648 v 643 cam

[wantafaster1]

Or 649 v 544 if you prefer! Can anyone who has tried them tell me at what rpm a 544 would lose out against a 649? Conversely it also must gain against it as it comes on the cam or in the midrange.

Its for a big capacity motor doing tarmac speed events. Has anyone also tried an old style piper HR300?

thanks in advance, all opinions welcome.

[Spider]

On 1275 - 1330 range engines with 1.41 Inlets and 1.21 Exhausts, roughly the usable rev range from a 643 is 2500 to 6250 (maybe 6500) RPMs. Same basic engine with a 648 goes from 4000 to 6500 - 6750. It will rev beyond those upper numbers that I've put here, but it's usefulness / effectiveness is questionable. A 'bigger' engine would pull from lower revs but not likely to rev beyond the numbers I've suggested, probably less.

Variables to these are head work, inlet tract (including carb(s)) exhaust etc, how the cam is timed in and the big one is Dynamic CR. I don't believe Camshafts can be looked at in isolation.

Certainly for the engine you've loosely described and the vehicles intended use, I'd probably start with something along the lines of a 648 and go from there. If you find something close to what you're after, playing around a little with Cam Timing can also pay dividends.

A good head is key here. Yes, we all like good head.

[Smiffy]

If it's really a competition car forget the 544 in fact I'd forget the 649 as well and go with the AGSP from MED.

[wantafaster1]

I've used a 285 style cam in the past and thought it not good enough, I've been told by an old hand re 649 " if it's not broken why fix it".
The piper hr 300 claims to be the best of both the 544 and the 649. But then everyone says their product is the best.
And the vp8c comes strongly recommended, to further confuse the issue.

Tell us more about the agsp!

[mk1coopers]

I've gone all out and gone for a Swiftune SW23T for my car (which does tarmac Sprints and hill climbs in the roadgoing class) once the engines back in the car it will be interesting to compare it with the 895 that was in it, I'm not to fussed about slow speed road manners with this car, on a road only car I've always used the 544 for the best of both worlds

[Smiffy]

To be fair anything in the 544/286/285 range just won't cut it in a competition car, heard good things about the SW23T but can't comment as I've not tried that one.
The other thing is you really need to build the motor around the cam, so as much lightening work as you can afford on the bottom end. As you'll need to be using 8000rpms to get the most out of it.

[JohnA]

AGSP is for Auto Grass Scatter Pattern its power band is 4000/8000 rpm,has anybody used or had any first hand experience with this cam(not in the pub)

[Smiffy]

AGSP is for Auto Grass Scatter Pattern its power band is 4000/8000 rpm,has anybody used or had any first hand experience with this cam(not in the pub)

Yes I have and not just in the pub, like I said I wouldn't be commenting if I hadn't tried it.

[JohnA]

I had a customer with an AGSP cam fitted in a very expensive show car,the engine unit had been supplied by a well know engine builder(often discussed on here,not favourably) with a 3.7 diff running 7x13 wheels. He'd had the car on a rolling road but wasn't happy with the way it was performing, I road tested the car on the country roads I normally use and found the car didn't have much usable power below 4000 revs. Before putting it on the dyno I removed the rocker cover to check the tappets and found the rockershaft screw locking plate and nut laying on the cylinder head. I refitted it, did the tappets, retorqued the head, checked the compressions, after checking the timing and fueling at lower revs I did couple of power runs and the head gasket blew (and no it hadn't overheated). The engine had done just over 700 miles. After a discussion the with the owner who had observerd everything we decided to strip and check over the engine an change the cam. On striping the engine the timing chain was so far out of line it had worn both sprockets and the camshaft bearings hadn't been replaced. The engine was rebuilt with an SW10 camshaft giving 1500 more usable revs and only 2 brake down at 7000 revs. The owner had the engine built when he started the project and as it took him more 3yrs the engine builder wasn't interested in his problems. Fitting camshafts for maximum power with narrow power bands aren't always best for sprints and hillclimbs especially if the driver is inexperienced, a slightly milder cam can often be better and can lessen the need to change the diff ratio, it can also be an advantage in wet especially on slow tight twisty venues. Just thoughts from personal experience

[mk1coopers]

Agreed, slow uphill / tight corners with steep camber changes can be more difficult with a narrow power band, especially in the wet, I'm really looking forward to trying the new combination of parts in my engine knowing that it's been put together by a excellent company who would have told me upfront not to bother with certain items if they thought it wouldn't all work together to produce a suitable engine, as said above it's more about the combination of what you are using than just the cam choice on its own