The Stovebolt Site Forums The Shop Area Engine Shop Cold Valve Adjust

I've tried just about every cold valve setting that people suggested on this board for my 62, 235. Adjusting the valves hot is a pain in the butt and not very accurate because the motor is cooling down as you work on it. A long time ago a Chevy tech at the local dealer told me to adjust them to these settings:

hot: intake= .008 exhaust= .010

cold: intake= .010 exhaust= .012

I just readjusted them this afternoon cold, and the engine sounds perfect. It just makes a slight ticking noise.

If I need to adjust mine cold I set them on the fat side, or "heavy duty" as the book calls it, then follow the book and adjust them again when it is hot. It only takes about 10 or 15 minutes and one revolution of the crank, I feel that it is still just about as hot when I am done. It works great for me, I'll even stop and adjust them at a rest area If I think they need it, it's that quick.

The engine shouldn't cool off if you adjust the valves with the engine running, and it takes less time.

I agree with grigg. I tried adjusting mine before with it running. A huge pain in the butt, and left me with a nicely chewed up feeler gauge. Once you get the hang of it, it will only take a few minutes to do it hot with the engine off. And, the engine will actually warm up within 10-15 minutes after it is shut down, because it has no water circulating.

Question. What would be the feeler gauge settings for a 261 both hot and cold? I believe that they are different from the 235.

The settings for a 261 with a 261 head might be different, but if you have an 848 head on a 261, wouldn't the valve settings be the same?

I never have understood why the valves have to be set hot, and if so, why does it need to be done with the engine running? I agree that setting them cold seems like an OK idea, but setting them hot WITHOUT the engine running seems like alot less trouble than having to loose a feeler gage in the process, try to be accurate in the process and wash down the oil from the fire wall and everwhere else it gets on the truck.
:mad:
I'm going to have to be very convinced that setting them cold isn't OK and very, very convinced that it can't be done with the engine hot and OFF!

Joe- the reason for setting them hot is to account for expansion of the parts as they get hot. Steel expands at a rate of .000006in/in/degree if I remember right. So a 12" long pushrod would grow approx. .009 when heated from room temperature to 200 degrees. The block, head, valves, and everything else are also moving around as they heat up. For that reason, you are better off setting the valves a few thou. loose when cold and heating the engine up to operating temp. and then resetting the valves hot. I just did a rering and valve job on a nice '48 Chev. sedan delivery last week, and set the valves a few times hot before I was happy with them. I didn't do them running hot, I hate the little hot oil burns on my arms!

:o
At this point, this may be the proverable "dump question", but if they expand when they get hot, wouldn't you set the at .009 more cold?
:rolleyes:
And . . . here's another one . . . are we talking solid lifters or hydraulic?

:confused:
What is a "dump question" you asked? It's a "dumb question" with a "p" instead of a "b".

What else can I say?

Well, the pushrods expand, but the valve stems (especially the hotter exhaust valves) also expand. And the block height is growing and you have to remember the rocker arm ratio too, so the pushrod growing doesn't mean you can just add the amount of it's growth to the valve clearance number. For mechanical lifters (solids), it's better to just add a few thousands cold or set them "fat" or "heavy duty" as grigg said, and then do the final adjustments when everything is warm. Hydraulic lifters are adjusted totally different. Those you would lash to zero clearance and then slowly crank a 1/2 turn or so into them. The hydraulic cushion will take up for any slight misadjustment from there.

6cylindersovertexas-

You actually set the valve clearance based on what cam/lifters you use, which head doesn't matter at all. For example, I'm running a solid lifter stock 261 cam in my 235, so I set the valve lash to 261 specs.

Thanks for the explanation guys!

Barry, I know that you know I should know this stuff, and some of what you, fab51 and the others said I've heard before, but it's good to get a full, sensible explanation!!

Thank you!

Joe

Joe- I have an advantage as I've worked on this junk for 30 years (since I was 12 years old!) and I've been a toolmaker for 24 years and am used to working with clearances and thousands of an inch and stuff. I've built and worked on many race car engines that all needed the valves adjusted nightly. Some weeks we ran 4-5 nights a week and adjusted the valves every night. So this comes as second nature to me. Lots of other stuff doesn't.

Think of solid lifters this way, if you set them to have zero clearance, and the parts expand as they warm up, you could get in a situation where the valve would be held open slightly and would never close. Would maybe even eventually burn the valve. So the clearance gives you some room for the parts to expand and contract and change their relationship to each other without hurting anything. Too loose and they would make an awful racket. The exhaust valves get much hotter and therefore expand more and need slightly more clearance than the intakes. That's why the exhaust valve clearance is always more than the intake valve clearance. And engines that are expected to be run under more of a load and hotter (like a 1-1/2 ton truck or race car) usually call for a little more valve clearance than an engine that won't be worked so hard. (like a car) Cam lobe profile also can determine lash. A smoother profile on a lobe can get by with less clearance than a radical lobe profile that slams the valve open and closed radically. Each new solid lifter cam you buy should come with a tag with specs on it including clearances for the int. and ex.

This valve adjust job is a bit of a pain but your engine diserves to be happy! Here's my method:
Get the motor warm, 20 minutes of running, install a cut down an old valve cover to stop the bleading, with motor running tweak the adjustment screw just until noise just goes away then recheck specs with feeler gauge. To fine tune the things I like to use an open end wrench till I'm done then recheck with a box end. Do that 12 times and have a beer. Oh yeah, better to be on the loose side if poss. so you wont burn any valves.

.010 intake .012 exhaust COLD worked for me

It's just a stinking, old motor that will outlive all of us. I'm not going to worry to much about it.

I haven't had any difficulty adjusting mine hot. I typically warm it up by driving it for 20 minutes, do three cylinders, then start it up and let it run for a few minutes and do the other three, and check the ones I did. Just letting it idle for 20 minutes doesn't seem to bring the oil up to full temperature.

Adjusting solid lifter engines with the engine running is a very dangerous idea. If the adjuster slipped you could easily have valve to piston contact and a very badly mangled engine, as well as tool or hand damage. Hydraulic lifters don't require you to stick a feeler gauge in a moving piece of machinery.

I have not spilled a drop of oil idling my 261 without the valve cover on it. Just park it on a slightly downhill level surface so the block is level and the oil will run right down the drain holes. The rockers don't move fast enough to splash at idle.

If you are unsure if your clearance is right it is a safe bet to leave them a bit loose. They may be a bit noisy but that noise is not causing any wear.

My BMW's valves have to be adjusted cold because if you did it hot you would stir fry your hands. However, it has an overhead camshaft. The Chevy valves are much easier to adjust.