440 Rocker shaft shims

[bobs66440]

I'm putting my 440 together and I have a question regarding rocker shaft shims for stock hydraulic lifters/rocker arms.

The stock pushrods were too long so I calculated the new length I needed to get approx .030-.045" preload. Well, I got the new pushrods, bolted it all together and I'm coming up with .055-.075 with most around the .060 mark. Somehow I miscalculated and I don't want to order new pushrods.

Mancini has .015 shims which would put me right in the ballpark. I have heard stories not to use them for various reasons. Comp tech said it would be ok and so did Mancini because it was so little.

What do you guys think?


Thanks

[Budnicks]

I would pretty much always trust Mancini's tech guys opinions, the shims have been used for 40+ years in shaft style rockers....

[heyoldguy]

There should be no problem with a .015" shim.

[oldkimmer]

..................I've used shims many times...............kim........

[Tom Q]

Assuming repeatable measurements I believe you are all set , go back and carefully recheck.
Does your zero point repeat? Does the measured point repeat?
please don't over think this-the limit is 0.090.
Sometimes the amount of shim may vary

When you are finished checking preload and ready to assemble set the timing marks at 15degrees BTDC on the compression stroke. Be sure the cam is prelubed with the proper product

[bobs66440]

Thanks for the replies guys.

I got the shims from Mancini yesterday and decided to put it together. I was just going to put it together without going through the measurement process, but I figured I'd better just in case. Good thing I did. Now it has zero preload! I don't get it. I carefully measured for the pushrod length and it was still too much, and now the .015 shims somehow negates over .050" preload? The measurement must get multiplied at the end of the rocker arm. I wish they had said that.

So I took the shims out and measured again and now they are in spec...all the ones I measured were around .053", so screw it, I put it together. Done. I used exactly the same procedure to measure, and each time it was repeated over and over during that day's process but somehow it's inconsistent day to day. When I measured originally, the measurements were pretty consistent but varied a little..maybe just a few thousandths. Plus I'm measuring the marks I make on the pushrods with a dial caliper, sort of eye-balling, so I know it's not going to be exact. Anyway, I'm fairly confident that it's around .055" now. I'm gonna run it...