Last week, the locating dowel on the mechanical camshaft in the motor in my brother's van snapped off the cam as the van was idling in his driveway. He said the motor ran poorly and eventually just died. Today my brother and I swapped the broken mechanical camshaft in his motor to a hydraulic camshaft and valve train I had lurking in my garage.

The hydraulic cam, lifter, rocker arm, and rocker arm shaft all came from a 1983 hydraulic slant six motor. The only new parts were the hydraulic lifters.

The installation went fairly smoothly. The cam fit in the block no problem, the lifters fit int he holes no problem, the rocker arms and shaft installed with the minor difficulty of having to drill out the rearmost bolt hole, otherwise it was easy.

Unfortunately, upon starting the motor, there was a HORRENDOUS amount of valve clatter and what seemed to be much less oil flow than would be usual to be coming out of the rocker arms.

Here is a short video (about 10 megs) of the motor running where you can hear the valve train clatter:

CLICK ME FOR VIDEO

This is far too noisy to be correct. It is even noisier than the mechanical lifter cam and valve train that was replaced. I double checked and the oil holes in the rocker arm shaft are pointed correctly. This is also definitely valve train clatter.

Surprisingly, the motor idles very smooth, revs well, and pulls over 20 inches of vacuum at idle. The noise did decrease the longer the motor ran. After running for a while oil was flowing out of the rocker arm tips and splashing about like it should, but it was still a fairly anemic flow.

Since the cam was in OK shape and the lifters are new, my only ideas as to the cause of the excessive valve train noise are insufficient oil flow to the lifters to pump them up and/or wrong viscosity of oil.

When we swapped the cam, I drained the old oil out of the motor and installed 5W-20 oil. Is that too thin?

More concerning to me is the possibility that the used hydraulic valve train is gummed up and prohibiting proper oil flow. The rocker arms and pushrods and rocker arm shaft are all used, have sat under my workbench for a couple years, and sat in someone else's workshop for several years prior to that. I didn't take the time to test the pushrods and rocker arms for flow through the oil passages on them. Is it possible that some of the rocker arm passages and pushrod passages are gummed up. blocking flow, and leading to noisy hydraulic lifters? Should my brother add a can of Marvel Mystery oil to the crankcase to try and help clean out the passages?

Is there something special I was supposed to do to the new lifters? I used lots of cam break in lube on the lobes of the cam and on the bottoms of the lifters. Was there some kind of pre-lube required for the plungers in the lifters?

I suppose a third possibility for the noisy valves is internal damage when the locating dowel snapped off the front of the mechanical camshaft while the motor was running. My brother drove about 30 miles home before taking the exit for his house. He said the van did fine on the highway, but idle rough and wanted to die when he got on the offramp. He only lives a few blocks from the highway and he was able to make it home but the van ran very poorly. He got the van parked in his driveway where it idled for about 30 seconds before dying.

I didn't think that the slant six was an interference motor, but could the cam stopping spinning while the motor was running cause the pistons to hit the valves? Obviously if the cam wasn't turning then neither the fuel pump nor the oil pump were turning. The carb didn't run dry, but could the motor have run long enough with the cam not turning for the lack of oil flow to damage the internals of the engine?

Any advice would be appreciated. Between the transmission troubles and the motor troubles, my brother has almost given up on this motor and is to the point of feeling like we should just pull the motor and rebuild it. I am almost there as well, but I am not ready to give up yet.

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Casually looking for a Clifford hyperpak intake for cheap.

This definitely sounds to me like a problem of insufficient oil flow to the top end. It's not killed lifters or a killed camshaft, and it's not improper oil viscosity.

Make sure the oil pump pressure relief valve is free and working. Pull the rocker shaft back off. Take another look to make absolutely certain you installed it the right way round and rightside up. If "oops", then fix it and try again. (Really check this very carefully; I've screwed it up more times than I care to admit). Otherwise yeah, it's worth pulling at least a couple pushrods and shooting carburetor cleaner through to see if it's clear. Same with a couple of rocker arms. Then probe the oil feed passages as much as possible with a thin stiff wire, then crank the engine and see if you can flush out whatever crud was restricting oil. Hope there's not a blockage upstream of the cam (or between cam and rocker shaft but resistant to rootering out with head on block).

De-sludging is not risk-free and shouldn't be done on a "just pour _____ into the crankcase before the next oil change" basis; see here.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan. I am not a fan of the"desludging" products on the market. The stock oil pressure gauge in the van reads at the halfway point, which is what it read before the whole cam swap. I am leaning towards sludged up rocker arms and pushrods, so I will tell my brother to take it all apart and clean it out, or at least bring them to my place where I can soak them up with some cleaner and blow them out with compressed air.

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Casually looking for a Clifford hyperpak intake for cheap.

Why did you driil rear most bolt hole? And did you use the correct rear bolt?

Used the correct rear bolt, as for why the hole had to be drilled, see HERE. The head on the engine is a 72 head, so it has the older, larger, rearmost rocker arm shaft bolt.

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Casually looking for a Clifford hyperpak intake for cheap.

The noisy lifter problem has been solved. My brother added a quart of Marvel Mystery Oil to the crankcase and let the motor run for a bit today and now the motor is running smooth and quiet.

I guess the problem was clogged up passages in the rockers and pushrods. Either the MMO or just running the engine more got oil flowing everywhere so the lifters were able to pump up. The engine pulls over 20 inches of vacuum at idle, idles very smooth, and the factory oil pressure gauge reads about half-way up the gauge. I am very interested to see how this cam affects performance.

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Casually looking for a Clifford hyperpak intake for cheap.

He'd better change the oil and filter right away…

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm going to do just that this coming weekend.

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Casually looking for a Clifford hyperpak intake for cheap.

Reed

concerning the bolt that backed off and caused the whole problem,

did you do anything different with the re assembly,,, verify the torque wrench used,, put loctite on the bolt maybe?

Yes, I did do something different. When I installed the old mechanical cam that broke, I did follow the factory torque procedure. This time, when I installed the hydraulic cam, I followed the factory torque procedure but torqued the gear bolt to 40 ft/lbs instead of the factory recommended 35 ft/lbs and used blue Loctite on the threads of the cam gear bolt.

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Casually looking for a Clifford hyperpak intake for cheap.