2nd wiped Camshaft OMC 460

[jhande]

Since it's just that one lifter blowing out so quick and you've been checking things already, there's only 3 things to look at.

Is the rocker arm making full travel to the open position?
Is there good oil flow coming out of the block in the lifter bore?
Is the lifter bore scored so much that the lifter doesn't move freely?

You should be able to slide the lifter up & down & spin it. You might have to use rubber gloves, a lifter tool or pliers.

The purpose of valve guide seals is to prevent oil from going down the valve stem into the head chamber. So if valves stop opening & closing it would be from bad valve stems or guides. But I've never seen that in 33+ years as an auto tech specializing in engine rebuilds & mods.

 

[Trevthefox]

Ok quick update. Just checked lifter bore clearances. The affected bore has .002" of clearance which still falls within specs according to the book. So maybe a quick hone of the lifter bore will help.

I did however find that I'm getting dangerously close to coil bind when the lifters are all the way pumped up with oil. I was first just measuring when the lifter bled the oil out. I think that might be one problem. Still doesn't explain why the same bore is giving me issues.

I also noticed that the valve springs that are in the heads are rated at 300-330lbs open valve and 87-90lbs seated. Comp cams wants 110-120 lbs seated and 260-270 open load. So if my stock springs still fall within specs they are pushing too hard during the break in process. Once again it doesn't explain why that one lifter/bore keeps getting eaten but another error on my part. I'll have to get lighter springs for break in or opt for the dual springs and remove the inner spring during break in. Basically more $ and I still don't have an exact answer as to why i keep eating the same lobe and lifter.

 

[jhande]

A quick/slight hone of the lifter bore and valve guide won't hurt.

Have you been able to check oil flow to that lifter bore?
Leave all the valve train installed except the problem lifter. Crank the oil pump and once you see oil coming out the top of all the other push rods check the empty lifter bore.

 

[Trevthefox]

A quick/slight hone of the lifter bore and valve guide won't hurt.

Have you been able to check oil flow to that lifter bore?
Leave all the valve train installed except the problem lifter. Crank the oil pump and once you see oil coming out the top of all the other push rods check the empty lifter bore.

I'll give it a shot. I did remove the oil plugs and I can see all the way down the passage that feeds the lifter bores. And because cylinder 8 lifters are not having any issues I just figured that the flow is fine. Because the oil has to reach cylinder 7 bores before #8

 

[gm280]

Reading all you threads concerning this problem, I get the gut feeling valve springs could be your problem. I suggest you buy the replacement valve springs from the place you get your new cam from at the same time. Comp cams do offer such springs and know what their pressures are at full open height, and the binding issues as well. So I would use their spring suggestions. JMHO

 

[Trevthefox]

Reading all you threads concerning this problem, I get the gut feeling valve springs could be your problem. I suggest you buy the replacement valve springs from the place you get your new cam from at the same time. Comp cams do offer such springs and know what their pressures are at full open height, and the binding issues as well. So I would use their spring suggestions. JMHO

Yes, this time just going to replace the springs and rocker arms and push rods.

 

[Trevthefox]

A quick/slight hone of the lifter bore and valve guide won't hurt.

Have you been able to check oil flow to that lifter bore?
Leave all the valve train installed except the problem lifter. Crank the oil pump and once you see oil coming out the top of all the other push rods check the empty lifter bore.

Did the test, and was able to watch the oil flow in real time. That problem bore was getting plenty of oil flow to it. So I'm pretty sure its get sufficient oil. I just hope the crank shaft is doing its job and splashing oil onto that particular lobe. (Not entirely sure thats how the lobes get oil but i read it on a 460 forum).

 

[jhande]

Good to hear it's getting oil. Yes camshafts get oil dripped/splashed on them mostly.

That only leaves one problem - the upper valve train.
It could possibly be that someone could have messed with different seats in the head but I doubt it.

Whenever we replaced a non-stock cam we ALWAYS got the suggested lifters, new push rods and rocker arms. Sometimes depending on the cam lobe & duration the rocker arm pivot ratio can change. Usually the push rods remain the same but since the motor was getting a fresh cam and lifters we always went the full nut.

I believe I read above somewhere that you were getting a set of replacement heads??? I think that would be a really good idea. Just make sure you get heads that will work for the year of your block. Then throw the new valve train in there.

 

[Trevthefox]

Good to hear it's getting oil. Yes camshafts get oil dripped/splashed on them mostly.

