PAC 1221 vs Comp 921
07-09-2010, 08:25 AM
#2
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You should list your intentions and cam specs with approximate RPM limit
at the very least.
Those springs are close, but not exactly equal in specs.
The Comp is a touch more aggressive, and has a bit more bind clearance.
Without any info, it's tough to recommend either...but a blind guess based
on the values: I'd go for the Comps.
at the very least.
Those springs are close, but not exactly equal in specs.
The Comp is a touch more aggressive, and has a bit more bind clearance.
Without any info, it's tough to recommend either...but a blind guess based
on the values: I'd go for the Comps.
07-09-2010, 11:55 AM
#4
Pac 1221
Seat Load: 135 @ 1.800
Open Load: 400 @ 1.150
Rate: 408
Coil Bind: 1.080
Max Lift: 0.650
Comp 921
Seat Load: 135 @ 1.770
Open Load: 400 @ 1.220
Coil Bind: 1.040
Rate (lbs./in.): 408
Max lift: .630
They are not the same spring they have different tolerances that in fact will make a difference. Now give us the cam specs to make an educated guess. If you don't have the specs or even a cam picked out this question is as useful as a cold bottle of fresh salt water in the desert.
Seat Load: 135 @ 1.800
Open Load: 400 @ 1.150
Rate: 408
Coil Bind: 1.080
Max Lift: 0.650
Comp 921
Seat Load: 135 @ 1.770
Open Load: 400 @ 1.220
Coil Bind: 1.040
Rate (lbs./in.): 408
Max lift: .630
They are not the same spring they have different tolerances that in fact will make a difference. Now give us the cam specs to make an educated guess. If you don't have the specs or even a cam picked out this question is as useful as a cold bottle of fresh salt water in the desert.
07-09-2010, 01:15 PM
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as useful as a cold bottle of fresh salt water in the desert.
Just to add; I saw totally different specs for spring rate, coil bind, and seat
pressure for PAC :
http://www.pacracing.com/Street_Stri..._PAC_1221.html
Pac 1221
Seat Load: 135 @ 1.770 (< recommended install height)
Open Load: 400 @ 1.120
Rate: 307 lbs./in.
Coil Bind: 1.050 ( < not sure how they arrive at this. shimmed perhaps?)
Max Lift: 0.650
07-09-2010, 01:48 PM
#6
Ha, nice
Just to add; I saw totally different specs for spring rate, coil bind, and seat
pressure for PAC :
http://www.pacracing.com/Street_Stri..._PAC_1221.html
Pac 1221
Seat Load: 135 @ 1.770 (< recommended install height)
Open Load: 400 @ 1.120
Rate: 307 lbs./in.
Coil Bind: 1.050 ( < not sure how they arrive at this. shimmed perhaps?)
Max Lift: 0.650
Just to add; I saw totally different specs for spring rate, coil bind, and seat
pressure for PAC :
http://www.pacracing.com/Street_Stri..._PAC_1221.html
Pac 1221
Seat Load: 135 @ 1.770 (< recommended install height)
Open Load: 400 @ 1.120
Rate: 307 lbs./in.
Coil Bind: 1.050 ( < not sure how they arrive at this. shimmed perhaps?)
Max Lift: 0.650
http://www.racingsprings.com/PDF/RS2009CAT.PDF
But again like i said it does nothing if there are no cam specs
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07-09-2010, 07:58 PM
#10
The spring rate for the PAC 1221 is 408 lbs. (See attached)
It is still my understanding that the PAC 1221 is remarketed by Trick Flow as its Part Number TFS-15201 and by Comp as the current 921. Coil bind specs vary based which retainer is being used. The lift specification varies based on the particular reseller's reasoned discretion.
Since this information is based on the specifications and informal phone conversations with various suppliers I cannot prove it and may well be misinformed. By all means feel free to believe what you want and buy from whatever seller you like.
