cam selection for 383 LT4
Thread Starter
Drifting
Joined: Oct 2005
Posts: 1,916
Likes: 48
From: Angier nc
cam selection for 383 LT4
I am being forced to rebuild my engine for the third time in 500 miles thanks to an IDIOT.That aside I am going to stroke it to a 383.I will be running cnc 195 afr lt4 heads and port matched lt4 intake with a 52mm tb.I have 4.10 gears and a 6 speed.
Driveability is important and I will gladly trade being able to cruise at 2000rpm in sixth w/o surging for the last 10hp.
Maximum rpm will be 6500rpm.
If you have one or have built one I would like to know what your specs were and if you had any driveability problems.HP AND TQ numbers would be great also.If you don't want to share with the rest of the class pm me.
My goal is to have massive tq in a broad range.The hp will take care of itself.
To clarify I am looking for cam specs.The duration at .050 and lobe seperation.
Thanks in advance.
Driveability is important and I will gladly trade being able to cruise at 2000rpm in sixth w/o surging for the last 10hp.
Maximum rpm will be 6500rpm.
If you have one or have built one I would like to know what your specs were and if you had any driveability problems.HP AND TQ numbers would be great also.If you don't want to share with the rest of the class pm me.
My goal is to have massive tq in a broad range.The hp will take care of itself.
To clarify I am looking for cam specs.The duration at .050 and lobe seperation.
Thanks in advance.
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
In my super rammed 383 with afr 195's I am running a Comp Cam.
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
Burning Brakes
Joined: Mar 1999
Posts: 858
Likes: 5
From: Fl,USA
In my super rammed 383 with afr 195's I am running a Comp Cam.
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
John
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
AI's (advanced induction) 226/234 cam is a nice setup. Its on a 110. gives some lope but should be very driveable yet make power to near 6000 rpm peak, you'll be done by 6500 where you wanted max rpm.
I ran a 230/245 on a 109 and had no problems in my 383 L98 HSR motor, but i think its abit much for your build. My cam would peak near 6300, flatline to 6500 and you could shift at 6700-6800 and not fall off. It loved rpm.
Somewhere between that and AI's cam would be nice. XFI 280 isnt a bad choice, its a 230/236 on a 113. Should be all in by 6500 as well and be very driveable. NO surge issues at all at cruise
I ran a 230/245 on a 109 and had no problems in my 383 L98 HSR motor, but i think its abit much for your build. My cam would peak near 6300, flatline to 6500 and you could shift at 6700-6800 and not fall off. It loved rpm.
Somewhere between that and AI's cam would be nice. XFI 280 isnt a bad choice, its a 230/236 on a 113. Should be all in by 6500 as well and be very driveable. NO surge issues at all at cruise
Thread Starter
Drifting
Joined: Oct 2005
Posts: 1,916
Likes: 48
From: Angier nc
AI's (advanced induction) 226/234 cam is a nice setup. Its on a 110. gives some lope but should be very driveable yet make power to near 6000 rpm peak, you'll be done by 6500 where you wanted max rpm.
I ran a 230/245 on a 109 and had no problems in my 383 L98 HSR motor, but i think its abit much for your build. My cam would peak near 6300, flatline to 6500 and you could shift at 6700-6800 and not fall off. It loved rpm.
Somewhere between that and AI's cam would be nice. XFI 280 isnt a bad choice, its a 230/236 on a 113. Should be all in by 6500 as well and be very driveable. NO surge issues at all at cruise
I ran a 230/245 on a 109 and had no problems in my 383 L98 HSR motor, but i think its abit much for your build. My cam would peak near 6300, flatline to 6500 and you could shift at 6700-6800 and not fall off. It loved rpm.
Somewhere between that and AI's cam would be nice. XFI 280 isnt a bad choice, its a 230/236 on a 113. Should be all in by 6500 as well and be very driveable. NO surge issues at all at cruise
It is easy for me to recommend parts for someone else.
I want to bounce ideas off you guys since I lose my objectivity on my stuff.
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
A recent article the dyno results showed what most of us already know; that as duration increases, torque down low drops off and HP up-top increases. Comparing two cams, the second one being the XF1 280, showed a 25 ft lb torque loss down low, but made much more power above 4000.
So the question asked in the mag article was, essentially, are you willing to give up torque down low to make more HP up top.
CompCams' Godbold said in an interview, that the XFI series lobes are the best they've ever done. So those lobes, themselves, are the the way to go. For good low end torque all I'd do is shorten the duration by 6 degrees on both intake and exhaust. So instead of 230/236 I'd look at 224/230 or even 218/224 to REALLY make excellent low end torque. Also, I'd keep the LSA on the wide side; at least 111, UNLESS the effective duration is below 220.
As an aside, one of the most often and biggest mistakes made in cam selection is over-camming the engine; installing a cam with too much duration and/or the wrong Lobe Seperation Angle. It's the "Bigger is Better" mentality rearing it's ugly head once again.
Just my views.
Jake
West Point ROCKS!
So the question asked in the mag article was, essentially, are you willing to give up torque down low to make more HP up top.
CompCams' Godbold said in an interview, that the XFI series lobes are the best they've ever done. So those lobes, themselves, are the the way to go. For good low end torque all I'd do is shorten the duration by 6 degrees on both intake and exhaust. So instead of 230/236 I'd look at 224/230 or even 218/224 to REALLY make excellent low end torque. Also, I'd keep the LSA on the wide side; at least 111, UNLESS the effective duration is below 220.
