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MG Midget and Sprite Technical - Cylinder Head Bolts

I was happily (and carefully) tightening the cylinder head bolts having just refitted the head on my 1500 midget ... and all was going well up to 43 lbs. I increased the torque to 45 (final torque being 46) and started another tightening sequence, but when I got to bolt six it didn't make the wrench click. I carried on and tightening the remaining bolts, reset the wrench to 43 and went round again - gently. Everything was fine. I tried again at 44 and the nut on bolt six moved but the wrench didn't click...

So near yet so far. Blast!!!

So what do I do?

The block is new and this is the first time I've refitted the head. The bolts however are older and were used on my previous block. They appeared to be in good condition

Is it possible that the bolt is stretching. I didn't feel anything give suddenly as I tightened it, as stripped threads sometimes do.

I could ignore it and hope for the best (it's holding at 43lbs) but I'll need to tighten the bolts after 500 miles so I guess that's not a great idea.

Alternatively, if I remove the head and find the thread in the block has stripped what is the prognosis?

Also - minor point - do I need to fit a new gasket if I remove the head, even though the engine obviously hasn't been run yet.


M Davies

pull it off now you only have wrecked one HG

my gues is that it is breaking and pulling apart.
Had it with my 1275 3 times in a row with used bolts.

Buy new (or ARP) bolts and tighten the in bigger increments.
when you are tightening you first have to over come the turning friction to get the nut turning which is higher than the force applyed down at that moment.
If you use to small increments you will not reach the needed torque value.
Onno Könemann

Swap the suspect bolt with one that tightens properly...if the problem follows the bolt, well, there's your problem!

Head bolts can get rusty & although they clean up good, you can loose precious torque surface area...could be pulling the threads off the bolt??

I'm not a big fan of re-using head, rod cap or main cap bolts when doing a rebuild, there's just too much at stake to take a chance.

But like I said, try swapping with a known good bolt, you won't have to replace the gasket by doing this, it's quick & easy, then go from there.

Not much help, an expert will probably be along shortly to shed more insight.

Good Luck

Dave Rhine ('78 1500)

They are studs with nuts, not "bolts".

It is common for the Spitfire/Midget nuts to be near stripped after some use, as they are marginal to start with. The studs are much better quality and are rarely damaged, even after stripping the nuts. And they should have case hardened washers under the nuts, instead if the tin Triumph ones.

I have never broken an OE stud, or stripped a nut that hadn’t been previously abused – OE Triumph head nuts are made of cheese, but they work if you are careful!

I replace Triumph nuts with MGB ones, which are better and longer, giving more threads to take the load. Current replacement MG nuts (commonly supplied in the US) are in fact “SAE high nuts”, longer still and you must be careful on Triumph or 1500 Midget, since they may interfere with the end rocker stands, easily fixed by cutting little notches with a die grinder or pocketknife to clear the nuts.

Some suppliers list "heavy duty" washers for MGB; some are good and some are not. They should be approx 1/8" thick, smooth finished and case hardened. I use tooling washers available from machine shop supply places.

Fletcher R Millmore

Well, there you go, an expert appears!

I haven't had my head off yet (not what the wife thinks, LOL), so I didn't realize we're dealing with studs...even easier than I first thought.

Problem most likely what FRM advises.

I love this forum, I learn something every day!
Dave Rhine ('78 1500)

Hi Onno, Dave and Fletcher,

Thank you very much for your advice.

Even though it's Saturday evening I decided to return to the scene of the crime and whip the head off. I'm relieved to report that the thread in the block looks intact, as does everything else! I can only surmise that the STUD (point taken) is stretching - it's probably been released 5 and tightened 10 or more times in its and maybe it's time to replace them. It may be relevant that I had to have my cylinder head skimmed when I took it off this time (to de-coke and retime an incorrectly installed camshaft - not installed by me I hasten to add) because of slight distortion. At the time I wondered if the bolts were stretching as I'd also noticed a tiny weep of oil in the region of the stud that is now suspect. Doh! I reckon I'll go for the ARP option.

Onno's point about not being too namby-pamby with the torque wrench is intersting. I'm more used to alloy motorcycle engines (I have a Norton Commando 750) so always treat torque setting with great - and obviously too much - respect.

Thanks guys. Any further advice greatly appreciated.

M Davies

Anyone know where I can buy ARP or similar cylinder studs in the UK?

The 1500 requires 10 (8 plus 2 slightly longer ones). Haven't found anywhere yet...

Or should I buy regular studs and just use up-rated nuts as Fletcher suggests.


M Davies

I've had another blown headgasket this year. decided to buy ARPs rather than reuse the existing. I could actually feel the difference when tightening them! got about 300 miles on them and so far, so good. Should have done it a long time ago.

don g

jigsaw racing are the acknowledged Triumph 1500 specialist..
David Smith

How tight should the studs be screwed into the block. I always done them hand tight (so that the un-threaded part of the stud doesn't damage the first thread in the block)

Also, am I being daft?

Have I got the studs the wrong way up?

There are 10 studs - 8 of the same length and 2 longer one to take the engine lift bracket.

All 10 studs have about 5/8" on one end, 8 have 3/4" and 2 have an 1" on the other (approx). Additionally the 5/8" end has a groove cut along it. I've always assumed that this was to release and oil etc. that might be caught in the hole... or does it mean 'This way up'!?

It would be a better use of the available thread to invert them, but they would be a bit on the short side...

M Davies

no more than hand tight, is correct

for the reason you stated, to allow the load to distribute over as many of the threads as possible (otherwise all of the load is on the last thread).

Norm Kerr

This thread was discussed between 10/07/2010 and 12/07/2010

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