20 replies to this topic

[walshy95]

A 1380 is normally built for better torque. High bhp means very little in a road engine. On a race track or rally stage it is different and the revs with, say, a 286 can be kept between 5000 and 6800 which is where the power will be generated, via a low ratio final drive and a s ASC CR gearbox to keep it 'on the cam'.

It is unwise to 'overcam' a 1380 because with the need for the use of higher revs the rate of engine wear will be high and at 1380 it may then need a new block, or very expensive machining to sleeve it back when a re-bore is needed.

If the car is for racing or rallying then that is fine, but for road use an engine with good torque is best and for this a 286 is completely wrong. The 286 gives max power at 6400 rpm and peak torque at over 4000 rpm - entirely wrong for a road engine.

thanks for the input, what cam would you recommend? iwas thinking of using the sw5, but im not 100% sure

[Cooperman]

I've not used an SW5, but it is said to be excellent for mid-range torque, which is what is needed.

However, I can recommend the Kent 266 or the very similar MG-Metro cam.

I'm often surprised by owners who have 'hot' cams in road-going cars, then they admit to not using the revs required to generate the max power, like 6400 rpm with a 286 (changing up at around 6800 rpm). So, in fact, they are not using the cam for what it was designed for and would be better off with a softer cam. The 266 will give maximum power at about 5700 rpm with peak torque - the really important figure - at a nice comfortable 3800 to 4000 rpm.

Make sure the compression ratio is around 10:1 or slightly higher and get a better distributor, such as an Aldon 'Yellow', which is better matched to a 266 cam.

[walshy95]

I've not used an SW5, but it is said to be excellent for mid-range torque, which is what is needed.

However, I can recommend the Kent 266 or the very similar MG-Metro cam.

I'm often surprised by owners who have 'hot' cams in road-going cars, then they admit to not using the revs required to generate the max power, like 6400 rpm with a 286 (changing up at around 6800 rpm). So, in fact, they are not using the cam for what it was designed for and would be better off with a softer cam. The 266 will give maximum power at about 5700 rpm with peak torque - the really important figure - at a nice comfortable 3800 to 4000 rpm.

Make sure the compression ratio is around 10:1 or slightly higher and get a better distributor, such as an Aldon 'Yellow', which is better matched to a 266 cam.

Thanks for the help! i think im going for the sw5! It would be interesting to see a dyno printout or results that mirror spec but with the sw5 and piper 255! Since posting last i've fitted a custom profiled dizzy from Avonbar who built the engine! Also fitted an Air Fuel Ratio gauge to moniter my set up. Feels alot better, no more flat spots, still feels as if its not giving me its all. Hopefully the sw5 can improve on the mid to mid-topend. 

Cheers, Sam.

[carbon]

Sam,

 

Would suggest that before ditching the 255 cam in favour of the SW5 you check exactly how much lift you're currently getting at the valves, as this can make a very big difference to how a motor performs.

 

Just use a digital vernier caliper, you can measure them up easily with the rocker cover off.

[mini13]

I would say get that vac advance sorted, as without it you ar throwing away MPG and part throttle performance.

 

I would look at a mappable system, megajolt is popular and works well.

[walshy95]

Sam,

 

Would suggest that before ditching the 255 cam in favour of the SW5 you check exactly how much lift you're currently getting at the valves, as this can make a very big difference to how a motor performs.

 

Just use a digital vernier caliper, you can measure them up easily with the rocker cover off.

removed the rocker cover and measured the lift, checked my results with the technical data fro the 255, my results where the same as the figures supplied by piper.

Thanks for the advise!

I would say get that vac advance sorted, as without it you ar throwing away MPG and part throttle performance.

 

I would look at a mappable system, megajolt is popular and works well.

meant to say, i re connected the vac when i put the profiled distributor. mega jolt isnt a bad shout! Thanks fro your advice.