Checked the previous posts, still haven’t come to a conclusion on what PSI will be needed for the spring swap to hold the valves up. Heard 30-40 and 90-100, but wouldn’t want too much to push the piston down. Any experiences?

I do know the rope trick also, not ruled out yet.

 

I've never done anything other than making sure the piston under the valve spring is at TDC, that way when I crank the spring compressor down on it the valve keepers pop loose from the valve just touching the piston top it won't hurt anything if you are gentle there was a sequence how to do it on "LS1 how to" back in the day

 

With a 2.000" intake valve and ls6 springs, technically you'd only need 30psi to keep the valve in place if the keepers were to try to hold on to the valve for a little bit of travel.

If the piston is at TDC, then you wouldn't have to worry about the air pushing the piston down as there's no lever action to the crank at TDC.

 

I only used about 50-60psi when I swapped my springs.

 

ProStock Paul Air Cups, I created the seal that made them possible (F-1 included)
We found 1000 PSIG was the best pressure
Lance

 

I'm a fan of the rope trick. I use clothe line syn type rope.

 

Rope wads up, I prefer using a length of vacuum hose. Also has the advantage of not having a million spots to pick up dirt and send it into your engine.

 

Having the piston at TDC is a safety because you know $#it happens.

80-100psi should be more than good. IF you're worried about the piston moving down the cylinder, you can also put a breaker bar with a socket on the crank bolt as a visual.

 

Thanks all, appreciate the responses. Actually doing the cam too so had the timing marks pretty accessible, and used the TDC method. #7 & #8 was the worst, but got through it all.

Just take your time and definitely ’cover’ the area/valves you are working on to capture those flying keepers.

 

I just did my springs a couple months ago using rope. I crammed about 18" into the cylinder and turned it over until it stopped then pulled the springs. Easy peasy