Violatorno1

iTrader: (3)

No, that is not a misprint. On 3 different cylinders pre load is measuring out at .170 to .176 . I know there can be around .005 +/- using my method but I know this is still way too much.

I marked the pushrod with a line of paint. Tightened the rockers slowly until they were at 22 ft lbs. Waited on lifter to bleed down including lightly applying upward pressure on the valve side of rocker to assure lifter had collapsed. Once the lifter was collapsed and I could wiggle the rocker I scribed a line in the paint with a razor blade. I then removed the rockers and scribed a line while holding the top of the pushrod with light pressure to assure it was still seated in the lifter cup. Did this twice on one cylinder then moved to 2 other cylinders with same results. Measured distance of lines scribed with a digital dial caliper. The rods I used to measure are 7.400.

I am thinking I need 7.300 rods that should put me around .075 preload. Would this be correct or should I go with a different legnth?







Thanks in advance.

vader99

iTrader: (4)

I would like to hear more about this as well.

Violatorno1

iTrader: (3)

I might add that this is with a set of AS 5.3 stage II heads supposedly unmilled, the new Lunati Voodoo 232/238 cam and Harland Sharp non-adjustable roller rockers. LS1 lifters.

I cannot see why there is so much pre load unless the heads were indeed milled. They are 853 castings.

heavymetals

iTrader: (3)

I don't measure from a preload point.

I measure from what it takes to get me from the lifter being "bottomed out" to the recomended gap.

That is also why I run adjustable rockers.

That is the easiest way to be able to "dial it in" and make sure all the valves have the same/right gap.

brad8266

iTrader: (23)

Your method isnt a very good one. You need a pushrod length checking tool to get a good measurement for what size PR you need. Thats the most accurate way to do this.

Violatorno1

iTrader: (3)

I figured that but I really do not want to pull the heads and fab up a solid lifter. I can say that with the rockers tightened down that there is no movement left in the lifter. If I put washers that measure .065 under the rockers and tighten them I then can feel the spring in the lifter so I know the pre-load is too much. With the washers I get a measurement around .112.

brad8266

iTrader: (23)

You dont need a solid lifter nor do you need to pull the heads for a good measurement.

1. With no pushrod installed snug down the rocker arm hand tight.
2. Slip PR length checker under rocker and onto lifter plunger and turn until there is no lash.

A already oil filled lifter will not collapse under this little bit of force.

vader99

iTrader: (4)

When you have installed new lifters, how do you get them filled with oil to get a proper pushrod length measurement? You don't want to measure pushrod length with a pumped-down lifter, do you?

Violatorno1

iTrader: (3)

Exactly. Your way would most likely have the same results. If I measure .175 the way I did it with the lifter collapsed and rocker tightened then removed rocker to extend the lifter, subtract .100 by changing from a 7.400 to a 7.300 then the final result should be a pre-load of .075. Tolerable from what I have read even though Lunati suggest .020 to .060 and Crane suggest .050 to .080 .
I could be off +/- a few thousanths.

If I use the checker as you described then I would be measuring distance at .000 pre-load then adding to that figure to get new legnth. Correct? Doing it that way then should give me a measurement of 7.225 +/- a few thousanths giving the difference in tension one would put between the lifter and rocker arm. Not everyone is going to tighten it the exact amount. Add .075 to that comming up with 7.300 compressing the lifter .075 also.

With that in mind, would it be safe to say I need a 7.300 pushrod or should I just buy a checker and measure that way? I hate this non adjustable pre-load crap. As good as the LS1 is one would think GM could have come up with something else.

Sales2@Texas-speed

iTrader: (5)

http://www.texas-speed.com/shop/item...d=913&catid=51

The ONLY way to do it right!

brad8266

iTrader: (23)

You can put the lifter in a cup of oil and push the plunger down and up multiple times to fill it. Once filled it takes much force to push the plunger, more than checking length will apply to it. And even if you didnt have a filled lifter you can still do the check since you can feel the point there the lash is all taken up and the plunger starts to move.

And it doesnt matter how much you tighten the rocker when performing the check because you cant push the rocker down farther then the rocker boss surface anyway so the rocker only needs to be snug before you slip the checker under.

You guys are making rocket science of something simple.

vettenuts

iTrader: (4)

It is very easy and you can do it with brand new unfilled lifters, you just have to be very gentle in your measurement.

Link to adjustable pushrod usage

Violatorno1

iTrader: (3)

No rocket science, just following the instructions that came with Lunati cam and trying to be sure I get the right pushrod by doing it their way.

Guess I'll hit up Keystone Performance Monday for a checker just to be sure then order up some pushrods.

Violatorno1

iTrader: (3)

OK, I purchased the Comp pushrod checker. I got barely over 9 turns to zero lash. About 9 1/8. If I'm correct this should equal 7.250 so I should then be ok with 7.300 rods or should I use a different legnth?

chuckyt1

iTrader: (33)

I've said it before but, this should be a sticky. Call it "What Size Pushrods do I Need"

Sorry for

brad8266

iTrader: (23)

Are your heads milled down at all? 7.33 seems too short for a aftermarket cam. Did you triple check your measurement also?

If you checked it a bunch of times in different spots and it is consistent then you want in the 7.34 area, that includes the 1/8th of a turn and a .080 desired preload on the lifter. 6.8 +.456 + .080