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Well, I understand what you're saying. BUT, if the springs were inadequate on the first cam, why was only one lobe worn? All 16 springs (VERY pricey 26921 Comp springs) were set up with the same installed height. No valve seals showed any interference, so there's that. On this latest cam, only a few lobes were worn, with #8 exhaust the worst. Both the old cam and the most recent one were only .600" lift, relatively tame by most built LS standards. Lastly, most (99+%) of this engines life saw rpm under 2,200 (70mph), and 200°-205° oil temps. I'm 70 years old, and don't run the living guts out of my engine like I did when I was 25 or 30! Plus, the guy at PAC told me that, as far as the springs are concerned, theres a huge difference in spring life between a .600" lift cam, and a .650" lift cam. He told me my 1905 duals (165lbs seat, 425lbs@max lift) could go 75,000+ miles at .600" lift, where a .650" lift cam would probably need the springs replaced at 25,000-30,000 miles, maybe sooner, depending on use. So, in my opinion, I believe the lobes are of questionable hardness. I still have a few contacts left in the toolroom that I worked in for 41 years. So one thing I can, and will do, is take the cam to the shop and check it on our Rockwell hardness checker. I'll report back with my findings, and post a few pics of the cam.......
The part in bold, that's a high number for a Valve Spring.
Which was my post in the other thread, lets investigate what the problem is here instead of blaming the Cam.
Originally Posted by Tony @ Mamo Motorsports
If I recall you had well over 30K on that build but I might be wrong
-Tony
As was posted in the other thread:
Originally Posted by grinder11
The 2nd cam that failed was only 4 years old/43,000 miles, so 14 years apart.
I think we may have found the problem. Testing the Springs wouldn't hurt at this point, need to come off anyway probably due for a change..
Last edited by the_merv; Aug 10, 2024 at 08:38 AM.
is lift the only variable that affects spring life, or do the lobe profiles also make a difference? seems like there could be many factors (hinted at by Tony). Maybe the PAC guy was being a little too general.
is lift the only variable that affects spring life, or do the lobe profiles also make a difference? seems like there could be many factors (hinted at by Tony). Maybe the PAC guy was being a little too general.
Lobe profile is a factor and so is spring quality.
IIRC something like a Comp Cams LSK lobe will wear springs out very quickly. So fast that Comp doesn't recommend the lobe for a street driven car.
Comp's XER lobe Cam typically might go ~30,000 miles with moderate use and reasonable RPM limits. Saying that based on my experiences with the XER and testing springs after removal.
The cam guru that spec'd the cam for my 99 T/A's 416 used LSL lobes. He'd ran ~70,000+ miles on his own car with the same cam and springs and spring were still good 👍 IIRC he planned to refresh valve train at 75,000 miles
Im very curious to check the spring pressures......
The 1900 series PAC springs are more general duty street springs aimed to reduce cost a bit. This is not their 1200 or 1300 series springs which are more premium options. In fact I urged Mike to install the 1200 series spring which comes in with very similar seat pressure and spring rate (PAC 1205's) and was glad that he decided to go that direction. It is a higher quality spring that should give you better longevity and less chance of breakage all things being equal.
Also, cam lobes most certainly effect spring life.....lobes that open the valve faster and drops them down on the seat faster are harder on springs and reduce spring life. Comp new line of low and mid shock lobes help to increase spring life with smoother ramp profiles and they still make good power with the right set-up.
I will update this thread at some point when I have had a chance to test the springs.....should be interesting actually. It would be very impressive if they were still relatively close to their advertised figures
Just an update.....I got my stuff today from Tony! Getting pretty excited about this stuff running again!!!! I used an entire can of brake cleaner on my old 1905 springs, then blew them off with compressed air so Tony wont jave a mess on his hands when he checks them!! I am taking the old cam in to the shop I retired from to have the lobes tested for hardness. I'm also taking my new cam along to compare the heels of each cam for distance above the cam bearing diameter. If they match, that's step 1 in seeing if I can run my old pushrods. Step two will be to take both an LS7 lifter and a Johnson 2110R lifter with me to check the plunger heights against each other. If the heels and plunger heights match, I'm good to go for PR length......
The part in bold, that's a high number for a Valve Spring.
Which was my post in the other thread, lets investigate what the problem is here instead of blaming the Cam.
As was posted in the other thread:
I think we may have found the problem. Testing the Springs wouldn't hurt at this point, need to come off anyway probably due for a change..
