Preload.. 1 turn = .047" is this really accurate?
06-23-2010, 07:11 AM
#42
I mis spoke about the pushrod length. I posted earlier based off memory which was wrong. 9 turns for the intake and 9 1/4 turns for the exhaust.
9 turns x .050=.45
.45 + 6.8(length of pushrod) = 7.25
7.25 + .047 = 7.297
so a 7.3 push rod is right? I hope I explained myself better and the 1/2 turn on the rocker bolt was to make sure it was tight.
Last edited by LilJayV10; 06-23-2010 at 08:31 AM.
06-24-2010, 02:33 AM
#44
After working at the shop all day I worked on the engine tonight.
I used the 1 1/2 turns to preload. I did this about 4 times on the intake and exhaust, starting at the factory 7.4 and working my way down.
I got 7.35 for the intake and 7.325 on the exhaust.
One thing I learned tonight is when you are using an adjustable pushrod checker is to use tape. When I would set the adjustable pushrod to a certain length then try to find zero lash I always found myself "adjusting" the pushrod down some. After doing this a few times it came to me to put a piece of tape around it to hold it where I put it at.
On both the intake and exhaust I got the lengths at 1 1/4 turn at 22 ft lbs. Every time.
I am confident that these are the lengths I need. I left the light weight checker valve springs in to make sure I wasn't preloading the valve any.
Is the .025 difference worth buying two lengths of pushrods? Would the extra preload on the exhaust hurt anything?
At this point it doesn't matter if I buy two sets of pushrods. I am this far in it, doing things correctly, (as best I know of) that another hundred bucks isn't going to kill me.
I made sure one valve was all the way open and checked the closed one.
I used the 1 1/2 turns to preload. I did this about 4 times on the intake and exhaust, starting at the factory 7.4 and working my way down.
I got 7.35 for the intake and 7.325 on the exhaust.
One thing I learned tonight is when you are using an adjustable pushrod checker is to use tape. When I would set the adjustable pushrod to a certain length then try to find zero lash I always found myself "adjusting" the pushrod down some. After doing this a few times it came to me to put a piece of tape around it to hold it where I put it at.
On both the intake and exhaust I got the lengths at 1 1/4 turn at 22 ft lbs. Every time.
I am confident that these are the lengths I need. I left the light weight checker valve springs in to make sure I wasn't preloading the valve any.
Is the .025 difference worth buying two lengths of pushrods? Would the extra preload on the exhaust hurt anything?
At this point it doesn't matter if I buy two sets of pushrods. I am this far in it, doing things correctly, (as best I know of) that another hundred bucks isn't going to kill me.
I made sure one valve was all the way open and checked the closed one.
06-24-2010, 04:38 AM
#45
GM lifters are pretty forgiving with the preload. Unless you are very light or very deep the 0.025 shouldn't be an issue. What may net you a more stable valve train and a few ponies up top (it did for me) is a larger diameter pushrod. Are the heads on the car yet?
