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C heads worth putting money into

C heads worth putting money into

Old August 16th, 2018, 04:58 PM
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C heads worth putting money into

I picked up a set of heads dirt cheap from a guy who gave up on his dreams. Along with a bunch of other parts

They are heavily ported
Have guide liners installed
3 angle valve job on the seat
Manley stainless valves
they are clean heads. Not burnt or corroded

The main problem is rocker studs are crooked as hell. They have been drilled 7/16Ē

I want to fill the crossover and weld the center divider which I can do on my own.

I will have to shop around for someone to correct the rocker studs. Sugggestions for how to do this is appreciated.

If these could make 450 hp with the work described Iíd be happy.
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Old August 16th, 2018, 11:40 PM
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sounds like all the hard work is done, it all really depends on how screwed up the rocker studs are, and if you have the time to do the exhaust dividers and the cross overs why not? I ported a set of B heads, got that part done then ordered some Bernard heads because of curiosity and i didnt want to wait for a machine shop to finish the B heads and then ended up buying the tools to redo guides and seats, so ill save the B heads for another project, i think cost wise and the performance you want you can get out of the C heads.
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Old August 17th, 2018, 08:28 PM
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Could you redrill the heads straight, and use heli-coils to restore the rocker arm holes sized correctly? Thatís about the only economical way I can think of to straighten them. Iím not a machinist either
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Old August 17th, 2018, 08:34 PM
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Maybe the helicoil would reinforce the thread. I just donít know if itís possible to re-drill a hole that has already been drilled 7/16Ē. I figured there wouldnít be anymore material there to drill into. But I donít know.

ARP offers a Pontiac stud that is 1/2Ē
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Old August 17th, 2018, 09:21 PM
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I donít know what drill size is needed for a 7/16 Helicoil, hopefully itís big enough to straighten out the hole, and leave enough metal to allow proper thread engagement.

I never would have guessed anything short of Top Fuel or some other nitro engine needing 1/2 rocker studs. Once again, Iím not a machinist but big block Chevy used a 7/16 rod bolt. I canít imagine a rocker stud under more stress than a connecting rod bolt!
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Old August 17th, 2018, 10:45 PM
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If studs are "crooked as hell", someone probably tried to use a hand drill, them sounds like to me. Another thing to thing about is where the hole location is. Most drill presses are loose enough the will try to follow the existing hole, no matter where it is. The stud should be located on a straight line between the valvetip/valveguide to the lifter location. You also need to have the threaded hole at a position that the rocker arm touches the valve tip correctly.
An old head could be used to provide a pattern. Or if you had a blueprint. One thing is for sure, at this stage a good "tight" mill like a Bridgeport, 2 axis digital readout and tools to true up the holes.
Depending how big the holes are when they are straightened out, Heli-coils would be one possible repair, if you don't hit a water jacket. I would also consider 4140 (or comparable) threaded rod with what ever thread inside that you want for the studs. These threaded inserts could be screwed in and "locked" by staking or other method.
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Old August 24th, 2018, 06:42 PM
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Thanks guys.

i talked to a machinist who specializes in cylinder heads this afternoon. He also had the 1/2Ē Pontiac stud in mind. He said to send him some pics of the heads. And he may be able to straighten them out on a mill.

Iíll follow up with how it goes.Valvetrain, rockers, etc. need to be on hand before he works on them

Last edited by VinMichael; August 24th, 2018 at 06:48 PM.
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Old August 25th, 2018, 12:52 AM
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Have the holes been drilled to 7/16" HOLE or drilled FOR a 7/16" thread ? I am betting he wants a pic of the heads with the studs you have installed. Be prepared to furnish a "good head" to chart hole locations. The heads can be saved, but it depends on how messed up the holes are now. Good Luck, keep us updated.
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Old August 26th, 2018, 11:48 AM
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Thatís right, they are tapped for a 7/16Ē thread. They came with guide plates and everything. Current studs are 7/16Ē x 3/8Ē

Last edited by VinMichael; August 26th, 2018 at 11:56 AM.
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Old August 26th, 2018, 01:12 PM
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I think you might be ok, there could be enough material to drill and tap for 1/2"........after the holes are trued up, in the proper location with a 7/16" endmill. The machinist will probably need a "good head" to determine the proper location...unless he has that now. You should also take the guide plates along in case the holes need to be enlarged for the 1/2"studs. Good luck.

Last edited by OLDSter Ralph; August 26th, 2018 at 01:24 PM. Reason: more info
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Old August 26th, 2018, 11:09 PM
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Made some progress today. I emailed photos to the machinist looking down the studs. They were just hand tight without the guide plate.

He told me to install the guideplate and torque them down. I thought to myself ďI already tried that, but okayĒ

However I realized I overlooked something the first time around. When I torque down the studs a few months ago with the guide plates, I didnít realize the stud was bottoming-out in the threads before clamping down completely on the guideplate. The guideplates are those really thin types.

So I removed the studs and (thicker) guideplates from a set of Procomps that I have. And torqued the studs to 45 pounds.

The stud alignment looks significantly better now

https://i.imgur.com/N5BBXYW.jpg
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