20 replies to this topic

[crazirob]

Thinking of putting in swiftunes SW23 alternativly a 649 what are peoples suggestions ? and also how do aggressive cams like this perfom for a weekend toy ? on the road ?

Cheers Robbie

[oltonlad]

race profile cams are a stupid idea for a road car............whether its a weekend toy or not, its totally pointless not having any useable power below 4000 rpm.......is your engine built to take 8000rpm then?......because that's how high you will need to rev it to make it go anywhere!!

[86mayfair]

If I remember rightly the 649 was the most extreme cam used by the works cars for road rallies and the SW23 is the cam used in Swiftune's App K engines with a power band between about 4 and 8k rpm. For a fast road car I would have thought it will almost certainly be too extreme as it will drop off the boil too easily. A 286 or SW10 would probably be a better bet

[Cooperman]

It always surprises me how many people want to put full race cams into their road cars. As 'Oltonlad' so rightly says the sort of cams suggested by the OP will require the use of 5000 rpm to 7000 rpm at all times. Imaging driving around the roads at those sort of revs with the very low FDR necessary just to pull away. With a race engine on a track the revs can be kept above 6000 all the time, but that really is impossible on the road.
Even a 286 cam, which is what a lot of us use in our full-spec rally Minis can be very lumpy and not too pleasant on the road even with, say, a 3.9:1 FDR and a SC CR gearbox.
To summarise, a road car is not a race car. The requirements are totally different. A race car goes to the track on a trailer, has its engine re-built very frequently and can be a 'pig' to drive other than on a track. A road car has good mid-range, i.e. 2200 rpm to 5000 rpm, torque, is smooth on the road, is reliable and lasts more than just a few hours running time.

[adam davies]

I decided to go for a kent 276 for my 1293. it's got a suitable power band for a road car that should deliver a good bit of power. Haven't finished the engine yet so I can't comment on results

[Cooperman]

I decided to go for a kent 276 for my 1293. it's got a suitable power band for a road car that should deliver a good bit of power. Haven't finished the engine yet so I can't comment on results

You will love it. Torque strong from about 2800 rpm and peak power at about 6100 rpm.

[bmcecosse]

You ask for a Race Cam - so the Super sprint is the one for you. But as other's have said, you will need to take it to the track on a trailer, and have the engine built for 8000 revs - maybe more! It's not going to be inexpensive. The most extreme cam I have ever used on a road car was the good old 544 -an excellent cam, but not ideal for idling along in traffic jams - but then , I don't do traffic jams !

[Cooperman]

Yes, the old 544 was great in a rally application and I've used them. The 286 is a more modern equivalent and a bit better, but max power is at 6400 rpm and for the road you do really need a close ratio gearbox and lower final drive and still it's lumpy in traffic and below about 3000 rpm when hot. To get optimum performance from a 286 equipped engine you need to be able to use about 6700 rpm often which means more frequent engine re-builds.
There is no point in having a 'hot' cam like this if you want to drive in day-to-day traffic on public roads.

[crazirob]

I had a 276 in my 998, and my cousin Dom has one in his mini and I can't say that I have seen anything amazing out of his as of yet .....
The engine is being build built to withstand up to 8000rpm it's actually being built to miglia spec but would only go that high on a very very rare occasion! I understand that full on race cams are meant to be driven hard hense the rev bandings, the next question I would then go on to which cam would then have the biggest rev range ? I am swaying still for the 649 cam as its a renound camshaft however with so many copies who's is the best .....

Cheers guys !

[phil hill]

I have an SW10 in a 1293cc with 10.5:1 static compression, twin 1.5 SU's and a 3.6FD on close ratio gears. It's very tractable and torquey, and will just about cope with traffic. It hunts a bit on and off the throttle and the idle is a bit lopy but passes emissions test every year no problem. IMHO I would consider this cam for a fast road car on a single 1.75 SU and maybe a 3.4 FD and standard gears to be "just about" acceptable for daily use if well set up, and that's the key.

In a previous engine (1380cc) I had a Kent 276 and it was ok on standard rockers but (IMO) lost an unacceptable amount of low end torque when I fitted 1.5 rockers. Admittedly I didn't check the static compression when the 1.5's were fitted, I checked after I stripped the engine and found it was down in the 9:1 area, which I would consider low for these types of cams.

The problem as already hightlighted is that of perception. One man's race cam is another mans daily driver. If you want a "weekend warrior" type of car then the SW10/286 equivalent is a good starting point, if it's more of a race car then go higher but don't expect it to be friendly in any traffic situations. A low FD would be essential, 3.6 or 3.9 for example.

I think (again IMHO) the old cam profiles should be confined to the history books, there are so many more "modern" grinds/versions which have proven to be better that I really wouldn't bother with them unless it's mandated by regulations in which-ever race or rally series you are running in. If the engine you're building is to miglia spec then the mandated cam is STR930, which is a metro-ised version of 649 (from memory !!).