As an aside, one of the most often and biggest mistakes made in cam selection is over-camming the engine; installing a cam with too much duration and/or the wrong Lobe Seperation Angle. It's the "Bigger is Better" mentality rearing it's ugly head once again.
Just my views.
Jake
West Point ROCKS!
Last edited by JAKE; Jul 1, 2009 at 02:56 PM.
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
The XFI lobes really smack the valve seats. I would maybe think twice about an XFI lobe in a 12,000 mile per year street car.
It seems like I remember reading/hearing that 96 lt4 uses his car as his daily driver.
Another thing to consider is what is the effect of the loss of torque down low. If you are making 400 Ft. Lbs. of torque off idle, giving up 30 Ft. Lbs. for upper RPM power isn't that big of a deal.
It seems like I remember reading/hearing that 96 lt4 uses his car as his daily driver.
Another thing to consider is what is the effect of the loss of torque down low. If you are making 400 Ft. Lbs. of torque off idle, giving up 30 Ft. Lbs. for upper RPM power isn't that big of a deal.
Pro
Joined: Jun 2006
Posts: 508
Likes: 1
From: Miami Florida
I just did a rebuild on my 89 L-98 and went to 383 cu.in with the Comp cam #270H and couldn't be happier with the performance. It has a nice lopey idle and the spec's are: .224 X .224 @ .50 with the lift at .480 x .480. I am also running 1.6 to 1 Crane roller rockers, Hedman long tube headers, slightly modified factory aluminum heads, and a .308 rear end ratio with an auto trans (unmodified). It now puts out 320 hp to the rear wheels with 368 ft. lbs torque on the dyno with 24 lb. injectors using the stock TPI system. Next stop will be for a FIRST Intake system to replace the factory TPI.
Carolina Machine Engines in Johnson SC did the engine for me and I highly recommend them not only for their good work but their excellent prices!
Steve
Carolina Machine Engines in Johnson SC did the engine for me and I highly recommend them not only for their good work but their excellent prices!
Steve
Thread Starter
Drifting
Joined: Oct 2005
Posts: 1,916
Likes: 48
From: Angier nc
It will not be a daily driver anytime soon.No where to put the baby seat that will arrive in October.
At this point all I want is a reliable car I can drive.Josh(neat) knows all to well what a nightmare this journey has been.
At this point all I want is a reliable car I can drive.Josh(neat) knows all to well what a nightmare this journey has been.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
The XFI opening and closing ramps are different; gentler on the closing side to set the valve down without causing it to bounce off the seat. This was factored in when the engineers designed the lobes.
Comp's, and other companies, been designing asymetrical lobes for as long as I can remember for just that reason; to set the valves down more gently. Give Comp a call and ask about the XFI ramps if it concerns you.
Remember, their engineers do their homework and Godbold said they're the best series of lobes they done yet.
In the most recent LT1 cylinder head shoot-out done by GM HighTech Performance magazine, guess which lobes they used?
Jake
West Point ROCKS!
Comp's, and other companies, been designing asymetrical lobes for as long as I can remember for just that reason; to set the valves down more gently. Give Comp a call and ask about the XFI ramps if it concerns you.
Remember, their engineers do their homework and Godbold said they're the best series of lobes they done yet.
In the most recent LT1 cylinder head shoot-out done by GM HighTech Performance magazine, guess which lobes they used?
Jake
West Point ROCKS!
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
They used XFI lobes in the shootout, and I have an XFI cam in my car. However, that doesn't change the fact that the XFI lobes set the valves down hard.
Believe what you want, it doesn't make a difference to me.
Believe what you want, it doesn't make a difference to me.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
However, that doesn't change the fact that the XFI lobes set the valves down hard.
Theres give and take with cam profiles, a gentler set of valve events will have more longevity and vice versa.
Most think they will build a hot motor and leave it that way, want it to last forever, etc. Ive found that you start wanting more or get the bug to change things so all that grieving and hair pulling trying to get it "perfect" is kind of a waste. Most cams, unless you make a large jump in duration will run pretty much the same ; meaning worrying about a 213 or a 216, 218 I dont think youll be able to tell much difference if you can tell it at all. Pick one, stab it in and go.
Race Director
Joined: May 2003
Posts: 10,749
Likes: 41
In my super rammed 383 with afr 195's I am running a Comp Cam.
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
230/230 @ 0.050" 0.598/0.598 lift with 1.6 Comp Cam Pro Mags , 110 Centerline.
Idle is choppy. I've spun mine to 6700 but I wouldnt' be doing that much, doesn't make the power up there. I shift around 6200. My RPM's are limited due to the Super Ram, whereas your intake will pull much higher.
No dyno numbers yet, sorry.
Idle
In car
I image somewhere in the 236/242 range would best benefit the LT4 intake?
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
In fact it's one of the reasons the valve train is so noisy with these cams. When I was spec'ing mine out the tech said the noise would be noticeable (and it is). Fortunately a friend of mine has these lobes and I was aware of the noise.
Gentler is a relative term...they're more gentle than an older style lobe.
Thread Starter
Drifting
Joined: Oct 2005
Posts: 1,916
Likes: 48
From: Angier nc
A custom comp grind with 230/236 @ .050 ground on a 112.I will have to get the cam card to be certain and to know the lift.The motor was dynoed(chassis)yesterday and I havent even seen it yet.