Hello fellas,

Got a problem. 1972 Oldsmobile Cutlass Supreme 350 4 bbl stock (as far as I know) except for a mild cam (which I installed.) So the back story is that when I bought the car the engine had a plethora of problems. Started with the rusted out freeze plugs and went from there. Once I got that under control, when I started it there was a bad knock coming from one lifter. Pulled the intake and the lifter had come apart and the pushrod was not seated correctly. So I decided to upgrade the cam and once I removed the old one I discovered that the same valvetrain had been "lobed" or rounded. Changed the cam (mild upgrade) and the lifters. Checked that the pushrods were straight by rolling them on a flat surface and they were clear of any debris (looked through them.) Now that it's reassembled, I starts right up. Then after a couple minutes what seems like the same lifter (or close to it) is knocking. The noise goes away as I adjust the distributer timing, but then it dies. The car was getting hot with only electric fans, thinking of adding the fan and clutch back to the water pump. Vacuum on the distributer is connected directly to the "ported" carburetor vacuum.

Any ideas? What should I try? Seems like the old timers are always the ones to ask before I go ripping into the engine again.

New:
water pump
fuel pump
oil pump
power steering pump
Quadrajet rebuilt (by me)

 

I dunno if I'm an "old timer" yet, but...

If the old cam was damaged by the lifter that came apart you may have excessive wear on the pushrod or rocker arm. You can check this by removing the valve covers and running the engine. Make sure you make a shield out of cardboard to protect the exhaust manifolds from dripping oil (ask me how I know).

Then you can pour oil over the suspect rocker arm. If the tick silences you MAW replace all the rocker arms, bridges, pivots and pushrods.

BTW, you replaced all the lifters, right?

 

Did you do a cam break-in procedure?

 

Before doing anything, remove the oil filter and cut it open. If it’s clean of debris, then you can continued with the diagnosis.

How much lift does the new cam have over the stock cam? If it’s considerably more, maybe the rocker is pivoting past the previously established wear marks? Did you change valve springs?

Some cams are just noisy, especially rowdy cams with aggressive ramps on the lobe. It sounds like your grind is fairly mild.

 

Replaced all the lifters. I'll try the oil trick. If it's just the rockers that should be an easy fix. At least I don't have to remove the heads...again.

 

I did not change the valve springs. I did however remove the keepers and installed all new valve seals.

I'll cut open the oil filter. I'm looking for (and not hoping to find) metal shavings?

 

I did do the break in procedure. Everything was thoroughly coated in the moly can grease that came with it. Soaked the new lifters prior to install. All pivot points got a good coating of engine assembly lube. Put a quart of cam break in oil. Ran for an hour over 1500 rpm. Changed the oil and filter with 30 W conventional oil.

Kinda wish there were a way to post a short video in here so everyone can hear the knock. It does get louder as the RPM increases. Low RPM its relatively quiet, but I can hear it. I'm weary of running it too much until I solve the problem. Not gonna try to put a load on it by putting it in gear until she's purring like she should. Weird thing is that she sounds really good, healthy even with the mild cam.... less the knock.

Hoping not to have to tear her completely apart again. I'm going to try the above inspections and adjustments and I'll let keep you all posted.

Oh, thanks by the way.

 

you can post video here. there's a pinned post at the top of this page on how to do it. sounds like your breaking went fine

 

You can also put an oil pressure gauge on her to make sure the bottom end is healthy before removing the valve covers. Here's a good thread.

https://classicoldsmobile.com/forums...essure-129364/

 

This is the cam I installed

Melling stage 2

Something i did notice was that when installing the new valve seals, one valve had what I can only describe as a "collar" on the stem. I can't imagine the valve got so hot that the valve stem "mushroomed" but at the same time I don't see how the valve was even installed. I've never scene that before. Reinstalled it anyways but now I'm thinking that may be what's knocking. I'll remove the valve cover today and take a Pic to show what I'm talking about. Anyone else ever seen that?

Oh and i did shave the heads a bit on a belt head surfacer. Not too many passes, just until it was consistently flat. Didn't make a measurement to know how much.

Supreme cut

 

Really surprised you didn't lose oil pressure when the lifter failed. Do you have a gauge on it? What is the oil pressure now?

 

It seems to me that you are describing the valve stem end as mushrooming. Do you have oil feeding to the rocker arm ? Was this the same valve that the lifter went bad and flattened the cam lobe ? You may have extreme valve stem wear from lack of lubrication.

Unless you milled (resurfaced) the combustion chamber side of the heads, you accomplished nothing good. If you used some kind of belt sander on the head bolt surfaces.....how do you know they are flat and perpendicular to the bolt hole and threads in the block ? The right way is use a piloted "spot facer" or end mill in a machine. :

 

If valve guide clearance is really excessive it will make noise. A stiffer spring used to be used to doctor/band-aid the noise, I would not recommend doing that. Remove the rocker and try moving the valve in the guide.

 

Are you sure it's in the valve train? Could be a collapsed piston they tend to knock when cold and make less noise as they warm up. Just a guess.

 

I do believe it is the same valve stem mushroomed that the lifter had been broken. I understand that bc the pushrod was off center of the valve there was little or no oil going to the rocker and in turn the valve. I guess I'll pull the head AGAIN and replace that valve and rocker.

And on the head resurfacing, just so nobody thinks I am a complete idiot, I did not take a hand held belt sander and go to down on the head surface. My neighbor is old school and he has one of these that we used:

 

Probably going to need guide work on that valve. Keep us posted.