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MG Midget and Sprite Technical - Midget Head Gasket Help - Replaced, Blew same day

77 1500 Midget

My background
was once an auto electrician, but have done a few cylinder head gaskets in my time - but certainly, no expert.

A few years ago this can had the engine replaced (after seizing with no oil)with a used engine.

Nothing was done with the engine other than check compressions and give it a service.

Recently the head gasket blew between 3 and 4.

A new gasket was fitted plus a very lightly skimmed head (<1mm skim) and bolts carefully torgued - as per user manual.

Unfortunately after just 2 miles this new head gasket blew on 1 and 4 at the seal between the cylinder and the water jacket hole (see image).

Seeking advice as to what to do to ensure this does not occur again.

My thoughts on possible causes:

++Warped head
not warped, checked with a steel level

++Too much skimmed off head
causing increased compressions or head bolts threads to 'bottom out' before gasket fully compressed.

This was a good head from the original engine. It was only ligtly skimmed as part of a refurb to convert to unleaded.

It's height has been compared to another head and the skim is around 0.5mm (so presumably not excessive)

++
Stretched head bolts
They look OK but I will order a new set.

++Wrong / bad head gasket
The experts will know that the 1300 (triumph) engine has the same bore diameter as the 1500, but the 1500 has liners which sit around 1mm lower than the top of the block, thus the head gasket needs raised seal rrings where is presses against the liners.

Presumably a 1300 gasket would do exactly what has happened on this occasion.

When fitting the gasket, I did not note how deep the raised seals were.

On removing the head again, I note the raised seal is compressed (as it should be), but the seal rings are raised and are similar depth to the original gasket that blew between 3 and 4.

MY MAIN HOPE
- is that this issue was due to this gasket not having good quality seal rings to fully seat into the liners and that a good quality gasket from a different supplier will resolve the problem. (Plus torguing the new bolts carefully and in the right order).

ANY SUGGESTIONS
Have I missed anything?
Any recomendations on a good head gasket brand?
Any other comments?

One last thought - probably not relevant
The gasket blew at both water jackets (1 and 4), these jackets are in the lock but not in the head.

Could someone confirm if that is correct - I assume it is as both heads (inc the original factory fitted head) do not have water jackets.

When you look at the proximity of the cylinder seal ring it does seem really close to the water jacket hole. One thought was that these water jacket holes should be blocked off with a brass plug.

But - the seal between the cylinder seal and the water jackets is no different than between the cylinders + assuming the block and head are both standard, then the proximity of the water jacket to the cylinders is 'as from the factory' - so will require no change.

Assuming this water jacket and head is standard then there is no point in thinking about this - it is just that both cylinder 1 and 4 blew at the same location, hence I do focus on this.

Any help would be apreciated.

The car is not at my current location so I have to travel a considerable distance to repair - so I want to get it right on one visit.

Thanks for taking the time to read.

Colin K





































C Kin

Not sure if I am not using the photo upload facility correctly, but it appears that only 1 photo will attach to the thread.

Here are 2 others
https://www.flickr.com/photos/126201791@N07/16624864373/sizes/o

https://www.flickr.com/photos/126201791@N07/17057312108/sizes/o
C Kin

http://www.triumphexp.com/phorum/read.php?8,704537,page=2

Post 22 here, refers to the unnecesary holes to the water jacket and how the writer blocks them off with brass.

Post 23 has useful comments about types of gasket + sealer (goo). I did add a tiny amount of copper grease around the top of the liners when I fitted this head.
C Kin

I have only done head gasket on my 1500 and am an amateur for car mechanicals of this nature.

If its just a road going engine like mine then:

Check all surfaces clean (I used a sharp wood chisel to remove everything from the two surfaces)
If some studs will not come out then make sure any rust is cleanly removed from base of studs to block juncture
Check both surfaces for flat with good known straight edge.
Clean all crud from cooling system holes in head and block.
Use original hardened washers, not soft washers from any old where - or even from an MG parts supplier, without checking they will do the job properly. (I used the original washers, nuts and bolts).
Use a High Quality gasket. (my first two attempts were with standard gasket, third attempt with Payen gasket)
Unsure that all threads on studs and nuts have been cleaned out and lightly oiled so torque settings are correct and not affected by nuts being resisted in threads.
Check torque wrench works as its designed to.
Follow appropriate assembly guide for torqueing up. (If its a Haynes manual ensure you are in the 1500 bit).

Mine has now done over 12000 miles so I recon its about being spot on and good quality parts.

Anyway, good luck.
BTW if you clear all the crud out of the cooling system now while the engine is in bits you will have an engine that does not overheat if its set up properly for standard road use.

Keep us informed, Dave

Dave Squire

I dont know much about 1500s... but there is an issue like you mentioned concerning the lip of the cylinder ... I want to say there are 2 differant cly head gsskets...

