ghettocruiser

iTrader: (17)

Hey everyone. Ive been around the forums for awhile, and one thing that I still cant get my mind around is cam/head combos and how to figure out the supporting parts like pushrods.

My motor has the mods in my sig below... The motor makes a lot of noise. Not really ticking like something is wrong, but its not noisy. Previous owner of the motor said it was noisy for him as well. I have stainless long tubes...and Ive heard that that doesnt help. But Ive also heard that the wrong length push rods can cause a lot of noise too.

So...if I get the specs of the parts that I have in the motor, is there a way to figure out what length the rods are supposed to be? Just so when I pull a few out I can check them. I know stock is something like 7.400...SO Im sure its just a matter simple math. Im not even sure the mods require different length pushrods.. Car is goin in for a tune in august, so if I dont figure something out, I might just have them check into it.

Anyway... Here are the cam specs... 228/224 .588/.581 113 +2. Heads are MTI Stage 2e 5.3L heads. Previous owner had them milled. I thought they were .030...but he said they actually only milled .010 - .015. The heads have double springs installed...but Im not sure of the brand there.

Im not even sure the length can be found just by that info... If you need more info Ill try to get it. I guess I might also just need to use a pushrod length measuring tool. Just figured Ide post up about it first see what you all have to say.

Thanks!

Justin

Grimes

iTrader: (3)

I think you already know that you need the tool to do it correctly - especially since you are not sure how much the heads are milled.

brad8266

iTrader: (23)

You need the pushrod length tool.

ghettocruiser

iTrader: (17)

Cool guys. I kinda figured thats where Ide end up. Any good lines on where to get one? A sponser preferably...

I might just see if the tuning shop will do it for me...but if not, Ill need to pick on up and learn how to use it.

Thanks.

J.

cals400ex

iTrader: (27)

how can you check preload even with a one of these adjustable tools? i don't understand where you measure from...

bsf

iTrader: (7)

The posters are not talking about measuring preload.
Preload is specified for the lifter you will be running. In a mathematical sense, preload is just an amount you add to the zero lash distance between the rocker arm and the lifter cup to “pre-load” your valvetrain when you are selecting pushrods.

ETA
For example, the preload range for LS7 lifters is ~0.075” - ~0.100”. Since stock LS1/6 rockers arms and stands are not adjustable, the actual preload you will have will be entirely dependent on three factors: your cam base circle radius; lifter (cup height); and pushrod length. Given that the base circle and lifter dimensions are constants (static state), you can only vary the pushrod. If the distance from the lifter cup to the rocker (as measured with an adjustable pushrod) when the lifter is on base circle is 7.30” and you wanted a preload of 0.080”, you would pick a pushrod that was 7.30” + 0.080” = 7.38”. Now pushrods are offered in lengths that are increments of 0.025”. The closest choices are 7.375” and 7.400”. I would probably choose 7.375”.

Disclaimer: I am new to this and guarantee nothing.

edited 07-15-07 1954 EST - Made faint a sentence that may be misleading or untrue.

cals400ex

iTrader: (27)

that makes sense now. i was reading how people would count the number of turns they make after 0 lash to figure out preload. that just doesn't seem to be very accurate, considering i don't know how much preload you add per turn you make.

so basically what you are saying is:
move to 0 lash on a cylinder that has both valves closed with the pushrod tool. add that length to 0.080 (for LS7 lifters anyways) to find out what length pushrods you need.

am i catching on yet?

cals400ex

iTrader: (27)

well wait, i dont' think i am catching on yet. lol
what do you mean by the base circle? also, the length between the lifter and the rocker will vary depending on how tight you have tightened the rocker bolt. i still don't see how to use those then...

bsf

iTrader: (7)

Base circle.

Imagine a camshaft. Focus on one cam. It is basicallya a circle with a bump. Remove the bump (lobe) so you have a perfect circle, or base circle.

No. Torque spec is 22ftlb. We do not increase or decrease torque to adjust preload. People talk about that, but I think that is old school (SBC) stuff. I actually do not know where it comes from.

Once again, I know as much about this stuff as brain surgery. I could be leading you astray.

ghettocruiser

iTrader: (17)

Actually...the post you made in here and in another thread that you started really helped me. I was alittle confused about the process of checking with a checker as well. So thanks for breaking it down.

Now I just need to decide if I want to get a checker and do it myself, or just see if my tuner will check things for me. My car just makes too much racket...and Im still thinking it might be pushrod length. Unless having stainless headers REALLY makes noise that much louder. Thing runs great, and I dont have anything bent or broken in the valvetrain that I can tell...

