Why is it that Subaru's don't seem to have any cam work in comparison to other cars? An Evo for example makes a good deal of extra power with some better cams, better powerband etc. So why aren't they used for us very often?

 

Are you kidding?

Plenty of builds around using aftermarket cams.

That said stock STI heads/cams are good for 500bhp+ even more so on stock AVCS heads.

 

No I'm not kidding. People don't use them unless they're going for big power it would seem, whereas on other cars, they seem to be a step even before upgrading the turbo in some instances..

 

As Daz said, the cams are good for 500bhp, so why bother is the simple answer. Also, they're a pain in the **** to fit and there are 4 of them.

 

I'd imagine the cams are good for 500bhp in a few cars, but surely there is a benefit to fitting them? Cost efficiency aside?

 

Its pretty simple really.
On the classic wrx and UK head/cams were reasonably restrictive. Swapping from them to stock STI/P1 heads gave good gains and as has been said are good for 500bhp plus.

Anything above that and you'd need to look at cams valves porting polishing etc.

The reason people dont swap cams at <500bhp is the cost.
A decent set of aftermarket cams cost around £600-£800
It's simply £600-£800 you dont need to spend unless going for more than 500bhp.

I'll be doing a back to back comparission soon on my newly built motor.
Everything in place for circa 600bhp going to run some 2006 WRX AVCS heads with new valves and double valve springs but with standard cams for the time being. Then once the motor is run I intend to swap for some Cosworth S2 Cams. I've always wanted to know exactly what difference cams make. Nothing else will be changed so it should be a good test.

But to summarise buying cams for less than 500bhp is pretty pointless to be honest.

 

Hey Daz, costs notwithstanding, could aftermarket cams be used inconjuntion with AVCS to help deliver torque 'earlier' in the rpm band - I mean even more than AVCS by itself? I know cams are usually profiled to aid top end power which, as you've highlighted here, is not an issue for us. I'm always on the lookout for anything which aids torque below 3000rpm.

 

while were on the subject of cams what are the limits of my wrx 98 import heads as im running 390bhp is there room for more or am i on the limit now

 

Different cams do different things so it depends what you want. Its a trade off to be honest if you want power low down you lose it at the top. The trick is finding the point of balance I guess. I'm no expert by far but for AVCS heads I think the Cosworth S2 cams are hard to beat they seem to have cracked it in that they aid low down response and Give power at the top. But that's the AVCS working too dont forget.

In non AVCS heads the DH22 cams are supposed to be pretty good. I've been in a car 600+car with them in and it was awesome.

I will state that I dont think cams are needed until you're well above 400bhp if you have STI heads.

 

Ahh, makes sense. Ok, pretend for a moment that I'm not interested in peak figures or top-end performance and all I'm looking to do is lift the torque up below 3000rpm. Could you point me toward cams that will do this with AVCS but better than AVCS on it's own? (BTW my car is nearer 320ish bhp). I do have STI heads presumably since it's a 54 STI8.

 

I cant in all fairness recommend some cams purely for this purpose. I honestly think that the cost of cams and re shimming would be better spent elsewhere first.

If you want an endorsement for standard heads and standard cams look no further than Duncan Grahams Time Attack winning car. That's had everything done to it apart from the heads which are as they came out of the Subaru Factory. Which will be the same as yours.

If you want quicker spool and more torque low down then look at converting to a twinscroll set up
but this again can be quite costly.

 

Ok, not to pin you down too much (hope not anyway!) - assuming that the better things had already been bought and done and cams were all that were left to look at. Could you suggest where to look then?

I'll 'guess' that Dunx cams are for mid-high RPM performance, i.e. totally opposite to what I 'may' be looking for hypothetically.

 

I'm going to be using the Cosworth S2 cams on mine. It might be worth talking to Mark @ Lateral Performance he'll be able to advise on something more suitable to your requirements.

Duncan Graham's cams and heads are completely standard.
Duncan Graham is Dynamix not Dunx btw

 

Oops - thanks, apologies to Dunx and Duncan. My Lysdexia surfacing again...

Will speak to Mark.

 

You won't gain anything at 3000 rpm by changing cams. We only bother if we're going over 600 bhp, with flowed heads as well.

 

Andrew .. just change gear

Get a T on there with a 2.5 bottom end and you will have all the bottom end torque you could dream for.

 

In fairness my heads arent 100% standard - I have had a single wire ring machined into the heads to give better clamping on the head gasket to stop head gasket issues. This has been fine with up to 2.8 bar of boost with 11mm ARP head studs.

 

I didnt want to complicate the issue with that.

I just wanted to demonstrate that changing cams was pretty pointless unless going for big power. As your cams and valve train are standard I thought you'd be a pretty good example to use

Hopefully now that other people have confirmed what I said earlier Axel will take the advice and spend his "cam" money elsewhere

 

indeed.

 

Wasn't there a thread on here about "swisstonyhasher" changing his cams and all the grief there was including Bob Rawle sorting out all the mapping LOL

Shaun

 

'Cam' cash duly diverted ....Sheepishly clicks 'remove item from basket'


Cheers for the gear tip Duncan. And I thought the big stick in the middle was to stop women sliding off onto the floor....

 

For what its worth, Im not that convinced the twin scoll setup will improve things much before 3k- I have fitted one to my classic, and its still mainly above 3k, although not happy with mapping so going to get it done again to see.

If you are really serious, nitrous low down, or if you are feeling super flush, a twin charger kit

 

Sorry mate.

Having seen what the heads and cams work do it is all top end.

I believe Andy F had 1.5 bar of boost on a T at 2500rpm on the 2.5 - should be a fair chunk of torque there. My 321V gets 2 bar at 3000 - again more than enough.

I will bring it down and take you for a spin in it to show you what low down torque is. Remember you have 25% bigger capacity to work with anyway so torque is way up even when the turbo isnt spinning.

 

That must be a nice wide powerband you have there Duncan when does power start to tail off?

 

7800

 

Nice!!!!

 

Can i just add that changing cams isnt just the cams.

More aggressive cams will generally have higher lift. This will cause the stock springs to be compressed outside of their general operating limits, or at worst to bind up.
This then means a change of valve springs to cope with the extra lift of the new cams. Aftermarket springs generally will have a higher seat pressure than that of stock springs to reduce float under high boost levels.

This increase in seat pressure adds even more stress to the valves. Stock valves are 2 piece items and in cases where the seat pressure is increased it can cause the valve heads to actually separate from the stems causing catastrophic engine failure.

So now youre looking at uprated valves too.

So adding cams is not only the cost of 4 cams, at £600-£800 but the complete swap of the valvetrain to cope with the higher demands of the more aggressive cams. This obviously involves the cost of the engine/head removal to swap out the valvetrain.

So add that little lot up and cams are not a cheap affair.

Gains below 550bhp on AVCS heads simply isnt worth the cost or work unless youre doing a full build anyway.