Valve Lash adjustment

[Joseph F.]

I will be adjusting valve lash on my 1961 270 hp engine. Any hints on how to get accurate adjustments with "poly lock" rocker arm nuts? Haven't done adjustments in a while and usually had difficulties maintaining correct clearance (.008" / .018") in the past.
Thanks.
Joe Feko NCRS 673

[Joe L.]

Re: Valve Lash adjustment

I will be adjusting valve lash on my 1961 270 hp engine. Any hints on how to get accurate adjustments with "poly lock" rocker arm nuts? Haven't done adjustments in a while and usually had difficulties maintaining correct clearance (.008" / .018") in the past.
Thanks.
Joe Feko NCRS 673

Joe------


If you have stock rocker arms, then I do not suggest using the "poly-lock" type nuts. I highly recommend stock-type, self-locking nuts.

[Duke W.]

Re: Valve Lash adjustment

Agree with Joe... the OE rocker arm nuts are the way to go. I've never seen a breakaway torque spec for them, but I figure if less than 10 lb-ft they should be replaced.

Also, a better valve adjustment spec for the Duntov cam is .010/.016". Do a Web search for the Hinckley Williams valve adjustment paper, which explains the reasons why and how to ensure that the lifter is on the base circle for each valve. Make sure you get the Sept, '08 revision. Earlier versions are also on the Web, but are obsolete.

Duke

[Richard M.]

Re: Valve Lash adjustment

The Sep 08 revision is here on our site.
https://www.forums.ncrs.org/showthre...603#post807603

File... Newer_Lash_Adjustment.pdf

[Frank D.]

Re: Valve Lash adjustment

I had very little variance between annual valve lash settings on my 270hp 61 using original style rocker arms...

[Joseph F.]

Re: Valve Lash adjustment

Thanks for the reply. Was considering self-locking nuts as the car does not see much racing these days! I would think I should be able to get nuts from any parts store unless there is a special nut for the solid lifter engine.

[Joseph F.]

Re: Valve Lash adjustment

Thanks for the reply. Will get the paper.

[Joseph F.]

Re: Valve Lash adjustment

Thanks for the reply. Got the paper.

[Joseph F.]

Re: Valve Lash adjustment

Thanks for the reply. Nice to hear from you again! Hood latches working just fine!!

[Joe L.]

Re: Valve Lash adjustment

Thanks for the reply. Was considering self-locking nuts as the car does not see much racing these days! I would think I should be able to get nuts from any parts store unless there is a special nut for the solid lifter engine.

Joseph------


The self locking nuts with stock type rocker arms are better whether it's racing or street use. The only reason I can think of to use poly-lock type nuts is for use with roller trunnion rocker arms. Those cannot use self locking nuts. I wish they could.

Self locking nuts should be found at most auto parts stores or GM #12557390 (about $1.75/each, GM list)

Also, Sealed Power # MR 1751.

[Ray K.]

Re: Valve Lash adjustment

Joe,

I also agree with suggestions as mentioned to use GM type rocker arm nuts if you have stock rocker arms. Original #3744341 -- but discontinued for some time. Probably available from Sealed Power or Federal Mogul.
Duke's suggestion about valve lash settings also has merit. Personally, I like the .012 / 018 settings. This was the original specification for 1957-59 270HP and 283/290HP FI engines. In 1960 they revised the intake setting to .008 which remained in place until 1963. I owned a 270HP /283 for many years and tried many different combinations of valve lash adjustments, and finally settled on the .012 / .018 as my preferred setting. Remember, this is a " hot " setting.

Ray

[Jim L.]

Re: Valve Lash adjustment

Joseph------


The only reason I can think of to use poly-lock type nuts is for use with roller trunnion rocker arms.

Joe,

There is one other reason: If you use ARP-brand screw-in rocker studs, they come with a warning against using self-locking nuts.

Jim

[Joe L.]

Re: Valve Lash adjustment

Joe,

There is one other reason: If you use ARP-brand screw-in rocker studs, they come with a warning against using self-locking nuts.

Jim

Jim------


Yes, they do have such a warning. However, as much as I like ARP fasteners, I use GM threaded studs for the rocker arms. However, I really think that the ARP studs could be used with self-locking nuts without any problems.

[Joe L.]

Re: Valve Lash adjustment

Joe,

I also agree with suggestions as mentioned to use GM type rocker arm nuts if you have stock rocker arms. Original #3744341 -- but discontinued for some time. Probably available from Sealed Power or Federal Mogul.
Duke's suggestion about valve lash settings also has merit. Personally, I like the .012 / 018 settings. This was the original specification for 1957-59 270HP and 283/290HP FI engines. In 1960 they revised the intake setting to .008 which remained in place until 1963. I owned a 270HP /283 for many years and tried many different combinations of valve lash adjustments, and finally settled on the .012 / .018 as my preferred setting. Remember, this is a " hot " setting.

Ray

Ray------

The GM #3744341 were replaced by the GM #12557390 I mentioned above which remain available.

[Jim L.]

Re: Valve Lash adjustment

Jim------


Yes, they do have such a warning. However, as much as I like ARP fasteners, I use GM threaded studs for the rocker arms. However, I really think that the ARP studs could be used with self-locking nuts without any problems.

I take ARP's advice at face value on my racing engines and use polyloks. I think they are a PITA but I haven't had any failures.

I'm not familiar with the GM studs. I assume they have a hex at their base for wrenching. How does the radius from the hex to the shaft compare to that of the ARP studs?

Jim