Cam Gurus.....Drop Some Science!
09-05-2019, 09:24 PM
#1
Cam Gurus.....Drop Some Science! OK....looking to get SERIOUSLY schooled on camshaft spec'ing. Please...and no offense meant....but If you are not 99.9% proficient in this area, sit back and do what I hope to do; learn!
My cousin has a '96 Buick Roadmaster Wagon (Heavy car!) with a stroked LS3 going in it. He will race the car occasionally, but he's really looking for a strong cruiser.....he will not be towing with the car.
His goal is to build for solid low-range and strong mid-range torque that will carry HP to the 6700rpm range; he asked me to recommend a cam. I'm 'pretty good', but I don't know all the "hows" and "whys" a specific cam grind would (or would not) work. I have spec'ed a cam and would like input from the 4 or 5 guys here who KNOW what's what, and don't mind sharing a bit. Don't be shy fellas.....most of us know who you are!!!
Car/Engine Specs as I know them with my best guess cam at the bottom:
4600 LB car (plus he weighs about 240 LB)
4L60E transmission
3200 stall TC
3.73 rear axle ratio
27" Diameter Tires
1.7/8" Long Tubes
2 1/2" Exhaust with cats and mufflers
Ported OEM TB
Gwatney Ported & Radius Rod LS3 Intake
TrickFlow 260 Heads
1.8 Roller Rockers
418ci LS3 with 11.8:1 SCR
Cam:
238*/254* @ .050"
113* + 3*
Lift .650" to .660"
IVO = 9*
IVC = 49*
EVO = 63*
EVC = 11*
Overlap = 20*
Many Thanks!!
KW
My cousin has a '96 Buick Roadmaster Wagon (Heavy car!) with a stroked LS3 going in it. He will race the car occasionally, but he's really looking for a strong cruiser.....he will not be towing with the car.
His goal is to build for solid low-range and strong mid-range torque that will carry HP to the 6700rpm range; he asked me to recommend a cam. I'm 'pretty good', but I don't know all the "hows" and "whys" a specific cam grind would (or would not) work. I have spec'ed a cam and would like input from the 4 or 5 guys here who KNOW what's what, and don't mind sharing a bit. Don't be shy fellas.....most of us know who you are!!!
Car/Engine Specs as I know them with my best guess cam at the bottom:
4600 LB car (plus he weighs about 240 LB)
4L60E transmission
3200 stall TC
3.73 rear axle ratio
27" Diameter Tires
1.7/8" Long Tubes
2 1/2" Exhaust with cats and mufflers
Ported OEM TB
Gwatney Ported & Radius Rod LS3 Intake
TrickFlow 260 Heads
1.8 Roller Rockers
418ci LS3 with 11.8:1 SCR
Cam:
238*/254* @ .050"
113* + 3*
Lift .650" to .660"
IVO = 9*
IVC = 49*
EVO = 63*
EVC = 11*
Overlap = 20*
Many Thanks!!
KW
09-05-2019, 10:28 PM
#5
Also, take note you will have 20 degrees overlap so this won't be a smooth driving camshaft.
You will get ti drive decently with a good tune.
If this is not a factor, then all good,.
If you require something with better driving manners overlap should come down to around the 12 degree area;
You will get ti drive decently with a good tune.
If this is not a factor, then all good,.
If you require something with better driving manners overlap should come down to around the 12 degree area;
09-05-2019, 10:41 PM
#6
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To be clear I do NOT consider myself in the top 15, let alone top 5 ...lol.
However I would not want 20* of Overlap with either
4800 lbs or a 3200 TC,...let alone both in a street cruiser/occasional racer.
Just my .02.
Waiting on the real Pros, Darth,Spanks,SpeedTigger,99Blackbird,KCS, etc.
However I would not want 20* of Overlap with either
4800 lbs or a 3200 TC,...let alone both in a street cruiser/occasional racer.
Just my .02.
Waiting on the real Pros, Darth,Spanks,SpeedTigger,99Blackbird,KCS, etc.
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09-05-2019, 11:26 PM
#9
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Kw, to be very honest I think that is too much cam for what you described. I am not near my computer to run the calculations, so that is just a gut instinct. With the weight of the car and to stated goals and stall I am thinking along the lines of a 232 duration on a 112 centerline and a 242 duration on a 116 centerline. That should peak around 6300 and carry to 6800 pretty easily. But again I would like to be at my computer to run the compression calcs etc.
My thinking is that cam should come into itself around 2800, which will work great with your stall, peak tq at 4800. A lot will depend on intake selection also but I will get back to you with a better spec later on. That is all just top of my head maths.
My thinking is that cam should come into itself around 2800, which will work great with your stall, peak tq at 4800. A lot will depend on intake selection also but I will get back to you with a better spec later on. That is all just top of my head maths.
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KW Baraka (09-05-2019)
09-05-2019, 11:40 PM
#10
I'd think anywhere from 222'ish to what D said @ 232 on intake duration. Mucho Lift @ .670 - 680
Factor in a Ls7 cam spec's.....just better and a shorter rpm @ 6700
Main thing is *5000lbs.*
We NEED TQ!
Added..........
Nice 115-118 lsa
Factor in a Ls7 cam spec's.....just better and a shorter rpm @ 6700
Main thing is *5000lbs.*
We NEED TQ!
Added..........
Nice 115-118 lsa
Last edited by Smokey B; 09-05-2019 at 11:46 PM.
