500 Camshaft Selection

[fastandcurious]

I know it's a subject that's been covered many times before and I've read v8 racing's 2007 write up on camshaft selection, but I just wanted to gather a few constructive comments on more recently fitted cams. I want the best all rounder with good idle, good mid range torque and good top end. It would be good to hear from those of you who have recently fitted cams and how the car drives and what the options are.


Many Thanks

Craig

[The Red Baron]

I've got TVR Power's 885 cam. Pulls very well all the way through the rev range and idles through town nicely too.

[Pupp]

fastandcurious said:

I know it's a subject that's been covered many times before and I've read v8 racing's 2007 write up on camshaft selection, but I just wanted to gather a few constructive comments on more recently fitted cams. I want the best all rounder with good idle, good mid range torque and good top end. It would be good to hear from those of you who have recently fitted cams and how the car drives and what the options are.


Many Thanks

Craig

What do you consider a good top end to be?

[chris52]

Mines a Dave Ellis 5.0ltr Hi-Torque cam, It has plenty of power throughout the rev range here is a graph
The red line was standard with just the cam the blue line is after I fitted the smoothbore pipes, magnacore leads and carbon trumpets.

Hope its of some help

Chris

[steve-V8s]

You are right it has been discussed before and if you have read Rob’s post you already know most everything there is to know. The single most important thing however is to decide how you want the car to drive.

In an ideal world there would be a cam that gave smooth tick over, nice progressive power delivery on a light throttle, and lots of torque right from tick over to the rev limiter. Sadly that is not possible.

My simplistic understanding is all cam profiles have a limited rev range over which they work well, cleverly designed cams have a slightly wider useable range than others. What you need to do is decide where in the rev range you want the engine to work well, If you want lots of power it will have to work higher up the rev range in which case it will not work so well low down.

Low down torque makes the car feel fast but you won't win the contest if bragging about peak BHP and probably wouldn’t win any races. Arguably low down torque makes the car much nicer to drive.

One way you can slightly broaden the useable rev range is to improve the induction system to let more air in and improve the engine management system so you can at least control the ignition timing but that is an entirely different question to what cam should I use.

[fastandcurious]

Pupp said:

fastandcurious said:

I know it's a subject that's been covered many times before and I've read v8 racing's 2007 write up on camshaft selection, but I just wanted to gather a few constructive comments on more recently fitted cams. I want the best all rounder with good idle, good mid range torque and good top end. It would be good to hear from those of you who have recently fitted cams and how the car drives and what the options are.


Many Thanks

Craig

What do you consider a good top end to be?

Something better than what I have now. My car has done about 80K on the original cam and I am aware that the cam must be showing some wear. Although it still pulls well with good mid range torque it doesn't seem so lively in the upper revs. I am hoping to achieve somewhere around the 300 BHP mark without sacrificing bottom end, albeit with the help of a 72mm throttle body and plenum.

[fastandcurious]

chris52 said:

Mines a Dave Ellis 5.0ltr Hi-Torque cam, It has plenty of power throughout the rev range here is a graph
The red line was standard with just the cam the blue line is after I fitted the smoothbore pipes, magnacore leads and carbon trumpets.

Hope its of some help

Chris

I would be very happy with those figures. That would be good enough for me!

[TVR Beaver]

The Red Baron said:

I've got TVR Power's 885 cam. Pulls very well all the way through the rev range and idles through town nicely too.

+1... I like mine!!

[fastandcurious]

steve-V8s said:

You are right it has been discussed before and if you have read Rob’s post you already know most everything there is to know. The single most important thing however is to decide how you want the car to drive.

In an ideal world there would be a cam that gave smooth tick over, nice progressive power delivery on a light throttle, and lots of torque right from tick over to the rev limiter. Sadly that is not possible.

My simplistic understanding is all cam profiles have a limited rev range over which they work well, cleverly designed cams have a slightly wider useable range than others. What you need to do is decide where in the rev range you want the engine to work well, If you want lots of power it will have to work higher up the rev range in which case it will not work so well low down.

Low down torque makes the car feel fast but you won't win the contest if bragging about peak BHP and probably wouldn’t win any races. Arguably low down torque makes the car much nicer to drive.

One way you can slightly broaden the useable rev range is to improve the induction system to let more air in and improve the engine management system so you can at least control the ignition timing but that is an entirely different question to what cam should I use.

