Arrowstorm

On my 72 350, I recently got the heads reworked and put everything back together only to find that the engine runs like crap.

With a vacuum gauge hooked up to the carb, the needle oscillates wildly between 5-15in and gets faster when throttling.

An Olds mechanic said that this is a valve issue and can possibly be caused by the valve stems being cut down, thus requiring the need for shorter pushrods. In addition, I sort of do remember when torquing the pivot arms down, seeing the valve actually being pushed down a little bit by the rocker arm.

Will shimming the pivot correct any sort of clearance issue that I might be having? If so, where can I obtain shims for that? I'm guessing that the ultimate solution is shorter pushrods, but if the shims will do the trick, I'm comfortable with that.


Also, at TDC, should those rocker arms be quite loose against the pushrod and the valve stem? They're not. Not at all. One mechanic said that they should be, and that's where the clearance comes into play, but then, the guy who redid the heads said that it doesn't matter.

Any help would be appreciated.

Thanks,

Buz

Oldsmaniac

Shims will help reduce lifter preload if pushrods are too long. When filled with oil the lifter plunger is a lot harder to compress. It is easy to compress an empty lifter. If both valves are closed when the rockers are bolted down there should not be any compression of the valve/spring assembly but enough tension to keep the rockers tight with maybe a slight wiggle from side to side. There is quite a bit of movement of lifter plunger before you have problems. If you dont have enough preload of the plunger your rockers will tap.

MDchanic

Here are links to shims on Amazon:






If I recall correctly (can't find my elaborate notes), you want the lifter to be compressed about 0.020-0.040", ideally about 0.030".

If you do the math, the original 5/16-18 rocker bolts will depress the rocker pivot 0.055" per turn. Since the rockers are 1:1.6 in ratio, that will result in a change in pushrod depth of about 0.088", so if you can turn in the screws on each closed valve about a third of a turn more between when the pushrod just sets in the rocker and when the screw bottoms, you will have about 0.030" of compression.

A 0.005" shim will get you 0.008" of compression.
A 0.010" shim will get you 0.016" of compression.
A 0.015" shim will get you 0.024" of compression.
And, yes, you can stack the shims, within reason.
And, no, this is not stable enough for high-rev, high-lift, heavy-spring applications.

- Eric

oldcutlass

There has to be a small amount of preload on the lifters, which is why as you tightened the pivots you saw them compress. The only rockers that will seem very tight are the ones associated with open valves. The rockers should not flop around on the closed valves. Oldsmobile valve train is not ajustable and have a preset amount of preload by design.

Shorter valve stems would result in rockers clacking, and shims would make the matter worse. To long of valve stems would result in the valve hanging open, and would show up as a backfiring.

Google reading a vacuum gauge for some additional clues.

http://www.secondchancegarage.com/public/186.cfm

MDchanic

Unless Bozo the Machinist cut the valve seats all at different depths, leaving the stems all at different heights.

- Eric

Octania

which does happen.

I have several thousand 0.015" shims and will mail you a bunch for postage.

first you should carefully find out what your exact setup/ issue is.

Read up on the process... it should have been done during mock and final assembly. I like to go one cylinder at a time, with crank at TDC compression. If this process is a mystery to you, now is the time to learn it.

oldcutlass

I agree and have had the problem of different length valve stems cause all kinds of issues from one extreme to the other. The OP needs to check his preload on all the valves to see. IMHO opinion he was fed some wrong info from his Olds consultant.

Some of his issues can be related to a combination of vacuum leaks, misadjusted carb, and some ignition issues. Can also be a weak valve spring, head gasket, or a sticking valve.

442Harv

Super Cars sell them, Buy you need them if the push rods are to long, not short

geoff442

Comp cams has a valve train kit that makes them adjustable, it works really nice.

rustyroger

That shouldn't happen. You should have seen the pushrod moving as it pushed down the dry lifter. I trust you removed the lifters and got the oil out of them before reassembling. It does sound to me like the valves aren't closing properly.


Roger.

Arrowstorm

No, I didn't. Should I have?

Can I now?

How does one get the oil out of lifters? Soak them in paint thinner or something? I actually was told to soak the lifters IN oil before dropping them in.

I definitely did not see the pushrod moving. I definitely saw the valve spring being depressed when I torqued down the pivot arms. In fact, when I was cleaning all the sealant from the block and heads after removing the intake, I even noticed that many pushrods were depressed a good bit into the lifters.

