3 replies to this topic

[Dan01]

Hi all,

I have a standard 1275 Mini Mayfair (the 50hp carb version)

A while back I (naively) bought a cylinder head off EBay which is apparently ‘stage 4’ with the following spec -

11 stud 12G940
Phosphor bronze valve guides
36mm inlet valves with waisted stems
31mm exhaust valves
Back cut 30 degrees
240lb double valve springs
New valve stem seals
Hardened seats for unleaded
Ported and polished, chambers reshaped and measure 20cc
Head skimmed by 0.019”

On reflection I think this head is way too modified for my car?

I’m wondering if it will be worthwhile trying to upgrade to match the head or just starting off with some steady modifications and light porting of the standard head that’s on the car now.

I’ve been reading some old posts about the Mayfair which say that the lower compression ratio is good to keep and a good upgrade is a MG metro head and 1.5 rockers… I have a HIF44 to upgrade from the 38 that’s currently on there.

I’m not looking for a bonkers engine setup, just something driveable daily, with a steady 70-80 hp

Any advice appreciated

[Zami]

I had a stage 4 longman head 1380 with a vp3 cam heavy duty valve springs some years ago.  Decided to bring it down a few notches.  Changed out the cam for a sw5 installed lower lb springs. Lowered compression to 9.7 to 1.  Runs great all the way to 6.5K rpm.  

[Dan01]

Thanks Zami, I imagined that this stage 4 head would be suited to a 1380 like yours

[Compdoc]

The combustion chamber volume seems very low for a road going 1275. Try putting the dimensions into a compression ratio calculator to get an accurate CR.

https://jscalc.io/ca...RNEglVkKLQir11T