Hercules

I had a thought today while I was checking the valve spring pressures of a set of 60 lb valve springs that I salvaged out of two cracked 12v heads that I was planning on using in my 12v. I began to wonder about camshaft and tappet wear as result of the much heavier springs. I ended up comparing the 60 lb springs with a set of stock 12v springs that we had laying around. I took measurements at two points. The first was at 1.950 inch to match what I think is the installed height of a 12v valve spring. The second was measured when I compressed the spring .400 inch more from the installed height. These values should be a good representation of stock installed height and lift of the intake...exhaust is .437. I did not subtract valve lash, which, I don't think .010+ will change the measurements much. Anyways, the difference between stock and the 60 lb springs surprised me.

Stock Springs
@ 1.950 in = 60-65 lbs
@ .400 lift (1.550 in) = 170-175 lbs

60 lb PacBrake Springs
@ 1.950 in = 190-195 lbs
@ .400 lift = 210-215 lbs

There's at least a 130 lb difference at installed height and only 40 lb at .400 lift. Since there's overall greater pressure at all times, this really made me wonder if camshaft and/or tappet wear is greatly accelerated. Especially with the newer diesel engine oils. Any thoughts?

Also, those of you who are using the 60 lb springs, how many miles do you have on them and do you have any experience with camshaft wear as a result?

renopker

If wear would have been a problem I dont thing Cummins would be installing them.

Skip H

Just my humble opinion- but your numbers look funny on the 60 lb springs?
Maybe they should be 90-95 lbs at the 1.950 measurement?

Hercules

Skip H, your right. I didn't even catch it when I was typing and, worse yet, doing the math in my head. Not that it's an excuse, but, my wife broke her leg that day, so, I've been a bit distracted. Anyways, they're still not as low as you think. I had to run back to the shop today, so, I double checked again. This time I had a new set of the 60 lb springs with me to check against the two used sets I salvaged. The correct measurements are below with the addition of measurements at .500 and .600 lift too. I stopped at .600 since that's about the physical limit for lift in a cummins 12v. Also, .600 lift leaves you with about .100 until coil bind, so it's a safe limit.

Used and New 60 lb Springs @...
1.950" = 150 lb
.400" = 230 lb
.500" = 250 lb
.600" = 275 lb

There was no more than 5 lbs +/- difference at each measurement.

I measured the springs on a Rinck-McIlwaine Inc. Spring Tester with a 0 to 1000 lb range. The dial indicator is calibrated to begin indicating spring height at 2.100" in thousandths. It will accurately tell you what the spring is doing at all points to coil bind. Me on the other hand, will accurately tell you what it's doing when I'm not worried about my wife.

renopker

I use my drill press and a bathroom scale.

2500

so what's the verdict? extra wear or not?

getting ready to install 60lb springs on my low mileage 12v.
was planning on doing exhaust and intake both....

been dying to install my Jake exhause brakes

carl48

my 94 only has 800,000 miles on the 60 lb springs but i think it will be ok

Hercules

Honestly, I think renopker is right and they won't be a problem. My common sense has been telling me if they were a problem then people would screaming about it just like when the KDP was realized to be problem. I simply think there's just not enough pressure to do any real damage. When I think of the spring pressures I'm using in big block gas heads to deal with monster cams and racing, the pressures from these 60 lb springs are half that. Also, I don't think cummins would use crap to make their cams. I've never tested the hardness of one of their cams, but, I've never had one that was destroyed to test on. They always get reused or returned to the customer if they're replacing it for something more aggressive. I've accepted that baring any catastrophic oil pressure problems, your more prone to blow a head gasket before eating a cam.

DNRCustoms

well, I guess that settles the debate right there.

Riflemanusmc

^x1. If not, camshafts would be going dead right and left.

RPegram

The wear on the camshaft is directly related to how well it oils (do a search on cam lobe wiped out and see what comes up or doesn't) and how clean oil stays. If pressure on cam is worry, think about pressure put on rod and main bearings. They are protected by a thin film of oil and can last 1 million miles. If still concerned think about a little air cooled engine. Only thing protecting it is a little film of oil scooped up on crank rotation. No oil pump and it has aluminum on steel.

Now if you were talking some of the '80's model 305 Chev., well then I would be worried, but we're talking cummins and they oil well.

renopker

The chev. problem was bad camshafts and it went back to 68 as I had to change a lot of them,we used to run the 426 battleship springs on are 440s with hyd.cams and after 20 hooks replace the cams and lifters.these were around 270# on the seat if I remember right these were roller cam springs.