33 replies to this topic

[Pauly]

Timmy thats a top class reply mate, thanks for that, very understanding and quite interesting.

I did think for the moment why the sw5 was said to be a high lift cam, many people say its very mild.

Paul.

[Shifty]

Problem with SW5 cam is the very high lift - wearing on moving parts - possible valve spring crush. It has very slack timing - gets the result from the lift - but that has many disadvantages.

Not if it's done properly and not with as many disadvantages as getting the result from timing alone (the old fashioned, out of date way of doing it)
Have you actually measured one? The SW5 doesn't have very high lift at all, 0.323" measured at the valve on the one i fitted, with the recommended 15 thou clearance. Thats only 5 thou more than quoted as standard. It may well have more dwell at full lift than standard though, which is the equal of high lift (raising the average port flow throughout the lift cycle) but without the negative effects of increased wear and tear. Much better to have a more rounded lobe and use the rocker ratio to your advantage to get the higher lift if you need it.

Any wear problems are likely due to using extra strong valve springs (due to out of date/incorrect advice) combined with high lift rockers (and likely resultant incorrect valve clearances), especially when used in road cars that spend alot of time idling in traffic, and more than likely with a modern off the shelf oil that doesn't contain the neccessary additives to protect sliding parts on older engine designs.

It seems many are afraid of progress and stuck into the old way of thinking when it comes to cams, and timing. This is probably the reason Swiftune have never released details of their SW5 because no-one would buy it looking at the figures. Same reason Piper have stuck with the 255 name despite the timing figures being much more like the SW5, and probably why no-one ever mentions the Kent sports-torque, (hotter than SW5 but still less than 250 deg duration).

Any advice being given to use such cams as the 731, 544 etc, to people spending their hard earned on building an engine they want the best from, i.e the best in 2009 not 1969, is not good advice in my opinion, especially when second hand.
The only valid reasons for recommending such cams is for absolute period authenticity, where the owner wants a totally period driving experience above all other criteria or they have to comply with period rules, or they have one already and cant afford a new one.
For example, why would you want to fit a 544 when a 266 with 1.5 rockers will make better power everywhere and be really smooth? And if you wanted the race/rally feel of a lumpy cam then why have that and sacrifice all the power at the top? You don't have to because there's the 286 which was developed using the 544 as a starting point and now the SW10 which is a modern development of the 286. And there is surely no argument for using a 731, even a standard MG metro cam (731 exhaust lobe, cooper 997 inlet lobe) only loses out to this by a couple of horse power at the top end and makes much better low down power into the bargain. Of course why would you use that even, when the 266 was developed using the mg metro cam as a starting point!
The list goes on and of course there are even more newcomers now.

I'm not saying the old way doesn't work, of course it does but you get more drivability versus power using modern cams which must increase the smile factor whichever end of the spectrum you wish to use.

Thats one the best replies to a Camshaft topic I've heard in ages, and I agree with every word.

(Oh yeah and the SW5 is a girls cam!!)

[TimmyG]

Thanks guys! A quiet weekend dayshift is handy for getting a point across! Another benefit of using modern cams that i forgot to mention was economy/emissions, a direct by-product of using less duration/overlap. Win-win really me thinks!

[Pauly]

Must have time on your hands then .

Paul.

[bmcecosse]

Something sadly wrong with that SW5 if it only has 5 thou extra lift! It must have worn down already! It has a LOT more lift than that when new. The figures are 'out' - but I just don't have them to hand I'm afraid - but someone will find them, I'm sure!
Edit - Found the figures - 244 duration, and lift is 0.281 at the cam - X 1.27 standard rockers is 0.357 "
Sounds like you have a standard cam there - NOT an SW5!

Edited by bmcecosse, 01 November 2009 - 11:26 AM.

[Asphalt]

I have some sets od data to the SW5:

Use: Mild Road
Name: SW5
Maker: Swiftune
Duration int/ex: 244/244
Intake lift mm: 7,14
Exhaust lift mm: 7,14
Int Lift inch: 0,281
Ex lift inch: 0,281
Power band: 1000-6000
Max RPM:
LCA: 108,0
Overlap: 28
Valve lift 1.25 Int: 0,351
1.25 Ex lift : 0,351
Lift 1.3 Int: 0,365
Lift 1.3 Ex: 0,365
Lift 1.5 Int: 0,422
Lift 1.5 Ex: 0,422
Lift 1.7 Int: 0,478
Lift 1.7 Ex: 0,478
Suggested C/R: 8.5-9.5

And the measurements by AC Dodd:

