Engine mystery

[miatawnt2b]

Put a good number of miles on the Vair this weekend. Took it to a show and a couple cruises, kids sports, you name it. It's not out of the ordinary though, the car gets driven probably 40 miles a week. Anyhow, I parked it Sunday after a 20 mile or so trip. Monday afternoon I get in the car, hit the starter, and the right side of the motor sounds like a coffee can with a bolt in it. I only ran the car about 45 seconds just to quickly determine the general area of the noise. I'm pretty confident it was in the right side valvetrain. Shut it off and ripped into it this evening.

So I pull the valve cover, and don't notice anything too out of the ordinary, except maybe the exhaust valves on #1 and #5 are slightly loose. I didn't notice any broken springs, rockers or studs.
I then grabbed an endoscope (thanks to Amazon). I bought one of the fancy articulating models. Pulled the plugs and took some pictures. Pistons all look fine, as do the valves. You can still see the crosshatching from the rebuild before I bought the car. Nothing was smacked, valve seats were all in place.
At this point I feel comfortable enough to crank the motor and do a compression test.
#1 - 120
#3 - 110
#5 - 90
This was a dry test. All the plugs looked the same and show no abnormal signs. Not too lean, not too rich, no oil fouling.

Well now I'm scratching my head. I throw the plugs back in and hit the starter. Noise is gone. Completely gone.
While it was idling though I inspected the open valve cover. Pushrods rotate very slightly/slowly, and drip oil. However, the exhaust pushrod on #1 spins rapidly... like way faster. It also does not drip oil, at least at idle.

So that's where I'm at. I have a real mystery. just for grins i'm going to perform the same on the left side of the engine tomorrow, I don't expect to find anything, but the valves probably need adjusted anyhow. The motor hasn't been touched since it was rebuilt by the PO in Phoenix maybe 8k miles ago.

Ideas? I'm guessing at the very least there is some issue with #1 exhaust pushrod or lifter. Engine is a '65 140.

[KenHenry]

One time the starter motor stayed engaged on my 140 and it sounded awful. Took me a few seconds to figure it out, but it disengaged normally the next time I started it. Cranked slowly though. I think the noise was pretty clearly coming from the starter in my case though… Ken

[Lane66Monza]

I may be wrong but I suspect the #5 exhaust valve seat is loose. That is the reason for the 25% compression loss. 10% is allowable difference, or 11 psi from center reading.in the case. Valve seat can go back in position, but compression loss is one symptom. Lack of ipiston mpact due to limited run may not be evident or missed if borescope probe not mainipulted to lower portion of piston surface.

[kmart356]

...snipped...
.... Monday afternoon I get in the car, hit the starter, and the right side of the motor sounds like a coffee can with a bolt in it. I only ran the car about 45 seconds just to quickly determine the general area of the noise. I'm pretty confident it was in the right side valvetrain. Shut it off and ripped into it this evening.
Nothing was smacked, valve seats were all in place.
...snipped...
Ideas? I'm guessing at the very least there is some issue with #1 exhaust pushrod or lifter. Engine is a '65 140.

This noisy valvetrain upon startup most often occurs when one (or more) lifters bleed down and lose the oil pressure they require. It is very discerning but will settle down after running the engine a few minutes or so. Hopefully your issue as just that the lifter lost oil pressure. It solves itself but makes for a nervous few minutes while it pumps back up.

[RexJohnson]

I would not adjust the valves unless there is a reason to. Hydraulic lifters don't need to be adjusted unless there is a reason.

[caraholic4life]

I may be wrong but I suspect the #5 exhaust valve seat is loose. That is the reason for the 25% compression loss. 10% is allowable difference, or 11 psi from center reading.in the case. Valve seat can go back in position, but compression loss is one symptom. Lack of ipiston mpact due to limited run may not be evident or missed if borescope probe not mainipulted to lower portion of piston surface.

I would have a tendency to agree with Al...
There is a good chance that a Valve Seat may have come loose and re-seated it's self.
I something similar happen with my Greenbrier, fortunately while it was at the Corvair Ranch for it's initial evaluation right after I bought it.
They were moving it in and our of the shop when they heard what they suspected may have been a potential valve seat dropping.
Since the powerpack was supposed to come out anyway, I had them go ahead and remove the heads and install deep seats just to be on the safe side.

[66vairguy]

Both the "temporarily collasped lifter" and "loose valve seat" are valid assumptions.

