4 replies to this topic

[mini rizzler U.K.]

I am wanting a little more go out of my mini and would like some advice on modified heads, cam shafts and roller rockers.

my engine is a 1275cc metro unit. it has twin 1.25 inch su carbs everything else is standard.

thanks

Si

[Cooperman]

Basic advice is to get a gas-flowed MG Metro head, an MG Metro or Kent 266 cam and an LCB exhaust manifold. Use a 1.75" internal diameter exhaust with Maniflow silencer boxes.
Also machine the head to give a compression ratio of about 10.3:1.
Gas-flow the inlet manifold for the twin carbs.
All together that will give a noticeable improvement after you get it all set up on a rolling road.
Don't bother with opffset rockers as they won't give any improvement unless you are going to use very high revs a lot.

[Mart8V]

Have you considered going to an HIF44 instead of the twins? With the Metro inlet it is good for up to 100bhp, I am told. When I first looked at getting mine on the rollers I spoke to Ray at T&M (carb guru!) who advised me to stay with a single rather than twins for straight horsepower and economy. Horses for courses, naturally, but I have been very happy with following his advice.

[Cooperman]

But as he has twins already fitted there would be no real improvement in spending out for a HIF44 or HS4 plus a manifold. Better spending that cash on an MG Metro cam and/or a gas-flowed head and gas-flowing his inlet manifold.
Just make sure that the compression ratio calulations are done. I recently stripped an engine which was supposed to be a 1275 Innocenti Mini-Cooper 1300 specification only to find that although recently re-built it had the wrong pistons fitted which meant a comp ratio of only about 8.9:1. I re-did the calcs, 'decked' the block by 0.050" and took 0.022" off the head which has brought it up to 10.4:1 with twin 1.25 SU's (as standard). Now it should go well. It is listed as having 71 bhp as standard, but this engine is now 1330 cc, so I am guessing about 15 bhp, the same as the original Cooper 'S' 1275. CR calcs are so important.

[cap'n crunch]

I would say coopermans first post is some great advice. My only concern is that Twin HS2 will be reaching the end of there carburation and you will start to lose out at the top end as it will not be able to supply enough air for a 1275 with a wilder cam and modified head.