chevy406

For the past several (3 to 4) weeks, I have been chasing a noise in my Corvette's engine. It was difficult to explain - sounding something like detonation but it was present faintly at idle and got louder around 1,500 rpm. When it started I had another C5 torn apart in my garage, so my car got a quick once over to make sure it didn't have a broken valve spring or rocker arm, and I kept driving it :oops: . Eventually I replaced the valve springs that had 47,000 miles on them, with no change to the noise. I temporarily removed both accessory belts, no change. During my analysis paralysis, I kept driving 100 miles per day, maybe subconsciously hoping for catastrophic failure so I could justify a new LS3 shortblock? Well, last Thursday at lunch I got a low oil pressure alarm at startup. I tried re-starting, gave it a little gas, and sure enough it didn't have oil pressure (rattle, rattle). A third startup the oil pressure came up and it didn't have any further pressure problems the rest of the day. I started tearing into the engine that evening, expecting to find something lodged in the oil pump and hanging the pressure relief valve open. I did find indications of small particles passing through the pump - some scoring on the pressure relief valve. Further engine teardown found my #5 intake lobe looking like this:


So I pulled the heads and found the corresponding lifter looking like this:


Both the cam, lifters and oil pump had 95,000 miles. I have been changing out my Patriot Gold springs roughly every 45,000 miles. I am guessing valve train instability lead to bounce on this lobe and eventually started digging into the cam. A weak #5 intake valve spring might explain why only one lobe failed? Notice the hump in the worn area - like the lifter was maybe bouncing?

81c3

I would say youre probably correct in your assumption. I did a cam in my 02 at about 76,000 miles and noticed more wear on some of the lobes. I believe #5 was one of the ones that had started to show a groove. Also, on that same cylinder, the valve seal was worn out . The spark plug on #5 had serious carbon build up (little chunks) from oil burn. I would say a weak spring would definitely cause valve instability causing the seal to wallow out and start letting the lifter bounce off the cam lobe which would look like the pics you show. Mine was alot less severe, but had the same wear pattern as yours. Like I say, the engine had about 20,000 less miles than yours, but I was on the same path.

I replaced my cam, oil pump, springs (single beehives), valve seals, push rods and had the rockers rebuilt by Hinson. That was 10,000 miles ago. Seems fine with very good oil pressure.

Have fun putting it back together!!

rebelheart

I would think you had a lifter failure first which then damaged your cam.

Ninety-Nine FRC

That's what I was thinking. I just pulled out my stock '99 cam (95k miles) and it looked fine. No noticeable wear.

81c3

Not sure Id agree. Lifter failure would be one of two ways. Either the roller fails, or the internal spring fails. Clearly the roller is still in tact. In my engine, I reused the lifters. I had alsmost the same exact wear pattern on 3 of my cam lobes. Its been 10,0000 miles since I installed a new cam and springs with no problems to date. In fact, I didnt have a problem when I did the cam, I was just adding some horse power At any rate, the weak link in our valve trains seems to be the springs. Id bet a weak spring was the culprit in the OP's failure and probably the begining failure of mine.

vettenuts

Couple of questions for the OP. Is this the original cam (I assume not) and are the lifter trays the originals? If the lifter trays are the originals and you look at the bottom of the offending cylinder's lifter tray, does it have a "10" stamped on the tray?

SMaster

You know, I hung out in the Thirdgen group for years and I never saw as much lifter failure as I see here. I've been seeing lifters pitted, turned, cams destroyed, etc. here. I belive two thing must be contributing. Higher RPM's than MOST tuned ports could turn, higher spring rates to control the heavy lifters, sub par materials and those lifter trays.

I ran link bars in my L98 at 6200 RPM with a Stealth Ram intake 383,(See my User CP photos) Trick Flow double springs for 15k and counting and never had any signs of failure. But, I did replace the springs that came on the Trick Flow heads twice and also a set of Sig Erson because they couldn't control the valve float.

I sometimes wonder around here what some guys confuse for rev limiter and actually the valves bouncing? It will completely stop the advance of RPM increase just like the electronic limiter. I'm not saying you did that but I see more lifter/cam failures here in a short time than I did the whole time I was on Thirdgen newsgroup.

BTW, I'd replace the cam, lifters and springs.

Also, something else I don't understand about the newer generation of hydraulic lifter setups is why they don't just use adjustable rockers? You still need the correct wipe patten but it would make the adjusting the preload simple.

Sorry, guess I got long winded at the keyboard and probably didn't help you much but I was just wondering all this the other morning when someone asked about a ticking noise that had started and it got me to wondering these things.

