Opening a Port

[vintage engineerParticipant @vintageengineer]

Yes that's the one, a typing error on my part. I ran a single 1 3/4" SU carb and 1 3/4" 3 branch stainless exhaust with this set up.

Posted by Phil P on 01/01/2020 10:54:53:

Hi Vintage Engineer.

I think you might be referring to the 12G295 head, I used to run one of those on my Mini van when I was a lad in the 70's. If I used one now I would need a bigger carb and exhaust to take advantage of it as well.

To be honest I am not trying to make the Traveller go a lot faster, I am just taking the opportunity to build the engine to a better standard than they were when mass produced, I am static balancing all the moving parts and being careful with the cam timing, fitting duplex timing set up etc etc. I am after a smoother running reliable engine that I dont need to be spannering in years to come.

Phil

[StueeeeParticipant @stueeee]

I've used the 12G295 or the near identical 12G206 Cooper 998/MG1100 head in the past on 1000cc 'A' series motors, One of the issues (other than rarity) with these heads is the large amount that needs skimming off the head if you're not using flat top (or 'pop up' pistons) a .070" plus skim often results in a break in to the rocker feed oilway drilling that runs across the face of these heads. Nowadays I use the 12G940 head from the 1275cc motors, It has bigger valves, less volume in the combustion chamber, so needs less skimmed off to attain a decent compression, the rocker oil feed drilling doesn't run across the head face, and if it's a late (1987 onwards IIRC) head it will have factory fitted hard valve seats suitable for unleaded petrol.

When this head goes on a small bore (i.e. 850/950/998/1098cc) motor it needs to be fitted along with the 1275 rocker gear and head gasket as the valve spacing is different on the 1275cc head. The 1275 exhaust valve opens over the edge of the cylinder on the small bore motors, so if the head has been skimmed, or you are running a high lift cam, reliefs need to be cut into the block.

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