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What would cause lifter failure in several cylinders?
My buddy bought an OBS short bed with an "LS swap", looks like an early 5.3 iron block/aluminum head motor with cathedral ports and a truck intake and some shitty accessory drive adapter kit. Rear o2s are tuned out.
specs given are a "stage 2 summit cam", comp cams 7637-16 pushrod set, and "ls7 valve springs"
This thing has destroyed half the lifters, literally broken the tops off. Valves look good, pistons show no signs of impact. Is this a case of improper pushrod length or too much for oem lifters to handle?
If the lifters need to be upgraded, what's a good replacement for street/strip?
TY
They all came out with a magnet, but I had to pull #3 exhaust with locking pliers. Most of them looked like they blew up on the top, #3Ex roller got f'd and ate into the cam lobe, funny enough that cyl was contributing. I've only pulled the LH head and half of them look like the retainer clip came out of the lifter.
You posted “ls7 valvesprings”. Exactly what spring is being used here? Any pics of the springs? How did this thing run before it ate itself? Typical Ls valvetrain noise, or was it noisy?
He showed up with this thing showing it off, I heard nasty metallic rattling, but he claimed it ran great. I never drove it. He said the drive ability got worse over time. I saw some melted plug wires and assumed an easy fix. Replaced plugs and wires with OEM AC delco parts. Ran a bit better, but I could hear backfiring through the intake. Told him it's off time or has some valve train damage . Pulled valve covers and found a few rockers very loose. Pulled the LH head and found destruction, mostly on the top of the lifters.
Anyway to check spring install height. I’m wondering if yours got into coil bind.
Hmm coil bind makes sense, cant think of another reason why these lifters were destroyed in this manner. I have some digital calipers i can use to get a rough estimate. I also have the head installed on the RH side, I can turn the motor over and check.
Hmm coil bind makes sense, cant think of another reason why these lifters were destroyed in this manner. I have some digital calipers i can use to get a rough estimate. I also have the head installed on the RH side, I can turn the motor over and check.
thank you
Yes coil bind makes sense, but usually bends pushrods…which are the second “spring” in the valvetrain…or breaks springs. Pushrods look straight? Roll them on a flat surface to see. Something looks off on the lifters to me. Oil channel is really tall, but could be the pics?
Last edited by Che70velle; 10-17-2022 at 08:57 PM.
The more I think about this issue…LS7 has a 5.190…ish valve length depending on lash cap being used, which is .060 from GM. The typical cathedral port head valve length is 4.867…ish depending on how you measure it. Take the LS7 spring and put it on a shorter valve and it should bind. Just might be the issue here, I’m just surprised it knocked the lifters out of it before it kicked the pushrods. Possibly some $69 lifters in the engine…
…edit…if in fact it is indeed a true LS7 spring designed for a 1.800 installed height…
The more I think about this issue…LS7 has a 5.190…ish valve length depending on lash cap being used, which is .060 from GM. The typical cathedral port head valve length is 4.867…ish depending on how you measure it. Take the LS7 spring and put it on a shorter valve and it should bind. Just might be the issue here, I’m just surprised it knocked the lifters out of it before it kicked the pushrods. Possibly some $69 lifters in the engine…
…edit…if in fact it is indeed a true LS7 spring designed for a 1.800 installed height…
I'm biting. Something pretty severe going on here in the valve train, and there's not many things harder on valve train than coil bind. Maybe the retainer hitting the guide seal?I agree with Che70velle-The difference in valve stem length on LS7 to the OPs setup would probably prevent much more than .300" valve lift before binding. Pushrods almost have to be bent. Maybe why valves were "loose?" However, if thats not the case, OP has some mighty strong pushrods!!!!
Ls7 lifters have a .200 total plunger travel. Coil bind would collapse the lifter down, up to .200 before the next weak link pushrods would bend. Depending on preload. That may have been the metallic noise the OP was hearing.
Last edited by jasons69chevelle; 10-18-2022 at 07:20 PM.
Ls7 lifters have a .200 total plunger travel. Coil bind would collapse the lifter down, up to .200 before the next weak link pushrods would bend. Depending on preload. That may have been the metallic noise the OP was hearing.
On the opposite side of things, if the pushrods are too short, the lifters will be riding with the plunger and the hydraulic pressure on the plunger against the spring clips. The spring clips could pop out of place and the lifter plunger then comes apart. I replace those spring clips with actual snap rings on all my lifters. While it is probably not what happened here, the snap rings are added insurance should the valves float that the lifters will not fly apart at high rpm.
Thank you all for the detailed info. The "LS7 valves" measure 1.825 installed without rockers, but it's very difficult to get an accurate measurement with the calipers. I ordered a dial indicator, gonna take some measurements on the lift and will report back.
10-16-2022, 09:03 PM
What would cause lifter failure in several cylinders? 
