Pushrod Length Checker
Thread Starter
Race Director
Joined: Apr 2004
Posts: 16,135
Likes: 5
From: Newberry FL
Cruise-In VIII Veteran
St. Jude Donor '07
Pushrod Length Checker
Just bought one and it showed up today and I am not exactly sure how it works. Any ideas? Thanks in advance.
Micah
Micah
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Assuming stock rockers the pushrod only determines lifter preload. On adjustable stud mounts, pushrod lenght determines preload and swipe pattern. Get the cam so the lifter is on the base circle of the rocker you are going to check. Then use the adjustable pushrod to determine length required to get to zero lash. Then add preload for lifter to measurement (0.080 - 0.100")
One caution, the different manufacturers use different length definitions. Comp uses Gauge length while Crane and Manley use OverAll Length (OAL).
One caution, the different manufacturers use different length definitions. Comp uses Gauge length while Crane and Manley use OverAll Length (OAL).
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Saw your post on LS1Tech, so I hopefully can explain further (or until my fingers give out).
First assumption, the rockers and stands are stock with no machining. This ensures the wipe patter is the same as the car came from the factory. So the only thing you need to do is get a proper length pushrod so your lifter is correctly preloaded. This assumes stock lifters.
1. Look in at cam, make sure lobes for cylinder #1 are not up so lifter will be on the base circle.
2. Install lifters on cylinder #1.
3. Install new driver's side head with old gasket and tighten to around 25 lb-ft with old head bolts. Torque is not that important as you just want to take out clearances, sealing is not an issue. Follow torque sequence in manual.
(Note: This assumes heads are not currently installed and tightened down, if they are that is fine just put in two pushrods in cylinder #1 and rotate the motor until they are both on the cam case circle)
4. Put on your rocker stand and then unscrew your pushrod and measure the length from end to end until it is 7.300" which is 0.100" shorter than the stock length.
5. Set the rocker on the stand and engage the pushrod. Push down on the center pivot of the rocker by hand and then carefully lift the end of the rocker to see if there is any clearance between the rocker and the valve stem. If there is, it will tick tick. If there isn't, you have not clearance and the pushrod is too long.
6. Remove the pushrod and either lengthen or shorten a small amount to get the rocker to tick tick. When you just remove the tick tick, shorten the pushrod about 1/4 turn and then bolt on the rocker and re-check. You are trying to find the pushrod length that just eliminates the clearance between the rocker tip and the valve stem.
7. Once you have the pushrod length correct on cylinder #1 intake, varify the length (don't change it) in the exhaust valve.
8. Once you have the length, measure it with a caliper. This length is Overall Length or OAL.
9. Now add the preload to the length so you have 0.080 - 0.100" of preload for stock lifters. So if you length came out to 7.289 a 7.350" pushrock would give you 0.061 preload and a 7.400" would give you 0.111" preload. The shorter one might be noisy.
10. You now have the required length in OAL, so you need to make sure the company you order from uses OAL as their advertised length. I believe Crane and Manley do, but Comp and I think Trick Flow use what is called Gauge Length which is measured at the end ball where the diameter is 0.140". Thus, if you order Comp with your measure length, you will end up with a longer pushrod.
I hope this helps, good luck.
First assumption, the rockers and stands are stock with no machining. This ensures the wipe patter is the same as the car came from the factory. So the only thing you need to do is get a proper length pushrod so your lifter is correctly preloaded. This assumes stock lifters.
1. Look in at cam, make sure lobes for cylinder #1 are not up so lifter will be on the base circle.
2. Install lifters on cylinder #1.
3. Install new driver's side head with old gasket and tighten to around 25 lb-ft with old head bolts. Torque is not that important as you just want to take out clearances, sealing is not an issue. Follow torque sequence in manual.
(Note: This assumes heads are not currently installed and tightened down, if they are that is fine just put in two pushrods in cylinder #1 and rotate the motor until they are both on the cam case circle)
4. Put on your rocker stand and then unscrew your pushrod and measure the length from end to end until it is 7.300" which is 0.100" shorter than the stock length.
5. Set the rocker on the stand and engage the pushrod. Push down on the center pivot of the rocker by hand and then carefully lift the end of the rocker to see if there is any clearance between the rocker and the valve stem. If there is, it will tick tick. If there isn't, you have not clearance and the pushrod is too long.
6. Remove the pushrod and either lengthen or shorten a small amount to get the rocker to tick tick. When you just remove the tick tick, shorten the pushrod about 1/4 turn and then bolt on the rocker and re-check. You are trying to find the pushrod length that just eliminates the clearance between the rocker tip and the valve stem.
7. Once you have the pushrod length correct on cylinder #1 intake, varify the length (don't change it) in the exhaust valve.
8. Once you have the length, measure it with a caliper. This length is Overall Length or OAL.
9. Now add the preload to the length so you have 0.080 - 0.100" of preload for stock lifters. So if you length came out to 7.289 a 7.350" pushrock would give you 0.061 preload and a 7.400" would give you 0.111" preload. The shorter one might be noisy.
10. You now have the required length in OAL, so you need to make sure the company you order from uses OAL as their advertised length. I believe Crane and Manley do, but Comp and I think Trick Flow use what is called Gauge Length which is measured at the end ball where the diameter is 0.140". Thus, if you order Comp with your measure length, you will end up with a longer pushrod.
I hope this helps, good luck.
