Adj. Rockers // PICS & ????

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FASTBACK340

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OK, I was expecting something like this to pop up. I installed the lifters & rocker arms/shafts tonight.
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I adjusted both valves on #1 cylinder and I have NO adjustment screw threads showing under the rocker. I remember being advised to have at least 2-3 threads visible. Nothing binds and the springs clear the rockers fine.
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I figure between the compressed #1008 FelPro gaskets and the possibility the block was decked when MP re-manned it I'd have a problem. Question: Should I shim the rockers? Of do I dump the entire pile of parts into a pick up truck and drop it all off at the machine shop and say "Don't call `til it's done...." Or leave it alone..
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SHIM THEM!!!!......i have them for my motor and mine are .010 thick...i dont know if they come thicker but im sure COMP CAMS will have them and ask them how thick they come.....OH YEAH....those are some PERTY LITTLE HEADS you got there!!! :thumbup:

ONE BAD BEAST (Medium).jpg
 
personally i would not shim the rocker shafts .i have done this before but belive i would of been better off to check the push rod length and this is what i recommend you do. that way you know the valve train geometry is correct even if you have to get the push rods cut or replace them.i think you would probably be better off in the long run
 
John , are those Crane gold rockers ? they look like it. I had oiling problems with my Crane rockers on Eddy heads until I shortened the pushrods so I had at least 3 or 4 threads showing under the rocker. It didn't oil properly and chewed up a set of adjusters, I posted on Moparts and a lot of people replied helping me out. The theory of only one thread showing doesn't work with the Crane rockers. Trust me go for 3 or 4 threads showing.
 
I figured I'd have to do some push rod tweaking....


<sigh....> I'll get this thing together sooner or later.
 
I wouldnt woory about shims on iron heads, but I wouldnt do them with aluminum. Jusr order shorter ones. A more important thing then the thread count is how the rocker tip rolls over the tip of the valve. It should start near the center, but towards the intake side, then roll over the center, then back towards the intake side again. Get that right, and you're golden. That's why you use the checking pushrods and trun the engine over a few times to get things right.
 
moper said:
I wouldnt woory about shims on iron heads, but I wouldnt do them with aluminum. Jusr order shorter ones. A more important thing then the thread count is how the rocker tip rolls over the tip of the valve. It should start near the center, but towards the intake side, then roll over the center, then back towards the intake side again. Get that right, and you're golden. That's why you use the checking pushrods and trun the engine over a few times to get things right.
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One thing to remember though if your running extreme spring pressure put on some "mock up" springs for rolling the engine over. Otherwise the adjustable pushrod might snap- I know it sounds pretty obvious but I can't even cont how many Chevy guys I know that have done this.
 
With all this information that has been posted here, I was wondering if I shoud have about three threads showing at the bottom of my rockers. I am using stock 1970 "340" heads with stock 1967 "273" adjustable rockers. As well I am using the proper Crane Cams shorter pushrods for this combination.
 
The number of threads showing" is n't going to be a deffinate between all engines or even all valves for that matter. You need to make sure that your rocker arm geometry is right first, it needs to be just to the intake side of the valve center (just slightly)on your base circle and roll towards the exhaust side, if it gets to close to either side of the vavle, you've got bent valves!
 
Pushrod length and/or amount of threads showing has NO effect on rocker tip geometry,[where the roller sits on the valve tip] the only way to change the rocker tip geometry is to raise or lower your rocker shafts.
With your 273 type rockers you should be OK with only one thread showing as these rockers oil differently to the Crane Gold type rockers.
 
i wouldnt say thats entirely accurrate. maybe with hyd cams, certainly not with mechanical cams and adjustable rockers. you cant change the height of the pivot point (and therefore the contact path of the tip) if it's really off without shimming or other fixes, but you sure can change the angle the rocker is on with a longer or shorter effective pushrod length. Not drastic changes, but saying "has no effect" is a little misleading.
 
mrspeeddemon said:
One thing to remember though if your running extreme spring pressure put on some "mock up" springs for rolling the engine over. Otherwise the adjustable pushrod might snap- I know it sounds pretty obvious but I can't even cont how many Chevy guys I know that have done this.
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Great insight, most people forget this, however he should be ok if he just removes the inner spring on his dual spring setup
 
My Snap-on guy just gave me his advice on this matter. If you're not building an 800 horse motor, don't worry about a thread or two difference...as long as the rocker swipes the valve correctly.
 
May be too late for a reply, but,............I think if you inspect one of the rockers you will find that, unlike nodular iron, the aluminum pieces have the bottom of the thread chase countersunk to clean up the tapping/machining process. You'll likely have your 1and1/2-2 threads just under the rocker. Sorry. No pics.
 
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