8 replies to this topic

[1275poorlyproject]

Entirely a question that some clever bod will chuckle over

 

What is it? Why would i need it?

Excuse my lack of expertise 

[ACDodd]

It's to increase the clamping area to the head gasket and specifically help retian the gasket at each end of the block when higher cylinder pressures are employed.

Ac

[1275poorlyproject]

Ac excellent thanks

I'd like to consider lifting my 1275 up to 1293 with the aim of supercharger at a later date,would 11 stud be necessary ?

Thanks David

[nicklouse]

debatable. some will say yes some will say no.

[Retroman]

I would stick my neck out and say for the road no, for a competition machine then yes

 

I have often thought the standard S does not need the 10 stud one bolt setup with a maximum CR of 10:1

 

It was ultimately designed to be homoligated as a competition engine so they had an idea when it was designed that higher compressions, power, revs and heat would be squeezed out of it, but not blowers and 200hp

 

That said if its an extreme road engine then yes

Edited by Retroman, 14 July 2018 - 01:02 PM.

[Spider]

I've not found the modification (unless present) worthwhile and can in fact have a debatable down side.

 

The Metro Turbo, which had the highest BMEP (Cylinder Pressure) of any factory engine only ran 9 studs.

 

Why I say it could have a down side is if you look at the deck of the A Series Engine, it has two rows of studs, the 5 at the front (and on the 'edge' of the block / head) and 4 at the back (just off the centre). To me, while I see how the arrangement came about, it's back to front. We have an edge, which is effectively supported on one side only, clamped down with 5 studs and then down the centre where there's far more surface area only clamped down under 4 studs, so the 'PSI' produced by the fasteners alone across the deck and gasket face is not even. Ideally, while I haven't done the maths on it, I feel the 'back row' should have had 5 or 6 studs. The extra 2 studs of the 11 stud set up are too far 'forward' to really take any advantage of them and that up nearer the water pump can only be torqued to circa 25 ft/lb as the deck here is thin and comparatively, unsupported, so does little if anything, in terms of clamping the head down to the gasket. Tightening too much on this one only distorts the deck and that will lead to gasket failure.

[Homersimpson]

I've not found the modification (unless present) worthwhile and can in fact have a debatable down side.

 

The Metro Turbo, which had the highest BMEP (Cylinder Pressure) of any factory engine only ran 9 studs.

 

Why I say it could have a down side is if you look at the deck of the A Series Engine, it has two rows of studs, the 5 at the front (and on the 'edge' of the block / head) and 4 at the back (just off the centre). To me, while I see how the arrangement came about, it's back to front. We have an edge, which is effectively supported on one side only, clamped down with 5 studs and then down the centre where there's far more surface area only clamped down under 4 studs, so the 'PSI' produced by the fasteners alone across the deck and gasket face is not even. Ideally, while I haven't done the maths on it, I feel the 'back row' should have had 5 or 6 studs. The extra 2 studs of the 11 stud set up are too far 'forward' to really take any advantage of them and that up nearer the water pump can only be torqued to circa 25 ft/lb as the deck here is thin and comparatively, unsupported, so does little if anything, in terms of clamping the head down to the gasket. Tightening too much on this one only distorts the deck and that will lead to gasket failure.

when you look at the block the rear row of head bolts are near to the side of the bore in a similar position to the front, surely the bolts are positioned to clamp either side of the bore where the pressure is produced and the 'overhang' at the back is just for the push rods and hence not critical?

[Spider]

 

I've not found the modification (unless present) worthwhile and can in fact have a debatable down side.

 

The Metro Turbo, which had the highest BMEP (Cylinder Pressure) of any factory engine only ran 9 studs.

 

Why I say it could have a down side is if you look at the deck of the A Series Engine, it has two rows of studs, the 5 at the front (and on the 'edge' of the block / head) and 4 at the back (just off the centre). To me, while I see how the arrangement came about, it's back to front. We have an edge, which is effectively supported on one side only, clamped down with 5 studs and then down the centre where there's far more surface area only clamped down under 4 studs, so the 'PSI' produced by the fasteners alone across the deck and gasket face is not even. Ideally, while I haven't done the maths on it, I feel the 'back row' should have had 5 or 6 studs. The extra 2 studs of the 11 stud set up are too far 'forward' to really take any advantage of them and that up nearer the water pump can only be torqued to circa 25 ft/lb as the deck here is thin and comparatively, unsupported, so does little if anything, in terms of clamping the head down to the gasket. Tightening too much on this one only distorts the deck and that will lead to gasket failure.

 

when you look at the block the rear row of head bolts are near to the side of the bore in a similar position to the front, surely the bolts are positioned to clamp either side of the bore where the pressure is produced and the 'overhang' at the back is just for the push rods and hence not critical?

 

 

Yes and that's why they are positioned as they are, but there's a load of 'land out back' of the longer studs. I was not referring to the cylinder pressures there, but the pressures on the gasket that are produced via the studs as a result, there's less 'PSI' clamping force across the port side of the head than the spark plug side.

 

Just coming back to the 11 stud debate for a moment, for them to be effective as they are positioned, there needs to be studs between cylinders in a similar row, but there's clearly no land for that.

[DeadSquare]

If you are going to supercharge it, I would suggest that retaining metal between the bores where the gaskets sometimes blow is more important than an extra stud at either end.