C3-1971 LT-1 Valve lash adjustment Q's

[Chuck Caldwell]

What is the correct procedure and specifications that others have used for adjusting the valve lash on a 1971 LT-1, mine has become somewhat noisy lately on the drivers side, particularly on startup and beore it warms up, once it warms up it becomes less noisy. The car has the original solid lifter cam, motor, heads etc... with a rebuild of about 3K on it.

I was planning to make the adjustments with the motor running by cutting the tops out of some old valve covers I have or can it be properly done cold.

Any advice on the proper procedure/specs and other things to consider would be appreciated.

[Clem Z.]

Re: C3-1971 LT-1 Valve lash adjustment Q's

the lash is intake .024, exhaust .030 when the exhaust valve on a cylinder starts to open set the intake on that cylinder. after the intake opens all the way and then almost closes set the exhaust on that cylinder. this can be done cold without the engine running. since the engine is cast iron and all the parts are steel the difference between hot and cold is very little. you can do one cylinder hot as per above and then check that lash the next day cold and see what the lash is now. if it has changed any just take the new lash setting and do the rest of the valves cold. the exhaust may change .001.

[Duke W.]

Re: C3-1971 LT-1 Valve lash adjustment Q's

Send me an e-mail and I will send you the Word file that explains, why you should lash them at .021"/.026", and why they should be lashed with the engine cold and not running in a VERY SPECIFIC sequence.

When lashed properly using these specs and procedure they should NOT be very noisy! If they are noisy the lash is way too loose.

Duke

[Joe C.]

Re: C3-1971 LT-1 Valve lash adjustment Q's

Chuck:

Don't bother with the hot and running valve lash procedure. It is very messy. I used Duke's method with excellent results. I have spread the news to a few friends of mine with 30-30 or LT1 camshafts. They all thanked me for it. Good luck.

Joe

[Warren F.]

How about the LS-6 ?

Would a procedure as recomended by you folks work for this engine also? I would appreciate any info as well.

[Joe C.]

Re: How about the LS-6 ?

Warren:

This procedure is applicable to "30-30" and LT1 camshafts. Duke or John H. should be able to help here. You might be able to use the easier (standard) procedure. The way I understand it, the 30-30 and the LT1 (exhaust lobes only), have very long clearance ramps. This MAY not be true of the LS6 camshaft. Also, your big block rocker ratio is not the same as that of the smalblock.

[Clem Z.]

Re: How about the LS-6 ?

my post applies to BBC also

[Mike McKown]

I would think your method applies to almost any

OHV block, any brand. Doesn't it? That's the way I've always done it and I've never had a problem with mis-adjusted or noisey valves. Some variation in the lash setting is discretional for your intended purpose.

[Clem Z.]

it puts you on the heel of the cam lobe

and that is all you need to get a correct lash no matter what spec you use.

[Duke W.]

Re: How about the LS-6 ?

The basic valve adjustment procedure for the 30-30 or LT-1 cam - what valves to adjust at each cylinder TDC, will work for ANY cam on any vintage Chevrolet V-8 with 18436572 firing order. The problem with BB cams is that I have never seen an accurate life-crank angle diagram of any BB mechanical lifter cam to verify the clearance ramp height, and I do not have any data on the ACTUAL rocker ratio of the BB rocker arms. Trust me, the 1.7:1 published ratio is just a marketing number. SB rockers are considered to be 1.5:1. They are actually 1.37:1 at the lash point and 1.44:1 at max lift. BB rockers will show similar characteristics, and in order to determine the correct clearance, both the constant velocity ramp height on the lobe and the rocker ratio at the lash point need to be accurately known.

You BB guys have some homework to do.

Duke

[Ray K.]

Re: C3-1971 LT-1 Valve lash adjustment Q's

Bill Nichols (C5/C6 Corvette Powertrain Vehicle Sytems Engineer) sent me your way in response to setting the lash on solid lifters for my '71 LT1 Can you send me the details on "why you should lash them at .021"/.026", and why they should be lashed with the engine cold and not running in a VERY SPECIFIC sequence." Thanks.

[Duke W.]

Re: C3-1971 LT-1 Valve lash adjustment Q's

I cannot send you an e-mail with an attached file from the NCRS Board, so if you send me an e-mail I will respond with the attached Word file that explains everything.

Duke