Rebuilding a stroker after a dead cam (Long..)

[Rob Patterson]

After buying the Hesco head from a friend, I was given his old stroker short block because it chewed up a lobe on #5 cylinder and the gear for the distributor drive looked chewed up. He says when he removed the cam and timing cover he did not notice the spring and pin to retain the cam. He says this is why it probably destroyed the gear for the distributor drive. Would this also destroy a lobe? He says this was the 2nd cam the motor destroyed. He was not the original owner of the motor; he bought the Jeep with the motor already in it and it was already on the 2nd cam when he purchased it.

I can already tell that the cam bearings are bad but I need to figure what else I need to do to get this motor running?

I have looked it over quickly and can tell that it has the later style 4.2 crank. It is also using the 4.2 rods and Sealed Power (Sterling) hypereutectic H802CP pistons. I checked the pistons and they appear to be approximately .020" in the hole using feeler gauges. It was using Fel-Pro 9076PT 0.043" thick head gasket. I looked at the cylinders, and 2-5 look excellent with the cross-hatch honing still very visible while cylinders 1 and 6 have smooth spots. These spots don't have any honing marks visible but there is no ridge. Like I said it is smoother than the rest of the cylinder and you can't feel the cross-hatching with your finger nail. What are these spots from and are they a problem? This stroker appears to be fairly low mileage as there isn't any ridge at the top of the cylinders.

Thanks

 

[nekocopter]

It ate the lobe because the cam walked either forward or backward.

Without that retaining pin, the cam is free to move around, even slightly.. Any such movement will eat a cam.

 

[Frank Z]

Rob,
I would also check the valve spring pressure. Too high and the cam will fail.

 

[Flash]

It ate the lobe because the cam walked either forward or backward.

Without that retaining pin, the cam is free to move around, even slightly.. Any such movement will eat a cam.

Could some on please explain this pin, and how it keep the cam from moving around?

Flash.

 

[JTwthaXJ]

Just dealt with this problem, I know on the 91-92 engines the bolt that goes into the cam has a hole in the center for a detent spring, the pin sits on that spring. The pin and spring push againist the timing cover to keep the cam in place. We thought that we had lost the bolt and spring, and were finally able to locate it in the shop. Both are needed and this could very well be the cause for the two cam failures. The spring doesn't have a lot of tension on it, but it is necessary. The 00 up motors don't have the timing set up the same way, but I know the early 90s do. Not sure about the cylinders being smooth, there is supposed to be an evident cross hatch pattern. It sounds like you may just need to get the spring for the cam, and a new cam. Just my thoughts...

 

[Flash]

AAaaaaaa! NOW THAT MAKES SENSE!!!!!!!:thumbup:


THANK YOU!

Flash

 

[MudDawg]

Things that kill cams...."walk" such as from not having the cam button mentioned earlier....excessive oil pressure....over 58# hot or cold will FORCE cam walk...wrong oil....don't use synthetics....use diesel oil (Shell Rotella or Chevron Delo 400 or other quality mineral oil in combination with GM Engine Oil Supplement).....Excessive idling.....not enough splash to lube the lobes (the lobes are lubed by whatever oil is flying around in the motor...idle...not much splash.....excessive spring pressure....valvespring coil bind....poor break-in practices.....there are more reasons than these....but these are the most common ones.

 

[corbinafly]

Excessive lifter preload is another.

Kyung

 

[tealcherokee]

muddawg, lotta mis info in your post.

do NOT run diesel oil
you SHOULD run synthetics, all that shit about synthetics is crap, and if you beleive it, well whatever i dont care
improper break in and heavy duty springs are bad for cams.... if your going to run heavy duty springs, break the cam in on the stock springs

 

[BBeach]

I dont know why nobody likes synthetics either, its manmade to have a little impurities as possible so you'd think it's superior. Im gonna have to agree with the rest of tealcherokees post as well.

 

[Frank Z]

The reason that Diesel Motor oil is recommended is that it contains Zinc, regular motor oil no longer does. My machinist swears by Rotella and uses it in every racing motor he builds.