My car still drives great at the low to middle revs and never feels slow. But could do with a bit more urge in the upper revs. 80k on its first cam isn't bad [it must be worn by now!] A newer version of what is in there might not be a bad idea.

[fastandcurious]

Quinny said:

fastandcurious said:

I want the best all rounder with good idle, good mid range torque and good top end.

Let me know if you find such a cam eh

That sounds like the voice of disappointment if ever I heard one

[fastandcurious]

Quinny said:

At 80k you say it must be worn.... but what makes you think so???

My mate Ash's car is over 105k now, and no indication that its had a cam change.... His car is pretty similar to mine, in performance...

In fact the only reason I get away from him is that I'm a far better driver

Forget the cam change I'll go on a driving course

[fastandcurious]

Quinny said:

fastandcurious said:

Quinny said:

fastandcurious said:

I want the best all rounder with good idle, good mid range torque and good top end.

Let me know if you find such a cam eh

That sounds like the voice of disappointment if ever I heard one

Not at all

But having tried a number of different cams, I'd be suprised if there's one out there that meets all your criteria...

My experience is

MC1... Brilliant tickover, very good mid range... Bit weak at the top end (275 bhp)
H404.. Poor bottom end, reasonable mid range... very very strong top end (302 bhp)
Stealth.. Good bottom end, fair mid range...reasonable top end...(288 bhp)


So for me, the best compromise, and that's what all cams are.. is the Stealth...

It seem that with pretty much any cam, you can only achieve 2 out of 3 if you see what I mean

Mine is like the MC1. A great drive most of the time, but could do with a bit more at the top. Do you really notice the 13 bhp increase from the MC1 to the Stealth?

[fastandcurious]

Quinny said:

Yes....

Just like I could tell the loss of the 14 BHP between the Stealth and the H404...

But I just couldn't live with the H404's low down bad manners..

You have to be realistic in your expectations.. its far more to do with how the car drives, than numbers on a dyno...

My car spends 99% of its time between 2k and 4k rpm... so thats where its important to run nicely.
Ok it may lack a few BHP at the top end, but how often do I go up there??? Not very is the answer, so a few BHP lost up there is of little concern...

I'd much rather my car to have strong overtaking ability, and be quick up to say 120, 130 mph...

Anything after that is pub talk, cos you never get to use it..

What you're saying makes a lot of sense. The beauty of these cars is you don't have to thrash them.

[clive f]

hello Craig, long time no see on here, hows things?

[domV8]

FYI,

My 4.6l RV8 running TVR Powers TVR885 cam - so you can see the cam characteristics...



Believe the torque drops early due to the 38mm intake runners strangling the flow, rather than the delivery characteristics of the cam.

Plenum & intake manifold to be switched to 45mm shortly, will report to show difference after that.

HTH...


Dom

[Pupp]

Interesting that everyone seems to think of 'top end' in terms of a particular HP figure (say 300), rather than in terms of usable rpm

[TVR Beaver]

domV8 said:

FYI,

My 4.6l RV8 running TVR Powers TVR885 cam - so you can see the cam characteristics...



Believe the torque drops early due to the 38mm intake runners strangling the flow, rather than the delivery characteristics of the cam.

Plenum & intake manifold to be switched to 45mm shortly, will report to show difference after that.

HTH...


Dom

Yes.. but nice low down torque... Increase the runner and you may reduce this a bit at the lower end... also fitting shorter runners will rob torque lower down and move it up a tad....

[dbv8]

I thought it was the valvetrain which was the limiting factor on the revability. These long duration cams are supposed to have high revving power bands but we always see the power and torque tail off not much more that 5000rpm ?????

[spend]

I can't say I'm convinced that the serp oil pump delivers enough pressure to the rumpy pumpy followers at higher rpm. The pump is good enough but its pressure relief valve seems to cut the delivery to early so that the pressure normally seen on pre-serps at high rpm is gone? Solid cams or upgraded followers do seem to have benefits greater than the sum of parts on the serps particularly I think, ie some pre-serps have made similar mods and been a bit disappointed - but they already had the rpms as a starting point IYSWIM?

Even the clockwork dizzy should still be quite happy to function above 6000.

The valve train itself should be good for 6500rpm bursts no problem.. whether the valves are opening exactly when you expect them to might be another matter?

It's only really if you want to exceed 6500 you start to need getting esoteric IMHO.

[Pupp]

On hydraulics but with outriggers on the rocker shafts... 6k was the limiter cut then but will spin on to 7 quite happily. If they want to rev, let 'em