Thats the area id explore 1st

Unfortantly only one photo at a time per post

Others with more experiance will comment shortly

Prop
Prop and the Blackhole Midget

Some gaskets come with a little data sheet that shows tightening sequence etc. These always state a retorque after a heating/cooling cycle has been done to get the final tightness. A collegue of mine omitted this part and had results similar to yours. The gasket looks like the same one he used.
Otherwise...check everything you thought of and do as Dave suggests. Get a Payen gasket. You get what you pay for.
Roadwarrior

Hey Colin,

Yeah, those holes so close to the bore are a 'mare. What were they thinking?! Especially bad news if the engine has been over bored at any point. My thoughts, in no particular order (and may repeat some of what has already been said):

- Yes, make sure you get the right head gasket for the 1500. It should have slightly protruding rings that fit in the ridges round the bores. It looks like you had the right one but hard to tell from the pictures alone.

- The redundant holes which you have pictured should be cleaned and dried out. If there is water left in them, it will heat up, expand and blow through the fire ring.

- Everything else, block and head should be super clean, especially the recessed rings on the block. But this is the case with any head gasket job.

- Make sure all your hardware (studs, nuts washers etc.) is clean, the washers are the thick, hardened sort and the nuts spin onto the studs without binding. Alternatively, you can get "uprated" flanged nuts that do away with the washers.

- Some say that the Payen gasket is the way forward. In the short time I have been playing with these things I have had both success and failure with both types of gasket. *Shrugs*

- The debate about whether to re-torque or not after a heat cycle will go on forever. The one time I decided to do a re-torque the gasket blew... take from that what you like. Roadwarrior says the opposite, the debate goes on :-) (I thought hot re-torques were for A-series with copper head gaskets?!)

- Filling the coolant correctly on a 1500 Midget can be tricky and a source of immediate HGF. You must follow the correct filling procedure. Also, taking out the thermostat and drilling a small hole in the face (2 or 3 mm) helps with filling and reducing the likelihood of trapped air. Squeeze all the hoses (especially bottom rad hose) to try to circulate coolant and move any air bubbles. Top up, repeat, repeat, repeat. Run the engine briefly and check again and check a few more times for good measure!

- I noted when a Payen gasket blew and I replaced with standard, the standard gasket is thicker, ergo reduces the compression. Don't know if this really means anything, but I thought it interesting.

Good luck!
Malcolm
M Le Chevalier

Thanks for all the suggestions.

It is good to hear different opinions. I need to cover all bases as this car is not sitting outside my own door.

Interestign comment from M Le Chevalier about water in the redundant holes. I certainly had not thought of that.

I have the gasket here and looked at it, the blow is down into the holes, but I will certainly make sure they are dry.

My Plan:

Get a good quality gasket - double check that it has raised seal rings to fit into the top of the cylinders

Follow gasket manufacturers guidelines regarding adding liquid sealant / not adding

Get a new set of head studs

Clean and check levels of head and block

Make sure I get a good torque wrench

Double check lb/ft conversion to n/m (wrench is metric only)

Tighten bolts in correct sequence

Folow all the other sugegstions in this thread.

If anyone could confirm torque settings in lb/ft and n/m I would appreciate it.

If I
C Kin

As a bit of clarity on my re-torque statement, I don't generally do it.
However, as I said, some gaskets have a little instruction sheet with them that say they need such treatment. It's common to ignore little bits of paper with words on it, but if they advise it, it usually pays to re-torque.
I'm not entering into the debate about re-torquing in general ;)

Great tip about coolant refilling as well, this is maybe more important than anything else mentioned!

Head nuts are 50 lb/ft (68 nm) and rocker shaft pedestal is 26-32 lb/ft (35 - 43 nm). I lightly oil the thread and the mating faces of the washer (or the nut if flanged).
Roadwarrior

Colin,

You probably know this, but I'll say it just in case. What ever the torque is, you need to divide that roughly by 3 and go around in sequence bringing each one up a little at a time. When you have finished the third round up to the full touque, go around again and see if any move any more.

Charley
C R Huff

Sorry Roadwarrior, misunderstood what you said. Ace, I am rubbish at debating anyway! :-)

Good shout from Charley too. I had a number of 63 Nm in my head for head studs but don't have my Haynes here to check, I will probably go to the garage this morning and have a look.

Cheers,
Malcolm
M Le Chevalier

My Spitfire Haynes says 46 lb-ft or 63 Nm.

Cheers,
Malcolm

M Le Chevalier

Hi guys,

Just replaced my head gasket after a light head skim.


Used new head studs but with A+ head nuts (ie Metro etc) with built in washers that can be torqued to 50lb/ft.


Regards Steve
SR Smith 1

Hey Steve,

Just to avoid confusion, the OP, Colin has a 1500 engine, not A-series.

Malcolm
M Le Chevalier

My figure of 50/68 comes from the workshop manual. Probably it doesn't matter as when you factor in the variables of nut/washer friction, expansion of studs, variences in calibration of torque wrenches and indeed the accuracy of the wrench in general...whats 4 lb/ft between friends!

Much more important to build up progressively and also the reason why starting with a low figure (often 25-30nm) then doing an X degree turn X times sets things up much more predictably for the end result. Only on modern(ish) engines do you see that though.
Roadwarrior

Yep I know that Malcolm, mine is a 1500 with a +60 overbore.



