Screw in studs with factory heads
#1
Screw in studs with factory heads
I was wondering about when converting a factory head to screw in studs, is it mandatory to machine the rocker pad surface for the thickness of the guide plates? I just wondered why- figuring you would have to use a custom pushrod anyway and if that .100 or so thickness made a difference?
#2
I was wondering about when converting a factory head to screw in studs, is it mandatory to machine the rocker pad surface for the thickness of the guide plates? I just wondered why- figuring you would have to use a custom pushrod anyway and if that .100 or so thickness made a difference?
Regardless of your rocker choice you should be checking for the accurate pushrod length anyway!
Thank, Gary in N.Y.
P.S. Here's a link with some info about roller rocker installations! They will fit with OEM covers and single-thick V/C gaskets.
https://classicoldsmobile.com/forums...questions.html
#3
I was wondering about when converting a factory head to screw in studs, is it mandatory to machine the rocker pad surface for the thickness of the guide plates? I just wondered why- figuring you would have to use a custom pushrod anyway and if that .100 or so thickness made a difference?
#4
Fwiw I didn't mill my pads. The geometry was not too far off to be honest . Not perfect but it was slightly off center on the valve stem but it didn't sweep across . Been running the same setup for many years with no issues. I'm running a pushrod that's on the ragged edge of making the rocker arm bind on the stud. If I could get it to drop another .050 like milling the pads it would be perfect but I found a pushrod that was .050 taller to avoid binding it up during valve lash . If I lash it past half a turn the rocker arms will bind up but at half a turn I'm at .040 preload so it's good. Not the best case scenario but I spent a lot of time making sure I could get it damn near perfect without milling the pads and what I ended up with was a pattern slightly off center.
Last edited by coppercutlass; March 19th, 2017 at 12:14 PM.
#5
I didn't mill mine either, I honestly didn't even know people were doing that. I just bought an adjustable pushrod to check geometry and see what length pushrods I'd need. Came out with pretty nice geometry
#6
It's common to mill the pad when running stock valve lengths with roller rockers. They always end up to short and the geometry is way off. Most aftermarket Olds valves are .100" longer than stock with the exception of the off the shelf Ferea valves. Those do not require the pad to be milled in most cases. Don't forget, most guys that are rebuilding OE heads also mill them. That also comes into play with the rocker geometry as well as different thickness gaskets and deck height. You always need to check with an adjustable pushrod to establish correct length, but the rocker placement over the valve is not effected by push rod lenth.
#7
I think the slotted rocker arms like the roller tips are affected slightly . When i did my original measuring i was still running the roller tips. The longer the pushrod length the closer to the exhaust side of the cylinder head the pattern would be in my experience. Although it does have a ball to pivot on i think the slot allows it to move slightly off center when compare to a roller rocker where its fixed in the center and it could not creep from that center point. The area the pivot ball sits on isnt exactly round either kind of an ovalish shape. I might add it wasnt anything extreme but if i where to describe it. The pattern i ended up with would be one pattern line over center towards the exhaust side. When i set up the checker to the length pushrods i had it would put it almost 2 of those lines past the centerline towards the exhaust side .
Last edited by coppercutlass; March 20th, 2017 at 08:47 PM.
#9
#10
Idk much about valvetrain but that's the impression I had/have. When I was building my 350 I checked with stock rods and my contact was off center seemingly a decent ways so I bought an adjustable pushrod tool and was able to bring the contact very close to riding across the center of the stem.
#11
Idk much about valvetrain but that's the impression I had/have. When I was building my 350 I checked with stock rods and my contact was off center seemingly a decent ways so I bought an adjustable pushrod tool and was able to bring the contact very close to riding across the center of the stem.
The most important aspect is that there is very little sweep across the valve tip, not necessarily where it locates on the valve tip. This can be done during mockup up and using a sharpie marker on the end of the valve tip. Coat it real well and run the rocker arm through its cycle. Take the rocker off and it will show you where the "sweep" occurs on the valve tip. Less sweep will be easier on your valve guides.
#13
I use a Bridgeport to drill and tap studs. That would be the most accurate way so as not to have the studs (once installed) make the head look like a porcupine.
I have in a time of need drilled and tapped by hand. They came out straight as an arrow but that was going from 5/16" to 3/8". The 5/16" hole allowed the drill size (which was 5/16") to follow closely. If you drilled in steps I bet you could get it dead on by hand, but I still wouldn't recommend it.
I have in a time of need drilled and tapped by hand. They came out straight as an arrow but that was going from 5/16" to 3/8". The 5/16" hole allowed the drill size (which was 5/16") to follow closely. If you drilled in steps I bet you could get it dead on by hand, but I still wouldn't recommend it.
#15
X2 with Run to Rund, be careful not to cut too much. I have successfully drilled and tapped Olds heads for studs with a drill press. I have also been successful with using the thinner 1/16" thick guide plates and not cutting anything from the pads. If you can still find them, Pontiac used a 1/16" thick guide plate on their 400 and 455 engines (5/16" pushrod). They can be sectioned apart and used on the Olds head with a screw in rocker stud and any aftermarket rocker.
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