I am changing the pushrods on my LS1 sure enough one was bent all to hell.... Do I have to spin the crank to get to TDC before tightening down the rockers???

 

You should to it at TDC but you can do it without spinning the motor.

 

it shoudnt matter if the rockers/pushrods are stock. Just tq them down, spin the motor a few times all the way around, then check them again.

 

Look at post number 10.

https://ls1tech.com/forums/showthrea...ocker+sequence

It will give you the sequence. That is the way I did mine and have not had any problems.

R/

Frat

 

OK... Where is the crankshaft at???

 

that post doesnt make sense. If the friction from the lifter affected preload on the rocker/pushrod, every cylinder would require a different amount of tq applied to it to defeat this friction. So if this was true, when cylinder 1 was TDC (lifter is off the ramp) cylinder 2-8 would all be at different valve events anyway. TQ'ing them all down to 22lbs and then spinning the engine and re checking ensures that they are all TQ'd correctly

 

how can I tell if the 1st piston is at TDC... Is it when the valve spring is completely compressed?

 

TDC is when both valves are closed.

 

I always tighten them. TQ them. Spein the engine a few times, then re-TQ them.

 

Thats how i do it too.

 

Nope. You mis-read the post. If you tighten them all then spin, some will fully compress the valve springs. The lifter is not of concern. The GM procedure only tightens the rockers whose lifter is on the base circle.

 

we could argue this for days, but there is more than one way to skin this cat. If for what ever reason you dont have the timing cover off, and dont know how to tell when 1 is at TDC, like the OP, he will be fine just tq them down and spinning it. Obviously we all have different levels of being **** about our cars. Kind of like degreeing the cam when you install it. 80% wont do it because they dont know how or just dont care.

 

I do them all at the same time normally, but I torque to 26lb ft. and retorque twice. On internally modded LS1's 22lb ft. just doesn't seem like enough and I had a few rockers loosen rather quickly when I used that torque specification, even with rotating the engine and torquing. Never had any problems at 26lb ft.

 

What I do for TDC is watch the #1 intake valve close by putting the pushrod in that location and watching it go down and stop. Once closed you know it is roughly 1/2 turn to the top so go 1/4 turn then use a straw or flashlight to track piston movement to top.

 

The BEST way to do it is like checking lash on a solid roller. Check the intake as the exhaust is opening, then check the exhaust as the intake is closing. This guarantees that the lobes are on the base circle.

Just FYI, be careful about looking for TDC because you can be on TDC and both valves can be open, ie "overlap".

 

Thanks for all the help. I did one side last night I am preparing to do the other side right now.

 

Why would the valves be open on the compression stroke?

 

Run into a problem. How do I get the last bolt all the way in the back? There are 2 hoses in the way. I can't get it off to get to the valve covers.

 

They shouldn't on the compression stroke, but @ TDC after the exhaust. My point was that you want to find the right TDC, not just TDC.

 

I'm assuming the last coil pack bolt. I use a small 10mm ratchet wrench on it, but you can use a regular box-end 10mm wrench also. A 10mm medium depth socket on a small ratchet would work too.

Throw that last bolt as far as you can into a vacant field also.