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Camshaft Choice Sw10 (Or Sw8), Re13Pp/re13Ot Or M E D X T

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#1 buzcooper

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Posted 10 February 2014 - 09:52 AM

Hi,

 

I'm in the middle of a refreshing my 1380 lump and will change the cam for a more sporty profile (not sure whats in it until later in the week)

 

I'm intending to do some more trackdays, sprints and hillclimbs and want some more power.

 

But the car needs to remain road legal.

 

It's currently got a Morspeed st3 head, which will be upgraded at a later stage.

 

It's got 1.5 ratio roller rockers and a HIF44.

 

The plan is to fit a set of close ratio set of gears to help keep "on-cam" (not sure for where as yet?).

 

I'm interested in any thoughts and experiences with similar setups, perhaps with the exception of the SW8 which is too new but tempting!

 

Cheers

Paul



#2 buzcooper

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Posted 10 February 2014 - 08:46 PM

Hmm so the engine is now split and the cam is out and it's a Morspeed 3....how does that relate the the ones I was thinking of buying?

 

The Morspeed phase 3 (trackday cam) Based on 1 example only; 

Checking height: 0.016" @ lobe 

Timing: (Intake): 27/63 (Exhaust): 63/27 

Nominal lobe lift: (Intake): 0.315" (Exhaust): 0.311" 

Duration (Intake): 270 (Exhaust): 270 

Lobe centre angle (Intake): 108 (Exhaust): 108 

Lobe separation angle: 108 

Lift on overlap: 0.065" 

Accuracy: Good 

 

 

The timing dots were aligned, so perhaps it wasn't timed up as per other threads, although it pulled ok.

 

(http://www.theminifo...e-3-cam-timing/)

 

http://s1300.photobu...6a9eea.jpg.html

 

http://s1300.photobu...b264d1.jpg.html

 

 

Don't know what to do now :ohno:



#3 Cooperman

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Posted 10 February 2014 - 08:57 PM

That is a pretty average cam about equal to a Kent 276.

For sprints and hill-climbs it would be best to go for a Kent 286 with a straight cut close ratio gearbox and a 3.9:1 final drive ratio. The engine will need to be fully lightened and balanced and be able to sustain 6500 rpm through the gears with a peak rpm of c.7000.
That with a really well gas-flowed head and good induction, exhaust and ignition systems will give serious power.

#4 buzcooper

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Posted 17 February 2014 - 05:37 PM

Ok, Thanks.

 

Any reason why a Kent 286 rather than a SW10 (286 with "but more efficient on idle to help the MOT emission test" according to the blurb)?



#5 phil hill

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Posted 17 February 2014 - 07:45 PM

I've not driven a car with a "straight" 286 but my trackday car has the SW10 and it's very tractable so my vote would be to go for SW10.

 

Having said that a friend of mine has an SW23 (which is a "modern interpretation" of the 649/STR930) in a sprint/track car and he raves about it.

 

Phil.



#6 Cooperman

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Posted 17 February 2014 - 08:47 PM

I really do believe that after 60 years of A-series engines, there is very little to choose between the various 'top end cams'. Of course, different companies will make claims that theirs are superior in one way or another, but in the end there cannot be very much difference if the cam specification is similar. It is also down to how well the head suits the cam, the build quality of the entire engine, the compression ratio, the ignition system, etc.

There might be a couple of bhp at the top end with one cam rather than another, or a lb.ft. extra torque at lower revs, but in the end the base unit is the same and all sorts of experts have been doing cam design for 60 years, so are they now just 'turd polishing'? I mean, there is not suddenly going to be a cam with the bottom end torque of, say, a BMC 510 and the top end of a Kent 296 or a BMC  649.

Then again, a lot of it is down to the gearing and final drive ratio used. It is not just about cam choice.



#7 buzcooper

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Posted 17 February 2014 - 09:18 PM

I suppose what I was after was a steer in the right direction and the hope that I'd pick a suitable cam from all the marketing bull that is around. I guess it's all a bit subjective and a case of suck it and see. I'm not bothered (at the moment) about ultimate BHP but didn't want to go too soft or too hardcore! I've plotted the swiftune "figures" and the SW10 looks good from 4000rpm and doesn't look too extreme....I wonder what a sw23 looks like!

 

 

 

NB: Figures read from online picture of power curve and should be taken with a very large pinch of salt!!!!

 

SwiftuneCams_zps70635e79.jpg


Edited by buzcooper, 17 February 2014 - 09:21 PM.


#8 Cooperman

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Posted 17 February 2014 - 10:21 PM

Are those independent figures or from the cam manufacturers?

I take all the cam claims with a very large pinch of salt as well and I still think it's 'turd polishing!'.

All the cam manufacturers will claim that their cam(s) will be better than anyone else's - well they would say that, wouldn't they.

I once did a group test for Mini Magazine of 9 historic rally Minis. The one with the genuine 649 cam, the LSD and the Weber was fastest down the standing start 1/4 mile, but mine, with twin 1.5" SU's and a 286 was noticeably quicker around the 'rally stage'. Another car with a standard 510 Cooper 'S' cam was fastest on an Autotest' type stage. So it's not just the cam, it's the application.

Of course, for circuit racing the ultimate bhp will be a bigger issue than for any other type of use and 2 bhp can be a few tenths of a second per lap, but still the quality and accuracy of engine build is critical.

One of the quickest Mini in overall terms I have driven had a fully blueprinted 1275 engine with an MG Metro cam and head together with a superbly accurate build. It gave 85 bhp at 5700 and with a 3.44:1 FDR was quite simply a delight to drive everywhere.



#9 buzcooper

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Posted 18 February 2014 - 07:37 AM

I wouldn't even claim that the figures are accurate, I simply "read" the figures off the picture of the power curve from the swiftune website, so yes big pinch of salt!

