Cylinder Heads; Mk1, Mk2 Differences

[V Mad]

Since Mk1 and Mk2 cylinder heads carry different part numbers, one can assume they are different, but in what respect?

I have visually compared them and not noticed any difference.

Does anyone know what the differences are?. Combustion chamber volume? Valve sizes?

Anyinterchangeability issues with Mk2 parts?

I have not looked at what suppliers sell yet; I assume they only sell one kind. The new Millenium heads are presumably OK for Mk2 and Mk1 fit?

[nib]

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Chris,ive always thought it was alright to have a Mk 2 head on either but a MK1 head has to be used on a MK1,on this basis I assume valves and domed pistons being an issue.Im sure Andy whos had a timing chain snap has a MK1 with a MK1 and MK2 head on his car like myself and he has domed pistons,so that throws that logic out.

Someone I thought mentioned the water transfer housing being different but im not sure.

Mark

[Andy Rundell]

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Chris,
Page 51 of James Taylors' Restorer's guide says the MKII heads have reworked chambers to suit the domed pistons. The same section also mentions that in '75 Triumph Service approved the use of MKII heads on MKI engines, and also approved the use of MKI pistons (but not heads) in MKII engines.

Based on the above i would expect the Millenium heads to be remanufactured MKII heads to allow fitting to both engine types (just ring Abinger Hammer Motors to confirm)

Mark is right, i have both MKI and MKII heads on my car - although i won't know for sure if the r/h bank (which has the MKI head) has domed pistons installed until i get the head off.

.........Andy

[DJT]

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Chris,

The combustion chambers are different, as mentioned. You should be able to spotthe difference if you have the heads side-by-side. Mk1 heads have the number V31** cast into them. Mk2 heads have V32**.

Like Andy, I ran odd heads for many years after I sent a Mk1 to Lincoln for exhange and got a Mk2 back. Never noticed for a long time as I didn't build the engine and I was fairly new to Stag ownership then.

Dave

[V Mad]

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OK I have just had another look and there is a difference between Mk1 and Mk2 headsbut it is quite subtle. The shape of the combustion chamber around the plug hole is a slightly different profile. Everything else looks the same.

I would conclude that Mk1 heads can be used on any stag engine without domed pistons (ie most engines nowadays) but toavoid any imbalance between left and right bank both heads should be the same.