16 replies to this topic

[samsfern]

looking at camshafts for my planned 1380 build, whats the difference between a scatter pttern and normal one??

many thanks

[Ethel]

Scatter pattern has different valve timing on individual cylinders. Because the A series has siamese ports the inner and outer cylinders behave differently so a scatter cam tries to get the most out of each cylinder.

[samsfern]

so presumably a scatter one will be best, best order a kent cams, md310 cam then, 310 duration eachway, tasty, but not very driveable, lol

[liirge]

yer the drivability will not be good on a scatter..
Scatter cams treat the A-series as if it were 2 2cylinder engines trying to optimise the pair of cylinders. It tries to prevent robbing of air\fuel between the inner and outer cylinders.

[bmcecosse]

310 is pretty much a 'racing' cam - are you sure you want that hassle ? I would go with something like the 544 cam - or one of it's more modern 'copies' !

[samsfern]

its fo my other mini which i use for trackdays and weekend play only, still road legal at the mo i have a 1330 with a kent 296 in it, which is great especially when the cam starts to come in, but want more power and want the cam to come in a bit more violently

what do you mean by hassle?

Edited by samsernie, 27 October 2009 - 07:57 PM.

[bmcecosse]

Well -go for it!

[richieg]

I'm thinking about using either a 286 or 286 scatter cam for my 1380 weekend toy build. What are the differences I can expect between the 2 in terms of driving and power differences. Also should I go for 296, would it give more power or loose torque?

[miniobsessed]

As said a scatter pattern is simply trying to optimise the valve timing for each cylinder given the charge robbing nature of big cams on our beloved 5 port heads (siamese ports).

If using a reputable scatter cam and it is set up correctly, the engine should come 'on the cam' a little sooner and give you a bit more mid-range and a little more top end.

If you're young and/or stupid (not really - just a figure of speech) fit a massive cam if you want to but make sure the rest of the engine is properly modified to make the most of it. Personally I like big cams in A series engines but it does take a lot more driver effort to get the most out of them

[Dave33]

With regards to the 310 kent cam,
According to vizard this will lose alot of mid and low down torque(what you need out of tight/slow corners),its designed for constant high rpm.
Even if this appeals to you,the main problem is using with a compatible engine build.
Compression ratio of 13.5 to 14.5 to 1,so that kinda rules out roadside pump fuels.
A well developed race spec cylinder head,that are generally designed for leaded fuels.
A well built bottom end that can take revs of up to 9000rpm.
A cose ratio box with a fairly low final drive will also be needed,otherwise the motor will 'fall off cam',it wont 'come on cam' til around 45000rpm.
also manifold,inlet and exhaust will need experimenting with to get the best from it.
its a misconception that you need a long duration cam to make good power,a 296 is a very good cam that alot of circuit racers use.
refering to scatter cams,these are an improvement over the standard type,which is why they were developed.
i previously used a 286 in my 1380,now use a 286 scatter,previously would pick up at around 2,250 and peak about 6000rpm,with no other mods it now picks up at 2000rpm and peaks around 7000rpm.
so from personal experience they work.
if your after more topend power have you tried altering the cam timing?
Retarded timing gives poor bottom end,and a big hit up top and generally revs further before peaking,
Advancing will bring it 'on cam sooner' and give good all round performance,
if you have a adjustable vernier its worth trying and seeing what works on your motor.
hth
dave

[Cooperman]

Just checked the cam graphs and the 310 will pull only from 4000 rpm upwards. Peak torque is at 6000 rpm and peak power at 8000 rpm. That needs a pretty special bottom end to take sustained 8000 - a full race engine, in fact.
With a close ratio box to keep it on the cam, my guess is that a 3.9:1 final drive will be about as high as you could go and still pull away from rest. In fact, a 4.1 might be needed which would give a speed of c.108 mph at 8000 rpm in top.

[hazpalmer14]

i thought scatter cams were used to stop charging robbing when using a single weber?

[Cooperman]

Someone I know says they are 'Witchcraft'.
For racing where a few tenths of a seconds per lap is important, maybe they are worth having, but for anything else a non-scatter is fine really. They just complicate things more. To get them to give any real advantage you need to set everything up on a dynamometer and 'fiddle' with the cam timing and mixtures until you maybe get those last extra couple of BHP at the top end which is what you do with a full-race engine and a wallet full of £20's.

[Azbornmini]

Here's an interesting article on scatter pattern cams.

Scatter cams, pros and cons

[Dave33]

Good link Azborn,i had read this before,
The trouble seems to be that calver and vizard who i both respect,have different views on the scatter cams.
i read the vizard book way before the calver article,and this made me choose the 286 sp.
I personally have found a an improvement in powerband width by fitting this.
Like said though it all depends on the rest of the spec if this will be the case,obviously was on mine.
the cost is alot more than a single profile cam,so this needs considering,since the 296sp is only available on a new blank this will be considerably more.
I suppose you either take a chance,you wont lose performance,or stick to single type cams,depends how much you want to spend.
hth
Dave