Rocker not centered
Thread Starter
Teching In
Joined: Apr 2010
Posts: 32
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Bringing this back since I have the money and time to work on the car again. I'm debating on just getting shaft mount rockers but am unsure of what brand. Of if I get the adjustable plates how exactly to I set them up? Do you get them inline then mark the plates, then take them off and tack em? Any help would be appreciated really wanna get this thing driving in the spring.
Welcome to a common SBC anomaly. Don't waste your money on shaft mounts unless you plan on running over 7500rpm. The way I did it was to hand tighten the studs onto the guide plates, set the rockers on top and move as necessary, then torqued studs down to whatever was recommended by GM specs. Welding them is not needed. It's a PITA to do it with the engine in the car. Removing the intake to see more of what the pushrods are doing make life easier, but not necessary.
When I did my Iskys, I found that I had to do some grinding on some of the guide plate tabs to make them smaller in width to get the best centered position. It was really weird how inconsistant the plate was from cylinder to cylinder.
Once I had them dialed in on the motor, I scribed a pair of 45 degree marks across the GP seams with scribe and then removed them to tack weld them on the bench. Yeah its likely OK to run them unwelded but i decide to weld them up in the event that they ever need to be removed, I would not have to spend all that time again dialing them in. The Iskys are a major pain in the *** but very worth it several hours later.
Once I had them dialed in on the motor, I scribed a pair of 45 degree marks across the GP seams with scribe and then removed them to tack weld them on the bench. Yeah its likely OK to run them unwelded but i decide to weld them up in the event that they ever need to be removed, I would not have to spend all that time again dialing them in. The Iskys are a major pain in the *** but very worth it several hours later.
Joined: May 2004
Posts: 1,593
Likes: 267
From: Halfway back on the Highway to Hell...again!
Adding something to this. Once you have it all installed, rockers adjusted and think you are ready to reassmble for starting, (hopefully you're intake is off).
Rotate the engine over 3 or 4 times. You're checking to see that the PR isn't hitting the bottom of the plate and forcing the lifter side of the pushrod up out of the lifter cup and on to the edge of the lifter.
This happened on mine. I used the Isky plates as well. Now just FYI, I am using 3/8" pushrods/plates. I had the set of fixed plates that came with my heads and the cut was much deeper (.225") than the Iskys. So I machined the Iskys to match the fixed plates, went through the whole process that being discussed here, again.
You may not have this issue using 5/16" PR's. I also did notice that the Isky plates are molded and have molding cast on the sides which make them stick. I did have to take a file to them so they would slide smoothly. I have to admit, Isky has not changed in 35 years. Someone told me the Comps are machined and smooth. But I haven't seen a set to know for sure.
Now the webs in the valve covers hit the rockers. So I'm in the process of fixing that,
Rotate the engine over 3 or 4 times. You're checking to see that the PR isn't hitting the bottom of the plate and forcing the lifter side of the pushrod up out of the lifter cup and on to the edge of the lifter.
This happened on mine. I used the Isky plates as well. Now just FYI, I am using 3/8" pushrods/plates. I had the set of fixed plates that came with my heads and the cut was much deeper (.225") than the Iskys. So I machined the Iskys to match the fixed plates, went through the whole process that being discussed here, again.
You may not have this issue using 5/16" PR's. I also did notice that the Isky plates are molded and have molding cast on the sides which make them stick. I did have to take a file to them so they would slide smoothly. I have to admit, Isky has not changed in 35 years. Someone told me the Comps are machined and smooth. But I haven't seen a set to know for sure.
Now the webs in the valve covers hit the rockers. So I'm in the process of fixing that,
Thread Starter
Teching In
Joined: Apr 2010
Posts: 32
Likes: 0
Hmm this sounds like its guna suck! The engine is already in the car. I hope I really don't need to remove the intake manifold. Guess it will be worth it after I have it all dialed in good and saved 800+.
Joined: May 2004
Posts: 1,593
Likes: 267
From: Halfway back on the Highway to Hell...again!
I think if you stay 5/16" PR, you should be ok. One of these guys should be able to chime in that's using them. From what I see the depth of the plate where the PR is, is the same for 3/8 & 5/16. It's just wider to accept the correct PR. Duh..Isky...!!!!
Out of the many SBC's I've built, I've never kept a 5/16" PR. When the cost is the same to get more strength, why not. Better to have more than enough than not enough.
Out of the many SBC's I've built, I've never kept a 5/16" PR. When the cost is the same to get more strength, why not. Better to have more than enough than not enough.
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