Camshaft Discussion Part III
04-11-2005, 10:36 AM
#101
Found it 
Comp 26921:
# of springs: Dual
Installed Height: 1.77
Outer Spring OD: 1.300
Outer Spring ID: .895
Inner Spring ID: .655
Spring Rate: 408
Damper: No
1.85: 102
1.80: 123
1.75: 124
1.70: 164
1.65: 184
1.60: 204
1.55: 225
1.50: 245
1.45: 265
1.40: 286
1.35: 306
1.30: 327
1.25: 347
1.20: 367
1.15: 388
1.10: 408
Max Coil Bind Height: 1.040
Ti. Retainer (Std Wt): 754
Seat 0.57 OD Guide: 4695 (.500 Guide)
Shims: 4753
Ok, Now what else is needed to see if the ramp on the proposed lobe would be too agressive.
.006 - 260
.050 - 220
.200 - 160
.353 lift (.600 with the 1.7 rocker)
Motor would be seeing 7400-7500 rpm. Again, this would be a hyd motor with Comp R lifters.
Any info needed on the Comp R lifter?
Or the rocker that will be used?
Most likely a reworked stock rocker since they seem to be the lightest over the tip. Possibly a Harlan Sharp roller since I have a set already. The HS's have a pin connecting 2 rockers through the pivot point helping to keep them from from deflecting side to side on the valve and pushrod. Not sure if the stock reworked ones from HS have the same set up, but they get rid of the needle bearings.
Comp 26921:
# of springs: Dual
Installed Height: 1.77
Outer Spring OD: 1.300
Outer Spring ID: .895
Inner Spring ID: .655
Spring Rate: 408
Damper: No
1.85: 102
1.80: 123
1.75: 124
1.70: 164
1.65: 184
1.60: 204
1.55: 225
1.50: 245
1.45: 265
1.40: 286
1.35: 306
1.30: 327
1.25: 347
1.20: 367
1.15: 388
1.10: 408
Max Coil Bind Height: 1.040
Ti. Retainer (Std Wt): 754
Seat 0.57 OD Guide: 4695 (.500 Guide)
Shims: 4753
Ok, Now what else is needed to see if the ramp on the proposed lobe would be too agressive.
.006 - 260
.050 - 220
.200 - 160
.353 lift (.600 with the 1.7 rocker)
Motor would be seeing 7400-7500 rpm. Again, this would be a hyd motor with Comp R lifters.
Any info needed on the Comp R lifter?
Or the rocker that will be used?
Most likely a reworked stock rocker since they seem to be the lightest over the tip. Possibly a Harlan Sharp roller since I have a set already. The HS's have a pin connecting 2 rockers through the pivot point helping to keep them from from deflecting side to side on the valve and pushrod. Not sure if the stock reworked ones from HS have the same set up, but they get rid of the needle bearings.
04-11-2005, 11:57 AM
#102
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This is what I would recommend:
If the LS1 has a stock height of 1.8", use 1.8" as the install height.
That will yield about 123 lbs. closed, and about 367 lbs. open (1.2")
which is more than enough @ 7500 RPM.
This leaves about 0.140" before bind which will handle pretty much anything
you can throw at this spring.
If you need to shim the spring (~ 0.020") , there is still sufficient clearance.
As for being aggressive on the ramp, the cam MFG. will normally indicate
the maximum rocker multiplier. Since you're sticking with 1.7 ratio, I don't
forsee any danger. The numbers you posted for duration at the lobe are
fairly common.
Finally for the remainder of the valve train components, you have selected
good parts. They are fairly light weight which will help.
The only question I have is the operating range for this cam. Will you need to
spin 7500 RPM?
If the LS1 has a stock height of 1.8", use 1.8" as the install height.
That will yield about 123 lbs. closed, and about 367 lbs. open (1.2")
which is more than enough @ 7500 RPM.
This leaves about 0.140" before bind which will handle pretty much anything
you can throw at this spring.
If you need to shim the spring (~ 0.020") , there is still sufficient clearance.