It is still my understanding that the PAC 1221 is remarketed by Trick Flow as its Part Number TFS-15201 and by Comp as the current 921. Coil bind specs vary based which retainer is being used. The lift specification varies based on the particular reseller's reasoned discretion.
Since this information is based on the specifications and informal phone conversations with various suppliers I cannot prove it and may well be misinformed. By all means feel free to believe what you want and buy from whatever seller you like.
07-09-2010, 09:42 PM
#11
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Well this is a friggin rats nest of info.
If the spring rate is the same, then there's nothing more to consider.
Apparently, www.pacracing.com and www.racingsprings.com are both
PAC official sites? If so, then they messed up specs for their springs
on pacracing.com.
In any case, the companies should not be measuring the springs with
retainers when issuing specifications. A spring pressure tester measures
the spring without retainers. When you setup a cylinder head, you insert
the micrometer between the spring seat and retainer.
The spring rate gives pressure at a certain height; the install height is the
height of the spring itself.
Certain cam companies need to follow one standard for data presentation.
Thanks for clearing that up Darkman.
If the spring rate is the same, then there's nothing more to consider.
Apparently, www.pacracing.com and www.racingsprings.com are both
PAC official sites? If so, then they messed up specs for their springs
on pacracing.com.
In any case, the companies should not be measuring the springs with
retainers when issuing specifications. A spring pressure tester measures
the spring without retainers. When you setup a cylinder head, you insert
the micrometer between the spring seat and retainer.
The spring rate gives pressure at a certain height; the install height is the
height of the spring itself.
Certain cam companies need to follow one standard for data presentation.
Thanks for clearing that up Darkman.
07-10-2010, 05:26 PM
#12
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The spring rate for the PAC 1221 is 408 lbs. (See attached)
It is still my understanding that the PAC 1221 is remarketed by Trick Flow as its Part Number TFS-15201 and by Comp as the current 921. Coil bind specs vary based which retainer is being used. The lift specification varies based on the particular reseller's reasoned discretion.
Since this information is based on the specifications and informal phone conversations with various suppliers I cannot prove it and may well be misinformed. By all means feel free to believe what you want and buy from whatever seller you like.
It is still my understanding that the PAC 1221 is remarketed by Trick Flow as its Part Number TFS-15201 and by Comp as the current 921. Coil bind specs vary based which retainer is being used. The lift specification varies based on the particular reseller's reasoned discretion.
Since this information is based on the specifications and informal phone conversations with various suppliers I cannot prove it and may well be misinformed. By all means feel free to believe what you want and buy from whatever seller you like.
I just put a set of Manley Nextek's on my motor.
07-10-2010, 09:11 PM
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Who are the other manufacturers that control the entire process front to back?
Does Patriot? Comp Cams? Twisted Flow? Lunati? Crane (if they are still around?) Chet Herbert? Howards? others?
I am curious. I just went through this entire ordeal looking for springs after I suffered a broken spring. I talked at length with quite a few people, some sponsors on this board, others not associated with this board and that's the info I was given to work with. I'm not claiming to be the authority, but multiple unrelated sources passed this info on the me.
Share....please. Its how we all learn. It wouldn't totally surprise that there are more, but I would also bet there is a lot of "repackaging" going on amongst the various companies.
Chris
Does Patriot? Comp Cams? Twisted Flow? Lunati? Crane (if they are still around?) Chet Herbert? Howards? others?
I am curious. I just went through this entire ordeal looking for springs after I suffered a broken spring. I talked at length with quite a few people, some sponsors on this board, others not associated with this board and that's the info I was given to work with. I'm not claiming to be the authority, but multiple unrelated sources passed this info on the me.
Share....please. Its how we all learn. It wouldn't totally surprise that there are more, but I would also bet there is a lot of "repackaging" going on amongst the various companies.
Chris
Last edited by 1QWIKBIRD; 07-10-2010 at 09:21 PM.
