Replace cam w/o removing head?

I have the unique (and dumb) position where I idled my motor too long on the initial startup of my 4.0 engine, so the cam was not broken in properly. So I am going to replace the cam and do it right. However, I would be allot happier if I didn't have to pull the head, get new gaskets, head bolts etc...

It's been a while since I have replaced a cam. Once you pull the push-rods, are the lifters the only reason to need to pull the head for cam replacement on this motor? In my situation, the motor has only run for 15 minutes total, so I don't see a need for new lifters. I was thinking of just buying 11 harbour Freight magnetic pick-up tools (I already have 1 good one) and just pulling the lifters to the top while I change out the cam. Does anyone see any problems with this, or a better way? I can get the pick-up tools for under $2 each, and that is cheaper than a new head gasket alone... (not to mention the time savings as well)

http://www.harborfreight.com/5-lb-telescoping-magnetic-pickup-tool-38392.html

The only problem I see is that you have no way to check the damage to the lifters. If the cam was damaged the lifters were most likely damaged too.

Pull the head and expect to replace the lifters and cam.

Use the correct Chryco additive for cam/lifter break in.

The key is as you said it "do it right" if you wiped the lobes out on the cam you also wiped out the bottoms of the lifters.

You need to replace more than the cam and lifters. With that much metal circulating, all your bearings, including cam bearings will need to be replaced. I wouldn't trust the oil pump anymore either. The valve guides could be hosed as well. The motor needs to come out and all the passages flushed and brushed.

Cam. Lifters. Inspect cam bearings. Inspect rod bearings. Inspect main bearings.

You're in for enough work that pulling the head is minor. If you wiped out the cam that quickly, you also wiped out all twelve of the lifters (I certainly wouldn't put them on a new cam, unless I wanted to scrap the new cam and overhaul the engine again before the week is out!) and the bearings should all be inspected for imbedment (which can cause a problem later.)

Pull the head, get new screws, get new gaskets. Don't half-ass this, or you'll be doing it again next week (and kicking yourself in the head - really hard! - because you didn't listen to us this time.)

A good break-in oil is a standard 30-vis non-detergent oil with an API service spec of SL or older. If all you can find is a 30ND in API SM, stop by the Chevvy dealer and pick up a few bottles of EOS - you'll need it (and not just for break-in. The EOS carried the organometallic anti-scuff additives that aren't present in API SM oil - which is why it doesn't carry a Diesel rating - and it will wipe out even properly run-in valvetrains, given time.)

Once you've run a run-in cycle and haven't found an abundance of particles in the second run-in oil change, you can switch to a more conventional engine oil (like a 10W-30, 10W-40, or 15W-40 Diesel oil) for regular service.

woo hold up he never said his motor was trashed. He just said he didnt break in the cam properly. That doesnt mean there is actually anything wrong. First things first how do you know the cam is wiped? Have you dropped the oil and looked for debris and cut open the filter to see what lies within? I would start there before you go jumping the gun. If it is trashed then the advice listed here applies.

I don't think there would be metal circulating in the oil yet. Just because he didn't break the cam in correctly doesn't mean it had failed yet.

However, when you replace a cam you have to replace the lifters. You can use a used cam with new lifters, but not the other way around.

The only way to remove the cam with out pulling the head is to remove the engine from the bay, flip it over, unscrew the rockers until the lifters drop down enough to clear the cam, but not all the way, remove cam, remove lifters.

milehigh said:

woo hold up he never said his motor was trashed. He just said he didnt break in the cam properly. That doesnt mean there is actually anything wrong. First things first how do you know the cam is wiped? Have you dropped the oil and looked for debris and cut open the filter to see what lies within? I would start there before you go jumping the gun. If it is trashed then the advice listed here applies.

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If the bumpstick wasn't broken in properly, it's fairly safe to assume it's wrecked. It doesn't have to show metal everywhere (the particles from the lifter feet will probably be grindings anyhow,) but the surfaces and tempers of the lobes and lifter feet will be wrecked - and if they're not munched, they're about to be.

I've seen a few trashed cams - and that's what happens. It's not obvious at first, but it gets ugly fast.

Thumb rules for lifters:

New Cam = New Lifters. Period.
Used cam may use used lifters if the lifters go right back on the lobes they were removed from.
New lifters can be put on a used cam, no trouble.

If you think that one or the other is trashed (from, say, improper run-in...) then replace both. Period.

5-90 said:

Thumb rules for lifters:

New Cam = New Lifters. Period.
Used cam may use used lifters if the lifters go right back on the lobes they were removed from.
New lifters can be put on a used cam, no trouble.

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