Anthony F

I'm currently replacing the yellow valve springs with new blues in my 2003. I'm using the TDC method while using a straw in the spark plug hole and watching the valve springs. My question is how precise does the piston have to be at TDC, if i'm off a few degrees will it be a problem or is in the ballpark good enough?

MY03C5Z

I used the compression method when I did mine, much simpler imo. If you already have the plugs out, I don't see why you wouldn't just do it that way. Once you attach the airfitting and the hose there's no question the cylinder is ready to go. Just saying.

Anthony F

I have everything out and ready to go and brought #6 up very close to TDC. I don't want to buy a compressor and biggest reason of all, i don't like the idea of losing pressure and then dropping a valve.

MY03C5Z

Oh I can see if you don't have a compressor that method makes more sense. I did the tdc method on my LT1 z28 before but it's been a while, never did it on an LS engine.

punz

I kind of did the same with the exception of, I inserted a nylon string, about 3/16 dia, into the plug hole, turned the crank with a socket wrench until it wouldn't pull out. When tougt the piston was near top dead and the string filled any gap between the piston and the valves. Make sure you have enough slack sticking out. I think the string was about 2 feet long, not all was fed in, maybe 9 inches and this process makes it pretty mindless and no worry of valve dropping or compresser failure. Tryed the compresser way but didn't like all the hissing and really wanted to take my time, being it was the first.

bumble-z

I agree w/Punz...No fear, no problems method.

Anthony F

Sounds great, thanks.

Anthony F

Took much longer then i expected but it's done! No cracks or any visible problems with the yellows.

MY03C5Z

Looking good, it's the best insurance you can get for the ls6

socal_Dad

Great job! I used the rope on a few cylinders and did a few without. How about you?

I found that once I got a feel for getting the keepers popped back in, I was OK at TDC without the rope.

Anthony F

I thought about it halfway through but just kept on with the rope.

punz

Glad it worked out for you guys, not to bad to do. I think the screw, front drivers side, that held the coil bracket was the toughest part.

socal_Dad

Funny you mentioned that! You can see in this picture that I backed out the alt mount bolt to get access to that one and I put some blue masking tape on that bolt so I would remember to tighten it back down.

punz

A little more info
Rope method is safe way and for tightening rockers, pic is from manual. To find #1 at TDC of compression use a straw or dowel rod and watch the intake valve, then put chalk mark on balancer for the second rotation. Once you do that your set.

~Josh

To clarify, my 01z had blue .525 lift springs from the factory. The modern blue are different of course, but this is a tidbit I wanted to share.

If you own an 01z and aren't the original owner, don't think your blues are the new style.