UPDATE on COMP918 Springs Removal...
05-27-2007, 01:51 AM
#1
Melting Slicks
Thread Starter
UPDATE on COMP918 Springs Removal...
I just removed the driver's side springs and replaced with stock. I am putting on TFS heads soon, so no need for the good stuff. Anyway,
4 of the 8 springs on the driver's side were broke. Will report in later on the passenger's side. They broke along the top of the spring. When I'm done, I'll post a "how to recognize the broke spring". It wasn't immediately obvious until I took them off and noticed a pattern.
I am surprised more people haven't reported this.
4 of the 8 springs on the driver's side were broke. Will report in later on the passenger's side. They broke along the top of the spring. When I'm done, I'll post a "how to recognize the broke spring". It wasn't immediately obvious until I took them off and noticed a pattern.
I am surprised more people haven't reported this.
Last edited by 427CPE; 05-27-2007 at 05:10 AM.
05-27-2007, 05:04 AM
#4
Melting Slicks
Thread Starter
10 of the 16 valve springs were broken.
Symptoms: down on power, felt like 40hp or so, loss of low end torque. Engine not as throttle responsive as normal. on physical examination, I noticed the valves seemed swayed and pushed to one side of the pushrod. Datalogs were normal. Springs still had pressure on them since the top of the springs was where the breaks occurred.
I strongly advise you at least check your valve train out if you have these springs. My car is a stock 02 Z. I had a 585 lift cam in it for a few months and added these springs. and NO, I do not bounce it off the rev limiter very often and the car really is not run that hard so this occurred under normal conditions.
Various Pictures:
Other pictures from a few days ago when Id idn't know for sure they were broken:
http://forums.corvetteforum.com/show....php?t=1704106
Symptoms: down on power, felt like 40hp or so, loss of low end torque. Engine not as throttle responsive as normal. on physical examination, I noticed the valves seemed swayed and pushed to one side of the pushrod. Datalogs were normal. Springs still had pressure on them since the top of the springs was where the breaks occurred.
I strongly advise you at least check your valve train out if you have these springs. My car is a stock 02 Z. I had a 585 lift cam in it for a few months and added these springs. and NO, I do not bounce it off the rev limiter very often and the car really is not run that hard so this occurred under normal conditions.
Various Pictures:
Other pictures from a few days ago when Id idn't know for sure they were broken:
http://forums.corvetteforum.com/show....php?t=1704106
Last edited by 427CPE; 06-01-2007 at 05:08 AM.
05-27-2007, 05:12 AM
#5
Melting Slicks
Thread Starter
The engine seemed down on power and vibrated slightly. Just didn't have that low end snap it always does. The car normally runs 11.8s@117 stock down to the air filter, so I have a pretty good feel when something is wrong with it. The vibration and loss of torque was just out of the norm.
05-27-2007, 08:27 AM
#7
Cruising
Member Since: May 2007
Location: Birmingham AL
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I recently removed a set of 918 springs with only a hundred miles or so on them and found a couple of broken ones. I was only lifting them about .560 and they were very safe on coil bind. Did you check the installed height on all of them when they were installed? If you had a comfortable margin to coil bind then this may be a bad batch. Mine came through Jegs about 6 months ago.
Michael
Michael
05-27-2007, 10:59 AM
#8
Drifting
How do you check coil bind? I have 918's and I know they are supposed to be good until .600 lift and I have .581/.592 and now I'm a little worried.
Also, the heads are already on the car with the springs installed.
Also, the heads are already on the car with the springs installed.
Last edited by 2004SpiralGrey; 05-27-2007 at 11:03 AM.
05-27-2007, 11:47 AM
#9
Melting Slicks
Thread Starter
05-27-2007, 01:27 PM
#11
Melting Slicks
Thread Starter
During Nov 06, a 216/222-585-116 cam was installed. Not aggressive by any means. I have a STOCK cam in right now but it was with the stock cam that I started noticing the power loss. I just got back from StarBuck's a few mins ago. The car is a monster again and gained every hp back.
My advice: REMOVE THE 918s and install either COMP 921's or PATRIOT GOLD DUALS. If one of those springs breaks other than where they did on mine, the piston and valve are going to get a chance to say hello to each other.
My advice: REMOVE THE 918s and install either COMP 921's or PATRIOT GOLD DUALS. If one of those springs breaks other than where they did on mine, the piston and valve are going to get a chance to say hello to each other.
Last edited by 427CPE; 05-27-2007 at 01:32 PM.
