another push rod question

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gunmetal72

gunmetal72

Life is a dark ride
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Well here I am asking for help yet again. I am measuring for push rods but I am not sure where the set screws on he rockers should be to get the correct length. Currently I have them set all the way in and the average measurement with is 6.75" or 171 mm. This is on a hrd roller lifters in a 340. Should the set screws be set all the way in? Also, where is the best place to buy push rods?
 
Adjusters should have about two threads showing under the rocker arm. IMO.
 
...or use Manton for pushrods. I'm no expert, but typically no more than two threads showing. I've only done stud mounted Magnum small blocks and big block stuff.

Have you verified that your rocker arm geometry is correct? You need to get them set up at the correct height first to get proper valve tip sweep. If not, be sure to do this before ordering pushrods.

What rocker arms are you running. T&D's require a specific amount of threads to be showing for oiling purposes. Others may or may not be the same.
 
Manton has a huge selection from toothpicks to baseball bats. pull tip out of a slant pushrod and start cutting tube. put tip back in and mock up/check, keep cutting and testing until you get your optimum length. measure and order. practically free.
 
Mopar Tim said:
Adjusters should have about two threads showing under the rocker arm. IMO.
Click to expand...
x2... I would set them like this to start. As you are checking, rotate the engine through a full 2 rotations and watch the cup to ball interface at the rockers to see if all stays clear.
 
I have measured 5 exhaust & 5 intakes with about 2 threads showing, All are within 0.30 of each other. When I order from Smith Bros. should I use the average of all 10 measurements?
 
Yes, that is a good plan and then adjust the adjusters to compensate.

Read up on the Smith Brother's site and make sure you measure the ball&tip pushrods like they tell you to do. IIRC, they use 'effective length' which is measured tip-of-ball to bottom-of-cup.

FWIW.... when you check for clearance from the cup edges to the rockers as you work through this, keep in mind that your checking pushrod cup may be shallower than the final cups. Our checking pushrod cups were .145" deep, and the real ones were .185" deep. So we needed to make sure that the checking pushrod cups cleared the rockers on all side by at least .090" or more to be sure we would have a decent clearance with the real pushrod cups of about .050" (or more). Just a minor subtlety for you to keep in mind to avoid any surprises.
 
If you have a very high lift it may be an issue. If you rotate the engine a couple of times the measuring pushrods in place, and you have clearance, you are good; if uncomfortable, or they touch at all, grind the holes out a bit. The pushrods are not going to move around much if the valves don't float and you get decent pushrods that don't flex. I don't get the impression that you will revving to 6k+ RPM all the time, like a circle track engine, where those issues become more of a concern.

I forget, what rockers are you using?
 
nm9stheham said:
If you have a very high lift it may be an issue. If you rotate the engine a couple of times the measuring pushrods in place, and you have clearance, you are good; if uncomfortable, or they touch at all, grind the holes out a bit. The pushrods are not going to move around much if the valves don't float and you get decent pushrods that don't flex. I don't get the impression that you will revving to 6k+ RPM all the time, like a circle track engine, where those issues become more of a concern.

I forget, what rockers are you using?
Click to expand...

They are PRW https://www.prw-usa.com/product/3231811-sbm-pqx-platinum-series-steel-shaft-rocker-arm-system
 
OK, well you may have another task. These rockers' spacers between the rockers need to be set up so that the rockers align with the valve tips AND the side clearance between the rockers adjusted with the shims to a certain range of clearance. That clearacen controls oil flow and needs to be right. The PRW instructions suck.... so you should read up on this here. This should be done first and the real pushrods installed and then the pushrod-to-hole clearance checked.

And BTW, if your checking pushords are the ones that come with the PRW kit, those PRW checking pushrods are SOOOOPER fat... much, much fatter than actual pushrods. So if these PRW checking pushrods are tight to the Edelbrock pushrod holes, ignore that. The real pushrods will have MUCH more clearance to the pushrod holes; don't sweat it. My son and I ran into the exact same thing on his 340 with PRW checking pushrods and Edelbrock heads. The real pushrods have beaucoup clearance.
 
nm9stheham said:
OK, well you may have another task. These rockers' spacers between the rockers need to be set up so that the rockers align with the valve tips AND the side clearance between the rockers adjusted with the shims to a certain range of clearance. That clearacen controls oil flow and needs to be right. The PRW instructions suck.... so you should read up on this here. This should be done first and the real pushrods installed and then the pushrod-to-hole clearance checked.

And BTW, if your checking pushords are the ones that come with the PRW kit, those PRW checking pushrods are SOOOOPER fat... much, much fatter than actual pushrods. So if these PRW checking pushrods are tight to the Edelbrock pushrod holes, ignore that. The real pushrods will have MUCH more clearance to the pushrod holes; don't sweat it. My son and I ran into the exact same thing on his 340 with PRW checking pushrods and Edelbrock heads. The real pushrods have beaucoup clearance.
Click to expand...

Yup, that is what I ran into with the checker push rods. Maybe the 5/16 rods will have plenty of room. I set up the rockers so they re directly over the centre of the valve stem. There is about 0.20 clearance the rockers. They move very smooth and seem very stable. I think they will be ok
 
OK on all, yes, just ignore the PRW checking pushrod tightness to the holes; the real pushrods will be fine for typical lift numbers. FWIW, we put our side clearance at .017" on an AL PRW rocker set, and others have mentioned .015". I just wanted to be sure you had done it at all!
 
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