Classic mini Small bore heads

[@Markycarandbikestuff]

Cracking video, i got a second hand 12G202 head, apparently was used on a 1000cc production saloon racer, seems really nice, has the same 33/29 valve sizes as your last head, was going to use this with a Kent 266 cam, didn't plan on rebuilding the engine as it's only done 43000 miles but it's an A+ which i've learned has dished pistons, seller did say head had been skimmed, think i'll need to measure the CC in the pistons and chambers and work out the compression ratio. Will need to get David Vizards book again, it was my bible back in the 90's lol.

[@gf845]

25 years ago I fitted the entire top end off my mg metro to the bottom end of my 998 mini. Everyone said it wouldn’t work. It did work. The raise in torque was immense.

[@jesscneal]

Good to see a vid from you Stuart. Hope you and the family are all well.

[@Vmaxporsch]

yep getting back to normalish now back to the videos !!

[@OnlineHousehusband]

Nice video, slight error you made though....The 12G295 and 12G206 are practically identical castings. The 202 is far more restrictive than a 206.

[@Vmaxporsch]

All the ones i've seen have not been as good as a 295 !

[@IsraelitesUnited]

Hi I've acquired a 12G295 head that is untouched but wanted to remove the valve boss casting but I'm concerned to how much you can removed without going through the water ways. Your 12G295 valve guide look quite pronounced in the chamber bowl. Did you remove quite a lot of material here? Thanks for your help.

[@Vmaxporsch]

just flatten the '295 boss, do not make that area concave.

[@OnlineHousehusband]

I'm assuming you are using 1275 valves at 33mm inlet and 29mm exhaust? In theory then don't you have to shim your rockers or change pushrods lengths as these are longer valves than the standard 998cc ones? Any advice would be great. 👍

[@Vmaxporsch]

yes you need to check rocker angle once fitted, this was going on a supercharger instal so the decompression plate levels things out perfectly.

[@josheastaugh2563]

Hey, Awesome video. is it possible to skim/ deck a 12G295 enough to lower the combustion chamber CC's to that similar of a standard 998 so that the block and pistons in a standard engine do not have to be tampered with? I have been asking around and some say it is possible and others say it isnt? Have you ever seen it done? Thanks!

[@OnlineHousehusband]

To run a 12G295 or 12G206 head on a 998 you need at a minimum flat top pistons. If you are currently running dished ones they won't work to achieve the correct compression ratio. 👍

[@Vmaxporsch]

some heads can be skimmed , check the thickness on the oil feed running across the face to feed the rockers

[@andyfry1970]

Hi, great video, interesting stuff! OK so I was reading some info of a test that Mr Keith Calver had done comparing a modified 998 and a 1098, same mods, stage 3 head, sw5 cam etc. The result of the 1098 was impressive from a torque and bhp point of view, power curve. These have quite a low compression ratio to start with, which I believe is needed when supercharging, so I was thinking would this make a nice package... Supercharged 1098, suitably modified? Have you supercharged many 1098's, and what were the results? How do they drive? Hope I haven't waffled too much lol, but I am interested thank you

[@Vmaxporsch]

Hi only problem is the crank - the 1098 crank has no 'overlap' of journal metal making it prone to breakage, 998 crank is bulletproof though !

[@andyfry1970]

@@VmaxporschThank you for replying. Oh, well I obviously didn't know that lol. So...my 998 it is then! So what plus thou is it safe to go to and which pistons would you use and do you have to have a decompression plate?

[@Vmaxporsch]

@@andyfry1970 use the powermax flat top type pistons with the oil holes in the oil ring groove, do not use slotted oil ring ones.

[@polini65]

What type valve seats are used? I can’t find them online in large size

[@Vmaxporsch]

minispares 1275 inserts

[@steveduffy1800]

The 12G206 is the same as a 12G295, not the 12G202