Interesting information on the rally car test, real world examples are the only ones to trust.

Is the magazine/article available anywhere?

#10 Midas Mk1

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Posted 18 February 2014 - 08:24 AM

Sw10 is simply awesome. 



#11 phil hill

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Posted 18 February 2014 - 10:41 AM

I know where you're coming from Peter, there can clearly be no "wonder cam" for the A-series, with both low down torque of a road cam and the all out power of a race cam.  As you know this is why many manufacturers have two-stage cam grinds or clever timing control mechanisms in modern engines. And gearing, compression, breathing and attention to detail all play a very significant part in how an engine performs.

 

There can only be so many variations on a theme, or so many degrees of timing to be played with.  I think (or maybe that is I hope.....) that the modern cam profiles have had some degree of intelligence behind their design, be that from experience of what works (as in the Russell/AC Dodd ones) or some modern modelling/simulation backed up with dyno time (as in the Swiftune ones).  This is what Vizard did for the Megadyne range back in the late 70's after all, but time and experience moves on.

 

As many "new" cams are ground on fresh blanks they can have much more lift than previous grinds, which seems to be where the "old" grinds were perhaps lacking, and although it does push the cost a bit it eliminates the variability of supply of serviceable "old" cams to regrind.  Many new grinds have less lift-on-overlap to help with emissions too. Modern grinding machines must mean that repeatability and quality are improved.

 

So rather than "turd polishing" I like to think of it more as "rolling in glitter". I know I'm splitting infinitives but the mere fact that people *are* still playing with A-Series cams after all these years must be a good thing, mustn't it ??  

 

Phil.



#12 Cooperman

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Posted 18 February 2014 - 10:48 AM

I wouldn't even claim that the figures are accurate, I simply "read" the figures off the picture of the power curve from the swiftune website, so yes big pinch of salt!

Interesting information on the rally car test, real world examples are the only ones to trust.

Is the magazine/article available anywhere?

It was a few years ago and I can't remember the actual date.

The guy who had the 649, LSD & Weber drove mine and asked if he could have my engine spec. I emailed it to him and he had his engine and gearbox re-built to exactly my specification (286, twin H4's, X-pin diff, 3.9:1 FDR, etc). On the next proper rally we did he just beat me into 2nd place with him winning - just. Maybe I should have kept quiet :D .

When it is said that this cam or that cam is superb, one must always ask, 'great for what'? For example, the graph for the SW10 shows what appears to be peak power at 7000 rpm, but no peak is actually shown, so what happens after 7000? From the graph it would appear that you would only fit that cam to get absolute maximum power and that you are prepared to build an engine (and frequently re-build it) that will be able to sustain 7500 rpm. That will be a very expensive build. Overall the SW8 looks a better cam unless it is a full race engine.

I would like to see an independent test comparing the profiles of the Kent range, the Piper range and the SW range on an otherwise identical engine. Even that would not really give the full picture as the top end cams would require a different head and induction system and probably a different exhaust for optimum power. I think there is very little difference between the top end cams for motor sport and, certainly on a rally stage, it comes down largely to the driver's ability so long as the engine gives adequate power.

Unless you are seriously racing I still think it's a lot of 'turd polishing' with minor gains and losses at different revs from the different cams.



#13 Cooperman

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Posted 18 February 2014 - 10:57 AM

I know where you're coming from Peter, there can clearly be no "wonder cam" for the A-series, with both low down torque of a road cam and the all out power of a race cam.  As you know this is why many manufacturers have two-stage cam grinds or clever timing control mechanisms in modern engines. And gearing, compression, breathing and attention to detail all play a very significant part in how an engine performs.

 

There can only be so many variations on a theme, or so many degrees of timing to be played with.  I think (or maybe that is I hope.....) that the modern cam profiles have had some degree of intelligence behind their design, be that from experience of what works (as in the Russell/AC Dodd ones) or some modern modelling/simulation backed up with dyno time (as in the Swiftune ones).  This is what Vizard did for the Megadyne range back in the late 70's after all, but time and experience moves on.

 

As many "new" cams are ground on fresh blanks they can have much more lift than previous grinds, which seems to be where the "old" grinds were perhaps lacking, and although it does push the cost a bit it eliminates the variability of supply of serviceable "old" cams to regrind.  Many new grinds have less lift-on-overlap to help with emissions too. Modern grinding machines must mean that repeatability and quality are improved.

 

So rather than "turd polishing" I like to think of it more as "rolling in glitter". I know I'm splitting infinitives but the mere fact that people *are* still playing with A-Series cams after all these years must be a good thing, mustn't it ??  

 

Phil.

I think that you are right in that current CAM manufacturing gives greater accuracy and repeatability, but we need to look at where the market is for these cams. On the road no driver is really going to notice any difference with a couple of bhp or ft.lbs as he/she is not driving against the clock. In motor sport it is very different, but really only racing will show this as a measurement in terms of lap times. In other forms of motor sport it will still not be noticeable. I have long used the 286, and before that the similar 544 in rallying and really cannot tell you how the 286 was better, although it did give a bit more on the rollers. I know there have been times when I felt I was a bit 'over-cammed' and wished I had been using a 276 as it 'fell off the cam' mid corner on gravel (exciting!).

Do some owners really drive about on the public roads at 7000 rpm+ most of the time?

Of course, emissions are a completely new game for tuners, but I don't know many who are too bothered and with classic cars it is not a big issue really.

Still, to be cynical, the cam manufacturers need to come up with small alterations whilst claiming their new offerings as 'groundbreaking' to keep the cash flowing in and to be seeming to be able to 'out-power' their rivals.

For racing a lot seem to still like the old 649. A true classic cam for a classic racing Mini or Sprite/Midget.







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