Engine Specs For Historic Road Rallying.
Posted 17 September 2017 - 06:15 PM
I'm building a car for hrcr road events. I'm running a metro cam, which is perfect for low down revs which is what I need in the tight and twisty tests. However I'm struggling to stay in first, every other car I have watched seem to be able to stay in first all the way around a test, mine I would find I'm having to change into second because I'm running out of puff. I'm running a completley std box, with 3.4 diff. Any recommendations on what I can do to help this?
Posted 17 September 2017 - 06:17 PM
what gearboxes and final drives are the others using?
any issue using second?
Posted 17 September 2017 - 08:06 PM
Posted 17 September 2017 - 08:41 PM
What speed are you changing up?
What spec is your head and rocker gear? Engine lightened and balanced with main centre strap?
Posted 17 September 2017 - 11:29 PM
The SC gear set used by most competitors has a very high 1st gear. With a 3.9:1 FDR and the use of 7000 rpm it is possible to stay in 1st for a lot of very tight tests.
However, with a standard box and an MG Metro cam the 3.44:1 FDR should be fine, so long as you use around 6500 rpm. If you go any higher with the FDR you will lose a bit of acceleration through all the gears.
One alternative would be to use a set of the original Cooper 'S' gears and a 3.44:1 or 3.76:1 FDR. They are slightly closer in ratio than the standard gear ratios.
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