Rocker roller coversion for 502 - push rod length? - need valve train expert
 

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.

I wander why none of the three companies i have talked to has mentioned that it takes a longer stud with roller rockers. Even when the set was bought it wasn't mentioned. That was when i had the heads off and could have done it easy.
One person i know changed from original stamped steel to roller types and did not have to go to a longer stud.

I'm just trying to make sure something else is not wrong before I have to pull the heads (that i just put on) to drill and tap the 3/8 out.

You're also going to need to spend another couple hundred dollars for taller valve covers too. I think the pro comp steel rockers have the roller tip but still use the bushings and work on the stock stud.

I just put full roller rockers on my 502. Biggest pain in the ass dealing with new push rods, new valve covers, and chasing down the correct poly locks because Summit sent me a kit missing parts (that's a different story). At this point I should've just stuck with the stockers, lol.

Well i've just spoken to two performance engine builder shops and both said that nothing should be needed to make this change to the roller rockers and if using the 1.90" studs. If there's not enough threads above the rocker, something is wrong. No need to go to a longer stud. That would also require to drill the guide plates or use adjustable guides.
I will keep looking at it. Going to get another pair of eyes on it.

Dumb question, but are you certain the valve you are working on, that the lifter is on the base circle of the cam when you set the rocker on there?

Also sure you got the correct # rocker for a big block chevy?

At this point I don't think there is a dumb question. Something sounds completely messed up. Can you post some pics or send to someone via tx so they can post. I've run into some weird chit over the years but... I can imagine mild thunder hated to even write his last post but sometimes you just gotta ask those questions as everybody has different abilities. I have a feeling it's an oversight. Walk away and come back and look at it again. I saw a great engine builder that couldn't get the distributor to drop in all the way. After several aggravating minutes for him I had him pull back out. He had the gear on upside down. True story.

Another possibility. The pivot shaft on the rockers. May have a high side and a low side with a flat machined for poly to seat against and might be flat facing down and poly seating against rounded bottom side...

at least were all coming up with something.

Mildthunder... yes im on the base circle. And part # is from engine Pro #1114. He says there is only ONE rocker from his company for a BBC. I feel like ordering a different brand. May go to a local engine shop tomorrow and look at various used rockers to compare the trunion size.

DereknKathy... are you talking about the small flat machined recess area on one side of the barrell(trunion) on the rocker? Yes i have looked at that. All cylinders are doing this identical.

Good questions. I dont mind yall asking as i do have limited experience, but getting good advice from a relative with mega experience. So far, things are just not adding up.

We just put the old stamped rocker back on just to look at it. It pushed the lifter down about 0.050"(about equal to one thread on the new adjustable rockers) when it bottomed out so that looked about right. To reach that same spot with the engine pro rockers we are at only 4 1/2 threads .. a little less than 1/4" ... not enough.

I will take pics.

These Engine Pro Rockers wouldn't happen to be private labeled from Speedmaster (used to be ProComp) would they ?

https://speedmaster79.com/engines-co...t=238&limit=36

Engine Pro : http://www.enginepro.com/downloads/n...RockerArms.pdf


Speedmaster BBC :https://speedmaster79.com/media/cata...B-SSTEEL_1.jpg

Wondered where u been.

i am a firm believer ,you get what you pay for,or less.

Smelling Chinese food. Hah !

BTW: I don't know who makes Engine Pro Rockers, but I never seen anyone with them and I smell something fishy......Chinese fishy....lol.

I know engine pro rods are manleys, their bbc hydraulic lifters are morels, just like howards, lunati, erson, and others. Their balancers are powerbond/dayco , and alot of stuff is made by the big companies . I have not known them to sell chinese crap . They supply alot of professional machine shops with parts. Not sure about their rockers though.

Good info.

Much like what PBM does then...but, PBM's house brand block was a ProComp. So....one needs to find out before they assume and buy something.

Part numbers look familiar ? 4603, 5045, etc lol

[ATTACH=CONFIG]554452[/ATTACH]
The number of threads gripped by the nut is a little bit less even than what shows because the first 1/8" or so of the rocker nut has no threads.

[ATTACH=CONFIG]554453[/ATTACH]

[ATTACH=CONFIG]554454[/ATTACH]

[ATTACH=CONFIG]554455[/ATTACH]

yeah I see the rust too, but nothing like it looks. Actually fairly smooth.
I had moisture from pretty bad reversion and condensation in the manifolds that i am working on correcting also.

[ATTACH=CONFIG]554456[/ATTACH]

does anyone have the lengths for the stock pushrods. A little hard to find it.
One site showed Intake 8.280 My current ones in the motor are 7.625

exhaust 9.252 my current is 8.625


But i don't think changing the lengths would help any because shortening them would drop the rocker, but as the pics shows, the rod cant be much shorter at all are the taper at the rod end will be in the guide.

GEN VI 502, black motors, not blue motors:

GM# 10227762 8 Rod Int, Vlv Push 7.575 in
GM# 10227763 8 Rod, Exh Vlv Push 8.525in

This is from my notes...but...that doesn't mean they are correct LOL.

Edit in: just did some checking and it looks like above is correct.

that pushrod is clearly wrong.you need longer pushrods on exhaust for sure.

What does the pattern look like when you marker the valve stem and roll the engine over ?

Well i did eyeball it to see if it looked close, but i need to do that now. Was kind of concentrating on the stud thread issue but i need to do that. Will do that in the morning and reply.

mike - i may need them for the proper angle, but if i went to longer pushrods, there would be even less threads on the stud above the trunion. Probably would barely be able to start the nut on the stud.

So I'm still trying to figure out why not enough threads sticking above the trunion when all the shops i have talked to tell me i should NOT need a longer stud-something else is not right. i am going to call Harland Sharpe tomorrow and talk to them to see if they have ever run across this issue.

Something is way out wack. Those exact 3/8 bottom-7/16 top rocker studs have been used by Merc on all the HP500's with Crane Gold Rockers.
I also used them when I upgraded the cam in a 454mag and went with roller rockers.

It looks to me like valve and spring are sitting too high. What is the installed height????

Are the valves and springs new????

Do you have the flat side side of the fulcrum facing up?????
It looks like its the round side in the pic????


BTW, I think adding roller rockers to a stock 502mpi is a waste of time and $$$.