I recently received a rebuild kit from Mabbco. Everything about it has been what I expected except for the camshaft. I thought I was getting a new one, but this thing looks like it was pulled from a junk motor, dropped a few times, wrapped in newspaper and put in a shipping box.

I'm going to send it back, but was wondering...is it THAT big a deal to have some scratches/pits on your bearing surfaces? I've been trying to find a straight answer, but it varies from "it's marred, don't use it" to "I'd run that sucker and never think twice"...

It's not rusty, and the lobes aren't polished, so I'm thinking it's NOS, but it does look like it's been rolled around on a dirty floor and the bearing surfaces have taken a beating..

I mic'd the one I pulled from my motor and compared the numbers and it only varies by about .003 on the small side compared to the "new" one..
The un-machined shaft diameter is .010 larger on the "new" one, but everything else is the same, give or take a few thousandths.

The one I pulled isn't pitted anywhere, and the bearing surfaces and lobes are shiny, although they need a good clean and polish. I'm wondering if I should just re-use it and keep whatever they send me in reserve.
I have another jeep 4.0 with high miles I'm looking to mess with...

So should I run it? Or re-use the old one after I clean it up? Or just wait to see what Mabbco sends as a replacement? My time is pretty limited, so the quicker I can get this build done the better.

Thanks in advance.

If I can figure out how to post some crappy cell-phone pics, I'll put 'em up.

 

If the lobes are scratched and pitted I would send it back.
You paid for a new one and you should get one imo.I am pretty stingy with my money and when I purchase something I expect it to be a quality part.If I know that there could be issues with what I purchase and I still purchase it then that's a different story.
If you are doing a build or rebuild or what ever you want to call it why take the chance with a defective part.

 

Critical - unless you like replacing lifters (and stripping the head off to do it!)

Bear in mind that the camshaft lobes run directly against the metal feet of the tappets, and both need to be polished in order to lap in properly.

This is why you can't mix up lifters from lobe to lobe, or can't put used lifters on a new cam (you can put new lifters on a used cam, tho.)

The parts also have a special grind - the surface of the camshaft lobe is a few degrees off of horizontal (it "has a ramp,") and the lifter foot isn't perfectly flat, it has a slight crown (circle with a radius of, typically, 36".) This is done to encourage the lifter to spin in the bore as it runs, so you don't wear through the lifter foot with the camshaft lobe (and wreck both parts in short order!)

You can identify proper wear on used parts by examining the camshaft lobe surface (there should be a shiny band, centred or slightly off, all the way around and about 1/8"-3/16" wide) and tappet foot (there should be a small polished "square" - about 3/16"-1/4" across - in the centre of the foot.) You will not see these polished bits on new parts, as they are a product of "run-lapping" and is a finer finish than most machine shops can do.

When you "run-in" an engine, you're primarily allowing the camshaft lobes and valve tappets to lap in and mate to each other - the most common failure resulting from improper break-in is camshaft failure.

 

Well, I FedExed it back to them this morning. They said they'd replace it no questions asked. +1 for Mabbco. I had to pay return shipping, but..eh..whatever.
I'm just bummed I'm not going to get this thing shortblocked this weekend...

 

it's official. -1 to these guys. just received my replacement. it's fine. i go to start the assembly. open the timing kit to bolt the sprocket to the cam for installation...AND THEY'VE SENT THE WRONG KIT!
so...it's either send IT back for the proper one, or just go get one from the auto parts store and get on with life...
How hard is it to stuff the proper parts in a box? Maybe check a few things before you wrap it in tape and ship it? I'm kinda beyond angry right now....

I DON'T recommend buying any rebuild kits from these guys...i wonder if they sent the right gasket set...brb checking that now..

 

-1 Mabbco!

 

If the original cam has no scratches on the lobes felt with your fingernail, if the bearing surface is free of scratches and only has .003" wear, i'd throw some cam lube on it and slide it in. New lifters or your original used lifters if you marked which ones go to its position you removed them from. Don't mismatch them...g/l

 

the new cam is good to go...it's the fact that i had to send the first one back and then discover they'd sent the wrong timing set for my motor...neither of these sprockets fit either the cam or the crank...what's a new set cost? about what it'd cost to send this mess back to them to them...
i'm keeping my original cam..i've got another jeep with a 4.0 in the same range...we'll see how that goes..
i'm just ticked about the lack of attention to any kind of detail when assembling my kit...
the gasket kit IS correct for my motor! hooray! :-)