Should i remove all the lifters and dry them completely? Or will I need all new lifters?

pogo69

it would of been easier to check your stock valve stem height or check with the machine shop if they installed them before the springs were installed the height for intake and exhaust is 1.876-1.906 and yes you can get different valve spring seat shims to give you that number but that can change your spring rate also depending on your build...easiest thing to do is spend a couple hundred and get adjustable rockers or check the valve height on each valve

pogo69

i made a mistake the valve height range of 1.876-1.906 i gave was for a 455 valve (@4.695 and 4.703 intake height) and you have a 350 so depending on what length valve you have you could modify the range...i dont have the exact range for the 350 so sorry if i confused things

cdrod

I had this happen to me a few years ago on a 350 rebuild. In my case, the valves were too high because of the valve job so I ordered washer/shims (I think they came from Crane cams), loosened all the rockers and adjusted them individually until each rocker stopped clicking. I then measured the clearance with feeler gauges to selected the correct shim thickness for that rocker.
This method works well with the steel bridge type rockers where the pivot and bridge are separate pieces. If you have the cast metal bridges (more common on later engines) where the pivot and bridge are a single piece, you could break the bridge if the valves have a large difference in height.
Hope this helps.

Rodney

jag1886

This is a common problem I have 2 sets of heads done by the same shop that did this and they are so stupid they didn't even understand what I was telling them when I found the problem. They are "suppose" to be one of the top performance machine shops in town. I bet there is a crap load of AMC's Old's, Ford's and Mopar's with bad valve jobs by them.

rustyroger

Take the lifters out and using suitable soft jaws squeeze them in a vise. Do this SLOWLY or you can damage them. You will see oil trickle out of the small hole in the side of them. Or you can remove the clip and dismantle them. I use the vise method, if you don't rush it works fine.
Don't soak lifters before installing them, they will fill with too much oil, and as you have discovered, the valves won't close properly.
Put them in dry and they will fill with the oil they need, they will clatter for a short while as they do this.
When you tighten down the rockers they should touch the valve stem, then move the pushrod down into the lifter a little. If the valve moves then it will be hanging open when you run the engine.


Roger.

Arrowstorm

Pulled the valve covers yesterday while my brother in law and his friend's dad were over and laid a straight edge over the valve stems and sure enough, that straight edge was rockin as though Judas Priest was playing live in that engine compartment.

So he suggested shimming the rocker arm bridges up a little bit, especially on the stems that were too high. I told him that I noticed that on at least two of them, I could observe the rocker depress the valve spring a little bit when torquing them down and he noticed that those lifters were already compressed, and when they would fill with oil when the engine started, that would cause the pushrod to depress the valve even further, thus causing valve leakage.

So I'm gonna get a set of shims and see if that resolve my problem. =/

oldcutlass

Certain valves will open depending on cam position when you tightened the rocker assy's.

Arrowstorm

When I installed them, I did them 2 cylinders at a time after rolling the cam into position so that both lifters were down.

rustyroger

You could take a little off the valve stems to bring them back to the correct stem height, I think was a fairly common practice way back on old some (but certainly not all) L head engines. Possibly this would go through the hardening nowadays.
The lifters should only fill with enough oil to take up any lash, unless the seats have been cut back significantly into the head you should have enough free play in the lifters. Pocketed valves won't do the engines breathing much good.


Roger.

Arrowstorm

I have a mechanic friend telling me that when the both lifters per cylinder are DOWN on the cam and both valves are CLOSED, that the rocker arms should have considerable play and be able to wobble slightly. So, I got some shims and went though each rocker arm assembly, turning the motor so both valves are CLOSED and shimmed those rocker arm bridges so that you can wobble those rocker arms when the bridge is torqued down to spec. Maybe even wobble them a little TOO much. I did that for all cylinders and fired the car up yesterday.

The vacuum gauge still shows the needle wildly going back and forth between 10 and 20 and moves faster on acceleration.

My mechanic friend tells me that this is because an intake valve is STILL hanging open. I just cannot see how any of those valves can still be open with the rocker arms being so loose. In fact, I've been reading about pre-load on the lifters and I'm pretty sure that when I shimmed those pivots, there is ABSOLUTELY NO preload on those lifters, as all the rocker arms themselves have no load on them when both valves are closed!

