VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Adjusting Valves on my 41

Not able to multitask or even having the time because of the Midland, Mi May flood I decided to take the advice of my well trusted Chevy friend Don Harbron. Don has a old friend (old also as someone in the auto repair business over the age of 70) to let him help me get my car started 3 weeks ago. I had assumed I had a condenser or coil problem. It took the gentleman only a couple of minutes to diagnose the starting issue as frozen points and bad timing. He said Chevy's were prone to starting issues when not started in a long time because the points could "freeze shut."

So without a gauge to set the points he had me turn the car over and when the points opened he set them by sight. Then reset the timing by rotating the distributor to the mid-point of the octane selector. Car immediately fired up and he proceeded next to say the idle was to low and adjust the idle screw on the carburetor half a turn or more. For me the engine was now racing...

What he did not know was that the last thing I did before deciding I needed help was take a point file and run it through the point gap. I never told him I did this. In hindsight I think I had opened the points so far that I wasn't getting the correct spark.

Next he told me I had a little tappet noise and he would be glad to schedule me for a valve adjustment. I had done this shortly after running my rebuilt engine about 500 miles I now have about 1500 miles on the engine. I did my adjustments with the engine warmed up, but not running, he did his adjustments with a hot engine running.

As he got started I noticed 2 things happening. The top of the electrolock cable, that attaches to the top of the coil was working itself loose and I noticed later it had a lot of oil in it from the lubricating of the rocker arms. Next about the time he was making adjustments on the 3rd cylinder the steering wheel started vibrating slightly. While the fibration never increased it also never went away. My tailpipe was even vibrating from hitting the frame or bumper.
When he finished his adjustments I mentioned the vibration to him and he said, "Chevy engines vibrate."

As I reflect back on his method for setting the valves he likewise did this by ear and not with any gauge.

My gut instinct is to go over the valve adjustments. I am hesitant to drive the car with the engine vibration. What might be causing my problem. I have not dealt with an engine vibration when the car was idling and not in gear.

Thanks, Mike

Obey your gut instinct. From 1600 miles away. I respect people who do things by ear but they are mostly musicians. He probably adjusted one of the rocker arms on #3 too tight. Probably the exhaust and the cylinder is now misfiring. Use Tiny's method for adjusting rocker arms. Pull the plugs, set the rocker arm clearances cold (I use max clearances, I=.008, E=.015), reinstall the plugs and warm the engine good, recheck that the clearances are in range and tweak those that need resetting. My experience is that I only have to tweak 2 or 3. Lots less messy that way and you can do it by yourself.

Valves or valve too tight.

Mike, I think Gene is right on.

Get a feeler gage, a short screwdriver and a wrench and tackle this job yourself.

Next warm the engine up. Put something in front of the radiator or trip the fan belt. No need to boil it over.

Nest back off the idle to as slow as it will still run to prevent the rockers from slinging oil. Put something down beside the sides of the engine to shield oil from getting all over everything. Guest room towels are best.

Use the proper sequence to adjust the intakes and exhaust valves,

If you err let it be a tad on the loose side. A thousand or or two is not going to hurt anything. Use a valve sound-dampening blanket to hid the noise.
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This here right here ain't no rocket science deal.

Best,

Charlie

I would check the points and timing too. Points should not be adjusted by eye.

The hardest part of adjusting valve clearance on a running engine is the need of 3 hands (screwdriver, feeler guage and wrench), I prefer to do them with engine not running.
Tony

I agree with Tony - 3 hands would be nice, but it can be done with 2. The trick is to use a box socket wrench to loosen the securing nut, not an open wrench.

There is a tool for this. It allows for loosening the nut and turning the adjuster without having to switch from screwdriver the wrench.

Best,

Charlie

Here are pics of the tool that I use to adjust the valve lash on my two old trucks.




Cheers, Dean

I just bought one of those but it's still hard to adjust valves.

After much procrastination I finally adjusted my valves and reset the points. I found not one single valve that was loose enough to fit a gauge under it with the engine cold. Some were several turns off. So much for not using a gauge to reset ones valves. I cold set all the valves to the spects Intake .006" Exhaust .013." I set the points from about .008" to .018" and adjusted the timing by ear. I will check it with a timing light soon! The engine no longer vibrates so much that the steering wheel shakes.

