Checking pushrod lenght
10-31-2009, 06:58 PM
#1
Checking pushrod lenght Have rebuilt my LS1, changed cam and milled heads (.014), have now used pushrod checked (torqued rocker, on the cam base circle and just snugged the checker screw) to get new lenght measurement. Now I 'm wondering how much to add to this measurement to get the proper lifter preload.
10-31-2009, 08:09 PM
#2
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Add .020 to the length just remember that pushrods come in lengths of .050 so get the ones over your measurement and you will be fine. Also make sure you check intake and exhaust.
10-31-2009, 11:55 PM
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this is the method I recently used. Its quiet as a mouse. CajunSS is co-owner of Thunder Racing
FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.
Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.
I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.
Here it is again in a nutshell:
1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...
I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.
If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.
THIS METHOD ALWAYS WORKS!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane
Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.
I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.
Here it is again in a nutshell:
1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...
I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.
If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.
THIS METHOD ALWAYS WORKS!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane
11-01-2009, 08:18 AM
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XtraCajunSS explained it about as well as it can be explained. Gengines, do you get ever get exessive noise with only .020" preload? Doesn't seem like enough to me. Later,Dean.
edit. G Engines I reread your post. I see you were not talking about only .020" of preload. But the NEXT longer length pushrod. This should be close also. Sorry about that, didn't want anyone to think you didn't know what you were doing. Dean.
edit. G Engines I reread your post. I see you were not talking about only .020" of preload. But the NEXT longer length pushrod. This should be close also. Sorry about that, didn't want anyone to think you didn't know what you were doing. Dean.
Last edited by DeanJ; 11-01-2009 at 08:29 AM.
11-01-2009, 08:33 AM
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edit: hijack, G Engines I see you live in Greensboro,NC. Ever get over to Piedmont Dragway. I am co owner of a '63 corvette we run in the Renegade class. 1 nos kit only, 2480 lbs 632" powerglide. best et 4.39@ 159, 1.00 60'
Last edited by DeanJ; 11-01-2009 at 08:41 AM.
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11-01-2009, 08:42 AM
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Morel lifters and the Cts V lifters call for .020 and if you go with the next length pushrod it usually has more like .030 to .040 preload so with that preload they don't make noise. Some of the Cts V lifters bleed off during deceleration and make a small amount of noise gm claimed this is supposed to help and is normal I question this but a lot of engines run them with out problems.
11-01-2009, 10:54 AM
#9
Morel lifters and the Cts V lifters call for .020 and if you go with the next length pushrod it usually has more like .030 to .040 preload so with that preload they don't make noise. Some of the Cts V lifters bleed off during deceleration and make a small amount of noise gm claimed this is supposed to help and is normal I question this but a lot of engines run them with out problems.
11-01-2009, 11:58 AM
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I talked to Rick Morel a couple of years ago and he advised me to use 0.030" - 0.050" with their lifters and an aluminum block/head motor (note that John Callies had the same recommendation). Currently running the higher end of that range and many of the startup noise issues attributed to Morels with the lower end of that range are now gone. Offshore guys are running them deeper as well.
11-01-2009, 04:57 PM
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I also noticed, my new LS7 lifters soaked in oil a week. I did it the way shane said and I could feel the lifter being spongy, allowing the preload. They then sat for a week in the motor before I finished assembly. By then they had no spongy feeling, they were hard as a rock.
11-01-2009, 06:42 PM
#14
Well, I am not sure how 1 turn of the bolt can be 0.047" of preload at the pushrod cup since one turn of the bolt is 0.049" and the pushrod cup will move more then the bolt. If you want it accurate, use a dial indicator to measure preload with a known length pushrod or use an adjustable pushrod to measure length at zero lash and add the preload to the measured number.
11-01-2009, 08:39 PM
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You could do what I've done and measure it yourself with a dial indicator. With the compound angles and rocker ratios not to metion slack in the rocker body, unless you are using trig to figure this out, you'll never get a good answer. Just buy a dial indicator and try it. I promise you, Jason99T/A and I performed the actual measurment years ago in my engine room. We did it to save us a lot of time and effort with length checkers. If you don't believe it, take the measurement yourself...
Shane Burgess
Co-Owner, VP Operations
Thunder Performance Group, Inc.
d/b/a Thunder Racing
Shane Burgess
Co-Owner, VP Operations
Thunder Performance Group, Inc.
d/b/a Thunder Racing
11-02-2009, 12:08 PM
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Not necessarily. The only times this exact method will not work is when using a shaft mount rocker with the pushrod cup adjuster. I have used the same method with Yella-Terra's, Comp Pro Magnums, and Harland Sharp. The differences between them is negligable and not worth considering on a stock type lifter. Even 1.8 ratio rockers work fine. The only time you really need to worry is if you are using a cheater hydraulic such as a Comp-R or Shubeck. These lifters run almost no preload, about .002"-.003" MAX. You must directly verify preload with a dial indicator when using these lifters. That being said, the EO/IC method works for ALL 4 stroke engines and should be used for both solid and hydraulic lifters to set lash/preload.
Shane
Shane
11-02-2009, 06:58 PM
#19
This is from Yella Terras Site by the way.
Do roller rockers need special push rods?
Usually no, with the exceptions being:
1. When screw-in studs and hardened guide plates are to be fitted (on engines not fitted with them originally). These need hardened pushrods.
2. When extremely heavy valve springs are fitted a more robust push rod than standard may be required.
What tappet settings do I use when fitting roller rockers?
Whether using Roller Rockers or standard rockers, the tappet settings remain the same as specified for your camshaft.
11-02-2009, 10:19 PM
#20
Pushrods Have rebuilt my LS1, changed cam and milled heads (.014), have now used pushrod checked (torqued rocker, on the cam base circle and just snugged the checker screw) to get new lenght measurement. Now I 'm wondering how much to add to this measurement to get the proper lifter preload.
Last edited by deelli; 11-02-2009 at 10:25 PM.