58 replies to this topic

[Cooperman]

276 works fine with a 3.44 final drive and standard helical gears. However, the rev drop between shifts is quite significant, so you would arguably want a closer ratio box for competition use.

For road use, the 276 is a fine cam though.

 

Yes, I've put a 276 in a road car with a standard box and a 3.44 FDR and it ran very well. The rev drop between shifts is noticeable, but not impossible, as it would be with a 286.

I like the MG Metro cam for a road car as it's just so 'capable' with a standard gearbox. I built a road-rally car with that spec and a 'blueprinted' virtually standard engine which gave 84 bhp at 5700 and never fell 'off the cam'. It seemed about ideal as a road car as well.

[minilee94]

I duna how this has got to camshafts lol but I'm not running any of the cams shown here

[Cooperman]

Tell us which cam you are running and we'll tell you what gearbox and FDR to use.

The gear ratio requirements are dictated by the cam as shown above. It the rev range at which best power id delivered which determines what the gap between gears need to be.

[minilee94]

I am using a piper xt cam
There is no info about it on there site only that power band is 2000 to 7000 and is alled the ultimate road cam

I spoke to lee on the phone at med and he said is ideal for my engine spec head , carb etc

And final drive I'm guna go for the one you said the 3.76.1

Edited by minilee94, 17 September 2013 - 08:57 PM.

[Cooperman]

With a 3.76 FDR and that cam you will find a standard helical gearbox fine. It an 'S'/'GT' gear-set was available it would be even better.

[seancv1]

I had a jack knight sccr gearbox in my car with a 286 cam it was really good at staying within the power band even with my road orientated final drive as for the noise it was there but not full on the knowledgable bloke who put the gearbox together did a very good job and to help noise matters further I had helical drop gears that's where a lot of the noise comes from I think.

[minilee94]

What you mean s/ gt gear kit Pete

I was only guna go for that FD as you said it would be great but I don't think I said I was guna go for straight cut gears

Edited by minilee94, 17 September 2013 - 09:11 PM.

[Cooperman]

The original Cooper 997 & 998, the Cooper 'S' and the 1275 GT had a gearbox with a slightly closer gear ratio from that fitted to the standard cars. I think these gears are still available and are slightly better than the standard ratios, but are helical and are not as close in ratio as the SC CR gear sets. They are a good compromise so long as the cam is not too wild. The 997 & 998 Cooper had a 3.76:1 FDR and the Cooper 'S' and 1275 GT had the 3.44, except for the 1071 & 970 'S' which were standard with the 3.76:1.

There are so many variations it can be confusing at times I know.

[jaydee]

Noise wise, i think the SC box is quite bearable, its the SC drops that became really annoying after 5 miles. Although you can find some sets of drops that are not that noisy.

[Vipernoir]

It comes down to personal choice at the end of the day - there is NO right or wrong answer, merely opinions when it comes to cams, gearboxes and gearing.

 

I've got an SCCR with a 3.1 fd under an 1150 in my estate at the moment, and it's an utter bugger to get off the line.  Once it's rolling, even from walking pace it is a joy to drive however and cruises beautifully on the motorway. 

Would I use the combo again ?
Yes, but with a much bigger engine and on a car that I didn't intend thrashing down lanes.

 

Straight cuts are fun toys on the road, but I probably won't have one in a daily driver again.  Not because I don't like the noise, but because people stare at you as you drive past and passengers don't tend to like the noise.  The 'box that is in the estate at the moment is probably destined for my Hornet with a 3.65 fd as it isn't going to be a cruiser.

 

The losses from straight to helical aren't as big as some would have you believe, and a helical gear is stronger than a straight cut one due to a much bigger root.  Straights are much easier to make as it is a far simpler process involving less expensive design and machinery, so they are cheaper and faster to bang out.  Having said that, not all gear kits are equal.  I've built a few up and there are manufacturers that I will never reccommend as the inevitable corner cutting has occurred on quality.

[minilee94]

Spoke to med and they said it don't matter what cam you run etc its all down to the final drive

[Cooperman]

Sorry, but that is not correct. Yes, the final drive is a factor, but the very high 1st gear you get with a SC CR box is of importance. In fact, the close ratio gears are designed to be close enough that when you use a 'hot' cam and you change gear you are still 'on the cam'. It becomes more important the 'hotter' the cam you use.

With a mild cam the spread of torque & power is wide, so a standard gearbox is fine. With a 'hot' cam the power band is narrow so a CR box is fitted. But then 1st gear is very high, so a low FDR is used in order to pull away from rest without lots of clutch slipping. But as a 'hot' engine will rev very high, in fact it must rev very high to obtain full power, the lower FDR won't matter as it will still have a good top speed, but at higher revs. (maybe like 7000 rpm).

That is how a competition car is set up, with the gear ratios to keep it all 'on the cam' and the FDR to enable the car to pull max revs on the longest straight. That is why  SC drop gears are used to enable the effective FDR to be altered for different circuits to still just reach max revs on the longest straight by just changing the drop gear ratio between events on different circuits..

[Old Bob]

Not thought of this before but how practical would it be to swop cams while the engine is in situ?   Would make things much easier when trying different options......

 

Bob

[Tamworthbay]

Not thought of this before but how practical would it be to swop cams while the engine is in situ?   Would make things much easier when trying different options......
 
Bob

My mate (Minimanjay on here) did his by cutting a hole in the inner wing. He says it was doddle, but I would think it would be tricky.

[Cooperman]

It's easy with a 998 or Cooper 'S' as there are cam chest covers which enable the cam followers to be removed once the head is off.

With 1275 engines (except for the 'S') the engine must be removed and the block inverted so that the cam followers fall away from contact with the camshaft and the camshaft can then be withdrawn from the block.