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OK, so which is it? (Pushrod length)

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Old May 19, 2011 | 04:19 AM
  #1  
watajob's Avatar
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From: Location, Location!
Car: 92 T/A 'vert
Engine: Mild .040 over L98 4 bolt mains
Transmission: Mostly stock 700R4, 2600 Vigilante
Axle/Gears: LS1 3.42
OK, so which is it? (Pushrod length)

Some call for centering the wear pattern. Others, the smaller the wear pattern, the better even if it is off center on the valve tip. Do I flip a coin? I'm gonna' wear out this checking pushrod!
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Old May 19, 2011 | 09:36 AM
  #2  
oH HorizoN's Avatar
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Joined: May 2011
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From: Arizona
Car: 1989 IROC-Z Camaro 'Vert.
Engine: 350, ZZ4 motor
Transmission: TH-700R4
Axle/Gears: 2.73 ... for now.
Re: OK, so which is it? (Pushrod length)

I was always told centering it, never heard of the other opinion.
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Old May 19, 2011 | 11:14 AM
  #3  
Apeiron's Avatar
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: OK, so which is it? (Pushrod length)

Go for the narrowest pattern. If all your components agree perfectly, this will also be centered on the valve stem.
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Old May 19, 2011 | 01:44 PM
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watajob's Avatar
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From: Location, Location!
Car: 92 T/A 'vert
Engine: Mild .040 over L98 4 bolt mains
Transmission: Mostly stock 700R4, 2600 Vigilante
Axle/Gears: LS1 3.42
Re: OK, so which is it? (Pushrod length)

I get a nice, tight pattern, with the stock length stick, (7.20), but it's almost 2/3 the way outboard. If I get it more centered, the pattern gets noticeably bigger and shows a push rod shorter than stock, which is REALLY confusing. I mean, I realize a shorter rod moves the pattern towards the inboard side but was under the impression that a bigger cam almost always needed a longer stick just to get back to where the stock one was. BTW, I've got Trickflow heads, (brand new, uncut), Scorpion 1.6's, Delphi/GM lifters, Mr. Gasket head gasket, (.038 compressed which is real close to stock from what I've been able to gather), the block is not decked but it is a small house cam grind. I'm starting to wonder if there's a problem with that. Although, the cam was run on a cam doctor and pronounced healthy.
Attached Thumbnails OK, so which is it? (Pushrod length)-cam-specs-small-.jpg  
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Old May 19, 2011 | 03:38 PM
  #5  
Apeiron's Avatar
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: OK, so which is it? (Pushrod length)

Originally Posted by watajob
a bigger cam almost always needed a longer stick just to get back to where the stock one was
If you only changed the cam, but you've changed everything.

Some things that affect the pushrod length are the base circle, lobe lift, lifters, rocker geometry, head geometry, valve length, valve seat depth, head gasket thickness, deck height and trueness...
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Old May 19, 2011 | 03:54 PM
  #6  
watajob's Avatar
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Joined: Sep 1999
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From: Location, Location!
Car: 92 T/A 'vert
Engine: Mild .040 over L98 4 bolt mains
Transmission: Mostly stock 700R4, 2600 Vigilante
Axle/Gears: LS1 3.42
Re: OK, so which is it? (Pushrod length)

So, a shorter push rod is not unheard of? Cool.
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