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1974 LS4 - Pushrod Question

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Old 04-25-2014, 08:35 PM
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Ryoga23
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Default 1974 LS4 - Pushrod Question

Prior to my purchase, the engine was just recently rebuilt to fully stock parameters, and in the process one of the rockers was overtightened and resulted in a bent pushrod.

So NOW, I'm working on replacing the pushrods, but the parts store tells me that they have two different diameters listed for my model year. The ones they said would be the best match are spec'd:

.310 inch
8.28 inch

and

.310 inch
9.252 inch

What exactly ARE the stock dimensions? Do I need to worry about the guides?

On that same note, I noticed that it looks like some of the rockers are 'shinier' than the others. I get the feeling that several have been replaced in the rebuild - they look to be the same overally, but is this okay, or do I need to replace all of them to be certain there are no differences.

Fun stuff!
Old 04-25-2014, 09:26 PM
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Mooser
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Originally Posted by Ryoga23
Prior to my purchase, the engine was just recently rebuilt to fully stock parameters, and in the process one of the rockers was overtightened and resulted in a bent pushrod.

So NOW, I'm working on replacing the pushrods, but the parts store tells me that they have two different diameters listed for my model year. The ones they said would be the best match are spec'd:

.310 inch
8.28 inch

and

.310 inch
9.252 inch

What exactly ARE the stock dimensions? Do I need to worry about the guides?

On that same note, I noticed that it looks like some of the rockers are 'shinier' than the others. I get the feeling that several have been replaced in the rebuild - they look to be the same overally, but is this okay, or do I need to replace all of them to be certain there are no differences.

Fun stuff!
The BBC pushrods are 2 different lengths. The 8.28 are the intake and the long ones are the exhaust
M

]
Old 04-25-2014, 10:42 PM
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Ryoga23
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Originally Posted by Mooser
The BBC pushrods are 2 different lengths. The 8.28 are the intake and the long ones are the exhaust
M

]
I just pulled the ones that were in it, and the seem to be just slightly shorter on the intake side than the dimensions of the ones on order, about .15inch less roughly.

I'm assuming that's not a show stopper for me?

As to proper install procedure I keep finding conflicting info - all sources say to tighten rockers to the 0 lash point by going until the pushrod no longer has and spin/play. But from there I've seen some say take it a 1/2 turn more, some 3/4 and a full... Which is real here?
Old 04-25-2014, 11:07 PM
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Mooser
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Originally Posted by Ryoga23
I just pulled the ones that were in it, and the seem to be just slightly shorter on the intake side than the dimensions of the ones on order, about .15inch less roughly.

I'm assuming that's not a show stopper for me?

As to proper install procedure I keep finding conflicting info - all sources say to tighten rockers to the 0 lash point by going until the pushrod no longer has and spin/play. But from there I've seen some say take it a 1/2 turn more, some 3/4 and a full... Which is real here?
I'd question a .150 shorter push rod. Non-stock lengths would usually mean someone's changed the cam, rockers or something. Set the cam to position a lifter on the base circle, pre-load it (1/2 turn), rotate the engine, and see where and how wide it's contacting the valve.

As for setting the lifters, it's all doing the same basic thing, some people set them shallow, some deep.
If you want, send an email to Lars (v8fastcars@msn.com) and ask for his paper on setting valve lash and make your own choice
M

Last edited by Mooser; 04-26-2014 at 07:59 AM.

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