deuce valve lash

I will be checking my valve lash tomorrow and I have been searching and the tm says 10 on intake and 25 on exhaust but it seems most set them at 15 and 25 is this correct what are the opinions on correct valve adjustment thanks for any help.

Vaughn

.010 and .025

I am gonna hit mine this spring

Better to hear em then smell em........

I am new to owning a deuce, so i don't know all of the lingo yet. what is valve lash?

The engine has solid valve lifters. So, since engine parts expand and contract with temperature changes. There needs to be some slack in there. Otherwise, as they heated up, they would be too close and start to bend and break. The intake doesn't get as hot as the exhaust valve which is why the two valves have difference clearance values.

bond024 said:

I am new to owning a deuce, so i don't know all of the lingo yet. what is valve lash?

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It is vitally important that the intake and exhaust valves close completely when they close. To assure that this happens, the valve rockers are adjusted so that when the valve is closed, there is a small air gap between the rocker, and the valve stem. This gap is called valve lash. The lash has to be wide enough so that when the engine heats up, and the valve stems and push rods expand from the heat, that the valve will still have sufficient lash to assure the valves close completely. This is why valve lash is usually specified hot.

As the engine runs, the valve heads, and valve seats wear a little bit, and that wear will eventually consume all of the valve lash, and allow the valves to not close tightly when hot. When that happens, compression is lost, making the engine harder to start, and lower power. Also, because the valve head is cooled by its contact with the valve seat, if the valve doesn't close fully, the valve won't get cooled as well as it should, and it can get hot enough to burn the metal.

How wide you set the valve lash helps to determine how often you need to re-adjust the valve lash to compensate for wear in the valve train. Setting it a little too wide usually won't hurt anything... within reason. The wider you set the valve lash, the higher the velocity the rocker arm achieves before it contacts the valve stem, and the more violent the contact becomes. This results in excess noise, and can actually expand (mushroom) the valve stems and rocker adjustment screws, just like what happens to the head of a chisel from being hit by a hammer.

It is best to stick to the manufacturer's specifications.

-Chuck

Thanks for the explanation guys

I set my Multi Fuel valves at .015 intake cold and .025 exhaust cold. the original manuals said .010 and .025, I agree. But .010 was pretty tite and we all decided the old guys were right, loose is a lot better than tight unless you're not talking about valves. JT out

OK I did it .015 intake cold and .025 exhaust. I started the truck with a friend watching the motor once it started it sounded good then it happened. I must have hit the oil pressure sending unit it broke off and oil was everywhere so I shut down immediatly. I will pick up a new 45 fitting tommorrow. I wont be able to work on it again till thursday. Well see how it goes then.My fingers are crossed.

Vaughn

jatonka said:

I set my Multi Fuel valves at .015 intake cold and .025 exhaust cold. the original manuals said .010 and .025, I agree. But .010 was pretty tite and we all decided the old guys were right, loose is a lot better than tight unless you're not talking about valves. JT out

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If 0.025 is safe for the exhaust, anything from 0.010 up to 0.025 is certainly safe for the intake.

The exhaust valve runs much hotter than the intake valve, and as a result wears more quickly. Intake valves don't wear much at all, so 0.010 is probably perfectly safe... IF... you check valve lash regularly. If you are a set it once, and leave it be for 100,000 miles type, you might have problems.

-Chuck

stumps said:

It is vitally important that the intake and exhaust valves close completely when they close. To assure that this happens, the valve rockers are adjusted so that when the valve is closed, there is a small air gap between the rocker, and the valve stem. This gap is called valve lash. The lash has to be wide enough so that when the engine heats up, and the valve stems and push rods expand from the heat, that the valve will still have sufficient lash to assure the valves close completely. This is why valve lash is usually specified hot.

As the engine runs, the valve heads, and valve seats wear a little bit, and that wear will eventually consume all of the valve lash, and allow the valves to not close tightly when hot. When that happens, compression is lost, making the engine harder to start, and lower power. Also, because the valve head is cooled by its contact with the valve seat, if the valve doesn't close fully, the valve won't get cooled as well as it should, and it can get hot enough to burn the metal.