Could having no preload on any of the lifters be the culprit here? Should I remove some of those shims so that when I torque the pivot down, there is some compression on the lifter?

The engine starts right up and runs, but it's rough and the vacuum gauge shows this concerning reading. I went to this http://www.secondchancegarage.com/public/186.cfm site and I can't find what the gauge is doing. It is almost like "Scenario 6" on that site except the needle is moving much, much faster. The valves are NOT burned because I just had the heads reworked and how could they be "constantly leaking" if I know for a fact that when the lifters are down on that cam, both valves are closed and not leaking?!


When I showed a video to my friend's dad, he immediately identified it as combustion coming back through the intake from the exhaust.

I just want this thing to run! Anyone got any other ideas cuz I'm all out!

68_convert

Ok... At some point you need to run a compression and leak down test to see exactly what is going on mechanically.

FMB42

As was mentioned earlier; cutting the valve seats (and/or milling the block deck and/or head surfaces) will throw off the non-adjustable valve preload. You, or should I say the builder, can sometimes grind the valve stems down to make up for this (just don't remove the hardening). Otherwise, you adjust the preload by shimming the rocker arm pivots as you suggest (when preload is too tight), or you can install adjustable push rods, or install an adjustable adjustable rocker kit.

Here a link that might help: <a href="https://classicoldsmobile.com/forums/big-blocks/19833-69-400-lifter-preload.html" target="_blank">https://classicoldsmobile.com/forums/big-blocks/19833-69-400-lifter-preload.html</a>

MDchanic

Then do not listen to him, because he is an idiot.



That was a really bad idea. I'm amazed that the car runs.



That's because the valve is burned, not open.



No crap. Ya think?

I have seen preload for Olds lifters recommended at between 0.020" and 0.060", and use 0.030" as a goal myself.

You have set them to something like NEGATIVE 0.030", that is to say LESS THAN ZERO.

Once again: "Mechanic" friend is an idiot.



You mean, as in setting it up the way it was when you got it, and the way it was from the factory? Yeah, that might help.



So, as 68 Convert says, have you done a compression and leakdown test?
Without that, you have no meaningful information here.
Put your engine back together the right way, check compression and leakdown, and get back to us so we can help you.

And don't listen to your "friend" anymore!

- Eric

edit: note my advice on Post #3.

oldcutlass

Eric pretty much summed it up. If you did not have the manifold off and looking down at the lifters while measuring preload chances are its all messed up. A good sign of no preload is that the valve train will chatter. I also recommend a compression and leak down check to see whats going on or find another mechanic to fix it for you.

Arrowstorm

Eric,

I hear what you're saying. But the thing is, since I got the heads back and reworked, it's not like I"ve run this car enough to even get it really warmed up. How could the valve be burned?

I will do another compression and leak-down test. Even though... I have done so already. Did a compression test with the rocker arms on and all cylinders were at about 110lbs I think, with no variation between them. And the leak-down test, as far as I could tell, there was no escaping air!

But... I will do it all again to make absolutely sure.

MDchanic

Okay, If you had good compression and leakdown once, they are probably good now.
For the sake of certainty, I would definitely repeat them, but if they are good again, then a bad valve is NOT your problem, vacuum gauge be damned.
You can run the engine to warm it up, and do the test with the rockers shimmed like they are now - it will eliminate any possible question that one of the valves could be pushed open.

As for how a valve could be burned, okay, I did not re-read the entire 2 month old thread before posting - I do not think it is likely to be burned, BUT it could always be slightly bent, which could prevent complete closing, and lead to burning later. You could be sure by starting with the heads off (too late for that now), resting them with the combustion chambers up, pouring gasoline, lacquer thinner, or acetone into the combustion chambers, and see whether any of them leaks.
At this point, you have ALL preload off of the valves, so you KNOW that uneven valve grinding depth, incorrect pushrod length, or weird lifter behavior is not causing your problem.

- Eric

68_convert

110 is a little weak on a new engine... Camshaft installed wrong? Bad grind? Timing marks lined up? Anyone attempt an offset key?

cjsdad

The hydraulic lifters are supposed to have a range of preload that compensates for minor differences in valve stem height. If the valve stems are too short the lifters will pump to their maximum and clatter. This happens if the rockers are able to "wobble" when the valve is closed. If the stems are too long the valves will not be allowed to close but the lifters will run quiet. This happens if the valve seats are cut too deep and the stems are too high above the spring seat. Head gasket thickness also has a lot to do with the pushrod length needed because almost all modern gaskets are thicker than the factory steel shim gaskets.

