6 replies to this topic

[rwg850]

Hi guys,

Hope this is the right area for this post.

 

I am about to undertake a freshen up of an SPi 1275 from a 1995/6 Rover Mini.

The head is off and I am going to get that ported a bit, and I want to raise the compression ratio.

What I would like to know is the standard dish volume, so the engine builder can work out how many CC the chambers should have to get my desired CR.

 

I have no idea if it is a "low compression" or "high compression" engine - is there any way to check?

Any help appreciated.

Cheers

Will.

 

 

[ACDodd]

Depending on what engine you have there are 2 types of piston fitted. Either 21962 or 21963. The 963 being the higher compression type. The dish size is the same on each pistonthe difference is the 962 piston as a 0.03" lower crown height. If you have the 962 pistons fitted it will also mean you have the sprite cam fitted. Fitting a a modified head on this engine is not going to make a massive difference unless you also fit 1.5 rockers as the cam profile is just too mild to make more power with a flowed head.

AC

[ACDodd]

Both pistons have an 8cc dish.

AC

[rwg850]

Thanks for the replies AC!
I am (don't shoot me!) contemplating running the Kent 276 camshaft.

I really love the way it idles, and it will be a weekend car, as I have an R53 MCS as my daily.

 

The rockers will be standard (at this stage - don't want to go too crazy on my monetary outlay), and I am hoping for a CR of around 10.5/11.0:1.

 

Are the part numbers stamped on the pistons to identify which type they are?
It is a 12A2DJ33 engine - no idea what the J33 prefix relates to, but from my research 2D should be a high compression (9.4:1) engine.

 

 

Thanks again.

Will.

[ACDodd]

Keep compression to 10:1 maximum. Low compression is 9.4:1 high compression is 10.1:1.

Ac

[rwg850]

I should mention that this engine will be using an HIF44 and be installed in my 1964 Morris 850.

It will be used as a weekender 'toy', and as such won't need the luxuries of a daily.

 

Is the 10:1 maximum to retain an efficient timing advance?

 

Cheers

Will

[ACDodd]

Yes.

 

AC