Need help and advise on valve adjustment with non adjustable rocker arms & shaft

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willyraz

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I did a engine swap in my sons 72 Duster from a slant6 to a 318 (1976 LA engine) that I had bored out .060 to clean it up.

I put in a Mopar purple Hydraulic flat tappet cam 4552761 268/272 degree 450/455 degree lift. We put a Edelbrock intake and 1406 carb on it. It's in the car and getting close to turning the key but I need to adjust the valves. The valves and seats have been cut so how do I go about adjusting these things?

I see summit makes a pushrod tool. This is my 1st Mopar rebuild heck it's my 1st rebuild of any kind in some time.. So what's the best way to check and do this?? Do you use this pushrod adjusting tool and then have to get diffrent lengh push rods or is it a must for a rocker arm change to the adjustable type.. What do you all recommend. I would like to do it right but with a limmited budget.
 
on a general rebuild,which sounds like what youve done, you shouldnt need to. now if you have had the heads cut the block decked u might want to set up a dial indicator and check how much preload your putting on the lifter. most all makes should be between .020-.080. personally i like them on the looser side. if im not mistaken, i think you can use the shafts and rockers from a 273 as they are adjustable due to those engines being factory equipped with mechanical cams. hope this helps and anyone please correct me if im wrong mt
 
There is no adjustment with the stock stamped steel rocker arms. If no material was removed off the deck or head sealing surface then there should not be a problem but the lifters should be checked and this is the way I do it. Start at no.1 cylinder TDC end of compression. With the rocker arms and rocker shafts all assembled and push rods in you should be able to push down ever so slightly on the push rod end of the rocker arm and feel the piston inside the hydraulic lifter compress, as long as you put the lifters in dry that is. If you can feel and if you want to measure with a dial guage, that the lifter pistons are compressing, lets say, .080" before bottoming out then you're close to the middle of their travel and good to go.
 
Try your stock rods and see if you get the suggested preload, if not measure with the tool and purchase new rods. Adjustables are not a must. If you do get adjustables match the adjuster to rod ball and socket.
 
If you are getting to much preload you can shim your rocker shafts. If you are not running enough preload you will need longer push rods. Or just get a set of 273 rockers and problem solved. I have installed shims up to .050 to compensate for milled heads.
 
Rocker geometry is not the same as pushrod length. The two are dependant on each other because the valve stems are leaned in slightly towards the rocker shaft. So when you raise the shaft, you effectively move the rocker's contact point towards the outside edge of the valve stem.

The valve job is crutial to proper rocker geometry with a shaft rocker system. If a shop sinks valves without reducing the stem length, or can't get all the seat heights in the same spot, you will have rocker/geometry issues. If the heads or block are milled or the head gasket you chose is different from the factory, the pushrods will be a problem. The right way to solve a pushrod probem is new pushrods. The right way to fix a geometry issue is have a good shop do the valve job from the get-go.
 
If you do use the 273 rockers you need the shaft as well. Stock clam shell rockers are hardened and run on a soft shaft, the 273 rockers are cast and need to be on a hardened shaft.
 
You could. Just like the rocker shaft shims. But at least in my opinion it's not the right way to do it. Assuming the caps fit your retainers, you'll end up with the rocker pushing the valve stem more sideways than it should as it goes thru the lift cycle, and will end up with faster guide wear. If the geometry is already not great, it can make the valvetrain less stable, leading to lower rpm potential and power too.
 
If your machine shop did their job correctly, no adjustment is necessary.
 
well they use a straight edge to check for equalized stem heights and set geometry, to start. like starting at one end and check with rockers being used, then do the opposite end and height and then with all valves installed....the straight will be raised up by the taller stems.....with a feeler gauge measure the gap between straight edge and already set end valves, thats the amount u need to cut from the taller stems....or u can start in the middle and feeler gauge the gap the end valves create...however u want to do it..lol

then they use an adjustable push rod to dial in the required push rod length 'since head gaskets and milling of heads/block will change required lengths' ...then once the length is found to provide the necessary .030 or so of pre load...they order up a set of custom push rods.
 
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