I have a comp pushrod length checker. Just looking for a step by step procedure to determine correct length to purchase(this is a hydraulic setup).



Thanks

 

With hydraulic lifters, you need to pump them up hard or install a checking spring. Basically, you adjust the pushrod to get the proper wipe pattern on the valve stem and then add your lifter pre-load to the length. If you are out too much, you may need to shim your rocker stands. The Lunati web site has some good information on this.

The Comp pushrod checker is in "Gauge Length" and many of the pushrod manufacturers use "Overall Length" (OAL) so be careful using the markings on the Comp adjustable and buying Manlet pushrod for instance.

 

Alright, so I have been searching/reading a lot and have seen many pics of wipe patterns so I THINK i know what to look for as far as a wipe is concerned. You want a thin 0.060 wide pattern down middle of valve stem. Now, whats the process when adjusting the pushrod?

1. Install rocker arm(what torque? 22?) with pushrod and rotate over engine and note wipe pattern? (step assuming either check springs or pumped up lifters with dual springs)

2. Adjust length until optimal wipe pattern is acheived(each time length adjustment made the engine must be rotated and wipe reviewed again)?

3. Lifter preload? How to measure? How to adjust/set? (people talk about preload 0.015..0.0XX ...etc. , not sure what measurement this is)


Say optimal wipe is achieved with a p-rod length of 7.35, and then the preload(although still not sure how to measure this) is 0.015. THen I add 7.35 and 0.015 so 7.365 (or whatever) and that is the p-rod length that I purchase from comp?

Please write in any errors you see if you could please. Thanks a bunch for the help.

 

You're on the right track. Provided you have a light weight checking spring, you won't have to worry about the lifter. Just get the pattern on top of the valve stem that is nearest the center of the valve stem and measure the length that achieved the correct pattern. Add to that length the preload you need and you've got it. Lifter pre-load doesn't have to be perfect. A range is normally recommended. I don't know the range off the top of my head but it's on posts here. I think with my setup the recommendation is around .090 preload with the crane/vinci variable rockers.

 

i belive proper preload shoud be around .030...so add that to measuremnet for push rod lenght

 

So then what is the installation procedure once the correct P-rod length has been determined? Just put p-rods in and torque to 22 ft-lbs, rotate once and retorque?

Thanks for the help! Still not sure what preload actually is though

 

yes...

 

I'm in the same boat as 99whitews6. Just got my Crane dual PR tool (99725-2) and will try to check my length tonight. I got some of my old lifter and threw some washers and JBweld in them to make them very stiff. Can I use these with the PP golds when checking the wipe pattern?

Should I measure how ever much I can compress them under load and consider that the lifter preload?

 

Very interesting topic, I'm getting ready to face this problem as well. I have 5.3's milled .050" using stock mls gaskets on a stock bottom end. I'm not sure if my pushrods will be to long.

 

I checked mine on the workbench first (adjustable Cranes) and found that with the checking springs, if you use a Sharpie or something to mark the valve stem you need to check fairly quick. The checking springs don't have a lot of pressure to wipe off the color.

If you torque down your rocker, and can adjust your pushrod in position without removing the rocker each time, you can simply bring the pushrod out so you get zero lash. Then check your wipe. If the wipe is good, add preload length. If the wipe is bad, then you will need to shim the rocker stand to correct the wipe.

The difference is with an adjustable rocker, the pushrod length also sets the rocker height, with the stock setup the rocker height is fixed by the rocker stand height. Hope this makes sense.

 

Please explain zero lash if you could. THanks!

 

Zero lash is when you have taken all the slack out of the lifter/rocker connection. In other words, you extend the pushrod until the rocker is just touching the top of the valve stem and the pushrod has no slop in its connection between the lifter cup and the rocker cup. If you extend the adjustable pushrod any further at this point you will either start compressing the lifter plunger or the valve spring. To check, very very gently lift the rocker tip and see if there is any "tap" "tap" between the rocker tip and the valve stem, if there is, lengthen your adjustable pushrod to remove the slack.

PS: I re-read my prior post and should have proofed it before I posted. I corrected it.

 

Thanks, I almost PM'd you on it because I was confused too. Adjustable rocker!

 

Cool, now I understand what zero lash is. Thanks.

 

How much play is in a pumped up rocker? Last night when I was checking things with the stock lifters it looked like I almost went to coil bind. I did put a lot of washers inside the lifter to make them "solid"

 

Did you have a dial indicator on the retainer to measure lift? I know on the beehives I am using I am at 0.551 lift and they look close to bind but are not.

You need to figure out your actual installed height, total lift and coil bind so you can determine clearance left.

Installed height - lift - coil bind = Clearance.

For my setup:

1.750-0.551-1.1 = 0.099 so I am OK.

 

Thank-you very much for the info vettenuts. I have been watching this thread as I will face this task in a couple months. How do you know what the lifter preload is? If I bought a set of Comp OE's 850-16, would they indicate preload? Thanks again.

 

This from another thread.....

Assuming heads are in place with the proper headgasket (or the same thickness shims during mock-up), the following is a quick rundown to check and measure for proper pushrod length:

Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)

Bolt down the factory rockers....

Set the adjustable pushrod to zero lash and remove

Measure pushrod, then add .050-.100 to that figure which now represents your pushrod preload into the lifter and the total length of the pushrod your engine requires. This is obviously quickie instructions for a factory rocker arm set-up (pedastal mount).

About the wipe pattern....



Guys....the only thing that effects the wipe pattern or geometry of that set-up is changing the height of the pedastal as I said earlier. Unless you are willing to shim or machine (for a lower height) the wipe pattern is FIXED....end of story. (Yes, it might wipe a little differently if you have more gross valve lift). Milling heads, thinner gaskets, etc., etc. will have ZERO effect on the wipe pattern of a stock LS1 set-up....that will only effect the proper pushrod length for that particular combination ONLY relating to how much lifter preload you choose (or simply end up with) running. Obviously a milled head with a thinner gasket would require a shorter pushrod if you were wanting to keep lifter preload the same.

You guys are getting the stock valvetrain confused with an adjustable stud mount where now the correct pushrod length also effects the height of the rocker in relationship with the height of the valvestem tip thus effecting geometry and wipe pattern.

Think about it....in a pedestal system the heights are fixed in relation to one another unless you machine the head or shim, once again.

Tony M.

 

Even better/easier for me as I don't have adjustable rockers. Now, when it says to add 0.050-.100, does that mean to just add .050? Does preload depend on what lifters you are using, meaning if you changed your factory lifters to mellings your preload changes? Finally, when your on the base circle of a lobe that valve is completely closed correct?
Thanks.

 

The preload is determined by what the lifters need. Morels need .030, stock is .060-.090 if I recall correctly. Not sure on Melling or comp-850's.