Another horrible thought is if the valve stems are too long (valve seats cut too deep) the valve heads could have hit the pistons and bent. They are not supposed to be able to do that unless the timing chain actually strips or breaks, but it sounds like you have a lot of things going wrong. Has the timing chain been replaced yet? A very loose chain could let the cam turn erratically and cause the vacuum problem as well. Did you make sure the distributor is not 180 out?

Just a few thoughts.

rustyroger

Start from the basics;
Do you have good compression showing even readings on all cylinders?.
If you do then you don't have a burnt, bent, or not seating valve.
Have you checked the ignition dwell and timing?.
Unless this is right the engine will never run properly, no matter what you adjust.

Assuming the compressions and ignition is good you need to go a bit deeper. First thing I would do is check the manifold for leaks. With the engine running spray WD40 or similar round where the manifold joins the heads. Any area where that makes a difference indicates a leak.
If you find nothing next step means some dismantling;
Remove the timing cover and check the valve timing is correct, if the marks on the sprockets line up correctly it doesn't definitely mean the timing is right, but it should be.
From what I have read on this thread my money is on valve timing out

If you aren't sure how to go about any of this You should get some help from someone who knows what they are doing. I think you have had some bad local advice.

Roger.

Arrowstorm

Ok....

So I redid the leakdown test. I thought I remembered doing it since I got the heads back from the machinist, but maybe I didn't I definitely did the compression test since then, though.

I did the leakdown test in firing order so I could dial down those shims as well. Many of the rocker arms were indeed just.... too dang loose. When I got to #4, I was getting air through the exhaust. To double check this, I loosened the rocker arms completely and shot air into the cylinder and..... lit a match a few inches away from the exhaust pipe and saw as it was immediately blown out.

So.. Next step? Pull the heads, right? Take them back to the machinist and ask him what's up with that? Since I got them back, this engine has not even run a grand total of ten minutes. Also, while I'm there, point out with a straight edge that the valve stems are NOT level across each head?

I will of course, have a look and see if anything is going on visually when I have the heads off, but I will also pour some thinner into the chamber with the heads upside down to see if there's leakage. I suspect there WILL BE leakage.

Does all that sound about right? Can you guys think of anything else? After I saw that match blow out by the exhaust, I pretty much stopped there because I knew I'd have to pull the heads.

Thanks in advance.

Buz

rustyroger

A much easier way to check for leakage is to stand the head on its side and pour thinners (I would use diesel fuel btw) into the ports.

If you put the engine together with full lifters there is a chance a valve has hit a piston, examine the piston crowns for marks if a valve or valves leak much.
If any valves are bent then you won't get an even line across the top of the valves, the bent ones will perforce be a bit low.

If you do have bent valves due to you putting it together wrongly you won't get much change from the machinist.

Roger.

Arrowstorm

Right. So... I pulled the heads and this is what I found.

That exhaust valve is wide open. It may be bent, I don't know.

Also, it looks as though it slapped the piston.

First, will I have to replace the piston? Or can I just smooth that out?

Secondly, what would cause just this ONE valve to slap the piston? None of the other valves look anything like that?!

I have to say again that this engine has not run even ten minutes since I got these heads back.

I'll be taking this one to the machinist and asking some questions and telling him my plight. Can't do that til monday or so though. Any advice from you guys would be appreciated.

don71

A tight valve guide clearance could have caused that valve to stick. Your machinist should take care of this.

I think the piston is probably fine.

The valve will need to be replaced, its bent now. I'd have your man dis assemble the heads again and have the guide clearances checked closely.

Arrowstorm

I feel the need to mention that when I dropped the heads off last time, the machinist showed me how the guides were quite worn on a few of the valves. They would wiggle a bit in the heads. He then explained how the guides on the Olds were kind of ribbed and he was going to replace those guides with smooth sided guides.

would that have anything to do with this?

MDchanic

NOW we've gotten somewhere.

