Selecting Cam Profiles.

[Nee-san]

Hey Guys,

I've searched around the various topics on here for some advice and couldn't really find anything satisfactory.

At the moment I have a built 26 in my 32 gtr.

My question relates to what cam profiles would most benefit my objectives.

Currently I have a 265 inlet cam and a 272 degree exhaust cam, both HKS with a 10.0mm lift, the head has had a quick port and polish and manifolds inlet and exhaust have both been port matched, with valve guides and seats replaced.

I don't like the idea of running unmatched profiles like this so I'm looking to retain one of the cams and match the other, my question is which one ? should i go up in the inlet profile to 272 or back down in the exhaust to 265.

My eventual goal for the engine is 400+awkw using either a big single t78,t88 or possibly a larger set of twins -5's etc.

There are a few of you boys on here who are pretty cluey with this sort of predicament so any help is much appreciated.

Cheers,

Mitch.

[N1GTR]

272's.

[R32 Driver]

272s with a big single

when you say larger -5s do you mean -10s?

[Nee-san]

No sorry i meant -5 and used bigger as an example

So you think the 272's are worthwhile for the bigger punch through the top end, I just would like to keep it to sensible sort of revs like 8-9k Rpm or are these two mutually exclusive.

[Adriano]

What is it about unmatched cams that you dont like?

[Swiper the Fox]

What is it about unmatched cams that you dont like?

x2....id keep what you have if its only a mild port job and you are running std valves...especially if you are getting no increase in lift by changing them.

bit left field but this little bit of info i found the other day supports my theory on camshaft selection...

On naturally-aspirated engine configurations, the cylinder head and camshafts are critical in determining where the power band of the engine begins and how much peak power is produced. While some believe that a good flowing cylinder head is not as important on forced-induction applications, the truth is that the cylinder head and camshaft combination make all the difference. In DRAG Sport testing, we've seen the same engine at the same boost level make twenty percent more power and come into boost sooner with a well-matched cylinder head and camshaft combination. For this application, Yokomaku ported the cylinder head and fitted 1mm-oversized stainless valves into the head. VeilSide's custom valve guides, valve springs and titanium retainers were matched to the VeilSide custom-ground camshafts. The camshafts feature an 11.6mm lift with 280 degrees of advertised intake and 290 degrees of advertised exhaust duration. To channel the flow of air into the cylinder head, Yokomaku used a JUN intake manifold mated to a 100mm VeilSide single throttle body.

the above is a quote from Veilside....yes big camshafts help bring an engine on earlier. We have tested our theory and have proven it to be correct.

Edited March 17, 2010 by Swiper the Fox

[rob82]

x2....id keep what you have if its only a mild port job and you are running std valves...especially if you are getting no increase in lift by changing them.

bit left field but this little bit of info i found the other day supports my theory on camshaft selection...

On naturally-aspirated engine configurations, the cylinder head and camshafts are critical in determining where the power band of the engine begins and how much peak power is produced. While some believe that a good flowing cylinder head is not as important on forced-induction applications, the truth is that the cylinder head and camshaft combination make all the difference. In DRAG Sport testing, we've seen the same engine at the same boost level make twenty percent more power and come into boost sooner with a well-matched cylinder head and camshaft combination. For this application, Yokomaku ported the cylinder head and fitted 1mm-oversized stainless valves into the head. VeilSide's custom valve guides, valve springs and titanium retainers were matched to the VeilSide custom-ground camshafts. The camshafts feature an 11.6mm lift with 280 degrees of advertised intake and 290 degrees of advertised exhaust duration. To channel the flow of air into the cylinder head, Yokomaku used a JUN intake manifold mated to a 100mm VeilSide single throttle body.

the above is a quote from Veilside....yes big camshafts help bring an engine on earlier. We have tested our theory and have proven it to be correct.

Edited March 17, 2010 by rob82

[Nee-san]

I have been advised it was not ideal (everyone has an opinion) Lol, however I do understand the benefit of 'scavenging' my main issue was that it could perhaps make the engine less friendly at lower RPM however unless we are talking gutless under 5k etc, I can live with it for the benefit of huge top end power @ around 8500 RPM.

I guess my question is what do i lose or gain by going either way ?

Thanks for your responses guys

Cheers,

Mitch.

[rob82]

x2....id keep what you have if its only a mild port job and you are running std valves...especially if you are getting no increase in lift by changing them.

bit left field but this little bit of info i found the other day supports my theory on camshaft selection...

On naturally-aspirated engine configurations, the cylinder head and camshafts are critical in determining where the power band of the engine begins and how much peak power is produced. While some believe that a good flowing cylinder head is not as important on forced-induction applications, the truth is that the cylinder head and camshaft combination make all the difference. In DRAG Sport testing, we've seen the same engine at the same boost level make twenty percent more power and come into boost sooner with a well-matched cylinder head and camshaft combination. For this application, Yokomaku ported the cylinder head and fitted 1mm-oversized stainless valves into the head. VeilSide's custom valve guides, valve springs and titanium retainers were matched to the VeilSide custom-ground camshafts. The camshafts feature an 11.6mm lift with 280 degrees of advertised intake and 290 degrees of advertised exhaust duration. To channel the flow of air into the cylinder head, Yokomaku used a JUN intake manifold mated to a 100mm VeilSide single throttle body.

the above is a quote from Veilside....yes big camshafts help bring an engine on earlier. We have tested our theory and have proven it to be correct.

