VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Weak Valve Springs on my 1941 Chevy?

As many of you remember, I just completed a new engine rebuild in January in my 1941 Town Sedan's 216. Shortly after the rebuild, I dropped two valves. I took the head back to the machine shop that had worked on it, he took it all back apart and blamed it on bad gas. He said there was a brown substance on the valves and that I had stuck two valves. He cleaned everything up, replaced the two bent valves, and I installed it back on my car last week.
Today, I added a gas additive to help with older gas and started the car. I also had put approximately 12 gallons of fresh gas in the car a few months ago. It ran fine but driving down the road, it lacked power going up hills and high rpm. We adjusted the valves two times and adjusted the timing many times. I installed new points, condenser, spark plugs, and other items. We still just couldn't get the final miss out of it when we'd race the engine or add high power. We checked the valves again and found the intake valves were unbelievably tight. When we loosened the adjusting nut on the rocker arms, the valve would rise meaning the intake valves were so tight that they were being held open. So, we figured that was why it was missing at high power. We adjusted the valves again and continued to run the engine for several hours. Then I heard a noise coming from the valve cover and immediately shut the engine down. I discovered the intake valves to be very tight again. Thinking I might have sticking valves, I decided to try pushing down on the intake valves to see if they would move. To my surprise, I found I could push the intake valves down easily with only two fingers. I also found that when I pushed the valves down, the rocker arm easily disconnected from the push rods. That was what the noise was I had heard. It's my opinion that the valve springs are too week for the valves to rise fast enough which will result in loss of power during high rpm's and will result in excess noise from the rockers from them disconnecting from the push rods. This was more than likely why I dropped two valves back in January since I had heard some of the same noises then but then they went away. Even though the engine shop said bad gas had stuck the valves before, I had a hard time believing that really hot brown syrupy stuff from bad gas would stick a valve while the engine is really hot. A cold engine that is starting, I could understand a stuck valve....just not one that had been running for several hours. What does everyone know about weak valve springs?

Brandon,

Well, not too much but I never was man enough to push them down with two fingers. Or three, even.

I think you have some weak valve springs and, possibly bad gas, too. The varnish in the old gas that has been created by sitting in the tank for a long time may cause a problem but I don't see that it would be enough to cause the valves to stick in the guides. Shirley, it wouldn't have been that rank.

I recommend a new set of valve springs. I also recommend you get a valve spring tool, you may be able to borrow one, and do the change over yourself. Easy.

Good luck,
Charlie

BTW: The rebuilder should have tested the springs for strength. I recommend you seek another shop. I would.

I would drop the gas tank and take the sending unit out and see whats inside. If you have a build up in your tank you will continue to have problems with valves sticking.
If your springs are that weak I agree that they should be replaced.

I guess I should also add:

A few years back, after the car had sat for many years, I had some sticking valves on a different motor in this car. I found bad gas to be the culprit. At that point, I installed a new tank, new gas lines, new fuel pump, and new overhauled Carburator from Chev's of the 40s. Since that time, I kept the car running at least monthly with no problems. Once I changed the motor, now I'm having problems. This is not the same engine as before due to the previous one developing a crack in the block. This head has new intake valves, new seats, and new intake valve guides.

every time I put gas in the 39 , I add stabil to it . the quality of gas is poor these days .5 years now & no gas problems other than evaporation in the carb from sitting . frank

Brandon,

I had the engine rebuilt in my 41, and am now installing it. The machine shop I used for the rebuild tested the new valve springs before they installed them. The springs were new from Kanter, but did not meet the specs in our 41 manual so they did not use them. They were too weak. I suggest you take your springs off and have them checked. I am surprised that your shop did not do this. The manual says they should each compress at 125-133 pounds.

Keep us updated, Mike

P.S. Kanter would not refund me the money for the springs nor the push rods that were 1/4" too long. They said, "they were part of a kit, and didn't refund individual parts from a kit."

I just love it when a vendor grabs at straws for a way to 'beat' you out of your money.

