valve lash adjustment - Team Camaro Tech
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post #1 of 8 (permalink) Old Sep 3rd, 03, 06:09 PM Thread Starter
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When I purchased me 67 it had a 383 with a solid cam. The cam sounds loppy but I don't have any specs for the cam. Any guess as to what to set the lash at? Hot or Cold?
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post #2 of 8 (permalink) Old Sep 4th, 03, 02:12 AM
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Hmm, I'd ask the previous owner if he has the cam card. If he/she doesn't have it, I would suggest [email protected] inches and [email protected] inches hot.

Use the method of adjusting a cylinder's valves the following way: remove the spark plugs, for easier turning by hand, watch the intake valve in its travel, when it starts to close, adjust the exhaust valve. Then, when turning engine, watch the exhaust valve. When it starts to open, adjust the intake. This method places the adjusting valve on its base circle of the cam lobe.

Intake=closing, adjust exhaust
Exhaust=opening, adjust intake

Adjust the other cylinders, any order, but firing order is good to follow. This method is for a SOLID lifter camshaft.

To determine solid lifter, turn engine over by hand to where pushrod just stops turning when rotating pushrod by hand. Wait a few minutes. Attempt to turn pushrod by hand. If it turns, it might be considered a hydraulic cam, lifter has bled down due to the spring pressure upon the lifter. If the push rod does not turn, then I would consider it to be a solid lifter camshaft.

If engine is equipped with a hydraulic camshaft, have engine at operating temp, turn the idle down as far as it can go without shutting off, cover the wheel wells and fenders with an old blanket/rags, remove valve covers, start at an end cylinder, loosen the locknut on the rocker arm and listen for clacking. When clacking, tighten the lock nut slowly to silence, then an additional 1/4-1/2 turn on the adjustment nut to preload the lifter. Tighten the valve adjustment if a locking device is used. Continue with the other cylinders using the same method. Restore engine back to its original configuration when done, i.e., idle & clean-up.

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post #3 of 8 (permalink) Old Sep 4th, 03, 06:08 AM
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Check the current lash, chances are more than less will be real close to where they were set the last time. The ones that are out should be within a thousandth or two unless something drastic has happened since the last adjustment. You should be able to figure it out once you've checked them and have the data on each.

Everett may be right on with his recomendation but not knowing what you have and knowing that there are some tight hot lash cams out there I personally couldn't be so bold as to throwing out numbers. Check this out from Crane... http://www.cranecams.com/mliftfaq.htm

...Dennis

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post #4 of 8 (permalink) Old Sep 4th, 03, 12:57 PM
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I would set them at .022 and .022 for a cast cylinder head and .018 and .018 for an aluminum head. Both hot lashes. These are specs for street cams.

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post #5 of 8 (permalink) Old Sep 4th, 03, 04:25 PM Thread Starter
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The previous owner who is a mechanic didn't know the lash(and he bought the engine from his engine builder, in other words he lost the cam card) and what makes it worse he adjusted them to what the majority of them were. However I have zero faith in his abilities and when I checked his settings they are all over the place. I also spoke to his engine builder to see if he would remember and no luck. These guys are all clowns. If I pulled the cam would there be any numbers on the cam? I am tight for cash and i don't want to buy a new cam. Is it possible to do much damage if they are set too far off?
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post #6 of 8 (permalink) Old Sep 4th, 03, 04:38 PM Thread Starter
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By the way my motor has iron heads
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post #7 of 8 (permalink) Old Sep 4th, 03, 07:13 PM
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I run a hyd roller and the builder used his tried and true method of adjusting the valves. The car ran ok but was a bit short on vacuum at idle. I had the oppertunity to adjust them per comps instructions and when done the engine made 2 more inches of idle vaccum. The mechanic only had them a 1/4 turn tighter than comps recomendation and a 1/4 turn less than a factory chevy cam would call for.

With solids too tight and you cause damage from excessive pressure, possibly bent pushrods, possibly a wipped lobe or two. Too loose and damage comes from the pushrod rattling or bouncing between the rocker and lifter. Add mushroomed pushrod ends and damaged rockers to the list above.

I'm not a cam expert but the amount of lash designed into a solid cam has a lot to do with lobe geometry and like the crane link I posted above shows you could have a cam requiring as little as .010" to as much as .035" Find a mechanic with some experience building performance solid cam'd engines and have him measure your cams lift and duration and try to identify what grind it could be.

...Dennis

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post #8 of 8 (permalink) Old Sep 5th, 03, 09:22 AM
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Like Dennis said, you HAVE TO figure out what cam that engine has. from there you can get the specs from the manufacturer. Whatever you do, don't just guess.

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