45 replies to this topic

[ACDodd]

It's only better if you drive over 3krpm. In actual fact the two cams are pretty much identical till 4 k rpm, if you are talking average torque. If you spend most time between 2 and 3.5 k the sw5 is king on these graphs. If you spend most time between 2 & 4 k rpm it's evens. If you send most of your time above 3k rpm the sw8 is the one to go for.


Ac

Edited by ACDodd, 03 July 2014 - 06:31 PM.

[PandO]

I'm also looking at the SW8. My build is based on an Austin 1300 engine at +40, a ported head with work to unshroud valves (36/29)will be used (Calculated cr of 10.5:1 with HC dished AE (Neural) pistons. I was planning to used a MG Metro cam but I have to source a set of rockers. So I'm wondering if my plan to use twin 1 1/4 SUs (because I have them and they look so right) with some MED 1.5 roller tipped rockers (not recommended for the MG Cam) + the SW8 give me a return for the bucks? Medium Maniflow LCB + RC40 twinbox exhaust is already chosen. Also an Aldon dizzy with the vacuum connected through the Amethyst electro wizardry is in stock. Then would it be NGK 6's or 7's with a skimmed head? I'd be very interested in what you guys think of this plan for my 1275GT. (1275GT engine removed from the car is in storage - keeping this incase all goes bang!

[TR7]

my plan is a 1293 engine stage 3 head med 1.5 roller rockers sw8 cam med stage 1 verto clutch kit and specialist components 5 port injection kit don't no what pistons to use yet? or compression ratio?

[PandO]

To keep on the topic of the SW8 camshaft - what experience has anyone had with it and what build was it used in? Does it require  greater than 10:1 CR to make it work? Would 1.5 rockers increase the need and/or the benefit of a higher CR? (I can keep ignition timing controlled with an Amethyst equipped Aldon dizzy and can time the cam  with a vernier). And - will it give a spirited fast road performance with a 1310. For this I have chosen 21253 pistons as they should be good enough for weekend blasts and show visits. 21253 pistons are approx 18 though higher in the block than standard from my guesstimates. This is a recently new cam (in an A-Series world) so feedback is useful for us all - any comments?.

[Cooperman]

Personally I wouldn't bother with the 1.5:1 rockers. When I fitted these to my 1293 'S' engine with its 286 cam, 11:1 CR, 35.6/29.5 mm valves, twin H4's, etc., I only gained 2 bhp at 5700 rpm upwards and lost a bit low down where it doesn't have much anyway. A lot of cash for no real gain.

Apart from that your spec looks excellent so long as you are going to keep the revs high.

[PandO]

So.... as a SW8 has similar characteristics to a 286 1.5 rockers would offer a lose/win then. My problem  is I need a new set of rockers and it's a choice between 2'nd hand sintereds for about £20-£25, 1.5 Minispares forged (£130) or something like MED 1.3 or 1.5 at £220.  I've heard tales of minisport roller rockers breaking so I will steer clear of those. A pressed steel standard set I have will be kept for a spare standard 1275GT engine I'm keeping so I can revert to original spec if ever needed.  I'm still wondering whether a SW5, 266, 276 or stick with my original plan for a MG Metro cam. Cam kits that offer a pump, followers and springs make a new cam more of an attraction. So much to consider and the IMM is in 3 weeks!  

[Orange-Phantom]

FYI the SW10 is Swiftune's version of the 286.

 

http://www.swiftune....t-camshaft.aspx

[PandO]

Thanks for then correction. I have experience of the Kent 286 - used one in a 5 speed Morris Traveller 1000 (Toyota box). It was drivable in traffic even with a huge step between 1'st and 2'nd gear (The ex Celica box was not ideal).  I tried it with 2 diffs (high/low) ratios but had an annoying flat spot circa 4,600 rpm which was not good and I'm not keen to have this in a 3.44 diff Mini at motorway cruising speed.  (I tried a HIF6 and needle swaps and a Weber with various adjustments - maybe I timed the cam wrong - I allowed a degree for chain stretch though). So am I right in thinking that the SW8 is somewhere in 266 or 276 territory and if so closest to which?  Cams are so important - get it wrong and you either learn to live with it or try again with time and costs mounting I'm grateful for any advice.  Thanks.    

[TR7]

this is why I asked the question as im at the point of choosing cam for my engine build and don't want to get it wrong

Edited by TR7, 09 July 2014 - 02:44 PM.

