PRC 650 Valve Spring
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Teching In
Joined: Sep 2012
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PRC 650 Valve Spring Anyone measured a PRC 650 spring back when it was new?
Unfortunately I did not.
I called Texas Speed and was very surprised at the lack of info the rep could provide. All he would say is that he has had them on his car w/nitrous and many drag strip passes and they're great, so I should be ok. I asked how he knows they're still good and he didn't have an answer. I asked what they were rated for and he wouldn't say (said he didn't know) and wouldn't give any guidance on how much of a deviance would still be considered acceptable. Said he would consult their engine builders and get back to me. He never called me back. I tried emailing Jason through the forum and got zero response from him as well. They've just gone from the top of my list for aftermarket parts to the bottom!
An internet search identified the pressures as:
145 lbs at 1.8"
450 lbs at 1.15"
Yesterday I measured eight of my springs on an MTS UTM (waaaaay overkill for just measuring a spring):
- Spring free length only varied by 0.02"
- 1.80" length = 147 to 152 lbs (looks good)
- 1.15" length = 418 to 422 lbs (maybe a problem)
So, is the low pressure at 1.15" an indication of a problem with the springs or just that PRC had overstated the pressure?
I'm guessing TSP originally recommended the 450lb spring because their cam (old design 228r) has XER lobes, but due to their lack of response I'm just guessing.
If you happened to measure them before installing, let me know what you got!
Thanks
Unfortunately I did not.
I called Texas Speed and was very surprised at the lack of info the rep could provide. All he would say is that he has had them on his car w/nitrous and many drag strip passes and they're great, so I should be ok. I asked how he knows they're still good and he didn't have an answer. I asked what they were rated for and he wouldn't say (said he didn't know) and wouldn't give any guidance on how much of a deviance would still be considered acceptable. Said he would consult their engine builders and get back to me. He never called me back. I tried emailing Jason through the forum and got zero response from him as well. They've just gone from the top of my list for aftermarket parts to the bottom!
An internet search identified the pressures as:
145 lbs at 1.8"
450 lbs at 1.15"
Yesterday I measured eight of my springs on an MTS UTM (waaaaay overkill for just measuring a spring):
- Spring free length only varied by 0.02"
- 1.80" length = 147 to 152 lbs (looks good)
- 1.15" length = 418 to 422 lbs (maybe a problem)
So, is the low pressure at 1.15" an indication of a problem with the springs or just that PRC had overstated the pressure?
I'm guessing TSP originally recommended the 450lb spring because their cam (old design 228r) has XER lobes, but due to their lack of response I'm just guessing.
If you happened to measure them before installing, let me know what you got!
Thanks
The last time I installed a set of PRC springs, I measured them before installation. They were all spot on as advertised, with very little variance from spring to spring.
Joined: Mar 2007
Posts: 1,151
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From: Saskatchewan, Canada - where arguing "DA" is for the slow and weak...
If the seat pressure is correct for your application, and the open pressure is in range; you are most likely fine. Seat pressure is where the game is won or lost - I believe this has to do with controlling valves bouncing off the seats.
Thread Starter
Teching In
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Good to know. We're you using the 650's?
More internet searching turned up these specs. This was from a company with them currently listed for sale. Don't know if its a new design or not:
144 lb. @ 1.810"
402 lb. @ .600" lift
425 lb. @ .650" lift
A bit weaker than the original advertised numbers but closer to my measurements.
I hate to throw away good springs. But due to a lack of response by TSP, I think I'll be placing a call to BTR.
More internet searching turned up these specs. This was from a company with them currently listed for sale. Don't know if its a new design or not:
144 lb. @ 1.810"
402 lb. @ .600" lift
425 lb. @ .650" lift
A bit weaker than the original advertised numbers but closer to my measurements.
I hate to throw away good springs. But due to a lack of response by TSP, I think I'll be placing a call to BTR.
Thread Starter
Teching In
Joined: Sep 2012
Posts: 17
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Thanks
Joined: Mar 2007
Posts: 1,151
Likes: 63
From: Saskatchewan, Canada - where arguing "DA" is for the slow and weak...
In one of these videos I believe Brian Tooley mentions it. I am sure you can achieve lofting and/or floating the valves with too little open pressure too. If you are concerned you can get a shim kit and retest for bind.
