3 replies to this topic

[MrBounce]

I need to settle a dispute between two friends of mine; they have a 1098cc engine and several 12G940 heads to spare between them, including one to similar spec as an MED Road/Competition head.

Can you fit a 12G940 head onto a 1098 block without the need for pocketing? And if so, will the bigger valves of the performance head above necessitate work that a more standard head will not?

One says yes, one says no and I am not 100% sure. Help!

[bmcecosse]

You want a standard valve size 940 for the 1098 engine. Save the big valve head for a 1275. You need to measure the clearance from valve top face to head space - you MUST have 320 thou using the standard 1098 cam (AEA630) or an MG Metro cam. Provided this clearance exists on the exhaust valves it's fine to fit. Otherwise - sink the exhausts into the head until there IS 320 thou.......

[new_zealand _minis]

well i have done this to my 1000 mk1 motor ... no mods just put it stright on with 998 gasket . no pocketing ... did not even have to fiddle with the mixture or timing ... valves did not hit the head . makes it pull real hard ...

but you are right ,, it needs to be made sure that nothing is going to hit .. i onld did it because same as you i had some heads lieing around and wanted to see what is going to happern

i put it on my **** motor just incase

and the smaller chambers in the 1275 head will do some good aswell

[bmcecosse]

Dangerous doing it without measuring - in many cases they WILL hit.