cam gear settings
As always the best cam timing compromise varies according to what the engine is intended to do. When it comes to stroker engines that shorten the rod/stroke ratio, they slow movement of the piston around BDC, which means the intake cam would need to be retarded by a degree or two to equal a zero setting with a 2.0. It also means stroker engines tolerate a bit more effective duration on the intake. This being said, for a GSC S2 with your setup on the street, I'd try 0/-1 or maybe 0/-2.
Reason I ask -- I did get this car dyno tuned. I was quite disappointed to be honest. I know I need to change the 02 housing (still stock) but the tuner did not like the cams. He suggested getting Kelfords (272). I really can't see the cam of choice being the issue. I'd believe the 02 housing over anything. But I want to make sure I have the cam gears tweaked correctly.
I'll also add this is a 2.4 build, stock length rods and stroke. The car only put down (on a Mustang Dyno) 370 hp and 400 tq (but only at 22 lbs of boost with the bbk-b turbo). We didn't crank the boost since the restriction in the flow didn't change top end power. No sense and stressing the block. So waiting for the o2 housing (for xmas I hope
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Last edited by Kronik; Dec 19, 2013 at 10:03 AM.
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As always the best cam timing compromise varies according to what the engine is intended to do. When it comes to stroker engines that shorten the rod/stroke ratio, they slow movement of the piston around BDC, which means the intake cam would need to be retarded by a degree or two to equal a zero setting with a 2.0. It also means stroker engines tolerate a bit more effective duration on the intake. This being said, for a GSC S2 with your setup on the street, I'd try 0/-1 or maybe 0/-2.
You said "retard"+"intake", but then mentioned 0/-1 0/-2 cam gear settings which mean retarded exhaust...
Is that a typo or am I missing something??
Last edited by Biggy VIII; Dec 19, 2013 at 10:50 AM.
At -3/-3, spool is going to be soft and late, although it may make a little more peak power.
I don't like the Kelford 272 or similar shorter duration cams for large displacement 4G63s - not enough valve timing, and a tendency to create knock issues. The larger engines do better with longer duration cams. You may run into this situation with these HKS cams, but I don't have enough real world info about them to be certain at this point. I recommend fitting a larger O2 housing first, before looking at different cams. And if it comes to that a GSC S2 or Kelford 280 is a better bet.
I just didn't explain it well enough. If he had a GSC or Kelford cam with a 107 deg intake LC, I would have suggesting retarding the intake, but the HKS cam is at a 110 deg LC, which about right for his 1.5 R/S ratio setup.
I'm suggesting actually setting them a 0/-1 or 0/-2. That will improve midrange and spool. If it attenuates peak power, you can try retarding everything by 1 or 2 degrees from that point and test again.
At -3/-3, spool is going to be soft and late, although it may make a little more peak power.
I don't like the Kelford 272 or similar shorter duration cams for large displacement 4G63s - not enough valve timing, and a tendency to create knock issues. The larger engines do better with longer duration cams. You may run into this situation with these HKS cams, but I don't have enough real world info about them to be certain at this point. I recommend fitting a larger O2 housing first, before looking at different cams. And if it comes to that a GSC S2 or Kelford 280 is a better bet.
I'm suggesting actually setting them a 0/-1 or 0/-2. That will improve midrange and spool. If it attenuates peak power, you can try retarding everything by 1 or 2 degrees from that point and test again.
At -3/-3, spool is going to be soft and late, although it may make a little more peak power.
I don't like the Kelford 272 or similar shorter duration cams for large displacement 4G63s - not enough valve timing, and a tendency to create knock issues. The larger engines do better with longer duration cams. You may run into this situation with these HKS cams, but I don't have enough real world info about them to be certain at this point. I recommend fitting a larger O2 housing first, before looking at different cams. And if it comes to that a GSC S2 or Kelford 280 is a better bet.
You see -- I keep seeing so much conflicting information on where to set the cam gears with this type of build. Everything I found, up until now, said you needed them at -3 / -3 to be "in the ball park of being in time. So I won't have any issues at 0 / -1?? The engine will still be in time and spool quicker? And your comment above made me think you may have thought I have HKS cams. i do not -- I have GSC S2s already in the car. So is the advice on timing still the same??
You described the way the car builds boost exactly to a T. It is soft and comes on rather late ...but once it does hit boost it's fun! So just a small change and I shouldn't have better spool and midrange??!! That's what I wanted with this 2.4. It has tons of torque (even off boost) but it seems flat until about 5k which was odd to me.
Last edited by Kronik; Dec 19, 2013 at 12:24 PM.
You see -- I keep seeing so much conflicting information on where to set the cam gears with this type of build. Everything I found, up until now, said you needed them at -3 / -3 to be "in the ball park of being in time. So I won't have any issues at 0 / -1?? The engine will still be in time and spool quicker? And your comment above made me think you may have thought I have HKS cams. i do not -- I have GSC S2s already in the car. So is the advice on timing still the same??
Ted,
Currently building up my car for auto-x. I will be running an HTA71 with BC272s. I know that you say you can't recommend cam gear settings for them because they're not as published. I am planning on degreeing them to find lobe centerline so I don't necessarily care about published specs, and at that point the numbers on the cam gears are only reference points. Once I've established true centerline what is your recommendation for optimum low/mid spool without a huge sacrifice on top end?
Currently building up my car for auto-x. I will be running an HTA71 with BC272s. I know that you say you can't recommend cam gear settings for them because they're not as published. I am planning on degreeing them to find lobe centerline so I don't necessarily care about published specs, and at that point the numbers on the cam gears are only reference points. Once I've established true centerline what is your recommendation for optimum low/mid spool without a huge sacrifice on top end?
First of all let me say thanks to Ted for all of the great information thats been shared so far in the thread!
What would you suggest as a starting point for my setup?
Cosworth 272's
GT35r
Weekend street use and occasional trips to the strip.
What would you suggest as a starting point for my setup?
Cosworth 272's
GT35r
Weekend street use and occasional trips to the strip.
In both cases I recommend leaving the GSC S2's at 0/0. These cams are already timed to give best possible spool without running into issues.
In the case of the GT 3071R, that turbo spools slowly for its power potential, so it needs all the help it can get.
As for the 2.3 with PTE 6262, ordinarily, I'd recommend a couple of degrees of retard to compensate for the different piston position of the 2.3, but with an open .82 AR T3 housing, it's going to need all the spool help it can get.
In the case of the GT 3071R, that turbo spools slowly for its power potential, so it needs all the help it can get.
As for the 2.3 with PTE 6262, ordinarily, I'd recommend a couple of degrees of retard to compensate for the different piston position of the 2.3, but with an open .82 AR T3 housing, it's going to need all the spool help it can get.
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From: botswana
In both cases I recommend leaving the GSC S2's at 0/0. These cams are already timed to give best possible spool without running into issues.
In the case of the GT 3071R, that turbo spools slowly for its power potential, so it needs all the help it can get.
As for the 2.3 with PTE 6262, ordinarily, I'd recommend a couple of degrees of retard to compensate for the different piston position of the 2.3, but with an open .82 AR T3 housing, it's going to need all the spool help it can get.
In the case of the GT 3071R, that turbo spools slowly for its power potential, so it needs all the help it can get.
As for the 2.3 with PTE 6262, ordinarily, I'd recommend a couple of degrees of retard to compensate for the different piston position of the 2.3, but with an open .82 AR T3 housing, it's going to need all the spool help it can get.