Good luck with your repairs. If you don't tear it all down I sure hope the filter caught most of the trash. I'd certainally run a few cheap oil flushes through it on startup.

Also, back then everyone said there were only one or two manufactures of hydraulic lifters and the retro fits were backordered everywhere. I have picture in my photo album of at least five different designs I took many years ago, so, it seem the design went through several changes.

chevy406

I apologize for not including all the information on my engine configuration in my original post. I copied it from another forum post, and somehow lost part of the information. This isn't a stock engine. Here is a quick summary.
At 155,000 miles I installed a Comp Cams 224/230 XFI lobe (.600"/.604" lift) with 112 LSA. Along with the cam I added new "LS7" GM lifters, new timing chain, new oil pump, and AFR 205 heads with Patriot Gold dual valve springs and Yella Terra rocker arms. I shimmed the rockers for a nice tight contact on the center of the valve stems. So basically only the block and rotating assembly are original in my engine.
This cam lobe failure occurred 95,000 miles later with an odometer reading 249,700.

Last night I pulled the oil pan and windage tray so I can clean and inspect crank/rod bearings. I removed 2 main and 2 rod caps and didn't find any sign of wear, but just a couple minor lines from debris. However, the cam bearings are showing copper. So the block is coming out for new cam bearings.

I just have to think that a relatively noisy valvetrain (i.e. impact loads) and 95,000 miles just flat out wore out some parts. In my humble opinion it was the cam lobe that started wearing first. I say that because there are several other lobes that have light wear indicators on the open / close ramp portions of the lobes. The lifter wheel on the failed lobe still spins and all of the needle bearings appear to still be in it.

doje

This is the fourth time I've seen a cam that wore like that - and the fourth time that the cam has been made by comp. I'm not saying its cause and effect - just an interesting coincidence.

rebelheart

I seem to remember some fellow racers talking about Comp Cams having a hardness issue a few years back.Not really sure though.

RonSSNova

Comp had issues with their cast core roller cams. Mainly solid rollers that couldn't handle the sprin pressures.
These are billet core.
I suppose it could be a cam hardness issue, but it did seem to last for quite a long time!
As far as the cam being ground by Comp, how many aren't ground by Comp?
Would be pretty tough to get to root cause on a failure like this.

Pretty dang impressive the short block being alive and well after 249K miles! Holy cow!

Ron

chevy406

Got the block out of the car last night so I can at a minimum replace the cam bearings. I'll have a chat with my machinist to discuss cylinder wear and ring replacement. With the front crandle and engine out of the car I have parts slung everywhere. Need to spend some quality time cleaning parts and organizing the garage again. Taking the hood off by myself last night was a little crazy. I'll be getting an extra set of hands to install it.

blades11b

had the same thing happen with multiple cam lobs on my f body after it had a Futral cam (made by Comp Cams) it was a bad cam turned out they had a bad run of them that were "soft" so although not common ive seen it before only on mine it was like 7 lobes

zeevette

I believe Ferrera had a similar issue with materiel hardness a few years ago, as well. My original TF heads had to be rebuilt after less than a thousand miles. They were equipped with those valves.

chevy406

Turned out the cam failure was somewhat of a hidden blessing. I decided to do a basic short block rebuild on my 250k mile stock engine along with new cam, lifters, oil pump, and timing set. Basic build just to get me by for another 250k miles... The cylinder walls all looked great, with no discernible ring groove. A quick hone had all the cylinders looking fresh. However, I did find #7 piston had a broken chunk between the top and second rings. The piece stayed in place during operation but fell out when the piston was removed from the block. So it was indeed a good time to freshen it up. I held off adding the stroker rotating assembly that I really wanted. My son is starting college this fall, and that's where my extra funds need to be headed. But life will soon be back to normal, hopefully after getting it reassembled this weekend.

algZO6

i remember that however his cams are ground by cam motion.

84REDCROSSFIRE

Thats why i always add Red Line's ZDDP oil additive with every oil change. Auto makers claim roller camshafts dont need ZDDP levels like the older flat tappet cams. I dont believe them, and now i see why. Even the ZDDP makers claim roller cams dont need extra leves of ZDDP, but i feel they are just keeping the EPA from shutting them down if they were to advertise for newer vehicles. Its cheaper to replace a cat converter than a engine.


Some links on ZDDP
http://www.redlineoil.com/product.aspx?pid=121&pcid=1

http://zddppluscentral.com/faq

http://zddplus.com/

pewter99

I got pics like that.....










new block bigger cam and forged internals this go round

yellowvette837

I have a cam and a lifer in the garage that look just like this ...

mchicia1

OP, did you get a video of the noise?

Did it sound anything like this?