VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 valve lash adjustment

My newly rebuilt 207 engine is just about ready to go. I'll probably show my ignorance here, but I'm not sure how I should set the initial valve lash adjustment. The repair manual describes the fine adjustment when it's running, using a vacuum gauge. But how do I adjust the rocker screws prior to initial start-up? If it makes any difference,I have a re-machined camshaft, new tappets, pushrods and rocker arms, and original tappet springs.

Adjust the valves (both I & E) at about .010 as you rotate the engine to the power stroke (both valves closed) for each cylinder. (Dead engine)

After the engine has run for awhile, you can make the final adjustments while the engine is running at idle.

After several miles you need to make an additional adjustment. This adjustment should be to the specifications described in your OM.

{Don't forget to reset the dwell and timing.)

That sounds easy enough. Thanks, Ray.

Randy:
After the car has been run and cooled a few times I suggest you re-torque the head to compensate for the gasket compressing. This will probably affect valve lash, so you'll want to adjust the valves again.
SOunds like you are making good progress on the car. Congratulations! Get her on the road and enjoy!

Thanks. We're getting close. Still have some body work and painting to do, but mechanical restoration is essentially done now. I did run into one other issue with the rocker arms. When I first installed them, I couldn't tighten down the rocker arm bolts. After doing a search, I came across your experience with rocker arm shafts. I had mine upside down, and the shoulder bolts wouldn't go in. Sound familiar? So your post definitely helped one other puzzled soul.

Gaaaaaakkk! I'm sorry to hear that...I thought I was the only one to mess that up! Hopefully there's no damage done. I recall having to file down the rocker shaft (where it had mushroomed a bit) so I could fit the rocker arms on it. Not one of my better moves. Once you take a close look at the shafts the answer becomes clear, but I'm usually in a hurry to get the car back on the road, and as we know haste makes waste!

Keep us posted on your progress!

One more question...I've now made the initial valve lash adjustment on all valves as Ray suggested. However, in other positions of the cam, some of the rocker arms are quite a bit more loose than the .010 clearance. Is that normal? or have I just not been able to catch the cam at the right spot? I watched for the lifter on the exhaust valve to fully bottom out, and the intake lifter to just barely rise before making each adjustment. I also verified that the piston was at the top (as closely as I could with a plastic rod in the spark plug hole).
I know I have to readjust after the engine is warmed up, but I just want to be sure I don't do any damage in the process.

I don't quite undersatnd what you mean by some are more loose at .010"....Is this after you set one and then turn over the engine to adjust another the first settng changes. If so you didn't have the lobe positioned correctly on the first one. The exhaust valves (one at an angle) will be set at about .014" after running. These can be a little more loose. The perfectly verticle intake valves can be set to .007" so they can be a little tighter.

I'll explain it a little better with an example. If I turn the crank until the #1 exhaust lifter comes to the bottom, and the #1 intake lifter just barely begins to rise, I assume that I'm at the right position in the power stroke with both valves closed. I adjust the clearance on the intake and exhaust valve at that point to .010. Now I move to cylinder #2, #3, etc. However, I notice that when I have another cylinder in the right position on the power stroke, say #3, the rockers on #1 are very loose. That would mean that the lifters go a bit lower at some point in the cycle than they are at the power stroke position with both valves closed.
Does that make sense? If not, I'll post some pictures.

Don't worry about the position of the piston, etc.,. You want the cam turned to the position where the gap is the most wide. Thats where you make the adjustment. The piston being on top only brings it close to this point. It will be necessary to to the engine over one way or the other to find the correct point where the valve is most fully closed.

I have found that adjusting the valves on each cylinder separately is not the best technique. Approximately 1/3 of all valves will be fully closed at any position. Some rockers will obviously be higher at the lifter end and lower at the valve end. Don't mess with them. Do preliminary adjustment at the valves that appear to be fully closed. Rotate the engine approx 2/3 of a revolution. Check all valves already adjusted to see if any are loose. You can check by grabbing the rocker arm and moving it up and down. If obviously loose then re-adjust. Then adjust the other 1/3 that have closed valves. Repeat the process until all valves have been adjusted and rechecked at least once. The adjustment sequence is published in most repair manuals. It gives the valves that can be adjusted then a given pair of cylinders is at TDC.

Thanks. So when I'm done with the initial adjustment, as I turn through the cycle, the MAXIMUM clearance on each rocker will be about .010, correct?

YES

OK. I've now adjusted them based on Chipper's suggestion. I think I was trying to make something simple more complicated than it really is. Thanks for the help.

Just to be sure, I went through the following method that I saw online and I was very close to the settings found with this procedure. So I'm confident I've got it right.

1. Hand turn the engine in its normal direction of rotation while watching the exhaust valve on one particular cylinder.
When the exhaust valve begins to open, stop and adjust that cylinder's intake valve.
(Why? Because when the exhaust is just beginning to open, the intake lifter will be on the base circle of the lobe,
so the intake is the one we can now adjust.)

2. After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is almost closed, stop and adjust the exhaust valve on that particular cylinder.
(Again, when we see the intake valve almost closed, we are sure that the exhaust lifter is on the base circle of the lobe.)

3. Both valves on this cylinder are now adjusted, so move to your next cylinder and follow the same procedure again.

It takes more time to do it that way but will work just fine. Even if you have one too loose it is easy to find it when engine is running. Just put a little pressure on the rocker ends and if the tapping noise goes away or gets less then it is too loose or the rocket tip is not properly radiused (ground).

Thanks. My machine shop didn't have the rocker radiusing tool, so I bought some NOS GM rockers. Hopefully te hey'll be fine. They're the same part numbers as the originals, but I noticed that the exhaust rocker ends are a bit wider than the originals.

They should be ok.

The way I adjust valve clearances Watch #6 valves when they are changing from exhaust close to inlet open adjust both of #1 valves then turn in normal rotation till #2 valves "rocking" and adjust #5 then continue through the sequence, only requires 2 turns of the crank.
Another method is remove distributor cap and adjust the valves on the cylinder at the plug lead position the rotor button points to.
I rarely adjust clearances while the engine is running as it is difficult to keep everything in place while they are bouncing around.
Tony

I would also strongly recommend setting the exhaust valve closer to their proper setting oof .015"....You might find that the .010" setting will cause hard starting and a rough idle.

Randy:
When you are done with all these techniques you may still find you have one valve that taps louder than the rest. To find the culprit I've used a short length of wood (a short broom handle)held against each rocker (engine running, fully warmed up) with the opposite end to my ear. The offending valve is usually easily identified by its louder rapping and you can adjust it with the engine running. Just don't get the valves too tight; looser is better.

I'm wating to hear Randy say....IT'S RUNNING, IT'S RUNNING !!!!!!
But its making a lot of noise and smoke.

Hah! Thanks for the vote of confidence, Gene. My 13-year-old son got a laugh out of that one. You guys will be the first to know when it's started...probably in a month or so. It's still on the engine stand and I'm painting it now (Filling Station dark gray, of course).