So I'm throwing together a spare motor out of stuff I have lying around.

It's basically an iron L33 for the shortblock and some 317 heads that have been cut .035 for a 66cc chamber.

The cam is a stock '99 y body ls1 cam .500/.500 209/198 ls119.5 117/122

now I figured with ls7 lifters, stock cam, heads milled i'd be able to run these 7.35 mantons I have laying around.

but when I check pushrod length with the comp cams tool I get a before preload length of 7.2125 ( 6.8" base length plus 8.25 turns at .050 a turn)

to get ~ .050-.100 preload i'd need a pushrod of around 7.26 to 7.3.....which seems really dang odd to me. I've never had pushrods that short.

but i've never used a stock cam before either....

scratching my head on this one

 

I don't see how accurate the turn and count method can be, it is so tight in that area,
you have to hold the bottom part of tool so it doesn't turn and at the same time turn the top
and count and try to be accurate at the same time. Can you just torque rocker and turn
tool to get zero lash then unbolt rocker and measure tool?

 

yeah you need to test fit a couple times to ballpark it.

first and foremost you gotta soak the lifters in oil for a few days, occasionally working the plungers to pump them full of oil.

in this case, I know the heads are milled .035" and the stock pushrods with preload built in are 7.4" so I take off .035" for milling and ~.075" for preload and end up with a no-preload nominal length of 7.29" so I start about there and move a quarter turn clockwise if I come up snug to the lifter before the rocker trunnion seats. counter clockwise if the pushrod has play. Once you get it right, pull the pushrod and count the turns clockwise back to zero. multiply number of turns by .050" and add to the zero length (6.8") to get your no-preload lifter length. each adjustment requires removal of the rocker arm.

I do this on 4 intakes and 4 exhausts and average them all, then I look at what off the shelf pushrod gets close and puts me in the middle of the preload range (.050"-.100")

anyways thats how i've always done it. if you know a better way please tell me, coz it actually takes about 2 hours to do with set up and clean up


i'm just stumped about the length i'm getting from this motor...seems really short...

 

I am suggesting having adjustable pushrod in place, torque the rocker arm down, then
adjust pushrod (by turning) till zero lash, this takes a feel, no more up and down and free turn is gone (of the push rod).
Then unbolt rocker, measure pushrod length, add pre load amount, and that is pushrod length.
Will this way not work?

 

it would except that when you compress the lifter it may not fully come back up.

i think most guys do this with a lifter they have converted to solid by removing the innards and packing it full of shims or JB weld.

either way ought work, but i'm still stumped on the seemingly short pushrod length i'm getting...anybody else out there end up with 7.300" pushrods?

 

Valves correct length? Nothing screwy with the valve seats?

 

hmm i didnt notice anything odd on assembly, but I did not check installed height

thanks, thats my next order of business

 

I run 7.300.

 

whats your set up?

 

243's shaves .025
5290 morel lifters
.040 cometics

running 7.300 put me at about .050 preload. I was getting measurements right around 7.250 at zero lash.

 

word, thanks. got some 7.29's on the way

 

FWIW I suggest getting a 8" or 12" caliper to directly measure vs counting turns on the pushrods adjustment

 

Why would a lifter get compressed on the valve you are setting up for zero lash ?

Using a solid lifter isn't needed on a zero lash measurement. The pushrod only need to lay in the lifter cup.

 

I have some 24" mitutoyo digis from my previous life as a machinist...same result

but you have to remember a caliper measures tip to tip, pushrods are generally measured from cup seat to cup seat....sometimes that can be tricky to remember.


if you have the pushrod checker adjusted too long and snug the rocker down, you end up bleeding down the lifter. sometimes they pop right back up, sometimes due to the oil pressure still in the lifter they hang a little and give a false reading.

as mentioned earlier it's best to "sneak up" from too loose to just right


the solid lifter is also nice to have to check the rocker wipe pattern on the valve tip

 

i did get to check the installed height last night too.

psi 1511ML all were 1.81"+/- .005 with the newer style combined spring seat/stem seal

so I think the heads have only seen a light valve job


my guess as to why my pushrods have come out short are

big base circle stock ls1 cam + stock MLS GM gaskets + ls7 lifters

got some 7.29 mantons on the way and we'll see what's what.

anybody need some nice 7.35 mantons PM me for a good price.

 

[QUOTE=truckdoug;19464144]I have some 24" mitutoyo digis from my previous life as a machinist...same result

but you have to remember a caliper measures tip to tip, pushrods are generally measured from cup seat to cup seat....sometimes that can be tricky to remember.




Do any Gen 3 or 4 engine pushrods have cups? I thought they were all ball ends,
and don't ball ends need overall length?

 

not sure what you are asking really, but you can't measure tip to tip because of the oil hole. it varies from manufacturer to manufacturer.

here's some reading for you.
http://www.compcams.com/Pages/417/va...-geometry.aspx

 

I see what you are saying with the comp link, I have not read that, I have only read this.

http://mantonpushrods.com/pushrod-in...ermine-length/