Replacing rocker stud on D7 Head
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From: Virginia
What I can't figure from your pictures is why the head is machined flat around the hole where the studs are pressed in. Most I thought where just rough cast there. Who knows what you have there and what has been done through the years. Another problem you run into, the rail rockers take different length pushrods than the later sled type rockers.
In the end, what you need to check is the valve lash. If you think the nuts you have are tight enough to hold without backing out, then you will need to adjust it like you would a chevy, turning the engine to #1 and adjusting that cylinder, and then turning the engine 1/4 turns and adjusting each cylinder in the firing order. I would take all the lash out and then turn them 1/2-3/4 turn.
If your nuts keep working loose, like I said before they make kits with nuts that lock you could use.
In the end, what you need to check is the valve lash. If you think the nuts you have are tight enough to hold without backing out, then you will need to adjust it like you would a chevy, turning the engine to #1 and adjusting that cylinder, and then turning the engine 1/4 turns and adjusting each cylinder in the firing order. I would take all the lash out and then turn them 1/2-3/4 turn.
If your nuts keep working loose, like I said before they make kits with nuts that lock you could use.
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More Turbo
Joined: Nov 2002
Posts: 543
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From: Tulsa
I've got a plan of action...
I've ordered a 3/8 stud w/ 7/16 base from ARP. I'll tap the head and install it with a guide plate to make sure the rockers don't wobble themselves to death. And set lash to 0 plus a half turn. I've gone to the local hardware store and found grade 8 locking nuts, which i'll be putting on all the rockers. It'll be a little while before I can fire it, but I'll post with results. #frankenstein
I've ordered a 3/8 stud w/ 7/16 base from ARP. I'll tap the head and install it with a guide plate to make sure the rockers don't wobble themselves to death. And set lash to 0 plus a half turn. I've gone to the local hardware store and found grade 8 locking nuts, which i'll be putting on all the rockers. It'll be a little while before I can fire it, but I'll post with results. #frankenstein
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From: Virginia
I would not use any guide plates unless you order hardened pushrods. If you use a regular pushrod with a guide plate, you will have shavings in your engine. With your setup it should not wobble, that is what the u-shaped groove under the rocker is for, that keeps the rocker on top of the valve stem.
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if you use screw in stud (for adjustable valvetrain) couple of things to remember. Do not use a rail rocker as it will not work. you'll bend rocker stud and crack the rocker arm and possibly bend the push rod. using screw in stud(s) require the use of non rail rockers and guide plates. Also the stud boss on the head has to be machined down and the stud hole tapped. take your head to a local machine shop they can supply and install an oversized pressed in stud. However, if you are using a comp cams setup you should have all the studs changed to screw in style and guide plates and non-rail rockers.
Moderator
Joined: Jan 2001
Posts: 56,984
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From: Virginia
if you use screw in stud (for adjustable valvetrain) couple of things to remember. Do not use a rail rocker as it will not work. you'll bend rocker stud and crack the rocker arm and possibly bend the push rod. using screw in stud(s) require the use of non rail rockers and guide plates. Also the stud boss on the head has to be machined down and the stud hole tapped. take your head to a local machine shop they can supply and install an oversized pressed in stud. However, if you are using a comp cams setup you should have all the studs changed to screw in style and guide plates and non-rail rockers.
What is the reason for not using a screw-in stud with a rail rocker? Does it hit the hex on the screw-in stud or something?
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my best opinion why the bosses appear to be machined is that these being d7 heads they were originally pedestal and someone had them machined down for press in studs(aftermarket). rail rockers designed for straight stud shaft. aftermarket screw in studs are tapered so they adjust to different installed heights requiring non- rail or roller rockers.
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Joined: Jan 2001
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From: Virginia
my best opinion why the bosses appear to be machined is that these being d7 heads they were originally pedestal and someone had them machined down for press in studs(aftermarket). rail rockers designed for straight stud shaft. aftermarket screw in studs are tapered so they adjust to different installed heights requiring non- rail or roller rockers.
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