jdoyle

iTrader: (27)

I am trying to find out if I am running the correct length push rod. I am running my stock rocker arm bolt down to zero lash but I have a question on what exactly zero lash is?

Is zero lash where you can move the rocker arm side to side (off to the sides of the valve) but not up and down? In this case I came out with 6.125 full turns to reach 22 lb. ft. This does not seem right to me. It seems to me that my valve tips would be FUBAR'd but they look good to me.

OR Is zero lash where you can neither move the rocker arm up and down nor side to side? I think that this is the correct answer but I figured that I would ask since knowing would give me peace of mind rather than wondering if my ride is going to blow up. In this case, I came out with 2.75 full turns to reach 22 lb. ft. I used a 7.4 inch push rod as my tester, which means that I need a 7.3295" push rod to reach .060" pre-load using a Comp 850-16 lifter. If I am right, it looks like I would need a 7.325" push rod.

My calculation:
1 full turn = .047"
2.75 full turns = 11 quarter turns
I want .060" preload, which is 5 quarter turns, so I need to get rid of 6 of the other quarter turns.
so, .047*1.5=.0705"
7.4-.0705=7.3295"

If it helps, I am running:

TR224 cam 224/.563/112
Comp 850-16 lifters
heads have been milled about .032 - .035"
rocker stands are shimmed up .030"
Comp 7.4 pushrods
stock rockers
patriot gold springs
Ferrera (spelling?) intake valves
I think stock exhaust valves

Can someone please verify that a 7.3295" push rod would be the push rod for me? I would really appreciate it.

Thanks,
jdoyle

P.S.: I have read in some cases that less preload gives you more power (basically), but in my case, I would rather give up the hp in order to get rid of the sewing machine.

bww3588

iTrader: (49)

zero lash is when you cannot move the pushrod up and down and you just start to feel resistance in the rotating of the rod.

that being said, your not going to find a 7.3295 pushrod. as far as i know, they come in .025 increments.

jdoyle

iTrader: (27)

i just looked back at my paper and found that i did the measuring wrong. i did the EO/IC method on the intake lifter when the intake valve was just about to start closing when i should have done it on the exhaust lifter. bummer.

back with updates on hopefully, sunday evening.

cowboysfan

piston @ tdc. by finger rotate both bolts till u feel some resistance. now try to rotate the pushrod. u should feel some resistance while rotating pushrods. if u rotate the rocker bolst more then 1 full turn u need to shim each rocker. this can only be verified on one set, if that one set needs a shim make sure all rockers are shimmed with the same size washer. if you can rotate each push rod by finger after shimmed and tq to 22ftlb then push rod r to small. best way to check for correct push rod size is to get a checking push rod so this way you can make sure push rod is sitting on the center of your valve stem.... hope this helps some.

vettenuts

iTrader: (4)

Zero lash is zero clearance between the pushrod, lifter cup in the fully raised position and the rocker arm cup. I have found the best way to get zero lash is to gently lift the rocker tip until you just get rid of the "tick" "tick" when you lift the rocker tip and release it. I have not had very good success when twisting the pushrod. Based on your description, sounds like you tightened way beyond zero lash and opened the valve. The rockers will move side to side with the valve closed due to the clearances in the needle bearings.

Some information on your calculations. One turn is 0.049" at the rocker bolt and 0.078" at the pushrod when corrected for rocker ratio. However, if this is the number that Shane from TR uses in his post, be aware that one turn is 0.047" because part of the one turn is after the rocker bottoms and the bolt is tightening to the final torque value. I checked his method last time I swapped pushrods and found that 1/3 of the one turn is after the rocker bottoms and as a result come up with his numbers when I calculate. Having said all that, if you go more then 1 turn it won't be a straight ratio to get the final preload, you have to remove the 1/3 turn for tightening and then account for the rocker ratio on the remaining bolt rotation to calculate the value.

jdoyle

iTrader: (27)

ok got an update for you guys.

i went through the process and came back with better results.
1st attempt was spot on just where i wanted it to be. 1.25 full turns which is i guess anywhere from 58 to 61 thousandths.

the 2nd attempt was not as reassuring (identical) as the first one but it was at least somewhat consistent. this time i got 1.125 full turns, or 4.5 quarter turns, which is anywhere from 53 to 55 thousandths.

vettenuts, i'd say that i followed your method the closest. i started the torquing process when rocking the rocker tip up and down stopped making any noise. i could also feel that the pushrod was pushing the plunger down if i lifted not so gently.

please let me know any comments about this, because i think that i got this right, hopefully others think so too.

jdoyle

iTrader: (27)

also, when I am reassembling the valvetrain after I have figured out the correct pushrod length, do I need to put every lifter on the base circle of the cam to install properly or can i just put all of the push rods in their holes and then torque them all to 22 lb. ft. one after the other?

vettenuts

iTrader: (4)

Make sure to prefill the pushrods with oil (I soak them in a Wal Mart pencil box of oil, pencil box was $1). Also, I like to use Redline Assembly Lube on the pushrod cup of the rocker and the top of the valve stem as it will take some time for the oil to get there once you start the motor. Otherwise oil things real well just before installing the valve covers. Here is the GM procedure:

jdoyle

iTrader: (27)

vettenuts:

I have four questions for you.

is there anything that I could use besides Redline Assembly Lube? what about ARP moly lube, would that do the trick?

when you say "oil things real well" the only other thing that I could think of oiling is the section of the rocker that contains the needle bearings. is there anything else that I am missing?

also, the left bank is the driver's side correct?

how do I know when piston 1 is at TDC? Is it the method below? I kind of hope not, because I don't really understand it.

-Take out #1 sparkplug.

Stick your finger over the hole.

Have someone turn the crankshaft with a breaker bar until you feel the compression blowing on your finger.

Put a plastic straw in the hole while still turning the crank in the same direction until it stops moving up. Do you want to put the straw in horizontally or as vertically as possible?

Rotate the crank 360 degrees from there, and again stick the straw in until you feel the piston reach it's highest point.

TDC.

thank you very much for your help in advance.

vettenuts

iTrader: (4)

I wouldn't use the ARP Moly lube as it has particulate in it. If you don't have the assembly lube, squirt some oil on the top of the valves and pushrod tips before installing your rockers. Just before putting on the valve covers, squirt oil in the rockers and valve tips again. You are just trying to ensure you don't start the car with a dry valve train until the oil comes up the pushrods.

Left bank is drivers. As for TDC, and since the valve covers are off, put a pushrod in the intake lifter hole for cylinder #1 and rotate the motor until the intake valve closes (pushrod will come up that go down but since the rocker won't be on simply watch the pushrod motion). At this point the piston will be coming up to TDC. Use a flashlight or put a straw in the cylinder (don't release the straw, just use it to feel for the piston) and rotate the motor until the piston is at the top. When you do this, you will need to keep a little downward force with your fingers on the pushrod otherwise the lifter will stay in the up position in the lifter tray because the spring won't be pushing it back down.

Hope this helps.

jdoyle

iTrader: (27)

definitely, thanks vettenuts

jdoyle

iTrader: (27)

PM sent to vettenuts.

are you supposed to turn the engine clockwise or counterclockwise after you have found TDC on number 1 and torqued the first 8 rockers down?

bww3588

iTrader: (49)

direction of normal engine rotation....clockwise.

jdoyle

iTrader: (27)

thanks man. i thought so, just wanted to make sure.

01ssreda4

iTrader: (96)

OP good luck