I think you've missed the point of what they were trying to say. If your theory holds then everybody needs 320@50 duration camshafts to bring there 1000hp turbos on at 1500rpm right???? Also notice that camshafts were not the only changes made so its hard to get 100% quantifiable results of the difference in camshaft only changes.

What I believe they were actually trying to say is that the right combination of parts is what will poduce the most area under the curve.

In selecting cams you need to look at where the turbos are going to start making boost - there's no point putting cams in that will work between 2000-5000rpm when your turbos aren't going to make boost until 5000rpm. Select the minimum duration for the rpm range required to make the horspower and get the biggest lift possible - this will keep it responsive off boost and should bring the turbos sooner. For the horsepower your after the 272 in and ex should be fine. The other piece of advice is to try and keep the dynamic compression up by increasing compression ratio.

[STATUS]

Hey Guys,

I've searched around the various topics on here for some advice and couldn't really find anything satisfactory.

At the moment I have a built 26 in my 32 gtr.

My question relates to what cam profiles would most benefit my objectives.

Currently I have a 265 inlet cam and a 272 degree exhaust cam, both HKS with a 10.0mm lift, the head has had a quick port and polish and manifolds inlet and exhaust have both been port matched, with valve guides and seats replaced.

I don't like the idea of running unmatched profiles like this so I'm looking to retain one of the cams and match the other, my question is which one ? should i go up in the inlet profile to 272 or back down in the exhaust to 265.

My eventual goal for the engine is 400+awkw using either a big single t78,t88 or possibly a larger set of twins -5's etc.

There are a few of you boys on here who are pretty cluey with this sort of predicament so any help is much appreciated.

Cheers,

Mitch.

Leave it and play with the gears, one of the best SR20 combos we build for customers uses a split setup of 264 intake and a 272 exhaust.

[Swiper the Fox]

I think you've missed the point of what they were trying to say.

What I believe they were actually trying to say is that the right combination of parts is what will poduce the most area under the curve.

I think you may have missed the point of what i was trying to say...

Ive looked at his combination of parts...rpm range and head mods (porting valves etc)

and told him not to change anything if he is not gaining an increase in lift by changing the inlet cam to 272.

Does this now make sense to you? Rob, what have you found when testing different combo's for low mount twins or high mount singles on GTR's ? If you have found something interesting from real world testing it would be nice to share some of the results here. A few guys testing them on circuit based racecars have also been surprised with running higher than normally is accepted combo's with low mount twins but only when combined with larger valves and extensive port jobs. Mark Berry's R34 is a perfect example of this and i know that Brad from Autosport in Sydney who specialises in circuit cars does more development than most has also found this correct.

Edited March 17, 2010 by Swiper the Fox

[rob82]

I think you may have missed the point of what i was trying to say...

Ive looked at his combination of parts...rpm range and head mods (porting valves etc)

and told him not to change anything if he is not gaining an increase in lift by changing the inlet cam to 272.

Does this now make sense to you? Rob, what have you found when testing different combo's for low mount twins or high mount singles on GTR's ? If you have found something interesting from real world testing it would be nice to share some of the results here. A few guys testing them on circuit based racecars have also been surprised with running higher than normally is accepted combo's with low mount twins but only when combined with larger valves and extensive port jobs. Mark Berry's R34 is a perfect example of this and i know that Brad from Autosport in Sydney who specialises in circuit cars does more development than most has also found this correct.

I'm not disagreeing with the your recomendations just the blanket statement "....yes big camshafts help bring an engine on earlier. We have tested our theory and have proven it to be correct".

In alot of situations this isn't the case. I have had high mount 3071's with custom grinds supposidly around the 300deg ad make less power in the entire rev range than a set of 280deg ad HKS cams with no other changes other than tuning. Both setups were extensively tuned. My thoughts are the that dynamic comp with the smaller cams increased to a point where igntion timing started yeilding resuls agian.

[Swiper the Fox]

I'm not disagreeing with the your recomendations just the blanket statement "....yes big camshafts help bring an engine on earlier. We have tested our theory and have proven it to be correct".

In alot of situations this isn't the case. I have had high mount 3071's with custom grinds supposidly around the 300deg ad make less power in the entire rev range than a set of 280deg ad HKS cams with no other changes other than tuning. Both setups were extensively tuned. My thoughts are the that dynamic comp with the smaller cams increased to a point where igntion timing started yeilding resuls agian.

when i say big cams lift is what im refering to. Thats why i said if there was no increase in lift swapping the inlet to 270's then he shouldn't bother. The 280's were a better match for your head/turbo combo obviously. 1200hp turbo's with a big head we have found work great with a 290/11.5+ set-up...the 300's were poorly matched to the turbo's and head combo therefore not suitable for optimum performance hence why you found the 280's worked better. My statement may have been better put this way "bigger camshafts than what is usually suggested/accepted can help to bring torque on earlier and hold it close to maximum for longer if the head and supporting mods are properly matched". "We have tested this and found this to be the case in most of the applications we have tested"

Edited March 17, 2010 by Swiper the Fox

[Nee-san]

Thanks for the replies guys,

I should have stated earlier that if i could get more lift i would, however i'de like to be sure that the pistons don't need to be 'scalloped' in order to accomodate great lift (>10mm).

As I've stated earlier I dont want to go above 9000 RPM as the valve train is rather standard apart from the changes I've listed, STATUS is right though, i need to put gears on it to take full advantage, this i will do shortly as the car is up on stands anyway...

Cheers,

Mitch.