1/2 a turn and re-torque. After each torque / re-torque check valve clearance after valve gear back on.

Sounds good to me; cool enough tonight to give it a go. Lost without the little old thing especially when the sun is out. The modern is an easy drive but I do like being in the Midget.
Dave Squire (1500)

For years, I confess I used a torque wrench and then "added a bit for good measure". i.e. if the recommended said 45, I would set the wrench at 50! I ignored the niceties of clean threads, or oiling threads and reducing the torque figure accordingly. All in all, might just as well not bothered using a torque wrench at all! Other than it did stop me stripping threads.

Surprisingly perhaps I had very few head gasket failures - only one in fact. (or 2 if you count the repair which lasted just 100 yards because it was the wrong gasket type!) A reflection of how tolerant these engines with CI head and block really are!

I then got to work on alloy engines of far eastern origin, which were far more closely engineered, and less tolerant of ham-fistedness. I realised the value of "doing it by the book". I also read Keith Calvers' little treatise on head gaskets and am now a convert. Do it right, do it once.
Guy W

Dave,

You almost got it right. The part you missed was going back over it after finishing the full torque value. As you go around the bolts in the order specified in your book, when you finish the last one to full torque, the first ones you did may not still be at full torque because tightening the other bolts causes more settling.

So, for example IF the final torque is 45, you would follow the bolt tightening order at 15, then follow that at 30, then follow that at 45, THEN keep going around at 45 until the bolts don't move anymore. Some also advise going off for a few beers and then coming back for another go around at 45 (or whatever the full torque value is).

Also, don't forget an important detail about the 300 or so mile retorque. When you back off and retorque each bolt, you ONLY LOOSEN AND RETORQUE ONE AT A TIME. If you loosen them all at once you may be doing this job again.

And, good that Guy mentioned clean oiled threads. Do that too.

Charley
C R Huff

Guy and Charlie, thanks for that. As we have all said before the obvious is often the last thing that is thought of and with me its definitely the truth.

Re assembly postponed till today but threads, nuts etc. are all now very clean. (what a difference to the two threads near the failure that has made!). When another pair of hands arrives today I will continue to re assemble.

I really can't wait to get out in it again. Driving the modern brings a certain pleasure but not a smile. :-)

Cheers, Dave
Dave Squire (1500)

Hi Dave

You asked about sources of engine bolts, apart from the obvious MG and Triumph places (e.g. Rimmers) have you looked at Triumph Spitfire/Herald suppliers such as Canley Classics and Jigsaw Racing?

www.canleyclassics.com
www.jigsawracingservices.co.uk

Best wishes
Mike
M Wood

There is an awful lot of good advice in this thread. You must always gradually torque up in sequence - that is very important.

I have just replaced with a payen HG - when you get one in your hands you can feel they are better quality.

The recessed head gaskets all have a tab sticking out the back, which says "top" on it to indicate which way round it goes - useful for identifying if you have the right one in.

Personally, I don't think anything of this head studs as a big issue... but it can't hurt.

You should definitely get a good straight edge and check if your head and block is flat... if its warped at all that could be why you are blowing between cylinders.

Also, the waiting 300 miles is a bit of a pointless wait... Personally I wait one heat cycle... get it up to temperature and then retorque... if you want you can retorque again after 10 miles... but nothing happens between the first heat cycle and one after 300 miles - theres nothing that needs to "bed in" that 300 miles will help with.

I also retorque when hot - but there is a lot of debate about this - it really depends whether the manufacturers torque specification is based on operating temperature or cold. Technically its probably cold, but I feel better knowing its torqued to 50 when hot.

Also note that a properly calibrated torque wrench is very important. But bear in mind that a torque wrench is a poor way of measuring the force in a bolt or stud, there are so many variables to the torque ( grease, fluids, assembly paste, carbon, bits of crap and variations in stud material, size of washer, use of 6 sided or 12 sided socket) that you are never going to get the exact torque required.. on this basis Guys' add a bit for good measure isn't such a bad idea.

Remember: A torque wrench is for the guidance of wise men and the reliance of fools
C L Carter

Thanks Mike and yes. I have started to speak in triumph 1500 terms to the non mg specialists as they understand this as a Triumph 1500 with SU H4 carbs. The bloke on the counter at Rimmers goes all 'far away' when you say Midget 1500 but is on the ball for Triumph 1500. I just make sure I know the part numbers (the same for both of course) and the pics in the catalogues.

Likewise Debs posts and write ups are excellent and of course there are lots of performance 'facts' written by some great authors (who I can't remember straight off) specifically for the 1500. As the Spit came with 3 engines in its life there are the on going debates etc. re 1300 v 1500 and camshaft materials etc. but all good stuff.

Engine mostly back 2 gether (too late Chris, stripped rocker stud with wrong torque setting and had to fetch new stud). Carbs, controls, fuel lines, then coolant and hey I can test it for compression before the great switch on.

Sun's out. Hopefully a drive in the sun tomorrow BNO (boys night out) tonight.
Dave Squire (1500)

Its running and sounds the best it ever has. Will check cyly pressures and go for a run in the morning.

Thanks for all your help and support. :-)

Dave
Dave Squire (1500)

Good job then, Dave.

Charley
C R Huff

Dave,
I think I've warned you before but in case not - I can advise you with absolutely certainty not to deal with the Triumph 'specialist' from Corby
Nigel Atkins

Dave, my old torque wrench was a 18 month old Clarke unit from Machine Mart. When checked against a borrowed RAF engineers calibrated wrench an indicated 100lb/ft turned out to actually be only about 60-70lb/ft!

Don't believe those Clarke jobbies, they lie.

As mentioned, they are only a good indicator due to loads of other variables but when they're that far out, is it even worth using one?

For regular jobs I now use a beam type wrench as recommended by Bill (SDGPM). I haven't checked it against a calibrated unit but I have a bit more trust in it. At least its consistent.
Bob T

Well everyone it is going good. Re torqued head this morning (I re torqued after a couple of 10 minute warm ups in the yard. 4 nuts in the centre went between 1/2 and 1 and a 1/2 turns further than yesterdays pre run torqueing and re torqueing until nothing else moved.

Adjusted valve clearance (had to loosen spark plugs and push in reverse instead of pulling on fan belt for a change).

Went for run, sounds good, no problems up to 4000 rpm and 60 on the clock (which is accurate) when warmed up :-) its a great smiley day.

Now; as I re torqued after the couple of warm ups should I schedule a re torque in 300 miles as well do you think?
Dave Squire (1500)

Dave,

1-1/2 turns sounds like a lot to me. I wonder if the stud is failing by stretching. See what others think. If that might indicate failing, it would be an argument to retorque at 300 miles or so.

As you probably have figured by now, head torque method is kind of like religion. When you say, "after a couple of 10 minute warm ups" I don't know if you then torqued it warm or let it cool. Some swear it should be done warm and some like me think it should be cold. I believe in cold because the temperature is constant and because the torque specs assume a cold engine since it can't be warmed up before it is assembled.

Charley
C R Huff

I agree Charley. It was cold. 300 miles it is and cold. I haven't replaced the head studs and as you say they may be the problem. In the mean time its going OK so we shall see.

Thanks again, Dave
Dave Squire (1500)

This thread was discussed between 09/06/2013 and 14/06/2013

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