7 replies to this topic

[Mrpeanut]

I'm confused about the clearances on my car.

Haynes says 11 to 13 thou for this engine, and in that range for all. That can't be right though as anything with an mg metro engine should ( I understand) be set to 14 thou on inlets and 17 thou exhaust. The rsp has an mg metro engine so ought to be the same. If you believed rover then the mainstream and the rsp had the same engine...

I've set mine at a loose 12 across all valves and 14/17 like an mg metro. More open feels "breathier" but with a low end flat spot.

Can anyone help with the best settings for this engine?

Edited by Mrpeanut, 14 November 2013 - 01:19 AM.

[Mrpeanut]

..
Duplicate

Edited by Mrpeanut, 13 November 2013 - 11:28 PM.

[Mrpeanut]

I have the official Rover workshop manual - AKM 6353 (2nd Edition 1991). This edition was specifically intended to include additional information for the RSP and Mainstream Coopers but not the SPi, which was the subject of a supplement and then a later manual.
Under Engine Tuning Data for Model: Mini Cooper with catalyst - year 1990 on it states
Valve rocker clearances (cold) Inlet and Exhaust: 0.013 to 0.015 in.
 
The same information is included in the 1990 Mini Cooper handbook. The late and much missed Taffy1967 made a pdf copy available on the Mini Cooper Register forum but I cannot give a link because there seems to be a problem with the site at the moment.
 
It is true that the RSP and Mainstream Coopers have the MG Metro block but a certain amount of development work was done by ERA for the new Cooper limited edition (RSP) and I would not be surprised if the cylinder head had differences. I must try and find out. The Mainstream should have the same head as the RSP.

Thanks, that's very helpful.

It's well documented (rsp register) that the rsp has an unleaded mg metro head. When I pulled my (original) head it was small valve so not mg metro.

It's the block that's interesting and when I pull it I'll see what's on it. Before now I've never read anything conclusive. If you can find Taffy's link that would be fantastic.

In the meantime I'll try those settings - cheers.

[Cooperman]

Consider why you have a valve clearance set at 'cold'. It is to ensure that when hot the valves will still correctly seat when the cam is at dwell position. So as the engine heats up and the valves get longer there will still be a clearance.

Personally I've never understood why the clearances vary from model to model. I mean, the valves in an 850 get to the same temperature as in a Cooper 'S', so the valve stretch at operating temp will be almost the same. It certainly won't vary by several thou.

Of course, with different ratio rockers the cold clearance should be increased by the difference in rocker ratio. If going from 1.3:1 to 1.5:1, take the nominal clearance and multiply by 1.5 and divide by 1.3.

I always use 0.012" cold for all engines from a standard 850 up to and including a 115 bhp 1310 cc Cooper 'S' and never have any problems.

[bmcecosse]

I suspect the thinking is that in harder driven/larger capacity  engines - the ex valves WILL get hotter, and expand rather more than in a humble 848.  It is very important that the valve gap NEVER closes up - or a burned seat (or valve) will follow soon after.  Therefore on later engines the original 12 thou was opened up by Rover to 15 thou - possibly because of hotter burning 'unleaded' fuel  - possibly just part of a strategy to try to prevent valve seat recession.  I use 12 thou in inlets (figuring they are kept cool by incoming charge) and 15 thou on exhausts.  I have to say - in the past I have tried different gaps (closing up the inlets etc) and was NEVER able to discern the slightest difference in performance.......  Perhaps it's just me - but I suspect any difference will be miniscule - just like the difference in the gaps......

[petehuws]

Hi guys, I have a totally standard RSP as Mrpeanut is aware of. On the weekend I removed the head off the car and with my digital vernier measured my inlet valves to be 35.6 & exhaust valves to be 29.2, not sure why following mainstreams potentially went down to 33 but I think right through the RSP & mainstream builds things were not totally standardised so all may have quirky differences, of course this is only my impression of that time;spi's & mpi's seem to of had a much more regimented and stable consistent build.