So we'll see. I have a few weeks before my tuning appointment. So this week I want to decide if I want to check the lengths myself or not. That way I have time to order new rods if I have to before the tune.


J.

Marc '99T/A

iTrader: (22)

But how do you know when you are actually measuring the base circle?

JimMueller

iTrader: (9)

http://www.cranecams.com/?show=techarticle&id=2

ghettocruiser

iTrader: (17)

Cool..good link. Havent gone over to cranes site to poke around yet.

As for preload...they have listed .020" to .060". Is that just for the crane lifters? Or is this spec good for all hyd. lifters including stock? I have no idea what lifters are in my car. I can probably find out though.

So, in a nut shell, with the cylinder in question at TDC, you would insert the pushrod checker and torque the rocker down to 22ft-lbs. Adjust the pushrod checker to zero lash, then increase the checker length by the preload, whatever that might be for the lifters in question. Then remove the checker, and measure it... Is that basically correct?

Justin

ghettocruiser

iTrader: (17)

Also..just so Im clear on something about checking whats in there now...

Crane's site mentioned using a straight edge and all that jazz... Is this the nutshell procedure for that as well?

Piston at TDC both valve closed, remove the rocker assembly. Allow the lifter to pump back up and be completely un-loaded. Then, set the rocker down and tighten the bolt until there is zero lash. Using a straight edge of some sort, mark the rod at that point. Then torque the rocker bolt to 22ft-lbs, and mark the rod again. Then just measure the distance between those lines and that gives you the preload right? If the measurement is out of spec, adjust pushrod length accordingly (too much, shorter rod, too little, longer rod).

Also...will too long of a rod cause more valve train noise? Or is that only with too short of a rod?

Thanks!

Justin

stealth71

iTrader: (15)

This seems mostly right, but you don't do anything with the preload other than add it to the length measured.

So, in a nut shell, with the cylinder in question at TDC, you would insert the pushrod checker and torque the rocker down to 22ft-lbs. Adjust the pushrod checker to zero lash. Now we have the length of the pushrod w/ NO preload. Say you measure 7.325. So 7.325 + preload say (.075 just a reference) = 7.40

That should be it.

ghettocruiser

iTrader: (17)

Gottcha... that makes sense. No reason to adjust the pushrod to get preload..just add it.

One last little question. Are all lifters the same as far as preload? In other words, how important is it for me to be 100% sure what lifters are in the car. The motor isnt stock... its an ARE set up...but since the block was built, the heads and valvetrain have been changed. So I really need to just bug the prev. owner to see what lifters were used.

J.

bsf

iTrader: (7)

I think you can get a new set of LS7 lifters from SDPC for ~$110 shipped.

ghettocruiser

iTrader: (17)

I dont think I need new lifters, and I certainly dont want to pull the heads to replace them at this point. The lifters that are in there cant have that many miles on them. The donor car had 33,xxx miles. The motor that I pulled was the second motor... So even if the prev. owner replaced the motor right off the showroom floor, the lifters would only have 33,000 miles on them. Im thinking they have more like 10,000.

I found a pushrod checker on Thunder Racing's website from Comp cams. It seems like a nice piece...something to keep in the tool box. So Im going to order it. I just need to get a good idea on what lifters are in there, or even if there is a generic preload measurement that would work good for all lifters... Then just pull the valve covers, again... check a few, average them, and see how that number checks against what rods are in there now.

J.

cals400ex

iTrader: (27)

the lifters will determine what preload you need. i believe in these cars with gm lifters, the norm seems to be around .080. however, comp lifters, require much less preload for example. i dont' remember the number exactly but i was thinking around .020. i will always replace pushrods and lifters with a cam/head swap. it may not be needed but i will do so.

most people on here will tell you pushrods a little longer will quiet the valvetrain. TSP told me they would be louder if anything due to increased seat pressure. i went with 7.425's over what TSP recommended (7.4) even with their heads. everysetup will vary though.

ghettocruiser

iTrader: (17)

Hmm... interesting (about the TSP recommendation vs. what you did).

As for replacing the lifters... like I said, Im not doing a head job. I see absolutely no reason to pull the heads off to replace lifters that have hardly any miles on them. I agree if I was replacing the heads or doing a cam/spring install, yeah, maybe then Ide replace lifters.

In the meantime, I have an RFI in with the previous owner...see if he can recall what lifters are in the motor. Ill go from there.

I can definetly see how longer pushrods (within spec) would quiet the valvetrain. Is there a "too long" condition when ordering new pushrods thought? Or can the longer pushrods cause noise...just as the too short ones could cause noise...kind of giving you a sweet spot that you need to nail to have a quieter valvetrain.