1. Don't worry about the piston - it's fine.
That is a nasty bite, though. You can compare it to the completely harmless ones on my pistons and see how the nick in yours would make you say "I bet that valve's bent."
Yes, I would smooth it out with a Dremel or similar, to reduce the chance that it will serve as a source of preignition.






2. Yes, a tight valve guide could have done this, but it's hard to say.
Removing that valve and a couple of others, and seeing if that guide is tight enough that it makes it hard to move the valve would help to find out (as noted, that one valve is toast now).
I know of nothing that you could have done while assembling a hydraulic-lifter motor that would have caused this, so I wouldn't let the machinist tell you it was your fault.
You did lube the valve guides, right?

As far as one type of guide versus another, As long as he reamed the guides to the right size after installing them, their inner texture should make no difference.

Now you've found the problem. I would check to be sure that the reason for it isn't in some other part of the drivetrain (pushrod the same length, rocker the same, rocker pivot at the same height, lifter the same length, valve longer than all the others; the valve depth looks about right), then bring the head (or headS) back and say "WTF?"

Good luck!

- Eric

oldcutlass

You haven't done the timing chain during this repair, did you?

67 Cutlass Freak

I have a couple suggestions. I think you should number the valves/ cylinders and completely disassemble your head. Check your machinists work. How do the guides feel? How does the valve job look? You should purchase a valve stem height gauge tool that looks like this-
CIMG4553.jpg
Your machinist needed this tool to set up the stem heights correctly. Did he put stock valves back in your heads? IMHO it makes no sense not to use stainless steel larger than stock valves. Most aftermarket Olds valve are .100" taller than stock to allow the use of better aftermarket springs. By the way, did he use the stock worn out springs? Your cranking compression of 110 PSI is pretty low. I would expect to see 130-150 PSI on a fairly fresh street build. I would also highly recomend you forget about the stock rocker set up, and go with Comp cams adjustable roller tip rockers. You will also need to purchase hardened push rods and guide plates. Your machinist is obviously not an Olds guy. I would not have him grind the valve tips to correct his mistake ridden valve job. He may grind right through the hardenned part of the tip. You should go back to him well informed, and armed with the knowledge of what all the mistakes were that he made. You might even want to suggest that he compensates you somehow for having to spend an additional $300 on an adjustable rocker arm set up. He may get upset with you for telling him how to do his job. Keep your cool. If he throws you out, there's always the option of small claims court. Lastly, find an Olds friendly machinist. Good luck, and keep us posted.

MDchanic

Also, if you're a cheap SOB like me, you can make your own height gauge:






I have the height dimensions around somewhere - they're different for big- and small-blocks.

- Eric

Arrowstorm

I have since read that you're supposed to do a compression test with all the spark plugs pulled out. That 110psi is across the board with the plugs IN. So I don't know what difference that will make.

I'm no mechanic. I do the work because I consider myself able. What I've learned about the inner workings of engines is 100% from experience from this car.

I was thinking of taking Eric's advice and bringing the heads to the guy and asking him "WTF?" He's a good straight forward guy. When I got the heads back, he stayed past closing 15 mins and we chatted about a local cruising event for about 45 mins after that. I don't think he did the work. I believe he mentioned that his son did, so there's a bunch of experience that didn't go into my heads. This guy has an exceptional reputation around my town, so I don't think he'd just poopoo on my situation and tell me to go pound sand. Especially considering that my plight is well documented with mechanic friends around here. The leakdown test was LAST on my list because I took for granted that because the heads were fresh, there would be no need.

I really believe the rest of the set up is legit and ready to roll. Well, except, as mentioned before, the valve stems on the driver's side heads were uneven. I'll definitely have to point that out. I kinda feel now that they should have never left the shop like that.

When I did the original rebuild, I put it all together and that sucker ran PERFECT. This time, my original problem was perhaps a sticking valve that might have been taken care of with some seafoam, but I don't know. I just feel that the heads should have been installed the same as before and fire right up. From the first minute, I THINK I MIGHT remember it running better, but immediately after that, it gave me the problem I have now. Lesson learned. Before pulling the heads and having them reworked, try seafoam and maybe a little carb rebuild.

The elder machinist probably knows his stuff and I'm kinda hoping I'll bring in the heads, tell him what's been going on and he'll say he'll take care of it, maybe even donate a head gasket set and I'd be willing to put everything back together and see what happens, hoping for a perfect start up just like the first time I put it together after the rebuild.

Buz