 

[corbinafly]

I wouldn't use synthetic (or any oil for that matter) unless it was diesel rated. ZDDP (zink/phosphorus) is the key ingredient. I'm running Amerilube.

Kyung

 

[Bones]

muddawg, lotta mis info in your post.

do NOT run diesel oil
you SHOULD run synthetics, all that shit about synthetics is crap, and if you beleive it, well whatever i dont care
improper break in and heavy duty springs are bad for cams.... if your going to run heavy duty springs, break the cam in on the stock springs

Crap?

Then why is it that Crane and Comp cams recommend Diesel oil (or racing oil) with their flat tappet cams for life (and especially at brake in) because of the reduction in zinc et al additives in car motor oils? The cam companies also specifically recommend NOT using automotive synthetic oil with flat tappet cam/lifter set ups.

I broke a cam in on non-synthetic auto oil then went to synthetic oils (Mobil 1 and Valvoline Full Syn) in my XJ. At every change (every 2-3K) the ONLY oil I used was synthetic oil after break in. I also used Lucas Synthetic oil additive to help in oil coating of parts when the engine was off.

I just had to replace the cam because of a lobe failure. The lobe had worn and the lifter cupped so badly that the lifter was grooving the cam when off lobe. I also found evidence of two other lobes beginning to wear. This was a Crane 260H with Crane lifters along with Mopar springs, retainers, stock sized SS valves, and keepers and proper pushrod lengths. No exotic spring rates or cam grinds, just a cam failure.

So what's so bad about CI4 (diesel) rated oil that I should know about? What in your opinion is so bad as to go against the recommendations of at least two cam companies for the health of the valve train?

It is my understanding that OEM’s have lobbied for reductions in the Zinc etc in the auto oils, INCLUDING SYNTHETIC, because as engines wear the burned oil causes problems with the O2 sensor and cat. Things the OEM’s have to warranty for a longer time and would have to replace in higher numbers if the zinc et al stayed.

I would much rather swap out a $60 O2 sensor than swap a cam again. I'll stick with what the cam companies recommend.

If you don’t have some significant reason for your recommendation then I’ll call a .

If you have (a) verifiable reason(s), I’d like to hear it/them.

Bones :skull1:

 

[Flash]

:scared: is that the actual lobe of the cam..........looks might round to me:scared:




Flash.

 

[Bones]

I dont know why nobody likes synthetics either, its manmade to have a little impurities as possible so you'd think it's superior.

Synthetic oil is superior to other oils for OHV and Roller cam motors, but for flat tappets it is so slick the lifters don't rotate and, because of this, the cam lobe and lifter set wear abnormally.
It was the ZDDP in older auto oils that helped keep everything happy. Today’s auto oils are almost devoid of ZDDP and non-syn oils are barely adequate to keep things spinning. Being slicker syn oils don't, thus contributing to lifter/lobe failure.

I wouldn't use anything but full syn in my OHV supercharged Mazda Miller Cycle engine, but I'll keep the CI4 (diesel) oil in my XJ from now on.


Bones :skull1:

 

[Bones]

:scared: is that the actual lobe of the cam..........looks might round to me:scared:

Flash.

Yep #6 exhaust lobe.

Bones :skull1:

 

[Flash]

Yep #6 exhaust lobe.

Bones :skull1:

so how is your project going.........got it running yet!

flash.

 

[Bones]

so how is your project going.........got it running yet!

flash.

Yes, I'm on my second tank of fuel with the new cam. I haven't made up my mind about this cam yet. I'll know more next week as I'll start dragging the boat around some. It does pull better than the crane did at highway speeds/RPM, but I don't know if I'm comparing the new one to the old cam when it was healthy, or just when it was a sick cam.

Bones :skull1:

 

[Flash]

I can sure understand.

you went with the comp 231 or 232?..........or did you put a MPP Cam in it?


Flash.

 

[Gil BullyKatz]

Bones...

Wasn't yours built by (now defunct) Accurate?

Not a slam on them...

Just wondering.