Never blamed the cam, or anything else. I WONDERED if anyone else had any issues with excessive lobe wear on CM cams. It was a QUESTION, NOT an ACCUSATION. I can't, nor can anyone else, title a thread perfectly when there's such a complex problem. People here seem to have no problem trashing COMP, and nobody knows the entire story on why the Comps cam wore excessively, either. I'm going to a lot of work, and additional personal expense, to try and find out what has happened. I want facts, if and when they can be found. Personally, what I'm trying to do here should make members grateful for the info. I thought that's what forums were mainly about is personal experiences and facts. I'm not trying to discredit anyone. As for .600" lift, the OEM LS7 cam lifts .591", .009" less, with less duration. Member here who works at PAC told me the 1905 springs would probably last 75,000 miles, maybe more, considering the way I drive my car, and the .600" lift. He said the spring life will see a huge difference between a .600" lobe and a .650" lobe. FWIW.......
I have an built LS7. Only posted here looking for issues with CM cams, and what, if any, root cause was found
We are just looking for facts. Every time you are asked a question about specifics on the build you dodge like this. Since you do not know the lifter preload you were running it appears you didn't measure. Just running a close to oem length pushrod without checking is a huge mistake. Improper preload which may have been way too much preload for the johnson lifter you were running could most definitely result with camshaft and lifter damage like you are seeing. It's also unlikely that every valve required the exact same pushrod length with a johnson lifter. Great lifter, but they still need to be setup with the proper preload.
This is one possible root cause of your problem. Just looking for facts not emotional driven opinions.
Yea, several things were dodged here. Mentions Forums are for advice and doesn't like hearing it.
Originally Posted by grinder11
I'm also taking my new cam along to compare the heels of each cam for distance above the cam bearing diameter. If they match, that's step 1 in seeing if I can run my old pushrods. Step two will be to take both an LS7 lifter and a Johnson 2110R lifter with me to check the plunger heights against each other. If the heels and plunger heights match, I'm good to go for PR length......
Yea the rest of us would actually get the whole thing together and measure when assembled, instead of that "method" above. There's some Forum advice for you...
Do it once, do it right.
Or make a post asking about damage, spend more money and do it again..
CamMotion 8620 core camshaft in my 01 SS. Brodix BR7 cylinder heads with PAC .660 lift springs. T&D billet adjustable roller rocker arms, Smith Brothers 3/8" pushrods and Johnson link bar style lifters. I installed the rocker arms and measureed for pushrod length at zero lash and ordered my PR's. I set the lifter preload at the rocker arm which is 1/2 turn from zero lash. No problems
Fast forward 6 yrs 9 mos...same springs on the heads. Car sees maybe 2K a year but after reading what Tony had to say I'm not starting it again until I get those springs swapped out. In case you're interested T&D makes a billet steel full adjustable roller rocker arm specifically desinged for the LS7 cylinder heads. I had a set but sent them back because they did not work on the Brodix heads. When I weighed them they were similar to the stock rocker arm with the bronze trunnions. Here's some pictures for comparison.
Steel is stonger than aluminum..Just sayin
We are just looking for facts. Every time you are asked a question about specifics on the build you dodge like this. Since you do not know the lifter preload you were running it appears you didn't measure. Just running a close to oem length pushrod without checking is a huge mistake. Improper preload which may have been way too much preload for the johnson lifter you were running could most definitely result with camshaft and lifter damage like you are seeing. It's also unlikely that every valve required the exact same pushrod length with a johnson lifter. Great lifter, but they still need to be setup with the proper preload.
This is one possible root cause of your problem. Just looking for facts not emotional driven opinions.
Who says I don't know the lifter preload I was running??? I NEVER said that! Only YOU did. You would think that since I know the existing preload, approximately .095", give or take .005", those that use logic would know my method of checking in the toolroom with precision measuring equipment on a surface plate would be dead nuts on for a hydraulic lifter. For a solid lifter, flat or roller, you couldn't do it the way I am going to. But this is a Hydraulic roller, so I can....
Who says I don't know the lifter preload I was running??? I NEVER said that! Only YOU did. You would think that since I know the existing preload, approximately .095", give or take .005", those that use logic would know my method of checking in the toolroom with precision measuring equipment on a surface plate would be dead nuts on for a hydraulic lifter. For a solid lifter, flat or roller, you couldn't do it the way I am going to. But this is a Hydraulic roller, so I can....
.095 preload is too much for the johnson lifters you are running. The recommended preload for the johnson 2110r lifters is .035 +/- .010 at 0.095 preload that you say you approximately have with your precision measuring equipment is .050 over the max recommended preload for those lifters.