How wide you set the valve lash helps to determine how often you need to re-adjust the valve lash to compensate for wear in the valve train. Setting it a little too wide usually won't hurt anything... within reason. The wider you set the valve lash, the higher the velocity the rocker arm achieves before it contacts the valve stem, and the more violent the contact becomes. This results in excess noise, and can actually expand (mushroom) the valve stems and rocker adjustment screws, just like what happens to the head of a chisel from being hit by a hammer.

It is best to stick to the manufacturer's specifications.

-Chuck

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An excellent explanation. Thanks!

Andy

I take exception to loose is better than tight. "Loose" needs to be clarified. If valve lash is too loose, performance degrades and the valve train parts get hammered to potenital destruction. The ramps on the cam lobes are designed to start gradually opening the valves with the correct lash. If the lash is incorrect, the opening happens higher on the lobes, resulting in shock loading to the push rods and rocker arms. Valve tips that have been run for prolonged periods with loose clearance show hammered appearance similar to what you see on the end of a used punch or chisel. Correct settings are critical at both ends of the scale.
Regards Marti

Hi Marti,

Do I take this to mean that you think a setting from 0.010 to 0.025 on the intake will do damage, but 0.025 on the exhaust won't?

-Chuck

Chuck:
I would definitely follow the specs, and yes, you are at risk of damage if you run your truck for many hours. We have had loose settings hammer valve tips and push rods. Virtually all engines specify a closer setting on the intakes than exhaust because the exhaust valve gains stem length from the heat it experiences on the valve head transferring up the stem. The intake valves have cooler air passing by them, keeping them cooler so they do not gain length like the exhaust valves, so they are designed to have closer settings. To explain it another way, the exhaust valves need bigger clearances because as the stem length grows from the heat, they close up the clearance while the engine is hot, so they need more clearance to start with. This is also why you should be sure top check whether the valves are to be set hot or cold when servicing an engine.
Cam ramps are also designed to spin the lifters as they initiate the lift. If the setting is too loose or too tight, the spinning is compromised, causing possible lifter wear in one spot. We have had engines that had this problem, which eventually results in a groove being worn in the lifter base because it is not spinning to distribute the wear evenly. If you have an engine that frustrates the heck out of you because at one time it sounds like it has a valve lash too loose on one cylinder, pecking more than usual, then at other times sounding like it should, suspect a lifter with a groove in the bottom. When the groove is aligned with the cam lobe, the clearance increases. When it dies not, the clearance closes up a bit resulting in the sound change. As you can deduct from this, if you happen to set the valve with the groove aligned with the lobe, your setting will be too tight when it is not aligned, or vice-versa.
Then, there is the problem of rockers that have a lot of hours on them or have been hammered. The tips where they contact the valve head will get an impression worn in them. The feeler gauge will not work properly when this condition is present. It will bridge the depression, giving a larger clearance than you think you are getting. If you have one or more rockers with this problem, it could be the cause of a valve(s) that peck even though you are sure you got the setting right. The rockers can be removed and the face dressed to remove the depression.
I do not in any way with my cautions about too loose settings invalidate or ignore the risks of settings that are too tight. This is damaging as well.
Best to follow the specs carefully, and check them regularly.
Regards Marti

Hi Marti,

Steel expands 0.0000063 inches per inch per degree F. A typical exhaust valve is 6 inches long, but most of the valve is kept near water cooled temperatures, and only about 1.5 inches is exposed to the fire. Therefore 0.025 inches expansion, over 1.5 inches, would require:

0.025/(1.5 x 0.0000063) = 2645 degrees F temperature rise.

Since the valve on a warmed up, but not running engine is already at 180F, that means the 1.5 inches of the valve that is exposed periodically to the fire would have to get to 2825F to cause a 0.025" change in length necessary to use up the 0.025" valve lash!

Cherry red is about 1600F.

Even though this analysis is only approximate, I think there is something else (other than exhaust temperatures) at play in deciding the exhaust valve needs 0.025 inch lash...

-Chuck

Have studied this post ad infinitum, and would like a resolution consensus?

Valve Lash

Thanks for the Thread. I just popped the heads back on today and am going to set mine.

OK, the book says: Intake .010" cold Exhaust .025" cold

If you are a by the book person, there's your definitive answer.

If you are a free thinker, do what you will.

Westex said:

Have studied this post ad infinitum, and would like a resolution consensus?

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I need to do mine when the weather is better. I am going by the -34 TM .010 on the intake and .025 on the exhaust. I just need to find a source for v/c gaskets.