18 replies to this topic

[Noris8322]

Hi,

I'm gonna be starting a 1310cc engine build soon, but I've got the age old question of which cam?

I'm not going for outright power, the idea is to keep it drivable at low speeds & in traffic but when I want to have a little sunday afternoon thrash it's still got plenty of poke. I was thinking of something with a slightly lumpy tickover, but with smooth(ish) power delivery.

My first thought was the Swiftune SW5 cam kits, anyone using one? If so, what's your opinion on them?
Also, I've heard good things about the Minispares Centre Evolution cam shaft, any reviews?

Any other ideas?


Thanks in advance

James

[Cooperman]

There is a huge amount of BS about cams, with every manufacturer claiming that their cams are the best.
In fact, a cam just releases the power available from the head, induction & exhaust systems. The way in which the cam releases this power (and torque) is down to the way the cam lobes are ground including total lift, duration and cam lobe ramp design.
To choose a cam you first need to decide how you want the overall package to perform. By this you need to consider what is most important. Do you want mega acceleration, a high top speed, or a smooth cruise at moderate revs. It goes without saying that you can't have all three, unfortunately. There are just so many combinations of final drive ratio (FDR), gear ratio, (ultra-close ratio or normal helical gear set), induction system (twin 1.5" SU, twin-choke Weber or single SU).
As a suggestion, and you'll get plenty suggesting other specifications, any of which may or may not suit your use, I would say the following:

Kent 266 or MG Metro cam - they are very similar, accurately timed-in with offset woodruff key.
MG Metro head (or MG Metro valve sizes of 35.6 mm inlet/30.5 mm ex)
Compression ratio of 10:1 with AE21253-40 pistons
Gas-flowed inlet and ex. tracts and smoothed combustion chambers with de-shrouded valves
Single HIF44 carburettor on a good alloy inlet manifold
Lightened flywheel
3.4:1 FDR giving about 16.7:1 mph/1000 rpm in top gear with standard helical gear set..
LCB ex. manifold and Maniflow two-box 1.75" exhaust system.
A distributor matched to this specification.

The last engine I built to this spec gave about 80 bhp at b5700 rpm and was/is great to drive.

The key to good performance is accurate and careful engine building as well as the correct components. For example, make sure the pistons come right to the top of the block, lap the valves in properly, match the manifolds to the head, etc.

Good luck with your engine.

[valve bounce]

ive drive a sw5 in a 1275 and it was very tame, the mg metro cam is a very good road going camshaft even in a smallbore. when i built mine i wanted alittle for so i fitted a 276 kent and i find it very good, ok the low end tourque isnt as good as the 266/mg metro, but mid range power is very good.

[Cooperman]

Agree the 276 is a very good cam with peak power is at 6100 rpm. When driving it to achieve full power about 6300 rpm is needed which means a centre-main strap might be a good idea and, maybe, a crank, rods, pistons, flywheel/clutch balance.
A 276 with 10.6:1 CR, twin HS4's, LCB, etc, can give up to about 90+ bhp at 6100 rpm, which is very good. Power from about 2600 rpm and strong from about 3300 rpm. All-in-all a nice cam.
It's a good idea to look at the Kent cam graphs for A-series engines. They show where torque & power are for each cam in their range.

[The Principal]

i have a 1310 with a Piper Magnum 285 and it goes fine above 3500 but having a great cam alone wont give you great drivability you need to increase the upgrades in association with other matched add-ons. Hot cams around town need to be driven as 'hot-cams' and can be difficult in traffic that said if you mix and match your upgrades it will put a huge smile on your face.

[valve bounce]

Agree the 276 is a very good cam with peak power is at 6100 rpm. When driving it to achieve full power about 6300 rpm is needed which means a centre-main strap might be a good idea and, maybe, a crank, rods, pistons, flywheel/clutch balance.
A 276 with 10.6:1 CR, twin HS4's, LCB, etc, can give up to about 90+ bhp at 6100 rpm, which is very good. Power from about 2600 rpm and strong from about 3300 rpm. All-in-all a nice cam.

mines similar to this infact, just its got a standard mg metro head and twin hs2's instead and currently it gives 70bhp and drives very well but i need more power, so now i know what my next move is to make more power

Edited by valve bounce, 30 August 2012 - 07:38 PM.

