rocker arm and push rod question

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68gts340

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ok ,here is the deal, i have a concern with the postion of the push rods in my 340, they are all very close to the cyl. head casting , almost to the point of making contact, no where near the center of the hole in the heads. is this normal and just part of the geometry problems in these motors ? or maybe a casting shift ? next ?... what to do about it? again thanks for the help.
 
I`m not real familiar with the smallblocks but, how about a rocker arm on the wrong valve? They should be stamped with an L or an R unless they`ve been replaced. You may check to see that each rocker arm is in it`s appropriate place and offset properly.
 
at first glance i also thought that was the problem, today i looked closer , the lefts and rights are in the correct order, but a couple of them are so far off that the valve stem is actually hitting on the edge of the rocker arm, and all of the pushrods are to close to the cyl. head casting , some are less than .030 from rubbing the casting. if this is the normal for these motors , they are the biggest piece of crap i have ever seen. i really hope i am missing something here but it looks bad.
 
ok ..now that i have that off my chest ,how do i fix this nightmare? does anyone make a set of rockers that use spacers so that i can center the rocker over the valve? question 2 .... it looks like i can use longer ratio rocker arms to help correct the push rod problem, but not on all of them. how much material can be removed from the pushrod cast hole in the heads, i would like to get at least .060 clearance around the push rods..... anyone have any thoughts or similar problems ? question 3 ..if this is a casting shift problem how do i tell? i can get different heads if it will solve the problem, but i dont want to go through all of that to end up with the same problem. these are 360 'J ' heads if it matters. and the motor is a numbers matching 68 340. the build date shows aug 67, ... I really need some help on this one guys ,any help is most welcome..... thanks
 
Mancini Racing has rocker arm shims to space the rovkers one way or another. If the heads are installed, you can rotate the engine by hand, ans see if the pushrods get any closer. If it's .030, that's kind of thight IMO. If the pushrods are good ones that wont flex, it might be ok as long as they dont get any closer during normal travel. Correct the rocker alignment, that can hurt performance, life, and oil use if left in that shape. Keep in mind, the factory lifter bores are just as bad as the rest of the machining. It may be the lifter bores in addition to the rockers that make it close.
 
I used Crane a 1.6 ratio rocker arm kit and a Hughes engines rocker shaft hold down kit which came with rocker arm spacers that I used in conjunction with the crane spacers. If you go this route, be prepared to spend some time getting everything right. Details and pics can be found here.
http://home.comcast.net/~360quadzilla/360-2.htm
 
Look at the bolt spacers on the rocker arm shaft. There are two width of spacers. The narrow spacers should be on the two outside and center bolts. The wide ones on two on either side of center. If the wide ones are out of place it will push the rocker arms over and out of position. Look to see if the rocker arms are center on the valve stems also. good luck.
 
I'm going through my own rocker arm pushrod nightmare!!!!!!!! If you get yours figured out let me know.
 
1.6 ratio rockers will tilt the pushrod over more than 1.5 rockers do. And can cause clearence problems. If you drill out the pushrod holes, you will enlarge the holes all the way around..and that will remove much of the ID in the pushrod dogleg (wall) area. This will limit the width of the finished port before breaking thru. You need to only open the pushrod hole in the front (adjacent to the manifold face) and the backside of the hole ( rocker side)and to not take any off of the sides. Good luck. Terry.
 
chuckl1966 said:
Look at the bolt spacers on the rocker arm shaft. There are two width of spacers. The narrow spacers should be on the two outside and center bolts. The wide ones on two on either side of center. If the wide ones are out of place it will push the rocker arms over and out of position. Look to see if the rocker arms are center on the valve stems also. good luck.
Click to expand...

I second that diagnosis but also would add that the pushrods also may be too short. You did not mention if the rockers are stamped or the 273 adjustable type. Stamped pushrods are a hair longer than adjustable rocker with cupped top pushrods. Just trying to offer more to look at. Keep us updated.
Jason
 
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