Cam Failure

[jeepinwi]

I feel like I'm skating on thin ice with my engine. I have about 25k miles on my stroker with the 753905 cam. At 23k miles I tore down the engine and the cam was in excellent shape with less than .003" difference among all the lobes; intake and exhaust seperate of course. I think the keys to my engine lasting has been the SL rated oil run in it since new and the stock valve springs keeping the pressure to a minimum. During the summer, I run an SL rated farm-grade oil that is only $14 for 2 gallons. It seems to me that this cheap oil is designed to be run in old tractor engines which are VERY similar to our engines. In the winter I ran Rotella 5W40 Synthetic which is also SL rated.

[gradon]

Just for a reference: Dino, what lobe went out on your crane cam(for some reason I think it's the same one as Frank, or at least an adjacent lifter in the back)? And what pump were you using? And while we're discussing the possibility of the pump: I still haven't bought the oil pump or timing set for my stroker build yet, but from what I've been reading over the past year or two, I should just go with the stock sets, right?

[dwg86]

Has anyone questioned any of the cam manufacturers about the lobe width? It seams as if the cam problems are still there even after all the precuations taken to supposedly correct the problem. What I don't understand is that stock cams are lasting over 200k miles without using any additives or special oil. My 2003 TJ has 88,000 miles. I used Dino oil for the 1st 18,000 miles and then switched to Mobil 1, and no problems. Are these after market cams cheap castings from China? Are they not ground correctly? Too much spring pressure on a narrow lobe? Poor hardening on the cams/lifters? Can new castings be made with wider lobes?
Has anyone ran and have had problems with some of the other cams other than Crane or Comp? There are several other companies out there making cams for the amc/Jeep inline 6...Reed, Schnieder, Lunati VooDoo, Clifford.
I did call Reed cams a few months ago. I had them grind me a cam for my 401 thats in my 1979 Jeep CJ-5. They said that they were not having any problems with there cams(I don't know how many Jeep 6 cams they have ground). They did say that their cam cores are USA made. Lunati also said there cam cores are USA made.
I would think that a company would want to correct a problem they have with thier product.
I am going to make some phone calls next week to question the cam width and problems with the lobes. Companies are in business to make money, and they will listen to concerns and take suggestions. Look at the KB pistons that are being made for our strokers. I also made a call to comp cams years ago about using a Chrysler hydraulic roller lifter with an AMC solid roller lifter tie bar to make a hydrualic roller lifter for the AMC V8. They already had all the parts(no extra tooling cost or parts to be made). Also the dist. drive gear on the amc v8 is bolted on the end of the cam, so a roller billet would be easy to make. He said he would look into it. About 3 months later...a new hydraulic roller lifter, and billet cam was made available for the AMC V8.

[seanyb505]

When I called crane they said they have the same lobe width as stock, and the guy pretty much said I was wrong when I said I had seen pictures of stock vs crane and the stock was wider. The Isky cam I ordered also came with narrow lobes. I talked to my machinist and he said it isnt just crane, but most companies are having issues. In 2006 he had 11 engines go bad due to cam failure, and not all of them were 4.0s. I guess most aftermarket places are getting their cores from the same cruddy place. I wonder if we could order blanks from Chrysler or something..

[FrankZ]

One of the guy's on a local forum I frequent is a Jeep tech by trade and has a lot on the ball, his response to the lobe width question makes alot of sense...reduction of parasitic drag/HP loss. If that is indeed the case, is the trade off worth it? I'd have to say no.

[oletshot]

Anyone care to explain the oil pump theory? I only keep asking because I just installed the HV pump a couple of days ago. It would be much easier to swap on the stand than in the Jeep, not to mention maybe saving the cam.

[FrankZ]

Too much oil delivered to the top of the motor and not enough making it to the front and rear of the motor. I'm just grasping a straw trying to make a broom at this point...all other causes have been eliminated.

