misfire now no power

[594rmm]

sorted out the slight misfire it was the lt lead gradually breaking down, its ran very well apart from that since I replaced the head gasket ,done about 150 miles but during the last week it has been gradually getting lower and lower on power moving off and uneven idle, sounds a bit like running on 3, has the head gasket gone again ?

[mogbob]

Possibly.....did you check that the head was perfectly flat ( and didn't need skimming ) against a steel ruler ? Did you tighten up the head , when re-assembling , in the correct workshop order and to the right torque setting ?

" Running on three cylinders " Are you sure there isn't a problem with the HT leads i.e you're getting a full spark on each spark plug ?

Bob

[bmcecosse]

Do a simple compression check -with the starting handle -Ign OFF obviously. Do they all feel even ??

[oliver90owner]

How did the previous gasket fail? Agree with mogbob. Other problems could be spark strength - what colour is the spark? Problems after only 150miles on a head gasket does not seem hopeful and must be a prime suspect. Any other work carried out 150 miles ago? Tappet adjustment still correct is yet another option.

RAB

[594rmm]

Compression good, water down in radiator, tappet clearance good, spark seems even, plugs good colour, replaced head with unleaded one torqued it down to 44, recently read torquing to 60 needed because head gaskets not as good

[oliver90owner]

recently read torquing to 60 needed because head gaskets not as good

Would you have a link or reference to this amazing news? Increasing the torque on those fixings by more than one third goes against the well documented engineering recommendations of decades gone by. You would be in the realms of yield point fixings, I would think!

I would think gasket quality is a bit of a red herring. There are always cheap/poor ssubstitutes for the correctly specified item. If the head is banana shaped, no amount of over-torquing will remedy the fault. Fixing the disease is better than just covering up the symptoms (as they might say).

I am suspecting you, or someone else, may be getting mixed up between imperial and metric torque figures?

RAB

[philthehill]

Rab
The reference to 60lbft can be found in Minor Matters July August edition Technical Tips.
I have already had 'e' mail conversations with Rob Thomasson re the torque setting quoted.
The maximum that should be used on original Minor studs is 45lbft.
If a higher setting is required use the Marina/Ital cylinder head studs with the accompanying flanged nuts. They can be torqued to 50lbft.
As stated in my other posts - both the head and the block should be checked for trueness especially the lands between the cylinders.
The use of good quality head gaskets is a must.
Phil

[bmcecosse]

60 ft lbf is crazy - you can strip the studs out of the block, I can't imagine you didn't feel the studs/nuts 'yielding' - and should absolutely never be necessary anyway. 50 ft lb is the highest recommended by any source I know - and that with the latest studs (Y or T marked) and the later flanged nuts. You are taking a great risk at 60 - not even the Turbo engines go to that level! Remember also the 1275 engine has a thicker top and is more able to grip the studs...the 948 and 1098 are thinner. Since you for some reason already have doubts about the head gasket - I suggest you lift the head and inspect for damage to gasket/head/block top face.