[Noris8322]

Cheers for the advice guys, I've got the complete spec if it helps

Spec -

1275 A+ block, bored to +40
Mini Sport road sport head (37mm inlet, 29mm exhaust, double valve springs, gas flowed, ported & polished)
C-AJJ3378/40 Pistons (from minispares ctr)
Balanced metro turbo crank
Centre main strap
Duplex vernier timing gear
HIF 44 or Twin HS2's
Maniflow LCB
RC40 twin box system

I've also got 1.5-1 ratio ratio rockers, would they be worth while fitting if I've got an aftermarket cam?

[Cooperman]

I think I would go with a 276 with that great specification and the HIF44. If you could get a pair of HS4's then that might be slightly better at mid-range in terms of throttle response, but twin HS2's are too small.
Make sure you measure and calculate the compression ratio, especially if it's a Mini Sport head. I once had a Mini Sport head which was not correct for my 1071 'S' despite giving them the required specification and chamber volume required. You should always check this anyway. With your spec I think I would go for about 10.4:1 and use 97 octane petrol and Castrol Valvemaster Plus if it's not an unleaded head.
I suggest a FDR of not higher than 3.44:1.

[valve bounce]

sounds a very nice spec but dont use the 1.5 rockers there not worth it they just move the power further up the rev range making it more difficult to keep "on cam"

[Cooperman]

sounds a very nice spec but dont use the 1.5 rockers there not worth it they just move the power further up the rev range making it more difficult to keep "on cam"

To confirm this, I gained all of 2 bhp above 5700 rpm when I fitted my 1.5:1 roller rockers and nothing extra anywhere else, but I lost a bit low-down. That's with a 286 cam and 11.2:1 C.R.

[dave-88_123]

i have a piper 270 in a road car its very good for driving in traffic and has plenty of grunt when you want it

[valve bounce]

There is no way I'd ever fit a 276 in a 1275 again,

really what problems did you have with it, i timed mine in properly with vernier timing gear etc and it goes very well, there are still improvements to be made. how ever i drove my mates 1330 with a 286kent with a highly flowed and polish small valve head and i really wasnt impressed, i reckon if the rest of the engine was up to spec it would be great but my 1275 with 276 and standard mg head just walks all over his

Edited by valve bounce, 30 August 2012 - 08:13 PM.

[Noris8322]

Cooperman, I'll work out the compression ratio when I get a spare 10 mins. I thought that the HS2's would give better low & mid range power over the HS4's or am I wrong? Also I was going for a 3.1 FDR

Valve bounce, I think I'm gonna ditch the 1.5 ratio rockers if they are gonna push the power to the higher end of the rev range

Dave-88_123, I wouldn't fit a Piper cam as I'm not a great fan of them. I had problems with a piper cam fitted to a 2.4 pinto in my old autograss car. After running in the cam as per the pipers instructions, but after two 6 lap races. I was complaining about a lack of power, then we found there wasn't a lobe left on it!!! Changed it for a Kent Cam on the same engine and never had a problem again

DILLIGAF, Its a 1988, so emissions shouldn't be too much of a problem.

Edited by Noris8322, 30 August 2012 - 08:21 PM.

[Cooperman]

Cooperman, I'll work out the compression ratio when I get a spare 10 mins. I thought that the HS2's would give better low & mid range power over the HS4's or am I wrong? Also I was going for a 3.1 FDR

The HS2's would be fine low down, but they might struggle a bit at the top end with a 276. HS4's would work well right through the rev range. I built an engine with a similar spec to yous with a 276 and it gave 92 bhp at 6100 rpm.
A 3.1 FDR might be OK, but for general driving around town or on twisty country roads the 3.44 would probably give better driveability overall. The only time a 3.44 might seem a little low would be on long fast main roads and motorways, but that's not what a Mini is for really.

[valve bounce]

well i would say if your fitting a 3.1 diff then go for a 266 cam other wise it will be difficult to keep on cam