My point is the A+ nuts can be safely torqued to 50lb/ft, they are the same 3/8unf thread but have the washers built in.



Regards Steve
SR Smith 1

Something else to remember when using NEW studs, they need to be pre-stretched ... but check with manufacture

Btw... I am a hot retorqure, but im sure thats because I hate jesus...haha

Just a side thought... anyone ever tried pressing in a section of copper /brass tubing into the hole next to the cly to keep the H. gasket from blowing out the side

Prop

Prop and the Blackhole Midget

Steve

The torque restriction on A series is the stud I think and not the nuts which are the same as Bs. If I remember correctly the plain ended studs are 42 lbs ft and the marked ones are 50 lbs ft with A series?

Peter
Peter Burgess Tuning

Hi Peter,


I'll have to look but I think all the A+ head studs and nuts were upgraded over the standard A?


The nut part no I used was CAM 4545



I didn't think the B ones had a washer built in, but used seperate hard steel ones?
SR Smith 1

I know the Metro ones have the inbuilt washer, The A series and B series as in MGB had the same nut and thick washer. MGAs had the same nut but thinner washer. As far as I know the A series had two different rated studs the unmarked one being the lower one, so one tries to build with the higher torque ones if not using ARP sets. Not sure of the rating of A+ Metro studs, are the Turbo ones different to the base versions?
Peter
Peter Burgess Tuning

The torque limit on head studs, assuming they and their nuts are in good condition, is to do with compressing the gasket to the right degree, without over compressing and distorting the fire rings. What is critical, is that all the head studs are tightened to the same amount, minimising the variation between studs. This is more important than exerting a particularly high tension. Over tightening crushes the fire ring with the result that the pressure is then distributed over the whole gasket surface rather than being concentrated on the all important fire ring seal. Pressure is then actually reduced, despite the torque on the nuts being increased.
Guy W

All true Guy, I agree. You might buy head studs/nuts that can take 70lbft (Assuming the block threads can too). But the gasket couldn't, unless it specifically say it can in the blurb that comes with it.

However, it's not enough to just seal the fire rings. If there's insufficient clamping on the rest of the gasket, water and or oil, will eventually seep out.

The picture in the 1st post of this thread, doesn't look to me like either too tight, or too loose has caused this. It looks to me like it's been clamped unevenly at different points.

How easily/well did the HG slip down over the studs. If it was binding anywhere, it could well have caused a lip in the gasket that prevented the head sitting evenly across the whole surface. I've had that before, and seem to recall Prop having that problem not so long ago.

Also, looking at the pictures, it looks to me like it was about to blow between either 1/2 or 3/4.

http://www.flickr.com/photos/126201791@N07/16624864373/sizes/o

http://www.flickr.com/photos/126201791@N07/17057312108/sizes/o

It looks to me like the whole head was clamped tighter on the manifold side than the plugs side.

You had the head skimmed. What does the block surface look like? That's not an Ally head is it?




Lawrence Slater

Thanks again for the input. The more I read and havign looked at the gasket (with nearly flat fire rings - at a couple of points) - I think I might have over torqued eithe rwith some incorrect conversion to nm or due to a faulty torque wrench. It did feel that I was havign to pull too hard.

@Prop and the Blackhole Midget

You mention "Something else to remember when using NEW studs, they need to be pre-stretched ... but check with manufacture" assumignthis is required, what is the procedure - torque the bolts without a head gasket fitted?

Thanks ColinK
C Kin

I think it depends on the manufacture

With the ARP you have to install them dry and torque toba certian spec "several" times as you say with no gasket

Ive seen others that have to be heated to a certian temp then torqued

Prop
Prop and the Blackhole Midget

Btw... im not sure about the 1500s but im assuming its the same as the 1275s

The studs are applied only finger tight, never tooled in.

Prop
Prop and the Blackhole Midget

Had a similar scenario years back with a Jaguar 4.2 head gasket blowing.

After a few iterations of head off and back on, then skimming and so on. It turned out to be the cylinder head nuts were jamming on the stud threads. So when the torque wrench clicked, the nuts were not tight, just stuck.

The studies were all new. So I guess that the threads were not as nicely cut as they should have been.

I liberally oiled the threads and the nuts wound down further and no more gasket blowing.

I know that torqueing is a science that does not want oiling of studs, but in this case needs must......

Roly
Roly Alcock

You have to run it up to temp and re torque, you'll find that the nuts have at least half a turn on them once it's been run for a bit. Albeit on a 1275, i have early signs of water in the in the oil before I realised that I had to do this, no issues since.
Robin Cohen

A common cause of failure on these is the wrong gasket. The gasket for recessed block engines (1500 and late 1300 Triumphs) looks the apparently same as that for the earlier non-recessed engines. The difference is in the fire ring thickness.

In the recessed block gasket, the uncompressed fire ring is 0.8 - 0.9mm thicker than the surrounding gasket material. It's an amount that isn't immediately obvious so I always measure each gasket to make sure it didn't get mislabelled somewhere along the supply chain (as has happened)
Paul Walbran

This thread was discussed between 23/04/2015 and 30/04/2015

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