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343 pushrod length

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Jav69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jav69 Quote  Post ReplyReply Direct Link To This Post Topic: 343 pushrod length
    Posted: Sep/15/2018 at 8:11pm
Hoping for help. I have a 69 343. I wanted to upgrade my rockers. I got the compcam magnum 1442 roller rockers. I have a cam with a 477 valve lift. I did buy the comp cam adjuatable push rod. I know how to acheive proper geometry. The o ly thing im not sure of is if the these rockers are non adjustable. So my questin Is when. Measuring for geometry to get push rod length do i torque down to 24 lbs then measure push rods or do i line up the stock size push rods to 0 lash and then torque down to 24 lbs. Also i read somwhere that the 68 and 69 343s do to need guide plates due to integrated guides already in the pushrod holes. Anyone know if there is truth to this. I have seen the guides on my motor. Any info is greatly appreciated
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 8:36pm
It looks to me that they are a direct replacement for the factory rockers and would be non-adjustable as supplied.

Torque to spec then use your adjustable pushrod to set zero lash, remove the pushrod, measure it’s lengh and add the specified amount of preload to that length, that is the length of pushrod you require.

To make these rockers adjustable, you need to change to non-shouldered Chevy style rocker studs and add poly-lock nuts.

If the pushrods go through slots in the heads, then you don’t need guide plates, the original factory heads will be like this. If you are running some of the later model heads, you might need to add guide plates.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jav69 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 9:32pm
That was the most direct and exact answer i needed. Thank you. Your inpug is greatly appreciated
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jav69 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 10:54pm
Westerred. One more question. I have hydrolic lifters. Os there a set measurement for preload
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 11:33pm
There should be something with the lifters or use factory specs, not sure of numbers off the top of my head, somebody will know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2018 at 12:24am
Pre-load is normally around .040", though it can be as little as .020 or less or as much as .060". Generally speaking the lighter pre-load will give a bit more power, less friction and rev a bit better without pumping up. Lighter pre-loads are harder on valve parts and noisier. 

The standard thread pitch on the studs gives about .060" for one full turn. That is why roughly 1/2 turn is the usual pre-load from zero lash. This gives a good blend of quiet, power and reliability. 

Personally, I would use the adjustable rocker studs, though for a stock rebuild they are definitely not neccessary. Non adjustable means you need to get the pushrods right, adjustable buys you some leeway if you have shaved heads or other changes. With your cam, you should probably get the adjustables. 

Chris 

PS: I run the exact same lift as you, with adjustable studs and without guide plates. 


Edited by ccowx - Sep/16/2018 at 12:27am
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Jav69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jav69 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2018 at 9:26am
Thank you. This will get me where i need
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2018 at 6:50pm
Those are adjustable rockers in a kit, covers olds and ford and amc. need to adjust to 1/2 to full turn of preload
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jav69 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2018 at 6:57pm
Thank you
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/24/2018 at 5:28pm
Factory rockers converted to adjustable, non-shouldered studs:



Polylocks:



Same would apply to the crane roller tip rockers.
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