Originally Posted by Horsepoweraddiction
I really don't know but I'm guessing 1.75 seems right and all I'm wanting to do is just swap the stock rocker arms for the set of rr arms .
Yes but it's not always as simple as the ad guys make it sound. The Devil is in the details and sometimes this doesn't even make it to the fine print. You are going to have to pull a rocker off and measure the stud length from the stud boss up. If these are indeed 1.75 inch studs then you're going to have to order something longer. A quick and dirty way of getting into the ball park with this is to stop at the hardware store and buy a foot length of 7/16ths USS course threaded rod with 3 matching nuts.
Go back to the engine to remove a rocker and its stud. Put a mark on the end of this valve stem with a permanent marker pen (blue, red, black something you can see scratches in). Screw in the threaded rod till it won't go, mark the rod where it meets the top of the boss this might need to be a filed groove so it isn't wiped off by movement, then run one of the nuts down to lock it in place. Now I guessing that the push rods are the correct length, if they aren't we have another problem but we don't know that yet. With the push rod in place drop the rocker down the threaded rod and run the other nut down till the lifter is correctly adjusted if a hydraulic or lashed if a solid. For a hydraulic you can't just use the rule of turns because the rod has course threads where the rocker stud is fine. But take a guess at how far it will turn to sink the lifter's plunger about .020 inch below the retainer. Once lashed up properly drop the third nut down and lock the nuts together without losing the lash adjustment. Now you're going to check for the push rod length by seeing where the rocker sweeps the valve stem end. Given the other rockers are being held on with only three turns of the nut, I'd take them all off before pulling the engine around by hand, take the spark plugs out it'll be a lot easier. After doing the rotation a couple three times bring it around to where the valve you're checking on is closed. Remove the rocker and check the travel path in accordance with the direction on this link:
COMP Cams® - Sorry...
Don't know about the "sorry" but it works when I link it from here.
If what you got doesn't match this data sheet, you need different length push rods. To find what the correct length push rod is you will need to either buy or make an adjustable length checking push rod. Many of the commercial length checkers are not strong enough to not bend against full spring pressure, so another trip to the hardware store may be in order to buy a couple feet of 5/16ths threaded rod, a threaded coupler and a couple nuts. Cut the rod in half, take a file or grinder and round one of the ends on each length. Cut each length so when connected with the threaded coupler a rod is produced that ranges from shorter than the push rods in the engine to longer. Run one of the nuts down to the coupler from each end so when a measurement is being tested the coupler can be locked at the needed length. Use whatever push rod checker you have and rerun the stem sweep till it's correct. Once the sweep is correct mark the threaded rod serving as the stud as to the top of the nut holding the rocker in place. Remove that nut, unlock the stud retention nut and measure between the earlier mark and the latter mark and you've got your rocker stud effective length. The push rod length can then be determined from the push rod checker. Try to get push rods that are within .05 inch or less. More than that will require a custom length. Do this whole operation for an intake and exhaust pair. A little variation is to be expected across the whole of the cylinders as valves are seldom sunk to the same depth on their seats especially after a valve job has been done, so don't get crazy over perfection in sweep marks and push rod lengths.
I plowed through this really fast so I’ll apologize for any spelling and grammar errors now.