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cant believe it make that much diff...and cheapest mod yet

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mutt
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Re: cant believe it make that much diff...and cheapest mod y

Post #51 by mutt » Thu Apr 11, 2013 2:48 pm

I've had chev 6 rockers in my '81 econo for a bunch of years. Its ALMOST a drop in. Heres the deal- sometime after 81 the pr holes in the head went from narrow straight sided with rounded ends to circular. the circular holes allow the pr too much side to side wobble, you need some sort of pushrod guide if you have round holes. You will also run out of thread before you get to 1 full turn past zero lash valve adjustment/preload, so you want a >hardened< flat washer between the nut and the ball. And, yeah, you gain power and RPM, and it won't bust you if you are stuck getting emissions tested where you live.....

maverick600
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Re: cant believe it make that much diff...and cheapest mod y

Post #52 by maverick600 » Fri Apr 12, 2013 9:34 pm

snb13 wrote:I have a set of rockers that I believe are the proper ones. PM me.


If you were posting to me I am not sure how to pm you on here. Email is davidpeto@cableone.net

Econo4spd
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Early vs Late 3/8" rocker studs: 3/8NF & 5/16NF Threads

Post #53 by Econo4spd » Thu May 16, 2013 12:54 am

Reading through numerous rocker swap threads and looking at the Chevy I6 rocker parts on Rockauto, I suspect I missed something somewhere.

I have a 1980 head with pressed in rocker studs. The shank is .372" diameter, and the threads are 5/16-NF.

The Chevy parts on Rockauto show studs with 3/8-NF threads.

Question: Did 1960's and 1970's Ford heads have .372" diameter stud shanks with 3/8-NF threads AND THEN A CHANGE WAS MADE so early 1980's heads were built with a .372" shank with 5/16-NF threads?

Is this why some owners of 70's Ford vehicles bolt chevy rockers right in, but others have to remove the pressed in studs and have the head drilled and tapped for a 3/8" screw in stud?

Thanks

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THE FRENCHTOWN FLYER
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Re: cant believe it make that much diff...and cheapest mod y

Post #54 by THE FRENCHTOWN FLYER » Thu May 16, 2013 12:58 pm

yes

The ones with 3/8 NF are designed to be adjustable.

The ones with 5/16 NF are designed for the nut to bottom out on the shoulder and provide the necessary lifter preload. IF you are using Ford rockers.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Econo4spd
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Re: cant believe it make that much diff...and cheapest mod y

Post #55 by Econo4spd » Fri May 17, 2013 1:28 am

FTF, thanks for clearifing that. Makes me wish I'd bought the '75 head I saw at the Portland swap meet a few weeks ago.


maverick600 wrote:I have a 76 300 with stud type head with 5/16 studs. ..... but my biggest question is....can I use (when I find some) chevy rockers on my stud type head with no problem other than replacing them.


Mav600, when you say "other than replacing THEM " are you refereing to the rockers or the studs?

Ronbo & mutt seem to be running chevy rockers on studs with 5/16" threads, given the year of the trucks they list, '83 and '81 if the studs are original. Ronbo said he had pushrod length issues. Other posts describe replacing the pressed in 5/16" threaded studs and drilling and tapping the head for chevy 3/8" stud w 3/8" threads and FTF's reply above tells me that's the right way to do it (drill and tap to replace the 5/16" threaded studs).
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