That said I agree with Rex --- if valve train is quiet I would not ADJUST the valves unless you are experienced. I've seen poorly done valve adjustment cause issues.

The collapsed lifter on Corvairs that sit is not uncommon. Typically it goes away after the engine warms-up, or you shut down the engine and if the collapsed lifter isn't under tension it fills up with oil and you restart the engine and all is quiet.

If a valve seat is loose it WILL come out again. If this happens do NOT rev the engine or drive it as the seat can break up.

I WOULD CHECK the fresh air hose from the top fan shroud to the heater box. When it rips from old age it will cause the #5 cylinder head are to overheat (and the seat comes loose) based on years of forum posts.

When I have the engine out I always check or replace the fresh air heater hose. I check it every oil change. Many just remove it and block off the hole in the fan shroud. The fresh air hose is durable, but after decades of age it is worn out and often ignored due to price (if a mechanic has to do it) of replacing it.

[miatawnt2b]

What's the chances of the seat coming out, reseating on shutdown then being fine again on initial startup a day later? Is that really a probability? A couple lifters were super loose, so I'd guess that's a more likely source of my noise that now isn't. no?
I've read that too much lash can cause a pushrod to not drip oil. The fact that one of my pushrods don't squirt oil and that it is spinning like crazy tells me my first step is to verify that lifter is good and/or set the lash properly on that valve.
Am I wrong? I'd want to fix an immediate oiling issue first, right?
-J

[RexJohnson]

I would think that with too much lash you could have less oil at the rocker because it was dripping at the lifter. If it was quiet, and now is loose unless you know a seat came out I would run it until they pump back up before doing anything. Yes a seat can go out and come back in. I worked on a car several years ago and the owner said that it would run rough so he would take it somewhere and they would say everything was fine. Shortly after he would get home it would run rough again. I checked it out and everything was good. He said to drive it alot to make sure. I put several hundred miles on it and it always ran great. I give it back to him and he gets half way home, stops at a rest area and when he restarts it, it is running bad and making noise. He was not happy. I brought it home and removed the head. You could see by the piston that both valve seats had been coming in and out as there were 2 half circles on the piston. The valve seat that was still in you could see a small gap around the outside from it coming in and out. I switched the head and never saw the car again.

[vairmech]

Are all of the rocker nuts showing the same amount of threads? The stock nuts will have about 3 threads showing and the aftermarket nuts will have about 1.5-2 threads showing.
With that all should be good. Valve seat??? Give it some time running, you say a rebuilt engine? Give it a chance to get the rings sealed properly.
Everyone always wants to jump back into an engine when some little thing happens when there is really nothing wrong.

[66vairguy]

What's the chances of the seat coming out, reseating on shutdown then being fine again on initial startup a day later? Is that really a probability? A couple lifters were super loose, so I'd guess that's a more likely source of my noise that now isn't. no?
I've read that too much lash can cause a pushrod to not drip oil. The fact that one of my pushrods don't squirt oil and that it is spinning like crazy tells me my first step is to verify that lifter is good and/or set the lash properly on that valve.
Am I wrong? I'd want to fix an immediate oiling issue first, right?
-J

Yes if the lifter is fully extended due to wear or mis-adjustment, then it has been suggested the lifter will not pump oil up the pushrod tube. Every time the lifter pushes the push rod the internal lifter valve closes and sends a little oil up the pushrod tube.

Note more than once folks found the pushrods installed UPSIDE DOWN. One end of the pushrod has a hole in the middle to match the lifter. The other end has a hole in the SIDE to squirt oil toward the rocker ball. UPSIDE DOWN and no oil goes up the pushrod tube!!!

At one time the incorrect thinking suggested the lifters "pumped up" at high RPM holding the valve open. If you adjusting them like a solid lifter, small amount of lash to fully extend the lifter, that would fix the problem. FACT is the actual problem is the valve train inertia at high RPM overwhelmed the valve spring tension so the valve did not completely close and the hydraulic lifter simply did its job, extended to fill the gap. Keep in mind the camshaft grind affects this, the more aggressive the cam, the higher the valve spring tension required.

After years of trial and error - the optimal adjustment is to find zero lash, THEN turn the rocker nut down 1/2 turn! This has proven to accommodate different lifter and cam tolerances. Vairmech is correct, stock rocker nuts should have about three threads showing. A crude check, but it will let you know if something is way off. I've done this check a few times before tearing things apart and it is a valid check.

