SatisTraction

iTrader: (2)

i have been reading about lifter preload. what i have not found is how to actually determine how much i have? ont STOCK rockers, should the rocker bolt turn one turn, two turns, or whatever after the pushrod contacts the plunger?

ArKay99

iTrader: (1)

The rocker bolts are ~.035" per turn. About .060" to .080" is the most recommended preload for aftermarket cams. So, hopefully you'll have to turn them 1 3/4 turns to get to 22ft/lbs. of torque. Anywhere between 1.5 and 2.5 turns will work.

PREDATOR-Z

"Turn" method on non adjustable rockers is retarded. Just put the cam on its base lobe, follow the sequence and 22ft/lbs.

If you are trying to determine preload, then You need an adjustable p-rod checker.

N4cer

iTrader: (11)

Yup they're non-adjustable. Torque 'em and go on with your day.

corvet786c

iTrader: (6)

I dont know about stock rockers, but Crane Gold 1.8 Roller Rockers require a 1/4 turn every 15min, to allow the lifters to bleed down. Refer to there page for more info.

BlackScreaminMachine

iTrader: (17)

Exactly.... I was having flash back on my old LT1 for a sec....

SatisTraction

iTrader: (2)

well i am used to adjustable rockers and that is all i really know. I "think" my pushrods are too long and causing so problems.

once you bottom out the rocker stud the 22ft/lbs will not increase the preload. you will have to start preloading before then. i just figured it would be about a turn before you bottom out.

PREDATOR-Z

Preload on non adjustable stock units (or aftermarket for that matter) is a direct product of p-rod length. Thus the need for an adjustable checker to determine closest length needed.

SilverSmoke

Dumb question, but with the stock rockers, or non-adj for that matter, do you have to torque to 22ft/lb at tdc for each cylinder, hence having to manually roatate the engine for each rocker to bolt down?

Viper

iTrader: (6)

Not a dumb question. Yes, you should be at TDC for each cylinder. With our engines, that means you can do multiple at once. Here:

Per GM SI website:

1) Install the rocker arms and bolts. Meaning put in the rocker arm bolts till hand tight.

2) Rotate the crankshaft until the number one piston is at top dead center (TDC) of the compression stroke. In this position, cylinder number one rocker arms will be off lobe lift , and the crankshaft sprocket key will be at the 1:30 position. Another way to say it is hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.) The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5, and 7 are left bank. Cylinder 2,4,6, and 8 are right bank. Off lobe lift means rotate the crank till both valvesprings come UP on cylinder 1, meaning the valves are closed. If you rotate too far, one valvespring will start to go down ( valve opening) ; simply rotate again till you see them both come up. Use a 24mm socket on the crank with a 3" extension and a breaker bar for rotating.

3) With the engine in the number one firing position, tighten the following valve rocker arm bolts:

• Tighten the exhaust valve rocker arm bolts 1,2,7, and 8 to 30 N·m (22 lb ft).

• Tighten the intake valve rocker arm bolts 1,3,4, and 5 to 30 N·m (22 lb ft).

4) Rotate the crankshaft 360 degrees

5) Tighten the following valve rocker arm bolts:

• Tighten the exhaust valve rocker arm bolts 3,4,5, and 6 to 30 N·m (22 lb ft).

• Tighten the intake valve rocker arm bolts 2,6,7, and 8 to 30 N·m (22 lb ft).

vettenuts

iTrader: (4)

If you count turns (not recommended, an adjustable pushrod is the accurate way or use a dial indicator when tightening), then you must also account for the rocker ratio. The stock rockers sit on the seat at a ratio of 1.54 so each turn results in 1.65 X thread pitch or for an 8mm X 1.25 thread each turn of the bolt depresses the pushrod 0.081 inches.

SatisTraction

iTrader: (2)

now that is what was talking about!!! I knew someone would know.

so it is safe to say that if you are at zero lash (preload) at one turn then you have about .080 preload at 22ft/lbs.

vettenuts

iTrader: (4)

That would be the approximate preload, always best to measure though. Also, preload is determined once bolt bottoms, not when tightened. In other words, once the rocker is seated the torque is used to essentially preload (stretch) the bolt and is not altering preload at all. So if you are using bolt rotation, it should be measured using rotation until the rocker seats. This is where a dial indicator is useful, otherwise it is all by feel and prone to error.

Slow 346

iTrader: (33)

A long time ago when I bought my H/C setup from Morgan motorsports they supplied different thinkness shims that fit under the stock rocker arm stands. They were as long as the stock stand with 8 holes in them where the rocker arm bolts went through. Are these still available?

PREDATOR-Z

You'll never get an accurate number like that. I read another thread where you said you fabbed a p-rod checker. That won't work because there is a difference between gauge length and AOL.

So do yourself a favor, either borrow, rent or buy a "correct" p-rod checker and take it from there.

vettenuts

iTrader: (4)

I can't agree more. I would understand if it was a $500 tool, but its only $20 and would save so many guys so much grief. Pushrod length is one of the most asked questions, and with the number of variables from one car to the next measurement is the only sure way to know the valve train setup.