Piper 310 Cam
Posted 02 November 2020 - 08:55 PM
Posted 02 November 2020 - 09:25 PM
Edited by imack, 02 November 2020 - 09:29 PM.
Posted 02 November 2020 - 10:36 PM
To get a high-overlap cam which has a very narrow power band at very high revs to work, you need an engine which will consistantly rev to over 7000 rpm. Since it will have virtually no low-end torque, a very close ratio gearbox will be needed. The consequence will be that 1st gear will be very high and an etremely low final drive ratio will be needed to pull away from rest cleanly without really excessive clutch slipping.
In fact, you will probably need something like a 4.3:1 FDR which will give a top gear with about 12 mph per 1000 rpm. That is fine for racing where 8000 rpm will give about 100 mph in top, but 6000 rpm at 70 mph on the road will mean frequent engine rebuilding.
A Piper 310 really is a full-race cam. In a road car it will be pretty useless and nasty to drive.
For a road car a Kent 276 or Piper equivalent is about as far as is sensible. My personal favourite is the Kent 266/MG Metro cam.
I run a Kent 286 in my rally Cooper 'S' and have a SC CR gearbox with a 3.9:1 FDR. That is OK, but it is not a road car by any means. I do drive it on the road sometimes, but 70 mph is just under 5000 rpm. For the road I much prefer my 1990 Cooper with a standard gearbox and a 3.44:1 FDR
Posted 03 November 2020 - 02:07 PM
Posted 03 November 2020 - 11:28 PM
I once built a 1071 'S' with a 649 cam. It had a SC CR gear set and a 4.1:1 FDR.
It was an FIA Group 2 full-spec rally car and very competitive on tarmac special stages. But even for rallying it was a bit too 'cammy' and I fitted a Kent 286 cam, leaving the 4.1 FDR and it was a bit better and could do gravel rallies. It really had little below 4000 rpm, even with the 286, but it was a competitive car in its class.
That is the car which my friend had me ship to the USA for him and which was sold at the Barrett-Jackson auction a short while ago.
Posted 14 November 2020 - 04:23 PM
Posted 15 November 2020 - 08:33 AM
Posted 15 November 2020 - 08:45 AM
Fitting a megajolt ignition system that can be mapped certainly helps the drivability of a high performance engine. Combined with the right gearing would make a great back road warrior. The worst that can happen is you have to remove the engine and swap the cam. A good weekend job.
Theoretically yes, a cam swap is potentially a weekends work, but presumably the engine will have been spec'd to suit the 310 cam.
Fitting something milder like a 276/286 is not necessarily going to work well with a head, compression ratio, carbs, final drive etc that were spec'd for a 310
Posted 15 November 2020 - 09:55 AM
Posted 15 November 2020 - 02:35 PM
So bit of a difference there
Posted 15 November 2020 - 03:47 PM
One man's meat is another man's poison!
A lot depends on what you're prepared to put up with and what the roads and traffic are like where you live.
In the 80's and 90's I used to use piper 285's and kent 286's in my daily driver in relatively heavy traffic, I didn't find them a problem.
These days I run a 649 based cam but the car is now only a weekend toy used in the lanes and traffic free roads, again I find it's fine, but others would hate it.
Plus wear rates and maintenance are higher with wilder cams, it's all a compromise.
Edited by imack, 15 November 2020 - 03:49 PM.
Posted 18 November 2020 - 12:27 PM
Thanks for the info guys, I think I’ll put the cam up for sale and get something more suited
what size engine are you building ?
Posted 20 November 2020 - 06:37 PM
Parts I’ve got for the build are
MED clubman head 20.2cc
Forged pistons 6.5cc
SCCR Box 3:2 final
And the 310 scatter cam that I’m not sure on.
Guess depending on what cam I go for I will also need to work out the best compression ratio for the machine shop.
Posted 20 November 2020 - 07:07 PM
Posted 20 November 2020 - 07:56 PM
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