[Cheromaniac]

Just for a reference: Dino, what lobe went out on your crane cam(for some reason I think it's the same one as Frank, or at least an adjacent lifter in the back)? And what pump were you using? And while we're discussing the possibility of the pump: I still haven't bought the oil pump or timing set for my stroker build yet, but from what I've been reading over the past year or two, I should just go with the stock sets, right?

I lost the no.6 intake cam lobe and the corresponding lifter was worn concave. The no.6 exhaust lifter was collapsed but not worn, and the no.6 exhaust cam lobe was fine.
I was running a stock oil pump for all but the last 4 months before the cam/lifter failure. I swapped in a Melling HV pump after my oil pressures started to become erratic. I never actually had a low oil pressure situation but at highway speeds it kept fluctuating between 35-45psi when it had previously been a steady 45psi. The new pump solved that problem.
I used Castrol GTX for the first 3000 miles after my stroker build and then switched to Mobil 1. Having heard of stock 4.0 engines going 200+k miles on Mobil 1 without any problems, I was confident that Mobil 1 would be good for my stroker.
I've heard all the stories about flat tappet cams needing ZDDP to protect the lobes/lifters, but I think the quality of the surface-hardening of the lobes/lifters by aftermarket cam manufacturers is patchy and they're just using the low ZDDP as an excuse for their cam failures.
If the cam manufacturing was very high quality, they wouldn't need ZDDP to keep them going in the first place so I think they're feeding us a load of bull. Modern engines don't have flat tappet cams these days so I guess the cam manufacturers are giving flat tappet cams very low priority.

[dwg86]

Some valve spring specs...
Stock valve springs(from alldata.com) spring rate 327lbs/in. Installed [email protected], open [email protected]. That would be .424 valve lift (installed minus open/1.64-1.216=.424). Using a crane cam 753901 open spring pressure would be [email protected] valve lift.(spring rate x valve lift + installed pressure./327x.484=158. 158+79=237) I don't know if stock springs would go to .484 valve lift without binding.
* Crane spring part number 96803, recommended for all amc/jeep BUT the 4.0, 330lbs/in. Installed [email protected] would be 267lbs @.484 valve lift.(330x.484=160, 160+107=267)
* Crane springs 96806, recommended for the 4.0, 204lbs/in. installed [email protected] would be [email protected] valve lift.
* Lunati springs 73804, 270lbs/in spring rate. Installed [email protected] would be [email protected] valve lift.
* Lunati valve springs 73126 (recommended for the 63500 voodoo cam/ [email protected] 218/213 lift .484/.484) 364lbs/in spring rate. Installed [email protected] would be [email protected] valve lift.

On cranes web site "master cataloge" how to choose a valve spring""
1) "FLAT-TAPPET" cam/lifter applications (Street & Street/Strip) seat pressures
a. Small Block 105-125# Seat Pressure
b. Big Block 115-130# Seat Pressure (Note: Big Block applications need higher seat pressures due to their
larger, heavier valves.)
2) "FLAT-TAPPET" Open pressures should not exceed 330# open pressure (sustained after spring break-in) for
accepable cam and lifter life.
a. Open pressures should be a minimum of 220# for applications up to 4000 RPM.
b. For good performance above 4000, open pressures should be at least 260# with stock weight valves.
(Lightweight valves require less spring open pressure.)
c. Spring open pressures over 280# can cause "pressed-in" studs to come loose; therefore,we recommend
screw-in studs for open pressures above 280#.

[seanyb505]

I've heard all the stories about flat tappet cams needing ZDDP to protect the lobes/lifters, but I think the quality of the surface-hardening of the lobes/lifters by aftermarket cam manufacturers is patchy and they're just using the low ZDDP as an excuse for their cam failures.

Modern engines don't have flat tappet cams these days so I guess the cam manufacturers are giving flat tappet cams very low priority.

Is there anything to be done to the cam once we get it to harden the lobes? Ive head of nitride or something like that for cranks, would it work on cams?

