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MG Midget and Sprite Technical - Head gasket virgin

Howdy all.
I am in the process of replacing the head gasket (and all other gaskets on the way to and from the head) on my 1979 MG midget 1500. This is the first time that I have attempted a head gasket replacement (on any vehicle) and I haven't done much mechanical work in the past (although learning quickly as I go, especially with this car).
I have a workshop manual by Robert Bentley, Inc., which I am following for this job. However, I have noticed that some of the gasket seals seem to have silicone/gasket maker in addition to the gasket, but the manual does not mention using anything other than a gasket. So, should I be using some sort of sealant as well as the new gaskets, or just the gasket?
Is there anything else that I should be aware of?
I have attached a picture of the head, taken almost immediately after removal. I will also attach a picture of the exhaust/inlet side and the top of the block.
Thanks,
Steve


gusangora

this is a picture of the manifold gasket. It looks to me that it has been leaking near the middle inlets?


gusangora

this is a picture of the block with the old head gasket still on. Are there obvious signs of gasket failure, or should I really take the head for testing?


gusangora

Why have you removed the head? Was there a problem with the gasket?
Dave O'Neill 2

yes, I was loosing a lot of coolant. The local mechanic did that exhaust gas test on the radiator, which came up positive for exhaust gas in coolant. Also, noticed whitish gunk in rocker cover (but not on dipstick).
Apart from getting hot and loosing coolant, the engine seemed to be running well.
gusangora

No additional gasket material required on the 1500 head gasket itself.
The most common problem on the 1500's is a leak between the cylinder bore and the water jacket on the gasket (I've replaced many).

I see you are using a standard graphite/metal gasket... those are marginal. Try a Payen brand gasket I've found those to be better. Or if you are willing to pay a penny.... get a Cometic copper gasket, fit it and forget it. That's what I did to my '76 (although isn't really necessary).

Remember when fitting new head gaskets, it is recommended that new head studs be fitted as old ones stretch. Install the head under the right torque specifications and sequence. Do not reuse your manifold gasket, replace with a new one as well. It all can be done in an evening, once you get familiar with everything- 1500 heads are actually really easy to remove and refit.

Take your time, do it right and you'll be set. Of course, a good head gasket cannot make up for any additional coolant system problems that you might have like a old water pump or leaky hoses and fittings (always check these as well).

Good luck! Please lets us know how this turns out for you.
Ron Koenig

I managed to put everything back together, and have used a complete set of Payen gaskets. I had a couple of issues with bolts: 1 x head bolt (front, closest to radiator and right/driver's side), which is exposed (ie not under rocker cover) and one rocker shaft bolt (rearmost) - these 2 bolts did not tighten to torque spec., they both seem tight but just kept turning, without getting any tighter! Does this mean that I need to get a complete set of new bolts? Will it be difficult to get the old bolts out? Will it be dangerous to run the engine with these current bolts, whilst waiting for a new set?
gusangora

Sounds like the threads are stripped either at the nut end or in the block itself. If the thread is stripped in the block, it will need a Helicoil repair. This is an engine out job, so I hope it is at the nut end. Without all of the head studs torqued down to the correct setting, the gasket will blow again very soon. Good luck.
P Ottewell

Why would fitting a helicoil in the block be an engine out job? With care, you can safely capture any metal swarf with a magnet.
Guy

With great care! Catch swarf with a magnet? I suppose it greatly depends which stud has stripped. You will need to ensure that the helicoil tap is perfectly perpedicular or the stud will not sit square to the block and you will not be able to refit the head. You will also need enough space to turn the tap wrench with both hands. Do not try and knife and fork it with a ratchet or spanner as you will not be able to keep the tap square and you could break the tap in the block. 33 years in precision engineering, but hey what do I know. Use parrafin as a lubricant with cast iron.
P Ottewell

Steve says it is the front one, so the easiest to get to. It is either a blind ended tapping, or I have an idea that on the 1500 it goes through to the water jacket. I would certainly give it a go without removing the engine, using a guide to keep the tap square and taking care over where the swarf ends up!
But, as you say, better still if it is just a thread at the stud top or in the nut!

And Steve - don't attempt to run it with that faulty stud - it will just blow the gasket again!
Guy

Second thoughts, it's more than likely that the thread in the nut is suspect, studs will be made from HT steel and will be tougher than the nuts. A good idea would be to change both the nuts and the studs as you don't know how many times over the last 30 years they have been reused. It's worth a try before doing anything else more drastic. Good luck and let us know how you get on.
P Ottewell

The Spitfire/1500 MGM head nuts are trash, and I've seen many stripped. Washers under them likewise. Studs are good and rarely a problem, and not commonly pulled out of the block. I use MGB head nuts and heavy hardened (MGB "HD")washers. With the MGB nuts, You need to check that the two nuts under the front and rear rocker stands do not interfere with the stands. The stands are very soft and clearance can be made with a Dremel or even a pocketknife.

Dark areas directly between two cylinders means it was leaking compression between cylinders. Also, dark areas on the gasket or sealing surfaces are where water was leaking. It these cross the cylinder edge ring, it was leaking combustion products into the water. If the dark areas extend to oil drains, it was putting water in the oil. If they get to the rocker oil feed passage it may have been forcing oil into the cooling system. Yep, it was bad!

