11 replies to this topic

[germini30]

Basically my 1275cc is sick so I am refitting my old 998 back in. Its been stood in the shed a couple of years. When I did a compression test on it when it was fitted in the mini I got 190psi across the 4 cylinders. I have taken the head off before I put the engine back in, to give it a once over. I have measured the combustion Chambers of the 12g295 and get 23.5cc on all 4.is this about right for me? Engine is a 1989 998cc with flat top pistons.

[Minigman]

Must have quite a bit skimmed off it to get it down that far. When I did this it cracked 500 miles in. Better off reworking a standard block.

Edited by Minigman, 23 June 2018 - 04:17 PM.

[Turbo Phil]

Assuming 2.8cc for the gasket and 0.010" piston to block face clearance at TDC you're looking at over 10-1 compression wise.
You really need to measure though to be accurate.
Phil.

[germini30]

Or just pop my standard 998 head on

[germini30]

Is 10-1 too much or on the limit?

[Retroman]

You will be fine with 10:1 but don't use crappy supermarket fuel. Use a 96/ 97 and you won'y have any issues.

 

You must have been a bit unlucky with the head cracking, I have taken them down loads more and not had one crack.

[germini30]

No, this head was on the car previously and it'll now need an overhaul. Will need 8 guides I think

[Dusky]

With a 295 you'll probably be using lead replacement too. Most of these serve as an octane booster.

[germini30]

Yes I would use the additive. Not worth doing the seats as I only do about 300 miles a year

[germini30]

Can anyone recommend what valve guides I should get as mine are worn

[Turbo Phil]

Are you using the standard type valves ? If so the iron guides are what you need. I always use the Minispares ones.

Phil.

[germini30]

Yes standard valves