Swiftune SW5
Checking height @ lobe: 0.016"
Timing (IN/EX): 16/48 52/12
Nominal lobe lift (IN/EX): 0.281" / 0.281"
Duration (IN/EX): 244 / 244°
Lobe centre angle (IN/EX): 106 / 110
Lobe separation angle: 108.0
Lift on overlap: 0.036"

Swiftune SW5-07
Checking height @ lobe: 0.016"
Timing (IN/EX): 10/52 47/15
Nominal lobe lift (IN/EX): 0.286" / 0.286"
Duration (IN/EX): 242 / 242°
Lobe centre angle (IN/EX): 111 / 106
Lobe separation angle. 108.5
Lift on overlap: 0.0385"

Also note that there are at least TWO versions of that cam! The 'old' SW5 and the renewed SW5-07! So if we talk about the 'SW5' we maybe should agree about which version of that cam we talk as they are obviously quite different!

What those figures hardly show is the concept behind that cam;
Rapid opening to allow early & good flow. As DV once suggested in his famous book.
Which I'd recommend to get a basic understanding of camshafts.

Edited by Asphalt, 01 November 2009 - 11:41 AM.

[bmcecosse]

Your lift figure confirms mine - I used 1.27 as the rocker ratio, but it's also often quoted at 1.25.
I suspect the reasoning for this cam is that it can be cheaply made by regrinding a standard cam - just take 30 thou off the base circle and tidy up the transition to the lobes!

[Asphalt]

So it would be interesting if 'billet' cams have more lift! Which I would assume they have (would be a waste if not)...

[bmcecosse]

Ehh? 'billet' just suggests they have been ground from a 'billet' of steel - rather than reground from a standard cam. The lift can be whatever the designer decides - within the limitations of the space inside the engine.

[Pauly]

Does anyone have the spec of the mg metro cam, just out of curiosity.

Paul.

[Asphalt]

Of course!

MG Metro, RSP Coopers, Metro GTA:

Checking height @ lobe: 0.017"
Timing (IN/EX): 16/56 59/29
Nominal lobe lift (IN/EX): 0.263" / 0.263"
Duration (IN/EX): 252 / 268°
Lobe centre angle (IN/EX): 110 / 105
Lobe separation angle: 107.5
Lift on overlap: 0.054"
ID: 1/4" single groove bet. lobes 7 & 8

From AC Dodds measurements...

@bmcecosse:
I meant it would be possible to get a higher lift from a billet made cam than it would be possible from a reground, if I'm not misstaken... And as I heared Swiftune now only offer billet made cams for that reason. But I don't know for sure... Got me now?

[edit] Cam timings list... Excell sheet. Right click -> save target as
http://www.mini-mayf...en/Minicams.xls

Edited by Asphalt, 02 November 2009 - 01:40 PM.

[TimmyG]

Something sadly wrong with that SW5 if it only has 5 thou extra lift! It must have worn down already! It has a LOT more lift than that when new. The figures are 'out' - but I just don't have them to hand I'm afraid - but someone will find them, I'm sure!
Edit - Found the figures - 244 duration, and lift is 0.281 at the cam - X 1.27 standard rockers is 0.357 "
Sounds like you have a standard cam there - NOT an SW5!

Thats what i thought after i'd checked it but no, it is an SW5 (not -07 or billet), a brand new one in fact ordered from Swiftune, and yes, at first i was a little dissapointed. However on the road it's great. I have it fitted to a 1030 with mg metro head and it goes very well indeed ( 50+hp@wheels).
The figures i obtained were very similar to those quoted earlier, 240 deg duration, 15/45 inlet, 50/10 exhaust, mild indeed.
The problem is the standard sintered rockers don't give anything like 1.27 ratio, in fact mine weren't even 1.21 at full lift if i remember correctly!
So in all likelyhood, the SW5 was giving more than 5 thou extra lift (actual) over the standard cam with the same rockers, but only 5 thou more than what is quoted as standard lift in the manuals. I never bothered to measure the standard figure at the time but i wish i did now for a better comparison.

[Pauly]

Would a piper 255 be a long the same lines as the mg cam?

http://www.pipercams...t.php?pid=BP255

Paul.

Edited by Pauly, 02 November 2009 - 09:08 PM.

[Shifty]

Sorry to Hijack Pauly!!(but I'm gonna anyway!!)

So based on the rocker ratio figures would a set of decent 1.3 ratio rockers make a difference then?

[TimmyG]

Sorry to Hijack Pauly!!(but I'm gonna anyway!!)

So based on the rocker ratio figures would a set of decent 1.3 ratio rockers make a difference then?

If it's compared to the sintered rockers, Definately!