As for being aggressive on the ramp, the cam MFG. will normally indicate
the maximum rocker multiplier. Since you're sticking with 1.7 ratio, I don't
forsee any danger. The numbers you posted for duration at the lobe are
fairly common.
Finally for the remainder of the valve train components, you have selected
good parts. They are fairly light weight which will help.
The only question I have is the operating range for this cam. Will you need to
spin 7500 RPM?
04-11-2005, 12:19 PM
#103
Being a 348ci large turbo motor I think I am going to have to spin it up there.. The T91 probably isn't going to see full spool till after 5k from what I am hearing. Maybe even closer to 5500.
The profile above was just something I threw out there for the lobe. Trying to just find a definative answer on being too agressive.
I'm really thinking about doing a solid roller though now.
Thanks for the info though..
The profile above was just something I threw out there for the lobe. Trying to just find a definative answer on being too agressive.
I'm really thinking about doing a solid roller though now.
Thanks for the info though..
04-11-2005, 08:39 PM
#105
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I don't know the equation. I'm sure it would be some sort of "velocity * mass / time " to estimate acceleration of load? It would also be a dynamic
equation as engine RPM increases, reciprocating mass would also increase.
You might have more luck searching the Net (as I'm doing since you've sparked my interest).
In the real world, dyno testing would reveal how much spring pressure is needed
to avoid floating and bounce.
By "rule of thumb", I was taught to add 0.020" clearance over the base clearance (0.040")
for every 500 RPM over the recommended values.
This only applies if the component mass stays the same because the additional
spring travel will account for extra open pressure.
At the point when you come too close to bind clearance, you need to change
install heights, or springs to achieve the same open pressures while keeping
a safe bind buffer...either that, or go to a heavier spring with less clearance.
This is where the cross reference charts come in very handy.
In any case, your setup is fine. You have tons of buffer zone at the open height.
equation as engine RPM increases, reciprocating mass would also increase.
You might have more luck searching the Net (as I'm doing since you've sparked my interest).
In the real world, dyno testing would reveal how much spring pressure is needed
to avoid floating and bounce.
By "rule of thumb", I was taught to add 0.020" clearance over the base clearance (0.040")
for every 500 RPM over the recommended values.
This only applies if the component mass stays the same because the additional
spring travel will account for extra open pressure.
At the point when you come too close to bind clearance, you need to change
install heights, or springs to achieve the same open pressures while keeping
a safe bind buffer...either that, or go to a heavier spring with less clearance.
This is where the cross reference charts come in very handy.
In any case, your setup is fine. You have tons of buffer zone at the open height.
10-17-2005, 11:39 PM
#108
I'm getting the FMS F11 so the following is just theoretical for kicks.
In theory would i be able to run a bigger cam as far as duration with less than .600 lift with a 110LSA with more advance ground into it, and have a similar peak and similar powerband but with more horsepower? The only downfall would be a rougher idle correct? Instead of a 228º intake duration, i would run let's say in the high 230's but with a +6 advance. The longer intake opening would fill the cylinder better but the advance would bring the powerband down into a usable area. If the PV clearance was too close, i would lower the lift a little but to compensate. Seeing as how J-rod mentioned stock(mine is an Ls6) heads have too much turbulence at higher lift, wouldn't it be better to have increased duration at the cost of lowering the lift a little bit?
In theory would i be able to run a bigger cam as far as duration with less than .600 lift with a 110LSA with more advance ground into it, and have a similar peak and similar powerband but with more horsepower? The only downfall would be a rougher idle correct? Instead of a 228º intake duration, i would run let's say in the high 230's but with a +6 advance. The longer intake opening would fill the cylinder better but the advance would bring the powerband down into a usable area. If the PV clearance was too close, i would lower the lift a little but to compensate. Seeing as how J-rod mentioned stock(mine is an Ls6) heads have too much turbulence at higher lift, wouldn't it be better to have increased duration at the cost of lowering the lift a little bit?