09-05-2019, 11:46 PM
#11
Cam Motion has a "Torquey Stroker" cam (232*/242*, 114* + 4*) that is VERY close to your swag for 10.5:1 to 11.5:1 SCR (yeah, I did some research
)Maybe start from that and work up to something that'll mate well with 11.8:1....or would that 0.3 additional compression even make a difference?
KW
Last edited by KW Baraka; 09-06-2019 at 03:16 PM.
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KW Baraka (09-05-2019)
09-05-2019, 11:55 PM
#13
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.3 VS .03 Compresiion.
Darth, Kinda close to what I was thinking ~232/242 114+3 .650-.670 Intake, .020 less for exhaust.
Must have remembered "Stealthy Stroker" lol.
KW The TFS LS3 (255) are great out of the box,
Look at BigDaddy's 447" with out of the box TFS LS3s with light valves & schmedium (for application) cam.
Strongly suggest 3/8 X .120 PR , TSP Rockers with bushing & roller tip vs 1.8 if you havn't ordered yet.
3600 TC & 4.10s.
Darth, Kinda close to what I was thinking ~232/242 114+3 .650-.670 Intake, .020 less for exhaust.
Must have remembered "Stealthy Stroker" lol.
KW The TFS LS3 (255) are great out of the box,
Look at BigDaddy's 447" with out of the box TFS LS3s with light valves & schmedium (for application) cam.
Strongly suggest 3/8 X .120 PR , TSP Rockers with bushing & roller tip vs 1.8 if you havn't ordered yet.
3600 TC & 4.10s.
Last edited by NAVYBLUE210; 09-06-2019 at 12:01 AM.
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09-05-2019, 11:59 PM
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Originally Posted by KW Baraka
Yeah...it's the compression that is most vexing to me.
Cam Motion has a "Torquey Stroker" cam (232*/242*, 114* + 4*) that is VERY close to your swag for 10.5:1 to 11.5:1 SCR (yeah, I did some research )
Maybe start from that and work up to something that'll mate well with 11.8:1....or would that .03 additional compression even make a difference?
KW
Cam Motion has a "Torquey Stroker" cam (232*/242*, 114* + 4*) that is VERY close to your swag for 10.5:1 to 11.5:1 SCR (yeah, I did some research
)Maybe start from that and work up to something that'll mate well with 11.8:1....or would that .03 additional compression even make a difference?
KW
Torque is cylinder pressure, so we want to maximize without knocking under load. Balancing act for sure. I actually started at a 48 IVC to keep DCR in check again without computer. Ideally with 93 octane I would like to get you at a 8.50-8.60. Went later on EVO to hold pressure in longer - again for midrange.
So will that last .3 make a difference? Depends on where the DCR is on this one.
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KW Baraka (09-06-2019)
09-06-2019, 12:06 AM
#15
He's locked into the TC and gears (3200 and 3.73's) for now.....he's had them for awhile and decided to stay with them.....plus....saves $1200+.
KW
09-06-2019, 12:26 AM
#17
I’d favor something short duration with tight centers. This beast is going to move off torque not trying to spin 6700.
Build as much torque as you can around where it’s gonna flash.
228/242 110+4
IVO is 8.0 ° BTDC ( - indicates ATDC)
IVC is 40.0 ° ABDC
EVO is 55.0 ° BBDC
EVC is 7.0 ° ATDC ( - indicates BTDC)
Overlap is 15 °
It should still make power at 6500 but will be much more powerful where it counts.
Build as much torque as you can around where it’s gonna flash.
228/242 110+4
IVO is 8.0 ° BTDC ( - indicates ATDC)
IVC is 40.0 ° ABDC
EVO is 55.0 ° BBDC
EVC is 7.0 ° ATDC ( - indicates BTDC)
Overlap is 15 °
It should still make power at 6500 but will be much more powerful where it counts.
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KW Baraka (09-06-2019)
09-06-2019, 02:49 AM
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Alright, I'm at my computer, and having gone through the calcs, I'm going to stand by my recommendation of 232/242-114+2. Here is my reasoning on this selection:
1. The 48 degree IVC with 11.8 SCR results in 8.67 DCR. I would actually rather advance it more, but you would need to either drop compression or run E85 or boostane with every fill up. Just one more degree of advance puts it at 8.75, which is really a bit much for 92-93 octane. And given that you are already at 11.8 SCR, I suggest controlling KR with the IVC.
2. I like the later EVO for improved midrange, even though it would sacrifice some RPM. 6800 rpm would still be no issue.
3. The overlap is neutral (neither intake nor exhaust biased), which should result in a good blend of midrange torque and decent power.
4. An earlier IVC would be better for torque, and would shift the powerband down in RPM. For that to work, you really would need to drop compression to 11.5. Even though the vehicle is large, I think the displacement and compression combined will compensate for the later IVC.
1. The 48 degree IVC with 11.8 SCR results in 8.67 DCR. I would actually rather advance it more, but you would need to either drop compression or run E85 or boostane with every fill up. Just one more degree of advance puts it at 8.75, which is really a bit much for 92-93 octane. And given that you are already at 11.8 SCR, I suggest controlling KR with the IVC.
2. I like the later EVO for improved midrange, even though it would sacrifice some RPM. 6800 rpm would still be no issue.
3. The overlap is neutral (neither intake nor exhaust biased), which should result in a good blend of midrange torque and decent power.
4. An earlier IVC would be better for torque, and would shift the powerband down in RPM. For that to work, you really would need to drop compression to 11.5. Even though the vehicle is large, I think the displacement and compression combined will compensate for the later IVC.
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KW Baraka (09-06-2019)