[ACDodd]

Happy the measure one if you need the specs. Just send it to me. This way we can compare it properly.

Ac

[PandO]

More to the suitability of the SW8 to fast road use (especially in a 1300). MED market cams made by Piper - their ST1 HT (High Torque) and RS (Road Sport). Figures they give for power band are 1000 to 6000 and 1250 to 6500 rpm repectively. Their sales desk said "expect 4-5 hp extra with the RS" and "both are ok with 1.5 rockers" (i.e no real trade off bwtween low rpm torque and high rpm hp). A kit with oil pump, followers and springs is identical in price (to a few pence) to Swiftunes kits.  Maybe I should check my date of birth (1949) and stick a MG Metro cam in and enjoy some mpg.  Nah - not what I'd really like - my daily car is a 6 speed 2ltr Diesel Turbo (2000 rpm is 80+ mph) and what I want is to have something that is a pleasure to rev. I'll be setting a soft rev limiter at 6,250 but with a switchable mode to allow 6500 or more if the need arises.   SW8, 266, 276, (286 or SW10 probably not), Piper ST1 RS, SW5 or MG Metro non Turbo version.  What to do.....

[Cooperman]

With a desired max revs of 6250 your ideal cam will give peak power at around 5700 to 5900 rpm, with the 'over-run' to 6250 enabling the engine to be kept right 'on the cam' when demanding maximum performance.

For competition the choice of cam can be critical as it can make a difference of up to, say, a second per lap, but for a road car is it that important? So long as the car drives well, pulls nicely through the gears and is 'friendly' to drive it will be a fun car. A Mini is never going to be fast by modern standards, so if it is a nice-to-drive 'nimble' classic car maybe that's about ideal.

All the cams listed will be OK, obviously excluding the 286 and SW10 which are really competition cams, and you will not notice great differences between them on the road.

Sorry if this doesn't help too much.

[mk1coopers]

I've just gone the whole hog and got a SW23T, this will be used in a car that does sprints and hill climbs, though it is road legal, if it's a bit of a game to drive it on the road so be it

[TR7]

With a desired max revs of 6250 your ideal cam will give peak power at around 5700 to 5900 rpm, with the 'over-run' to 6250 enabling the engine to be kept right 'on the cam' when demanding maximum performance.

For competition the choice of cam can be critical as it can make a difference of up to, say, a second per lap, but for a road car is it that important? So long as the car drives well, pulls nicely through the gears and is 'friendly' to drive it will be a fun car. A Mini is never going to be fast by modern standards, so if it is a nice-to-drive 'nimble' classic car maybe that's about ideal.

All the cams listed will be OK, obviously excluding the 286 and SW10 which are really competition cams, and you will not notice great differences between them on the road.

Sorry if this doesn't help too much.

so what cam would you say would be good for my spec sw5 sw8 or meds st1 rs ?

[Cooperman]

Everyone drives in a different manner, be it on road or track. So the engine characteristics to suit an individual will be different for different drivers.

Some drivers love good mid-range torque and value it over sheer top-end power, so they will choose a mild cam.

It is not the cam choice which determines the rate at which a car can be driven down a road, it's how well the driver used the available torque & power to carry the speed smoothly through the corners. 

I come from a serious rallying background and the successful drivers were not necessarily in the most powerful cars. Success was from driving very smoothly, carrying the speed through the corners and having the car set up to give best road-holding combined with superb handling. If you can exit a corner 5 mph faster, then you will carry that speed up to the next corner where your better brakes and car balance will enable later braking and, again, faster speed through the corner.

I used to tell people who wanted to modify their cars to start with the suspension & brakes, then move on to gearing and, finally, to engine modifications.

Then learn to drive very, very smoothly and to carry the speed through the corners.

I know this doesn't answer the cam question but, in a way, it leans towards saying that final cam choice is not critical and a well set-up car will always be quick in relative terms over a given piece of road.

I well remember the 'works' rally Minis which were not really highly tuned and, for some events, had standard 510 cams. They were so torquey that they got good results combined with reliability and ease of driving. 

So, in terms of which cam for road use, I would say whichever gives the best torque at 3500 rpm. Check the cam graphs for the answer to this. Then build the engine very carefully and accurately. I think that, except for racing or hill-climbing, cam choice is a bit irrelevant.

I hope this helps