On a test drive with the choke all the way in the engine began bogging at about 15 MPH in 1st gear and 25 in 2nd. Eventually I remembered that the engine has never run well with the choke all the way open, but did run well with the choke about 1/2" closed. Now in 1st the car continues to accelerate to at least 20 in 1st and 35 in 2nd.

Looking at the warm up chart on page 167 of my '41 Manual and also in the '42 to '47 Manual I see that the valves should be gapped on a cold engine at .006" on Intake and .013" on exhaust AND should be set at the same #s after 30 minutes of running. I assume that as the metal is heated the valve gaps enlarge and need to be brought back to their cold settings. What are the reasons to do this? Better engine performance, less valve wear, less tappet noise?
Check the chart Clearance Change from '41 Manual

On page 168 the manual recommends Intake at .006" to .008" hot and Exhaust .013" to .015" hot. If you favor the higher numbers are you ending up with a quieter or noisier engine?
Intake .006" to .008" Hot Exhaust .013" to .015" Hot

Thanks for all the suggestions,
Mike

Mike,

I think you have it basackerds. The gap will decrease as the engine warms up. The gap will be wider cold.

If you want to get it about right without all the hassell you can use a cold setting. Just use the relative .008 and the .015. settings.

The sound of the engines valve train will be slightly louder but all the valves will be seating as firmly as their condition permits. A bit too loose will never harm anything other than your ears and, perhaps, pride when others are hearing it run. The only negative result will be an almost undetectable lose of a bit of power owing to valves not opening for a wider and longer period in the firing cycle. The gap will never increase through wear that a problem will occur such as a pushrod jumping out of place, at top or bottom.

Don't sweat the small stuff or over-think it.

Best,

Charlie

Hey there Charlie..
I've been thinking exactly the same thing. Set them cold and leave them alone. I have a 1946 overhaul manual with the same clearance versus temperature chart that Mike linked to above http://chevy.oldcarmanualproject.com/shop/1941/41csm167.htm
From that I noticed that the clearances settled out to exactly their cold setting once the engine temperatures were equalized to where the manual wants them to be. I also noticed that if my engine hasn't quite reached that point yet without me knowing it, I could be a long way out on either the intake (as at the 5 minute mark in the chart), or the exhaust (as at the 20 minute mark). At the 20 minute mark both the oil and coolant were well warmed up, and yet the exhaust clearance widened out by .005" over the next 10 minutes.
Another consideration is this... if you are being fussy about your work, or are as slow as I am... the engine cools off between the first valve set and last. How much difference in running clearance will I end up with in the end?
So why should I burn myself on the heater hoses etc when Chev's own chart shows I might as well set them cold? :-)

Respectfully Ole

The lesson I have learned from this thread is that you either set them cold or with a fully stabilized hot engine. Any conditions between create problems.

The chart in the '41 manual has some logic behind it. The thermal expansion rates of steel and cast iron are every similar. So push rods and valve stems get longer as things heat up in the same proportions as the cast iron block and head grow. Even the rocker arm stands grow at a similar rate. The key is getting everything to a stable operating temperature.

One variable is that the exhaust valves will operate hotter than the intakes under heavy loads. I would expect the exhaust clearances to decrease slightly in that situation.

Let's put this in perspective. Steel and cast iron expand at the rate of 6.5 parts per million per degree Fahrenheit. So a 6 inch long valve grows .0039 for a 100 degree temperature rise. A 4" thick head grows .0026" and the 2" rocker arm stand grows .0013" fro a total of .0039". And the pushrod has expanded at the same rate.

I agree completely with everything Rusty says.

Intake valves heat up slower that everything else because of incoming air, so their clearance widens before settling back during the warm up period.
Exhaust valves heat faster than everything else for obvious reasons, so their clearance narrows before settling back.
So if I set at any point between cold and equalized hot I won't just be evenly wide or evenly narrow, I will likely just be wildly wrong.

I find it easier to be sure I'm cold equalized than warm equalized, and I have all the time I want to fuss with things without worrying about the engine cooling off while I'm working.

Ole

I would like to thank all for their input, especially Ole for his thorough explanation. The manual chart now makes sense to me. As someone with a bit of mechanical aptitude and little automotive experience this site continues to inspire me to work at and through the many challenges of owning my 41 Chevy.

Best wishes to you all, Mike