Formula for pushrod length?
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Joined: Jul 1999
Posts: 3,647
From: Winnipeg, Manitoba, Canada
Formula for pushrod length?
For LT1s is there a general formula for how much shorter a pushrod should be if you are going with a higher ratio rocker and higher lift cam?
Like a 1.7 rocker on a .510/.525 lift (with 1.5s) cam?
Like a 1.7 rocker on a .510/.525 lift (with 1.5s) cam?
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
It depends on a couple of things: cam base circle diameter and rocker arm configuration and of course valve stem length. If you change heads that's another factor. If the cam is higher lift there's a good chance the base circle will be smaller, and you'll need a longer pushrod rather than shorter.
Of course, milling the heads, or decking the block shorten the required pushrod length.
Rather than try to calculate, it's probably better, and a lot easier to use an adjustable measuring pushrod to get the correct contact pattern on the valve. I'm not telling you anything new, just that measuring then buying the correct length is easier than trying to figure it out and having to buy and return a couple sets of pushrods.
Often Bret sends a cam/valvetrain customer all the valvetrain parts except pushrods, and includes a measuring pushrod. The customer installs everything, determines the correct length and sends back the measuring pushrod so that the correct length pushrods can be ordered and drop-shipped. It works out quite well.
Of course, milling the heads, or decking the block shorten the required pushrod length.
Rather than try to calculate, it's probably better, and a lot easier to use an adjustable measuring pushrod to get the correct contact pattern on the valve. I'm not telling you anything new, just that measuring then buying the correct length is easier than trying to figure it out and having to buy and return a couple sets of pushrods.
Often Bret sends a cam/valvetrain customer all the valvetrain parts except pushrods, and includes a measuring pushrod. The customer installs everything, determines the correct length and sends back the measuring pushrod so that the correct length pushrods can be ordered and drop-shipped. It works out quite well.
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Gripenfelter
Where could I find an adjustable pushrod?
Where could I find an adjustable pushrod?
http://compcams.com/Technical/Catalo...3/HTML/293.asp
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Joined: Oct 2002
Posts: 1,639
From: Toledo, OH
This might sound dumb to you guys, but how do you know even with a measuring rod how long it should be? I mean you could technically use different length pushrods, since you could just adjust the lash differently right, but that wouldnt be good, so how do you know what the exact length should be?
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Originally posted by jonaddis84
This might sound dumb to you guys, but how do you know even with a measuring rod how long it should be? I mean you could technically use different length pushrods, since you could just adjust the lash differently right, but that wouldnt be good, so how do you know what the exact length should be?
This might sound dumb to you guys, but how do you know even with a measuring rod how long it should be? I mean you could technically use different length pushrods, since you could just adjust the lash differently right, but that wouldnt be good, so how do you know what the exact length should be?
Rich Krause
Advanced Tech Moderator
Joined: Aug 2001
Posts: 2,262
From: Nashville
Originally posted by jonaddis84
This might sound dumb to you guys, but how do you know even with a measuring rod how long it should be? I mean you could technically use different length pushrods, since you could just adjust the lash differently right, but that wouldnt be good, so how do you know what the exact length should be?
This might sound dumb to you guys, but how do you know even with a measuring rod how long it should be? I mean you could technically use different length pushrods, since you could just adjust the lash differently right, but that wouldnt be good, so how do you know what the exact length should be?
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