What kind of problems does incorrect pushrods and/or preload cause?
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From: Bossier City, LA
What kind of problems does incorrect pushrods and/or preload cause? Can they cause my ls1 to sound almost like a desiel from the clatter?
What about a sharp decline in power past 5500 rpms?
Any info related to this is appreciated!
What about a sharp decline in power past 5500 rpms?
Any info related to this is appreciated!
It's a common source of extra noise in the valvetrain (more often with too little preload). Too much can actually have valves hanging open and can cause a no-start condition. Also, with too little preload, when engines get to full temp and clearances expand, we've seen them actually turn to lash (opposite of preload basically) and that can really start to beat the heck out of parts and tear stuff up. In some of the endurance testing we've done on our new EHT springs we've seen some nasty harmonics/resonance in those conditions that tear up springs very quickly!
ALWAYS measure your preload....we've had Plain Jane XeR lobed cams go into completely stock LS1 long-blocks and require different than 7.400"....it would have been trouble if not for measuring and setting them up correctly!
ALWAYS measure your preload....we've had Plain Jane XeR lobed cams go into completely stock LS1 long-blocks and require different than 7.400"....it would have been trouble if not for measuring and setting them up correctly!
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Could be too long, I'd recommend like I said above to measure and be sure. There's enough variance in machining in the stock long-block brand new from GM that it's worth while to emasure....after you've changed the heads and cam I'd say that is even more true now!
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Staging Lane
Joined: Jul 2008
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From: Chicago, IL
My engine has some serious chatter and it's not from preload. I spec my PR's out with a checker and made sure they were on the tight side of the clearance.
This being my first LS1, I've been told the valvetrain noise is common, and because I have XER lobes that have sharp dropoff, combined with longtube headers that amplify/echo the valvetrain events, the "chickita, chickita, chickita" sound is normal.
I don't like it.
If I had to do it over, I'd probably use less aggressive lobes. In the short run, I'll be wrapping my headers to see if it helps muffle the noise some.
This being my first LS1, I've been told the valvetrain noise is common, and because I have XER lobes that have sharp dropoff, combined with longtube headers that amplify/echo the valvetrain events, the "chickita, chickita, chickita" sound is normal.
I don't like it.
If I had to do it over, I'd probably use less aggressive lobes. In the short run, I'll be wrapping my headers to see if it helps muffle the noise some.
Could be too long, I'd recommend like I said above to measure and be sure. There's enough variance in machining in the stock long-block brand new from GM that it's worth while to emasure....after you've changed the heads and cam I'd say that is even more true now!
EDIT: Every single answer to the pushrod length question is always "measure". Measure measure measure. I guess I won't be buying it as a package then but rather buy heads and cam, install, measure, then buy correct length pushrods.
Last edited by X-ray; Apr 21, 2010 at 06:12 PM.
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I'm planning on buying a heads/cam package from you guys sometime, in the near future hopefully. If that's true, how would I know what length pushrods to order (since they come with the package)?
EDIT: Every single answer to the pushrod length question is always "measure". Measure measure measure. I guess I won't be buying it as a package then but rather buy heads and cam, install, measure, then buy correct length pushrods.
EDIT: Every single answer to the pushrod length question is always "measure". Measure measure measure. I guess I won't be buying it as a package then but rather buy heads and cam, install, measure, then buy correct length pushrods.
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From: Turnin' Wrenches Infractions: 005
It should, its simple enough. Some people just dont get it. I had my engine ready to go together and back in my car and measured for PR length, then sat with my thumb up my *** for 3 days waiting for them. Thats just how it works 
That's the way to be, although not as feasible for some who use the vehicle as their DD and all. That's a long 3 days waiting, huh? Luckily the pushrods are light enough that rush shipping doesn't cost an arm and a leg (maybe just an arm).
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Not to thread hijack, but I am in the process of putting the new top end of my motor together (408ci iron block). My heads are untouched 241's. I know the block was decked, but the issue is I am unsure of how much. All that is on my build sheet is that the block was decked to achieve -.010 piston popup. I also made a cam swap from the TSP 233/239 to the TSP 248/254. I have been told that I may need a new pushrod length. I already have the Comp pushrod length checker. What is the easiest way to measure pushrod length? I have read that some people take lifters out and make them solid. I would prefer another way since my heads are already torqued on. I was planning on reusing my 7.400's, but this thread has me rethinking.
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From: Turnin' Wrenches Infractions: 005
Not to thread hijack, but I am in the process of putting the new top end of my motor together (408ci iron block). My heads are untouched 241's. I know the block was decked, but the issue is I am unsure of how much. All that is on my build sheet is that the block was decked to achieve -.010 piston popup. I also made a cam swap from the TSP 233/239 to the TSP 248/254. I have been told that I may need a new pushrod length. I already have the Comp pushrod length checker. What is the easiest way to measure pushrod length? I have read that some people take lifters out and make them solid. I would prefer another way since my heads are already torqued on. I was planning on reusing my 7.400's, but this thread has me rethinking.
From Shane at TR. This is the method I used and my motor has done perfect and is quiet.
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
Thanks for the reply. I will set my adjustable pushrod to 7.035 and start workin from there since I am told I MIGHT need a shorter pushrod to make up for the block decking. I am also running the thicker GM MLS headgaskets, not .040 Cometics, so I was hoping that would make up for the decking. But after reading this thread, I dont want to install the 7.4's and have them be too long. Once again, thanks for the help and I will post my (hopefully successful) results.
Last edited by CJJones87; Apr 22, 2010 at 02:59 PM.
Or, the other way to do it to save time is to order multiple lengths, LOL. Then you can start at the longest and go shorter until you get to the right preload.
That is why I have two news sets of push rods sitting around.
Anyone looking for some cheap. I guess this is the downside of doing it my way. But it did save me down time from ordering the other size.
Good Luck!!!
That is why I have two news sets of push rods sitting around.
Anyone looking for some cheap. I guess this is the downside of doing it my way. But it did save me down time from ordering the other size.
Good Luck!!!
