340 Cold Valve Lash Unknown Cam

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340inabbody

340inabbody

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Ok, I am a glutton for punishment. I know you’re supposed to set valve lash close to running temperature, its 120°F in my garage so I won’t. I will set it at ambient.

I know you’re supposed to have a card for your cam, I don’t. As Schultz used to say I know nothing about this cam.

Engine: 340 AT, solid lifter with 273 adjustable rockers arms. Cam is aggressive. Compression high 11’s? Compression testing yielded 190 psi across all cylinders.

Given this I want to check and adjust valve lash as it is a bit noisy.

What valve lash (Intake/Exhaust) would you use and why?

IMG_3085.jpeg
 
340inabbody said:
Ok, I am a glutton for punishment. I know you’re supposed to set valve lash close to running temperature, its 120°F in my garage so I won’t. I will set it at ambient.

I know you’re supposed to have a card for your cam, I don’t. As Schultz used to say I know nothing about this cam.

Engine: 340 AT, solid lifter with 273 adjustable rockers arms. Cam is aggressive. Compression high 11’s? Compression testing yielded 190 psi across all cylinders.

Given this I want to check and adjust valve lash as it is a bit noisy.

What valve lash (Intake/Exhaust) would you use and why?

View attachment 1716310971
Click to expand...
Well, "Down in Joe's Garage" we set 'em at .020 cold and tweek them from there.
That's with iron heads... aluminum slightly more.
 
As above check the lash COLD now. Write it down. Fire it up and drive it. It’s not good enough to just warm it up. Get it to temperature and put a few miles on it.

Then pop a valve cover off while it’s hot. Check several valves and write down what it is.

Compare results. They should be looser hot.

If that hot number is somewhere between .014 and .028 for the intake and .016 and .032 on the exhaust you are golden.

If you like the way it runs with that lash drive the wheels off it. Then you can play with lash a little bit and see how it feels.

I always set the valve cold. Always. Because A) I hate working on hot, oily stuff and B) even if you can set valves like Jack the Bear (meaning lickety split) the temperature change while setting the valves can affect your actual lash.

That’s why I said check several valves hot. Three maybe four and then the engine cools off.

When the engine is cold at least everything is the same temperature.

The rule of thumb is if you have iron heads and block the lash will grow about .002-.004.

Iron block and aluminum heads will be about .004-.006.

An aluminum block and head will grow .012 to about .024 or a bit more.

I’ve only seen the high number with a blown alcohol deal. You could sit there and watch the blower belt tighten up while it was warming up.
 
If the correct lash is unknown, then you certainly do NOT want to set lash at 028/032". Many modern grinds use 018 -020" lash. Ultradyne [ now Bullet ] use 016 lash. Setting lash way too large slams the lifter into the cam flanks, & not the clearance ramps as designed, shock wave to the valve train.
For safety & long parts life with an unknown cam, you should set the lash to 012 - 014. It will not hurt anything but may idle rougher & lose some low end tq if cam was designed for 028/032 lash.
With experimenting I did on one of my 440s, stock head & block, I found no measurable difference in lash between room temp & operating temp.
 
In situations like this I always try loose first. So I'd try .022 and .024.
 
Another thing to consider:
You say you have "273 adjustable rocker arms". Are they stock, or have they been adapted to locking adjusters? The stock friction fit adjusters get notoriously loose after 60+ years of use and may not be holding the proper adjustment, leading to the noisy valvetrain.
MRE Shaft-Type Rocker Arm Adjusting Screws
Converting involves spot facing the arms so the locknuts have a flat surface to seat against. You may also want to check the rockers for spring/retainer clearance, since they can interfere with some aftermarket springs. It can all contribute to excessive noise.
But when all is said and done, don't expect it to be as quiet as a hydraulic tappet motor- there will be a bit more with solids. Kinda depends on what your definition of "noisy" is.
 
Bewy said:
If the correct lash is unknown, then you certainly do NOT want to set lash at 028/032". Many modern grinds use 018 -020" lash. Ultradyne [ now Bullet ] use 016 lash. Setting lash way too large slams the lifter into the cam flanks, & not the clearance ramps as designed, shock wave to the valve train.
For safety & long parts life with an unknown cam, you should set the lash to 012 - 014. It will not hurt anything but may idle rougher & lose some low end tq if cam was designed for 028/032 lash.
With experimenting I did on one of my 440s, stock head & block, I found no measurable difference in lash between room temp & operating temp.
Click to expand...


No one set the lash at .032. No one.

It was said to check the lash as it now is because it’s running and evidently not killing itself.

Since the OP or none of us know what the cam is, there is just as much possibility that the cam is a DC grind and the lash for most of those cams the lash was .028-.032.

So if per chance the OP finds them that loose he has no reason to panic and start changing lash. It may be what is called for and he can change the lash from there and observe the results.

I have seen some tight lash rollers that called out .010-.012 lash but he doesn’t have a roller cam.

I’ve also lash hydraulic roller lobes with solid lifters at .003-.004 but the OP doesn’t have that either.
 

Newbomb Turk said:
No one set the lash at .032. No one.

It was said to check the lash as it now is because it’s running and evidently not killing itself.

Since the OP or none of us know what the cam is, there is just as much possibility that the cam is a DC grind and the lash for most of those cams the lash was .028-.032.

So if per chance the OP finds them that loose he has no reason to panic and start changing lash. It may be what is called for and he can change the lash from there and observe the results.

I have seen some tight lash rollers that called out .010-.012 lash but he doesn’t have a roller cam.

I’ve also lash hydraulic roller lobes with solid lifters at .003-.004 but the OP doesn’t have that either.
Click to expand...
Right not a solid roller but am running a solid flat tappet.
 
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