pushrod length?
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
Originally Posted by Z06 Steve
what length?heres the combo.afr's 205's milled.024 62cc,40 cometics.224/228 114+1 cam.anyone with this combo?
Last edited by ArKay99; May 17, 2005 at 05:25 PM.
Le Mans Master
Joined: Dec 2003
Posts: 5,561
Likes: 448
From: Atlanta metro Ga.
Well, you lost length with the base circle on the cam (what is the lift?), but you gained it back w/ the head milling.. There are ways to calculate this stuff.. I downloaded a pushrod calc from LS1tech just last week.. (ex. I'm installing an LPE GT2-3 cam.. All other parameters stock.. I'm going for 7.425" push rods. Stock 7.4" are a bit too short to retain lifter preload.)
Lot's of folks run bigger cams and don’t change the pushrods.. Lots of folks have motors that sound like sewing machines as well. It will work, but is it "correct?"
IMHO you should either calculate the proper length, or get one of those measuring push rods.. Or at least take an educated guess.
Lot's of folks run bigger cams and don’t change the pushrods.. Lots of folks have motors that sound like sewing machines as well. It will work, but is it "correct?"
IMHO you should either calculate the proper length, or get one of those measuring push rods.. Or at least take an educated guess.
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
Dan, you are correct. I dl'ed that calculator also. But for it to work correctly you need to know the base circle measurement. I don't see that as a published spec from the cam companies and it would take some of the guesswork out of it. It's different for different lifts, as you probably know. That's why we bought the pushrod measuring tool. I set it for different lengths and measured my preload with a dial indicator. With 7.400" pushrods I got .112" of preload and the rocker tips were off center of the valve stem tip. With 7.350" I got .062" of preload. More importantly the rocker tips were 'centered' on the valve stem with 7.350" on mine. We found on BLACKTOP2000's that the 7.400" were much closer. Also with an .040" gasket you are effectively 'milling' an extra .012" of the heads.
Racer
Joined: Mar 1999
Posts: 413
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From: Pennsville, NJ
I have that exact setup and I measured .095 with the 7.4 and .040 with the 7.35's (don't ask me where the other .005 went 
). Right now, I'm getting a new shortblock at ECS and they're keeping the 7.4's in it. Except now, I have the .045 Cometics. When I did my measuring with a dial indicator, I had .040 Cometics...
). Right now, I'm getting a new shortblock at ECS and they're keeping the 7.4's in it. Except now, I have the .045 Cometics. When I did my measuring with a dial indicator, I had .040 Cometics...
Last edited by Byter; May 18, 2005 at 05:27 AM. Reason: Added Cometic info...
Burning Brakes
Joined: Feb 2004
Posts: 885
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From: Point Pleasant wv
You can measure to find out if they are too long or too short! Take two of the rockers off and take a marker and coat the end of the push rod turn the motor over a couple of times without starting it,remove the rockers if the tip is clean it were you want not too short or too long , if its wear off the intake side its too short if its off the exhaust side too long ! Hope this helps ! 
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Originally Posted by Z06 Steve
what length?heres the combo.afr's 205's milled.024 62cc,40 cometics.224/228 114+1 cam.anyone with this combo?
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Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
Originally Posted by Flareside
-.024" for the heads, -.014" for the gaskets (if stock is .054"), +.040" for the cam (I have a Comp XER 220/224 and have measured it). Total difference from stock is only -.002", or almost nothing, so you need stock length 7.400" pushrods to stay at the stock preload. Hope this helps.
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Originally Posted by ArKay99
Flareside, are you saying the base circle is -.040" or -.080"? If it's -.040" it is only -.020" less preload. I think you need to take the radius for a preload calc, not the diameter. Still, it's only -.022" so a 7.375" pushrod would be called for.
I've also measured the stock LS6 cam, and found .050" smaller diameter, or .025" smaller base circle, and my LPE that's .100" smaller, or .050" base circle. I'm yet to measure an aftermarket cam that's actually the .030" number that lots of people throw around on the forums.
Safety Car
Joined: Sep 2003
Posts: 3,558
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From: Cape Coral FL
Originally Posted by Flareside
No, the XER lobes I've measured are around ~.080" smaller (as measured with a mic), depending on the exact lobe. .040" is the difference on each side of the lobe, hence my base circle calcs. This stuff is easy to mix up for sure, but I think I have it right.
I've also measured the stock LS6 cam, and found .050" smaller diameter, or .025" smaller base circle, and my LPE that's .100" smaller, or .050" base circle. I'm yet to measure an aftermarket cam that's actually the .030" number that lots of people throw around on the forums.
I've also measured the stock LS6 cam, and found .050" smaller diameter, or .025" smaller base circle, and my LPE that's .100" smaller, or .050" base circle. I'm yet to measure an aftermarket cam that's actually the .030" number that lots of people throw around on the forums.
We need to keep in mind though that the stock pushrods are 7.380" in length, not 7.400".
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Originally Posted by ArKay99
We need to keep in mind though that the stock pushrods are 7.380" in length, not 7.400".
Depends on who you talk to. I can tell you that the stock pushrods in my 03 are 7.400, I've measured them myself. Every online catalog I've seen also lists stock as 7.400" (Comp, Manley, Scoggin Dickey, etc.)
Safety Car
Joined: Sep 2003
Posts: 3,558
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From: Cape Coral FL
Originally Posted by Flareside
Oh geez, not that can of worms... Depends on who you talk to. I can tell you that the stock pushrods in my 03 are 7.400, I've measured them myself. Every online catalog I've seen also lists stock as 7.400" (Comp, Manley, Scoggin Dickey, etc.)
Depends on who you talk to. I can tell you that the stock pushrods in my 03 are 7.400, I've measured them myself. Every online catalog I've seen also lists stock as 7.400" (Comp, Manley, Scoggin Dickey, etc.)
I know. But GM has them listed as 7.380". I got that info from the parts catalog. I remember reading an informative article on one of the cam sites, Comp or Crane, that showed the differences in the types of pushrods and how to measure them. One manufacturer's or style of pushrod will be different than anothers... 
I wish I had a 7.5" caliper, mine's only 6". I also know about what all the vendors state as stock length... Bottom line, I believe, is to buy a pushrod length checker, establish the proper rocker arm height by checking the valve stem wipe pattern and shim if necessary, then set the preload to .060" cold for stock lifters, or the manufacturers spec for 'special' types.
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Originally Posted by Z06 Steve
I'm getting 7.4's and 7.350's as the ones to use but flareside is making some good sense.
If you really want to make your head hurt, think about the rocker arm wipe that ArKay99 mentioned above. His procedure to check it is right on, but you'll need an adjustable pushrod and a set of "checker springs" that are weaker than the plunger spring inside the lifter to get an accurate measurement. Otherwise, the lifter plunger will start sinking as soon as the lifter rises and throw off all your measurements.
If you haven't changed the rocker or valve, the wipe should be pretty close. Unfortunately, when you get into higher lift cams it gets out of whack, and then you have to start moving the rocker to keep it centered on the valve stem during its full travel.
Pushrod length will not effect this, it only changes the position of the plunger inside the lifter (so, pushrod length cannot change the wipe).
