I supposedly have a stock 1999 502MPIMag that i bought in a boat last year. I have just done a valve job by a knowledgeable person and R&R the heads myself. I am installing ENGINE PRO rocker rollers and pulling the stock stamped rockers.

The stud for the rocker only protrudes through the new rocker about 4 threads(1/4 inch or so). Looks like i need about 0.3 shorter push rods to get the stud protruding higher above the rocker and get the 8-9 threads with the adjusting nut that AFR recommends and which does make sense. Other people i know that have converted did NOT need shorter push rods-just changed the rockers out.

Point is..... Why should i be needing to shorten the rods, and having to buy lower guides, when others i know have not. EVERYTHING seems in place correctly from the heads to valves to studs to lifters. Stud length is 1.900. Installed valve height has been checked. lifters are bottoming out. Cam in correct rotation for each cylinder, etc. All valves are identical - not enough threads above the rocker.

Pretty much at a loss here at this point. thanks for any advice.

Also, if i put in the shorter push rods, that will put the push rod guide just into the taper part at the end of the push rod and put the guide 1/4 inch from the rocker... seems odd. I believe there are shorter guides available though. Need some suggestions on what is different here.

My push rods are 7 5/8" intake and 8 5/8" exhaust. I believe stock is supposed to be 8.280 and 9.252 per tech at a nationally know cam company.

I think if you shortened your pushrod the geometry would be off, a longer rocker stud would be the fix same thing I went through months back.

Yepp, ARP has what you need.

get longer studs,magic marker the top of the valve,use your push rods(stockers),roll engine over,check paattern on top of valve stem.should be tight and in the middle for the most part.adjust length accordingly.

It does sound like you need taller rocker studs. Arp makes many differnt sizes.

Pushrod length isnt determined by threads on the rocker stud. Threads on the rocker stud, are what you deal with after you get the correct geometry.

Like sutphen says , you need to follow the procedure for checking pushrod length. Once that is established, you see what changes you need to make. Roller rockers themselves are very different from brand to brand, in how they effect the geometry, let alone going from a stamped rocker to roller.

Some checking springs, adjustable pushrods, and a valve spring compressor are what you need. Dont pay attention to what the books say you "should" need for pushrod lengths, you just need to check it. Variances in lifter seat heights, valve lengths, rocker style, rocker ratio, etc all play a part.

Also, check to see if your rocker tips are centered when doing this. Dart makes some adjustable guide plates that are cheap and easy to setup.

It sounds like a pain in the azz, and it kinda is , thats why on a stock 502 mag, i wouldnt bother changing things , unless of course a cam swap was done. Stock, hardly think its worth the effort and cost to replace a 1.7 stamped with a 1.7 roller rocker.

Well said.

I have checked with ARP and other places and they said they do not have a longer stud than the ARP ones i bought.
These are 7/16" on the rocker, by 3/8" in the head.
They are 1.90" from the machined side (opposite side) of the hex nut, to the end of the stud. Basically 1.9 includes the hex.

I agree thats pretty much all i need and cannot locate longer ones than the 1.9. Checked ARP, Engine Pro, Comp Cams so far.

thank again folks. Getting short on time before the Tickfaw 200 near New Orleans, La.

I agree.

now i understand,you are going to need to drill&tap the heads for 7/16 threads,then you will have no problem- finding the correct length rocker stud.