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Pushrod length ?????

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Old 11-11-2008, 11:30 PM
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Default Pushrod length ?????

OK, I've been going over and over everything I've done to my motor looking for little bits of HP here and there. I've now discovered that my pushrods might be too long. What issues will come from having pushrods that are too long? How does it affect the power? Any advice would be great. Thanks
Old 11-12-2008, 12:15 AM
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How much too long? Might have EXTREMELY low compression numbers.

I would suggest a pushrod checker. Figure out length at zero lash and add .08-.10 for preload and growth.
Old 11-12-2008, 08:42 AM
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I am using 7.4 pushrods so I doubt I am much too long. Ijust had my heads milled for this setup and didn't even think about that until now.
Old 11-12-2008, 09:38 AM
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Get a push rod length checker and find out what you need...

Last time I did it on dry lifters it was a very sensitive operation.. I set it to 7.000" and expand the tool in single turns until it stops spinning.. but it's DELICATE! You can't spin it like threading a bolt by hand, it's like you have to use the tips of your fingers.. . My buddy and I both did it twice and we came up with the same measurement..

Then add .050 - .075 on to your measurement for preload... (IIRC) After my H/C swap, I ended up with a final number of 7.350... So the 7.400" hardened pieces would work fine. ( .050" of preload won't kill a lifter... IMO)
Old 11-12-2008, 10:31 AM
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Originally Posted by bayer-z28
Get a push rod length checker and find out what you need...

Last time I did it on dry lifters it was a very sensitive operation.. I set it to 7.000" and expand the tool in single turns until it stops spinning.. but it's DELICATE! You can't spin it like threading a bolt by hand, it's like you have to use the tips of your fingers.. . My buddy and I both did it twice and we came up with the same measurement..

Then add .050 - .075 on to your measurement for preload... (IIRC) After my H/C swap, I ended up with a final number of 7.350... So the 7.400" hardened pieces would work fine. ( .050" of preload won't kill a lifter... IMO)
Good advice! To add to it, the lifters actually run quieter with some preload on them. GM sets them up as high as .100" on some engines! We typically recommend .050"-.080" on stock lifters or the LS7 lifter kit.
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Old 11-12-2008, 10:49 AM
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Originally Posted by 05JUDGE
OK, I've been going over and over everything I've done to my motor looking for little bits of HP here and there. I've now discovered that my pushrods might be too long. What issues will come from having pushrods that are too long? How does it affect the power? Any advice would be great. Thanks
My builder swapped in a comp cam and ported heads in my 05 LS2 Vette. The original pushrods were 7.40" and with the .030 milling of the heads he said the new pushrods needed to be 7.35". I am not sure how much difference that would make on the engine's performance. But he advised me when we got the heads back.



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