I have the Comp pushrod length checker and proceeded to measure Cyl. 1. It took 9.5 turns to get where I was comfortable with zero lash. The intake valve I couldn't really move at this length, but the exhaust valve would lift very little (without a tick, tick sound). So, at that many turns, I got 7.275" + what ever preload I choose. I think I want to shoot for 0.05".

I wanted to double check so I moved to Cyl. 6. On these two, I got 10.5 turns to zero lash. That gave me a length of 7.325" + desired preload.

I had no real way of measuring TDC other than my eyeball, so I'm guessing that's why the pushrod measurements are equal lengths apart, in different directions? Am I correct in assuming that? Meaning, If I was slightly off TDC, but had an accurate way to measure, would my number of turns be 10 on cylinders 1 AND 6?

I know the Comp tool is measured in gauge length, so how would I equate that into my measurements?

Right now, It looks like I'll have to order some 7.350" pushrods with my 0.05" preload. I read that this is a great preload for a quiet valvetrain, but it doesn't seem to be well understood on the interwebz. I have a set of Texas-Speed 7.400 pushrods, but I'm afraid they will be too long.

 

http://ls1tech.com/forums/12589703-post10.html

 

Thanks for the link, but that doesn't help me with my questions.

 

in the write up by Shane at Thunder Racing, he states the TDC method is not a very good way to check.

 

I'm using this writeup by VetteNuts:
http://www.ls1tech.com/forums/7957678-post2.html

I've used this before without a problem, but I didn't get different measurements like I am now.

Cylinder 1 takes 9.5 turns to close and cylinder 6 takes 10.5 to close. I'm checking both cylinders without turning the motor over. These are the pistons that are at TDC, visually.

 

I dont like the TDC method so i use this one to measure each valve individually one cylinder at a time:

-When the exhaust valve begin to open,it means that the intake valve is on the base circle;
-When the intake valve is closing,it means that the exhaust valve is on the base circle.

Before taking my measurement , i always wait like 15 to 30 mins after removing the rocker and pushrods to relief the pressure and let the lifter cup get back at his normal height.
I also never use the gauge lenght and the turn thing because it is not enough precise for my taste.Im running morel lifter that require between .030 to .050 preload(they tend to like more .040 to .050 to be quiet).I use real lenght(overall lenght) with some Manton custom real lenght(overall) pushrods.

Vettenuts show me this method
Im using a 8inch dial caliper with some blade type filler gauge.I set my comp cam adjustable pushrods to 7.2120 real lenght then i lock it there with some tape.Then with a filler gauge i measure the space between the top of the valve and the rocker to find zero lash/no movement/no clicking.I then divide this measure by the rocker ratio(1.72) since i took the measurement at the tip of the valve.I then add the correct preload.With this method i get really precise measurement and perfect result.

EXAMPLE:

Exhaust
Checker set @ 7.2120 with dial caliper (overall length)
Space measure with the Filler gauge between the tip of the valve and the rocker = .068
.068 / 1.72(Using 1.72 roller) = .040
.040 + 7.2120 = 7.252
With my manton 7.300 overall length im at .048 preload

Intake:
Ckecker set @ 7.2120 with dial caliper (overall length)
Space measure with the Filler gauge between the tip of the valve and the rocker = .041
Using comp cam 1.72 roller
.041 / 1.72(Using 1.72 roller) = .024
.024 + 7.2120 = 7.236
With my Manton 7.285 overall lenght im at .049 prelaod

By the way i dont know what lifter you are using but if those are some ls7 one,i would go for a little bit more preload(.075 range) but thats just my opinion

 

That's interesting. I like it.

How do you account for the little cup in the rocker where the pushrod sits? I don't think my feeler gauge will fit in there.

 

There are basically 3 methods to define the length of a pushrod.
1) Theoretical length (end-to-end if the ***** didn't have a flat in them)
2) Flat-to-flat length (Manton pushrods are specified this way, using a ~0.115" dia flat)
3) Gauge length

I don't know any pushrod maker that uses theoretical length, but I do know Comp Cams uses gauge length, and that's probably why their length checking tool also gives gauge length.

Pushrods with a 5/16" dia ball end will be approx 0.015" shorter in "gauge length" than the same pushrod measured "flat-to-flat". So a pushrod that is truly 7.400" flat-to-flat will be ~7.385" gauge length.

Funny thing with Comp Cams is that their so called "7.400" pushrod is most likely 7.400" flat-to-flat and 7.385" gauge length. Yes, it's confusing.

Bottom line - ask the manufacturer how they have specified the length of the pushrods you're going to use.

 

Did you have any valve work done? If so, you could see some variance if all the valves are not sitting exactly the same distance down in the seats and/or the valve stems are not exactly the same length.

 

They are new Manley valves and I had a 3 angle valve job done by a Serdi Valve machine. I don't know how non-precise the machine can be?

So, if number 1 is at TDC, is number 6 also? It sure looked like it.

 

Saw your post on Tech. Thank you.

 

Saw your response. Sounds like that was your issue. Let us know if you get more consistent measurements now.

 

Will do, tomorrow.

 

You insert the feeler gauge between the top of the valve and the tip of the rocker, not between the rocker cup and the pushrod.Since you actually lifting the rocker a little,that why you need to divide by the rocker ratio.

 

Sh*t. I knew that. I had a severe lack of comprehension in this thread. Things will be better tomorrow after this exam is out of the way hahaa

Thanks for all the input.

I am going to measure another cylinder to confirm my initial measurements using the TDC method and will probably triple confirm using the method you wrote about.

 

Dont worry it took a couple of clear instructions from vettenuts before i began to totally understand everything.Keep us posted with your result

 

Ok, so I turned the crank 360* to check number 6 cylinder and I get basically the same that I did for cylinder 1.
Here are my findings:

Cyl 1: intake=9 turns, exhaust=9.5 turns.
Cyl 6: intake=9.5 turns, exhaust=10 turns.

What gives here?

I'm about ready to say screw this method. I don't have a caliper that goes past 6", so I can't do the feeler gauge method. I also don't have a torque wrench that goes below 25ft/lbs, so I can't do that method. Looks like I'll have to buy some tools or find a happy medium within my measurements.

 

Your welcome to try a set of 7.350's and if they work, you can have em for $80. If not, send them back...

 

I'll take you up on that. I can't guarantee when it will start and I will know, but I would guess within a couple weeks. I can send some good faith money if necessary. That's really cool of you to offer

 

No problemo... sent you a PM