Curly wrote:
jacks1071 wrote:
Curly this is a very valid point. What ratio gets your vote?
I'm running 10" wheels, close ratio straight cut gearbox.
Does anyone have a ratio calculator? I think if I can gear it for a top speed of somewhere around 110 miles per hour at say 7000rpm?
Anyone know what I can safely rev a 1071cc engine to? It has the propper cooper s crank, standard bearings on the crank (too many varying opinon's on the extra bearning so I didn't do it). I've got good valve springs with pleanty of pressure.
I'm going to run a rev limiter on the car, our plan was to dyno it and set the limiter to cut in just before we start hearing bad noises. Interested for feedback.
My choice would be a 3.76 ratio LSD coupled to your close ratio gearbox. This is the same setup I've been running for ages on my road registered, 1293cc Grp N car and it seems to be a good compromise and suitable for most circuits, hillclimbs and fast road use. (I hate changing diff ratios in a mini
)
As to what you can safely rev your 1071 to - if it's been well put together, balanced and has deep breathing capacity (head, cam, carb, extractors etc) I would expect that it should be safe to 7500 and the occasional 8000rpm. This is what my 1293 gets, and the 1071 should be more capable with its a shorter stroke (less piston speed) and the same bottom end.
Go ahead and get it dynoed, there's no point taking the revs very far past the peak power power point if the output drops off dramatically - and don't wait until you hear bad noises - it's too late by then.
Curly I spoke to the engine builder today. He wants to run it with the diff we have, we'll do a dyno run to work out where peak power drops off and we'll make a call from there. I'm thinking a 3.9 as long as it'll safely rev to 7500 or so. He reckons we are just guessing until we've done the dyno run - I was trying to avoid the labour costs of pulling it all appart again but better that than waste $600 on the wrong ratio...
I have an RE13 Cam, the head has been professionally flowed by a specialist on the Gold Coast, everything is balanced, we have cermaic coated extractors, heaps of valve seat pressure, some special valve springs as the fancy "mini" ones I bought didn't give enough seat pressure, compression ratio is 10.5:1 - I have a 40 and 45mm webber - we plan to run the 40mm at this stage.
I've invested in an electronic rev limiter which we'll configure after the dyno run.
What is the norm for these, I was thinking set it to cut out maybe 300rpm past maximum power?