Head gaskets have the correct sealant already applied from the maker, use no other. Head and block clean, dry, oil free. Torque as WSM, get it hot, retorque hot. Retorque again in a couple hundred miles or a month if not used much. Gasket compression and therefore bolt torque is time and heat/cool cycle dependent. Retorque again at 1000 miles or a year and every year or two thereafter.

All kinds of people will BS you on this, but I have made long term measurements and checks and I NEVER have had a blown headgasket after doing it this way - thousands of gaskets done in 47 years of fixing these things.

FRM
FR Millmore

Yep, sounds like good advice....
P Ottewell

I had to fit hlicoil on the second stud in i packed all areas with tack mat to catch swarf all ok torqued down ok


mark (1977 1500 Midget) Preston Lancs

Finally got to look at the nuts & bolts today (it's difficult when you don't have a garage and leave home before daybreak and get home from work after nightfall!). Anyway, as suspected above, it is the thread on both nuts (one head, one rocker shaft) that have failed, so mini crisis averted.
However, it was mentioned above that the standard nuts are "suspect" and MGB nuts & washers recommended. I would have thought that any 9/16th nut would fit the job and just got some from the local hardware or nut & bolt store, is this crazy talk? If I specify hardened nuts/washers, surely they would be the same as the recommended MGB nuts?
Please advise.
Steve (The Ignorant One)
gusangora

MGB cylinder head nuts are of good quality AND about two or three threads longer than standard nuts (or the OE TR/MGM ones). The now commonly supplied replacements in the US at least are "SAE HI NUTS", a bit longer yet. The HD washers are about 1/8" thick and hardened. Some of the replacements are not hardened, and may or may not be better than the 1/16" thick washers originally supplied on the MGB, but they are still usually better than the thin cheese washers on the TR/MGM. I buy 1/8" thick case hardened setup washers from a machine shop supply place. Any grade 5 SAE standard nut & washer is sufficient for the rocker pillars.

FRM
FR Millmore

Thank you.
There is a specialist nut & bolt place down the road, I will go pay them a visit tomorrow.
gusangora

Okay, so I got a couple of new nuts and washers and fitted this afternoon; all tightened to correct torque spec - all good.
While I was doing that, I decided to put new spark plugs in. I purchased NGK BP7ES (I have a fast road cam, ported inlet and exhaust, extractors/headers, head work etc).
My car wont start! I can't get it to turn over, not even a splutter. I have double checked all the leads etc, nothing. It was starting first time prior to changing the head gaskets. I removed the new plugs to check that I had set the gap correctly (0.25) and did notice oil on plug 3 - is that a problem?
Any ideas?
gusangora

Steve,
The first thing is to mentally go back over everything that you may have moved , altered, adjusted etc during the recent work and to double check that its all back together as it should be with any adjustments and settings such as valve clearances correct. But that is obvious enough and I think you have done all that. Check that you have a spark at the contact breakers (remove dizzy cap and with ignition on, flick them with your thumbnail) and if OK there, then check for a spark at the plugs.

Oftentimes, when a cylinder head has been removed an engine seems to need more persuasion to get it to fire up first time. There was a discussion on this 2 or 3 months ago. Often towing the car in gear will get it started.

I believe it is because there is no residual fuel vapour in the chambers to start the process, and the engine doesn't spin fast enough for the carb venturi action to properly vaporise the fuel. I have used an unlit gas blowlamp to "inject" gas directly into the cylinders either via a spark plug hole or down the inlet duct (you have to fiddle to raise the piston and open the throttle butterfly by hand on the SU carb.
Guy

" I can't get it to turn over,"
if true then the starter motor is faulty or not connected
David Smith

Sorry, wrong terminology. The starter motor is working, just refuses to fire up. I'll try to check spark tomorrow.
gusangora

Steve, did you get it going, if what was the solution.
P Ottewell

Not yet, unfortunately. There is spark but it wont fire up. I have booked it in with the local mechanic for tomorrow. Luckily, they are downhill from me, all the way, so I should be able to just roll there. I am hoping that I can roll-start it on the way.
Steve
gusangora

I managed to roll-start it on the way to the mechanics. It seems that I had not correctly set the valve clearances and that was causing my issues. So, its running again but is quite rough. The local mechanic thinks the carbs are out but didn't want to touch them. Whilst I'm still learning, and yet to buy the necessary equipment, I think I will book it in to a classic car specialist for tune-up.
Is it normal for the tune/carbs to be thrown out after a head gasket change?
I also got them to pressure test coolant system, which was all good, and compression test, with the following results:
Dry: 1-100 2-100 3-110 4-100
Wet: 1-110 2-120 3-120 4-115
Those figures are much lower than I expected, should I be worried? UK spec 1500.
gusangora

Extra info: when I bought the car (a year ago), it had done 89000 miles, the compression was 150 dry and 160 wet, except number 1, which had a burnt out exhaust valve and was reading 100 dry 110 wet. Do those figures mean that all my valves are bad? It has now done 98000 miles.
gusangora

This thread was discussed between 12/05/2011 and 28/05/2011

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