Over the years Chevy issued bulletins for different adjustments depending on the type of lifter used. Today the 1/2 turn works. Chevy initially adjusted the new engine valves to allow for "break-in" wear. Keep in mind after a new engine build (new cam and lifters) and "break-in" there should be little wear IF the engine is maintained properly.

I use 1/2 turn after zero lash on a new engine and check the adjustment of the valves at 1,000 miles. Any change due to wear is minor and I never worry about it again. Just me ---

[66vairguy]

The fact that one of my pushrods don't squirt oil and that it is spinning like crazy tells me my first step is to verify that lifter is good and/or set the lash properly on that valve.
Am I wrong? I'd want to fix an immediate oiling issue first, right?
-J

See my previous about PUSHROD INSTALLED UPSIDE DOWN.

Due to the cam and lifter design the lifter and pushrod should turn, but the rotation seems to vary and I've never read why this is. Of course there is always the possibility of a defective cam or lifter, or worn lifter bore.

Before jumping to conclusions, check the pushrod orientation.

[66vairguy]

Are all of the rocker nuts showing the same amount of threads? The stock nuts will have about 3 threads showing and the aftermarket nuts will have about 1.5-2 threads showing.
With that all should be good. Valve seat??? Give it some time running, you say a rebuilt engine? Give it a chance to get the rings sealed properly.
Everyone always wants to jump back into an engine when some little thing happens when there is really nothing wrong.

While this is uncommon --- a buddy found a pushrod riding on the edge of the lifter. The give away was the rocker nut wasn't showing any threads. Someone had adjusted the valve with the pushrod out of place. It would jump in and out of the lifter center causing noise to come and go. Again uncommon.

[vairmech]

Over the last few years I have changed my mind on the amount of valve "lash". I used to be of the same thought, don't want the lifter to pump up and cause problems. More times than not though I would have a noisy lifter. Why? The smaller your adjustment the more precise you have to be in finding zero lash to begin with, 90% of the people that call themselves mechanics can't do it! Obviously off and on neither could I.
On most lifters I have found out that it takes about 3-4 full turns to bottom out a lifter. So how do I adjust lifters? I am now pretty precise on finding zero lash and then going one full turn down. I do this even on my race car where I turn the engine to 7000 rpm and sometimes more. I haven't floated a valve yet.

With stock early 80hp small springs any engine would float the valves at about 6000 rpm sometimes less if it was an older engine. The HP and newer style larger dampened spring had a little more pressure and that helped the valve float. I routinely took my stock 140 engines and hit 6000 in first and second, No valve float.
Any more I do not believe in the lesser 1/4-1/2-3/4 turns to eliminate valve float.

[66vairguy]

Over the last few years I have changed my mind on the amount of valve "lash". I used to be of the same thought, don't want the lifter to pump up and cause problems. More times than not though I would have a noisy lifter. Why? The smaller your adjustment the more precise you have to be in finding zero lash to begin with, 90% of the people that call themselves mechanics can't do it! Obviously off and on neither could I.
On most lifters I have found out that it takes about 3-4 full turns to bottom out a lifter. So how do I adjust lifters? I am now pretty precise on finding zero lash and then going one full turn down. I do this even on my race car where I turn the engine to 7000 rpm and sometimes more. I haven't floated a valve yet.

With stock early 80hp small springs any engine would float the valves at about 6000 rpm sometimes less if it was an older engine. The HP and newer style larger dampened spring had a little more pressure and that helped the valve float. I routinely took my stock 140 engines and hit 6000 in first and second, No valve float.
Any more I do not believe in the lesser 1/4-1/2-3/4 turns to eliminate valve float.

You are correct that the 1/4 after zero lash is NOT adequate and I've seen were folks using 1/4 turn have a rocker oiling problem.

Finding the full range of the lifter and setting to the middle is a good approach, but as GM learned the lifters they used (different suppliers) varied. They also found the valve train geometry is affected by how far you turn down the rocker nut depending on the lifter design (different suppliers).

Since the heads I installed were rebuilt the gasket surfaces were machined. To compensate I use the 1/2 instead of factory 1 turn after zero lash. This is why I double check after engine wear in. I would not go any LESS than 1/2 turn. If I had NOS heads I'd go with the 1 turn at build and never check them again.

Gee this gets complicated --- see the Chevy service bulletin about different lifters and adjusting lash.

[RexJohnson]

Pushrods have oil holes in the center of both ends. The "upper" end also has a side hole to lube the rocker ball and the valve stem. The hole in the center at the rocker arm lubes the rocker arm to pushrod socket.