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Old 01-31-2013, 12:28 PM
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I recall that the SBC double hump heads, casting numbers 3917291 and 3782461, do not have screw in studs. Those are probably the "double hump" heads you have.

I had a pair of 3917291 heads on my '56 Chevrolet. They had pressed-n studs and were pinned. They were ported and flow tested by the late Joe Mondello in 1970. Mondello told me that they were the best of the "double hump" heads.


Last edited by MouseFink; 01-31-2013 at 12:53 PM.
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Old 01-31-2013, 01:58 PM
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Whenever I convert early Dbl Hump heads to screw-ins I touch off and remove .400 from the bosses.

The other thing to look at are rockers with a wider slot below the trunion area.

I've also seen rockers where people have chamfered the inside edge of the slot slightly to clear the radius of the stud to avoid tearing everything back off the motor.
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Old 01-31-2013, 02:58 PM
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You can get screw in studs with no taper or hex to tighten them and you don't need to machine the bosses they have been around for many years I used them in the early 60s in gas and modified classes a good source for these are "Pioneer" Part # RM-348-16 for small block chevy and other applications. If your not using guide plates they are fine and of very good quality, and without machining the early head, You have much more thread area holding the stud before entering the water jacket cavity! The early head castings sometimes when machined because of the water jacket only left room for a few threads when tapped!!


I forgot there is no taper or hex to interfere with rocker arm movement and more thread for adjustment. Only an alternative for some reading the thread. But at over 6000 rpm you need fully race prepared heads with a very light vave train!!!!

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Old 01-31-2013, 03:00 PM
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Originally Posted by shane.,herold View Post
I am going to take it to the machinist to look at. Im thinkin the head bosses need to be cut about .0350. And the rockers are Harland Sharp, a very high quality company, not summit. The cam is from summit, and since there are only a few places in the country that grind cams it really doesnt matter what brand they are, pick the one you want, and thats what i did. I have had excellent luck with all summit products because they are usually name brand stuff with a differnt label on them and a hell of a better price.
If the machinist was shooting to get the tops of the studs equal to where they were stock, that could account for the lack of clearance. This is because the studs have a rather generous radius between the stud and hex for strength (arrow below, ARP stud). If they made the studs at a sharp 90 degree angle there, the studs would be MUCH more likely to crack/break at the juncture of the stud and hex. Dart studs have probably the least amount of radius.

If you're using 3/8" studs/rockers, this might be a good time to consider going to 7/16".

I don't know who grinds the cams for Summit, but they have a decent reputation.

Last edited by cobalt327; 01-31-2013 at 03:21 PM.
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