I love being put on the dont care list.

[dwg86]

Crane offers something called Mikronite. Its expensive!!! $135.00 fro a cam and $200.00 for a set of lifters(16).

[FrankZ]

Cryo perhaps? Guess we need to find a decent metallurgist to post up here.

[Flash]

OK, my previous thoughts on the width of the cam.........Well, it's not holding as much water as i thought

I still thing the width of the lobe is part of the issue......just can't come up with the reason why?????

Here is were my head is at, today. The cam lobe is ground on a slightly different degree then the lifter lobe.This is what allows or cause the lifter to rotate in its bore. When you look at the good lobes you can see the thin line that the cam runs on. It gets wider as the lifter travels up the the lobe...and maybe thats were the wider lobe comes into play.
Maybe as the crown of the flat tappet surface, as it starts to ware down(whether it normal or abnormal wearing) begins to be gourge or cut by the edge of the lobe were as the wider lobe would require a lot more wear before this could happen.

One other reason, that the smaller lobe would cause wear to increase, would be that the cam is trying to spin the lifter in the center(smaller circle) as the wider lobe would spin or rub the lifter close to the outer part of the lifter surface( more surface to cover in one rotation of the lifter.

MY Theory, is that our blocks may have an inheritance problem........such as a lifter bore that isn't square or true too the block or cam,.......... or has a oiling problem....................Hmmm

There's a QUESTION!

How does the lifters, too cam lobe, get its lube..........Isn't it from the crank/rods. That throws oil onto the cam.......or is it lubed thru the lifter bore...........If it get is lube from the crank/rod......these cam saver lifters, maybe well be worth the time!!!!!!!




I can't under stand how the HV oil pump could create a cam failure BUT, IT SEAM THAT MOST CAM FAILURES, HAVE A HV PUMP installed, WHEN IT FAILLED.........RIGHT?

HOW dose the oil pump affect the cam? does the driving of the cam try too force the cam to the back of the block or the front?
If the cam driving the oil pump, in return, cause/tries to push the cam forward against the preloaded spring in the cam button................ that might make sence(Don't know how much this theory hold water either.

WHY is it, that it's # 5 or 6? Has any one had #2 or even a #4 cam lobe failure??

SOAP BOX TIME!!!!!!

ZDDP.....It is and extreme pressure lube additive......In other words it is for a High pressure, metal to metal ware contact surface..........cam lobes(Flat tapppet cam lobes)...........But even rod and main bearing will benefit from this additive..............the only thing ZDDP is bad for is you cat. converter
It would be beneficial in your/there new 2008...what ever!
It is just like when they took the lead out of gas........would it cause any problems with any 2008 auto(or the unleaded cars of the 80's and 90's......Probably not! IT WOULD HOW EVER PLUG A CAT VARY VARY QUICKLY!!!!
AND, even the car manufacture are tying to convince us that the lack of ZDDP in no big deal.........WHY, because they don't want to have to replace a cat under warranty......because of the ZDDP in the oil........And they don't have a flat tappet cam to CARE, what were dealing with
Soap Box Over!!!!!!!!!!!

[Flash]

Crane offers something called Mikronite. Its expensive!!! $135.00 fro a cam and $200.00 for a set of lifters(16).

That's after you have bought the cam and lifters....right?

Hijack!!!!!
I wonder if that would help a stock cam that was ground for a roller, like SIXPAK did!


More on this story here:
viewtopic.php?f=5&t=105
Fourth page, 2nt post!
Hijack over!!

Flash

[John]

This link might prove interesting. http://www.camshafteng.com.au/fail.htm Read just below the Bullet Major lobe tip wear, major follower wear on isolated lobes only:- Be sure to look at the photo of the lifter bottom.
Check out the home page and you will find it interesting too.

Check out this link to cam lobe tip failure photos. http://www.sacskyranch.com/camshaft.htm

John