That only leaves one problem - the upper valve train.
It could possibly be that someone could have messed with different seats in the head but I doubt it.

Whenever we replaced a non-stock cam we ALWAYS got the suggested lifters, new push rods and rocker arms. Sometimes depending on the cam lobe & duration the rocker arm pivot ratio can change. Usually the push rods remain the same but since the motor was getting a fresh cam and lifters we always went the full nut.

I believe I read above somewhere that you were getting a set of replacement heads??? I think that would be a really good idea. Just make sure you get heads that will work for the year of your block. Then throw the new valve train in there.

Well I bit the bullet and bought all new springs, rockers, retainers, and I'll get pushrods soon. I'm not getting replacement heads but I am taking them in to get a proper valve job. Guy is gonna have to machine the guides for the new springs. My worry is I still haven't 100% concluded what exactly happened. Because we wiped our 1st cam with the stock camshaft and springs which worked just fine before. So fingers crossed when we put it all back together.

 

[gm280]

Seeing the lifter shaved off on one side pretty badly looks like the lifter may not be setting perpendicular to the cam. I would also have the machine shop verify they are... Just an idea...

 

[Trevthefox]

Seeing the lifter shaved off on one side pretty badly looks like the lifter may not be setting perpendicular to the cam. I would also have the machine shop verify they are... Just an idea...

Yeah I was thinking about that too. Any way to do that at home without paying a machine shop?

 

[gm280]

Yeah I was thinking about that too. Any way to do that at home without paying a machine shop?

You could install a lifter and see if it sits flat on the cam lode without any light showing on any side if you have access to see that. Can use a feeler gauge to verify it sits flat without and edge allowing a feeler gauge to fit.

 

[gm280]

Could also coat either the lobe or the lifter with a type of transfer color and spin the cam to see if it wipes clean across the lobe or only at one edge...

 

[froggy1150]

Dykem layout fluid

 

[Scott06]

If the cam he took out did not have a damaged lobe then i wouldn’t think it was a bore alignment issue

 

[gm280]

If the cam he took out did not have a damaged lobe then i wouldn’t think it was a bore alignment issueThe cam is usually harder then a lifter. But no damage to the cam lode doesn't mean the lifter isn't sitting crooked to the lobe.

If the cam didn't have any damage doesn't negate that the lifter isn't sitting crooked in the bore to cam lobe. Usually cams are pretty hard metals and the lifter not as much.

 

[Trevthefox]

If the cam he took out did not have a damaged lobe then i wouldn’t think it was a bore alignment issue

2 cams came out with same damaged lobe

 

[Scott06]

2 cams came out with same damaged lobe

Yes but wasn’t it a running engine before you dug into it for a transom leak ?

 

[Trevthefox]

Yes but wasn’t it a running engine before you dug into it for a transom leak ?

That is correct. We figured, hey we have it out, let's make sure everything is good on the inside. Made the mistake of not keeping the original lifters in order so we bought all brand new lifters and didn't do a proper break in with just the new lifters on the old cam. Then the problems started to occur. Found a damaged lifter in intake bore of 7 cylinder. Also through touch we could fell the lobe was wiped. In order to get a couple trips out of the fishing season we decided on replacing the bad lifter. And then we did a proper breakin. That new lifter spun in the bore just fine but after 2 trips we heard the chatter from the valve cover. Removed the lifter to find it had been coned in, and thats when we decided it was time for a new cam.

Granted we only took the boat out for a few trips pre-1st tear down, but it was running. Makes me wish we never even touched the thing. Lol. Oh well. Now I'm here.

 

[jhande]

Old cam mix up old lifters = bad.
Old cam with new lifters usually = bad.
New cam, new lifters all properly pre-lubed (cam break in lube) = good.
Some motors the lifters don't sit 100% over the cam lobe. Some overhang to one side a bit. Lifters tend to spin slowly in it's bore which wears the contact points evenly. Not all, but some.

Old GM 305 cu.in. cams were made for awhile with a softer metal which caused very short life spans. Done tons of those recall/fixes at the dealership.

If the motor had a lot of miles/hours on it before taking it apart and messing with it, I highly doubt the lifter bore is not parallel with the cam lobe. If it was, cams and lifters would get chewed up "really" quick.

I really think it's all due to improper cam & lifter match. Improper spring pressure and possibly spring height. As long as evrything is getting properly oiled, which it sounds like it is.