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MG Midget and Sprite Technical - Cooling and head torque settings


Severe cooling problems over the weekend with the car - 73 RWA - basically overheating, urinating coolant from overflow, and generally being a royal pain.

The obvious was attended to - all unions tightened, new thermostat, system flushed, coolant changed etc. Tried again, same result. Basically it gets hot in traffic and does not cool down afterwards. Of course, I then thought head gasket woes, but then hit upon checking the torque settings just in case - they were a bit on the low side, and thus after tightening, so far, it seems to hold pressure and prevents the blowback which seemed to be over-pressurizing the system.

Head is actually modified and looks to be ARP studs/nuts.


Is correct torque for these things 50 lbf/ft?? as per Haynes manual for drill point studs...
Any moly/graphite grease required on the threads?

Mark O

on a tangent here and not saying it's so in your case - wrong or faulty pressure caps can suddenly throw coolant for x-flow it's 15 lbs/in2 but there appears to be two possible lenghts for some of the earlier cars with 7 lb/in2

a few here are very good on engines, including professionals, so when they see this will be able to tell you
Nigel Atkins

If they _are_ ARP, then ARP recommend 45 lb/ft with the ARP lube (moly based IIRC). 25 lb/ft for the bolt if it's an 11 stud kit.

I think if they're good studs (and in good condition), and you're using a good gasket (Payen), 40 lb/ft should be enough for anyone. Do not over torque.

As an aside, it may be worth measuring the studs, as they may have stretched (over torqued?) causing the initial issue. You should change them if they have.
P Dodd

Nope... Dont use hayens or any other manual if you got ARP...

And know your ARP got 30w oil, the long time NOW discontinued moly lube, and finally the new improved pig snot lube, called ultra (i think)...they each have there own torques... You will need to read there website or visit a performance hot rod shop

as to your overheating and the coolant system is NOT the culpret... Put a vacume gauge on the intake, and google how to use a vac gauge...that will tell you a lot

Id say vacume leak is the most likely offender, or something causing a lean fuel situation... BUT i seriously doulbt its your A/F dont touch it,

also check the timing ... WITH A TIMING GUN LIGHT, not by ear, if your planning on just listening to the timing ... May i suggest blinking your eyes rapidly while watching the timing marks, i think that would be so much more acurrate
Prop and the Blackhole Midget


Update on this is a blown head gasket. Bubbles and exhaust fumes are clearly evident in the overflow container with the cap off and the engine warm.

Looks to be a relatively straightforward replacement job - anything in particular I should watch out for - never done a midget.
Mark O

The ARP website will give you the figures I gave for the ARP Ultra lube. I still think that with a good, flat head/deck and a quality Payen gasket, 40 lb/ft will give good clamping and little risk of over stretching the studs.

I'd still recommend checking the stud lengths if you're removing the head, and changing them if there is any sign of stretching.

Nothing in particular I can think of for changing the gasket, it's fairly straightforward. Check the head and deck for trueness with a straightedge, measure the studs and clean the mating surfaces well of any old gasket. And use a Payen gasket.
P Dodd

Merci Beaucoup M. Dodd! Trolled around Interweb and found a Payen head gasket from Bumper to Bumper spares - never used them before - any good?

Studs - well got them to 48lb before I stopped torquing up. They have a dimpled end on the stud and fluted nuts - not your usual hex head. They do look to be ARP

Many thanks once again
Mark O

what makes you think they are ARP?
the studs sound like standard 1275 Midget, the nuts like late A series, maybe Metro?
And IIRC the factory figure for those studs is 50 lb/ft, even if the nuts are ARP if the studs are standard then 50 it should be.
David Smith


Just that photos on the web look very similar. Haynes states 50lb for studs with drill points/marked up with 22, considerably less - I forget just what - for anything else - which I assumed was standard.


Mark O

I find mini places are usually the cheapest for stuff like head gaskets that aren't spridget specific (though I haven't done any scientific analysis). Minispares have always given me good service and competitive prices.

There are 2 commonly used Payen gakets; BK450 and AF470. They are very similar, but AF470 has a little rubber sealing ring round the oil hole at the front. BK450 is preferred, I believe, but both are fine for a road engine. There may be a little superstition involved, but that little rubber sealing ring has been accused of "causing problems".

If they're standard studs and nuts, the 50 lb/ft is a dry torque setting, so if you're using lube use a lower figure. If you're using moly lube, I suspect you'll end up not far from the 40 lb/ft you'd do an ARP stud up to :)

P Dodd

My ARP head studs have holes in the top to take an allen key rather than just a hole.
frogeye Gary

As do mine - forgot about that - might be an easy way of identifying.
P Dodd

aha - now you tell us! yes they are deffo not standard...
David Smith

Not sure I understand David - it was Mark who was asking initially and who is unsure of his studs. I know mine are ARP and I think Gary does too - just providing possible identifying tips for Mark O.
P Dodd

sorry PD - mistaken identity of course - it's been a long day!
David Smith

If his studs have the hex hole, and a slight bevel at the top of the stud and 12 pt nuts, plus a grahpite paste on the threads from former use say the odds are good there ARP...but who knows what china mischief is up to

Prop and the Blackhole Midget

This thread was discussed between 24/09/2012 and 26/09/2012

MG Midget and Sprite Technical index

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