I have had many problems over the years by providing the parts to a machine shop/or an installer. You just provided the vendor with an 'escape'. It is best to have the shop provide the parts, then you can fall back on the shop when something goes wrong.

An example: I purchased a top for my 71 Impala convertible, took it to a shop to install. They managed to rip the top on both sides. The shops defense: A piece of junk. Original vendor: Your man was the one that damaged it. You can see where this is going.

Problem could be weak valve springs. Install a set of springs for a later 235 engine. In the later years Chevrolet recommended them in a 216 for heavy duty use.
Could also be that they installed later 2 grove valves and have the keepers in the top grove where the seal would be on a later engine.
Valve seats could be ground too deep into the head. Then would require shims under the valve springs to make up the difference.
Oil the valve guides....did they ream the new guides for proper fit. You should feel a slight amount of side to side movement (stem in guide).(.002")

Mike,
The valve springs were checked by the shop and were good. But for some reason, when they get hot, they get really weak. I've already ordered new springs and will install them when I get them.
As for Kanter, I don't like to deal with them.

There's nothing wrong with the guides. We've checked that now twice after installing all new ones. The real problem here is that I can push down the intake valves with only 2 fingers. That's way too week.

I have never seen a valve that I could move with just two fingers.

Just wondering,are the valve guides solid cast iron as per original,or have they been fitted with thin wall bronze sleeves?
If they've been sleeved with bronze,that may be the problem,as the bronze expands at a faster rate than cast iron would.Just a thought.

I guess I need to clarify something from my original post. When I said the valves were too tight, I meant, After I had set the valve clearance between the valve stem and the rocker arm, the clearance would tighten up. For example, after setting the intakes on .013" hot, an hour later after running the engine, the clearance would be zero and the adjusting nut had not moved. I'd been setting the valve clearance the old school way by turning the engine till the valve comes to the top. I've gotten a vacuum gauge now and will readjust the valves using that to make sure I'm right on it.
I've ordered new valve springs and will change those when I get them and see what happens.

They are solid cast iron.

I think we found the problem today with my engine. In January when I dropped two valves on a new rebuilt, they were intake valves. The exhaust valves were fine. The engine shop blamed it on bad gas sticking the two valves. Today, I think we found the real problem. The engine shop replaced only the intake valves. We found today that they replaced them with valves that had 2 grooves and not the original 1 groove valves. Then they put the valve stem keepers in the top groove. This allowed the stem heigth to be too short when I added the intake valve oil caps. So when the rocker pushed down on the oil cap, there was space between the oil cap and valve stem. Once pushed down, the spring compressed before the valve moved. That's how the stem keepers fell out and why we never could get the last bit of tapping out of the valve adjustments. We're moving the keeper down the bottom groove which put the stem heigth right...we think. This is also why we couldn't get full power because it knocked the valve adjustments all out. I hope to be driving this car July 4th!

Years ago we would replace the 1941-1947 EXHAUST valves with the later two grove valves. They always used the bottom grove and had no problems. The later exhaust valves were 45 Deg so the ground the seats to 45 Deg.

Well, with me being in Florida for 2 weeks, my father has been working on my car. He called this evening to let me know that after moving the valve stem keepers to the bottom groove, setting the valve/rocker clearance, THE CAR RUNS LIKE A NEW ONE!!! And it should after changing every part and bolt on the entire car! He's now looking at servicing the front shocks and then will make an appointment to get the front end aligned. We just might be back in business!

Owing to good things happening whilst your are away and your dad working on the car, sounds to me like you may want to consider extending you trip to Florida. Just saying...

Charlie

Charlie, I have to agree. Much has been done while I have been gone. He even pulled both rear axles and changed the bearings and the axle seals. Before I left for Florida, I told him that restoring my car was no longer fun after 17 years. I still couldn't drive it and it seemed that for every step forward, I took 10 steps backwards. I asked him to either fix the car or find someone to fix it. I told him I was done and over it. I explained to him that I would be back home in two weeks and I expected to get in my 41 and drive it home. I think he took me seriously.