8 replies to this topic

[cookie4343]

Need help knowing how to convert my standard 1098 block to fit a 12g295 or 12g206 head
Any pics would help me know as to which galleys to block and what to block them with.
And is a standard head of a 1098 mini speacial engine got the same amount of head bolt holes as above.
Also which head gasket would i use a standard 1098 or the 1275.

[Asphalt]

12G295 and/or 12G206 are standard smalbore heads.

Which means you don't have to plug, drill or tap anything (well, with a little exeption - read on).
And followed by that a standard smalbore (850/998/1098) headgasket does the job.
(Make sure it's not a copper-ish one!)

BUT an unmodified 295/206 has 28,3cc chambers, whereas the 1098's head (12G202) has 26,1cc chambers.
So compression would drop if you put on an unmodified 295/206 head.
Next BUT: But many of those heads are skimmed or modified and therefore have differing chamber-volumes!

And that means:
- measure the distance from block to piston's surface on TDC
- measure the 295/206's chamber volume
- measure the piston's dish volume
- measure the gasket's thickness
-> calculate the amount the head needs to be skimmed to get the compression you want.
(It propably has been discussed how to calculate in great detail -> do a search)

Hope that helps,
Jan

[liirge]

This Thread might help you:

http://www.theminifo...mpression Ratio

[cookie4343]

Thanks for help but sounds to complicated to me but thanks anway peaple.

[Dan]

So when you though the conversion involved plugging and re-drilling oilways and studs and custom matching a head gasket you were prepared to try it but now that there's a little maths involved it's too complicated? Give it a go, the 12G295 was the standard head on MG spec 1100 engines and if you have flat pistons you'll probably find it will be a direct swap. The maths isn't hard and neither is the fitting. Even if you need it to be skimmed it's not complicated and you can get it converted to unleaded at the same time. It really is a much better head and worth the swap if you can find a good one.

[nomininolife]

Do you have the head already?




David

[cookie4343]

Do you have the head already?




David

Not yet just looking in to it as i have a 1098 engine sitting in my garage and left deposit on a new project for after christmas which has no engine so thinking more power before a transplant also been cleaning and painting everythink up ready.
P.S Im no good at maths.

[nomininolife]

Nor am I any good at maths but its not as hard as it sounds, the main thing to do is measure the depth of the head when you first get it.




David

[Jammy]

Well, you do have to have very accurate measuring apparatus, so if you haven't got that then you'll need to find an engineering firm to do the measuring anyway, in which case they'd do the calculation and skimming for you too.