05-27-2007, 03:02 PM
#12
Melting Slicks
Thread Starter
For same, .588 lift cam, force req to open .588"
Crane 144832-16: 207 lbs
Comp 918: 184 lbs
Comp 921: 240 lbs good for high rpm
PRC Gold: somewhere between crane and 921s.
Example Cam: Crane Z Cam: 228/232: requires:
Closed 112 LBS @ 1.800, result 112 w/ Crane Springs
Open 330 LBS @ 1.200 , result 337 w/ Crane Springs
Crane 144832-16
O.D. outer: 1.275
O.D. inner: 0.937
I.D. inner: 0.667
112 lbs @ 1.800
352 lbs @ 1.150
coil bind: 1.045
MAX LIFT 0.650
spring rate: 352 lb/in
Comp 918's
O.D: 1.055(top)
I.D: 0.885 I.D: .650 (bottom/top)
O.D. 1.055/1.29 (top/bottom)
114 LBS @ 1.85
318 LBS @ 1.20
COIL BIND @ 1.10
MAX LIFT 0.600
Rate: 313 lb/in
Comp 921's
O.D: 1.300
I.D: .870 (outer spring)
I.D: .655 (inner spring)
135 LBS @ 1.770
400 LBS @ 1.220
COIL BIND @ 1.040
MAX LIFT .650
rate: 408 lb/in
PRC golds
O.D 1.29
135lbs @ 1.800
385lbs open
coil bind @ 1.08
.650 lift
LS6 Springs:
90 lbs @ 1.800"
280 lbs @ 1.250"
coil bind: 1.160"
Max lift : 570"
After looking at vavle springs, cam spring reqs, etc. looks like the best spring for HIGH RPM is the 921 COMP. The PRC Gold looks like a good competitor.
Last edited by 427CPE; 05-27-2007 at 03:06 PM.
05-27-2007, 11:36 PM
#14
Melting Slicks
Thread Starter
921s:http://store.summitracing.com/partde...5&autoview=sku
918s:http://store.summitracing.com/partde...5&autoview=sku
Last edited by 427CPE; 05-27-2007 at 11:44 PM.
05-27-2007, 11:49 PM
#15
Pro
Member Since: Oct 2006
Location: N.J.
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Yes, the 921s are cylindrical shaped and have inner springs like a normal valve spring. The 918s are those POS in the picture and are behive shaped.
921s:http://store.summitracing.com/partde...5&autoview=sku
918s:http://store.summitracing.com/partde...5&autoview=sku
921s:http://store.summitracing.com/partde...5&autoview=sku
918s:http://store.summitracing.com/partde...5&autoview=sku
Thank You 427CPE
05-28-2007, 08:20 AM
#16
Team Owner
There have been a number of instances recently about 918's breaking, and with very low mileage (one case was under 50 miles). Someone on the Camaro forum called Comp and was told they had changed spring vendors and were having problems with the spring. Comp then retracted the statement, but it sounds like the only plausible explanation as these springs have been a solid performer for years and now this. Somewhere someone posted the lot numbers that Comp suspected had the problem but I don't remember where I read this.
If you still want a beehive spring, I would take a close look at the PSI 1511.
If you still want a beehive spring, I would take a close look at the PSI 1511.
05-28-2007, 12:08 PM
#17
Melting Slicks
Thread Starter
There have been a number of instances recently about 918's breaking, and with very low mileage (one case was under 50 miles). Someone on the Camaro forum called Comp and was told they had changed spring vendors and were having problems with the spring. Comp then retracted the statement, but it sounds like the only plausible explanation as these springs have been a solid performer for years and now this. Somewhere someone posted the lot numbers that Comp suspected had the problem but I don't remember where I read this.
If you still want a beehive spring, I would take a close look at the PSI 1511.
If you still want a beehive spring, I would take a close look at the PSI 1511.
05-28-2007, 08:19 PM
#18
Team Owner
05-30-2007, 06:26 PM
#19
Melting Slicks
Thread Starter
To be fair, I wanted to let CF.COM know that Comp Cam's rep said to send in the springs and they would consider giving me a credit. They did not guarantee a credit, but I thought it was a good faith effort on their part. He did mention a bad batch of springs at some time in the past so I guess that means they all aren't bad.
05-30-2007, 07:18 PM
#20
Team Owner
I think they are trying to sort it out. It must be a tough situation for them, failure could mean someone destroys a motor yet they also need to figure out what is wrong to prevent future occurances. As and aside, I just posted some information I got from the Crane newsletter on their new beehive spring.