Check out the modern grinds from Swiftune, Russel Engineering/Keith Calver and ACDodd to name a couple of others to research.

Phil.

[Cooperman]

With a road going car, do owners who fit 'hot' cams which peak at maybe 6500 rpm or higher, drive around the public roads at those revs all the time?
If they don't then they have the advantages of a 'hot' cam, but don't really use this advantage. They do, however, have the disadvantages at mid and lower revs and have to tolerate the lack of driveability in day-to-day traffic.

[phil hill]

With a road going car, do owners who fit 'hot' cams which peak at maybe 6500 rpm or higher, drive around the public roads at those revs all the time?
If they don't then they have the advantages of a 'hot' cam, but don't really use this advantage. They do, however, have the disadvantages at mid and lower revs and have to tolerate the lack of driveability in day-to-day traffic.

Agreed Peter, but again this can be some-what mitigated by carefully selecting a modern (high lift/short duration) cam design and using a suitable compression ratio to offset the low torque output/VE at lower rpm. The engine will still display some of the anti-social trates inherent in the cam design, but at least won't feel quite so "cammy" in use and provide "acceptable" performance when "off cam".

I think the trick is not to delude yourself into "over-camming" an engine which is generally going to be used in "normal road traffic" situations. Back to the perception problem again !!

Living in Lincolnshire I don't have such a problem with traffic, so the foray's into 6K+ rpm are possible, and as the car is basically a road legal Mini Se7en it's pretty anti-social for daily use anyway. Using the car for the commute in traffic,as I have done in the past, is less pleasurable !!

Phil.

[Cooperman]

With a road going car, do owners who fit 'hot' cams which peak at maybe 6500 rpm or higher, drive around the public roads at those revs all the time?
If they don't then they have the advantages of a 'hot' cam, but don't really use this advantage. They do, however, have the disadvantages at mid and lower revs and have to tolerate the lack of driveability in day-to-day traffic.

Agreed Peter, but again this can be some-what mitigated by carefully selecting a modern (high lift/short duration) cam design and using a suitable compression ratio to offset the low torque output/VE at lower rpm. The engine will still display some of the anti-social trates inherent in the cam design, but at least won't feel quite so "cammy" in use and provide "acceptable" performance when "off cam".

I think the trick is not to delude yourself into "over-camming" an engine which is generally going to be used in "normal road traffic" situations. Back to the perception problem again !!

Living in Lincolnshire I don't have such a problem with traffic, so the foray's into 6K+ rpm are possible, and as the car is basically a road legal Mini Se7en it's pretty anti-social for daily use anyway. Using the car for the commute in traffic,as I have done in the past, is less pleasurable !!

Phil.

I have that issue with my rally 'S' which has a 286, 11.2:1 CR, 1.5 rockers, twin H4's, etc. Even with a 3.9:1 FDR and SC CR gearbox it is quite nasty in traffic and nowhere near as nice as my Innocenti 1275 Cooper which has an original 510 'S' cam and twin HS2's. That is lovely to drive in all road conditions, will cruise at 80 mph all day, is brisk the same as an original 1275 'S' and with the suspension settings I have has excellent road-holding and predictable handling.
I often wonder whether people fit these really 'hot' cams to road cars before driving a similar set-up to see if they like it.
Unless a car with a 'hot' cam is driven in the best rev range all the timer, it will actually be slower overall than a less 'hot' cammed car. It's the useable area under the cam graph which determines how the car will perform.

[phil hill]

I have that issue with my rally 'S' which has a 286, 11.2:1 CR, 1.5 rockers, twin H4's, etc. Even with a 3.9:1 FDR and SC CR gearbox it is quite nasty in traffic and nowhere near as nice as my Innocenti 1275 Cooper which has an original 510 'S' cam and twin HS2's. That is lovely to drive in all road conditions, will cruise at 80 mph all day, is brisk the same as an original 1275 'S' and with the suspension settings I have has excellent road-holding and predictable handling.
I often wonder whether people fit these really 'hot' cams to road cars before driving a similar set-up to see if they like it.
Unless a car with a 'hot' cam is driven in the best rev range all the timer, it will actually be slower overall than a less 'hot' cammed car. It's the useable area under the cam graph which determines how the car will perform.

Yep I understand. For my daily driver mini I'm using an SW5 on a 1275cc with a nicely modified head at about 9.5:1 static compression and a single 1.75 SU. Should be nice for the daily run, maybe a little too tame, but we'll see when it's finished !!

Phil.

[crazirob]

so im confused now ? if i put in a sw10 it will be ok? i understand that the "hot cams" are going to be a bit "pigs" when in traffic, this car is pretty much being built for a rare daily commuter and like you say a weekend warrior and track machine, im pretty sure from memory the FD in my gear box is 3.4 also that the Carb i will be using is a weber 45 dcoe, im told with the correct cam i could potentially be getting a power figure of about 115-125 hense why i am doing a little bit of research.

thanks again