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Discussion Starter #1
if I tighten down the rocker to 16-18ft-lbs between 1/4 - 3/4 turn past zero lash like your supposed to, should I be able to twist the pushrod by hand? if the pushrod wont budge after tightening it do I have the incorrect length pushrods? I'm running into this problem and cant find info about this... thanks for any help
 

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You're doing it right. It probably won't budge, but this may not always be the case. It might spin on certain valves and not on others. You'll be good either way. Also, if you check the pushrod that didn't spin a few minutes later and now it does spin, it's because the lifter bled down.
 

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Discussion Starter #3
ok so it doesnt really matter if I can spin the pushrod or not... but what if after tightening it down I cant shake the rocker side to side at all.. does there need too a little play in the rocker for side to side movement or is it okay if it doesnt move and is like rock solid?
 

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Are these pedestal or stud mount rockers? If they're stud mount you don't want to go any tigher than the 1/4 to 3/4 turn past zero lash.
 

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iv been wondering about this also..i have stud mount RR's and after zero lash iv been going 3/4 turn and there is no way thats even close to 18lbs of torque...i put a torque wrench on it and id have to turn it a lot more to get it to that...also...

in the middle of the rocker nut is a screw...after adjusting the arms the screw is almost the exact same on all the RR's..like the distence in they have to be screwed....BUT there is one nut on each side that the screw had to be screwed why farther in then the rest? are these RR's not adjusted right or...??
 

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Pedestal and stud mount rockers are really totally different things. You do not want any side to side play in the rockers when they are tightened. If you go over 1 full turn before reaching the correct torque then you need shims (pedestal). If you cannot reach a 1/4 turn before correct torque then you need longer pushrods. If you go to Cranes site they have great instructions in PDF in case you weren't aware.
 

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the more you tighen the rocker nut dosnt that just push the pushrod down in the lifter?
 

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Discussion Starter #8
ok thanks everyone some much for your help... but I have one more question.. I tightened down all of my pedestal cobra rockers last night and all of them reached correct torque between a 1/4 turn and 3/4 turn after zero lash except 1 rocker! (exhaust valve on #1).

this is what happened with that 1 rocker: I would tighten it down to bring it to zero lash but it would get real tight and torque down to 18 ft lbs and still not be at zero lash.. it was very close though! I could spin the pushrod freely and there was a very very small space between the valve tip and roller. So does this just mean I have to shim that rocker or get a different size pushrod for that one rocker? thanks again!
 

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Discussion Starter #9
ohh.. one more thing.. I tried a different rocker on the #1 ex. valve and it did the same thing... I forgot to mention these lifters and rockers are from my old engine I just pulled out.. so is it possible maybe that one lifter is bad and causing it not to tighten correctly?
 

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Think about the geometry - placing a shim under the rocker is going to move it further away from the head - and the valve/pushrod. If you have a gap when the rocker is torqued all the way down, the shim is going to make the gap bigger. If your lifter is ok, then you're going to need a slightly longer pushrod for that one. Odd that it should work out that way. Is it possible that the one pushrod or valve stem is bent?
 

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Discussion Starter #11
well... they are brand new edelbrock heads and brand new pushrods and the engine is on a stand.. the only parts I've re-used from the old motor are the lifters/cobra rockers/timing cover/ misc bolts and accesories..

The thing is sooooo close to being at zero lash but just didnt get there.. is it possible the lifter is collapsed and bad?? or is there a way to grind down the little pedestal the rocker sits on?? it only needs to move a very very small amount.. i mean I can barely move the pushrod in a up down motion.. almost cant move it up and down but I know its not right.
 

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Maybe you could take the one rocker to your favorite machine shop and have them take about .060" - .090" off the bottom of the rocker. Should be able to tape up the rocker to keep debris out; or disassemble it, do the machining and put it back together. Be sure you cut enough - you can always use a .030" shim to pick it back up. That way you don't have to pull a head, or shop for one different pushrod, be grinding/filing on the pedestal with the head on the engine (shavings everywhere - yikes!!). This approach will also change geometry a bit - where the center of the roller tip is hitting the valve, but you can check that.

Another approach would be to see if any of your other rockers tightened to torque real close to a 1/4 turn. If so, you might try swapping that rocker with this one and see if that rocker is a bit shorter than the one you've got on there. Of course, if it is a rocker dimension issue, then you've just transferred your "gap" to another valve. I wouldn't put it together the way it is - it's definitely gonna make racket and that part of the train is gonna be hammering away at things.
 

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...oh, if you go the machining route for the rocker, have them mark it some way so it's easy to figure out which one goes back on that valve.
 

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you can order just one pushrod from summit i beleave

here is a comp cams pushrod set of 16

CCA-7823-16

see the 16 at the end..means 16 pushrods...just use the part number put at the end just use a 1 and it comes up as one rod
 

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Discussion Starter #15
well since i have stock length pushrods now.. what length would i need to get?? I cant remember what stock size is again.. 6.275??? should I just get .1 inch longer pushrod or something close to that??
 

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Michael Yount said:
Maybe you could take the one rocker to your favorite machine shop and have them take about .060" - .090" off the bottom of the rocker. Should be able to tape up the rocker to keep debris out; or disassemble it, do the machining and put it back


if i'm not mistaken Mike wouldn't you just shave pedestal down instead of screwing with rocker arm itself ???? that way you can use it later without problems....

Just a thought

good luck
 

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ps. only reason i say that is that you put shim under pedestal to get height .if you lose height wouldnt you shave it down ie.. belt sander LOL or good machine shop better choice
 

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Discussion Starter #18
well Im not sure what length pushrod to get.. u think 6.4" would do the trick? I think for now Im just gonna take the little pedestal that the rocker sits on and sand it down some on the bottom of it to see it that helps before I go order one pushrod.. hopefully thats all i need to do.. anyone have a suggestion as how to shave off some metal evenly?
 

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must have just crossed coments

i have used belt sand with fine paper just kep it square to guide and a little push goes a long way so take your time
 

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Lots here - if you're gonna replace the pushrod, you should measure the length of the one you've got and you add to it 1) the amount of gap you have when the rocker's tight now plus 2) the amount the bolt moves when it's turned 1/2 turn (get the number of threads per inch and you can calculate it).

I think he has the heads on the car already (maybe I'm wrong) - sanding on a pedastal while the engine's assembled - well, I wouldn't do it because of all the mess it makes inside the head/engine. Also, you'd have to machine the whole pedestal, which is gonna throw the intake rocker off in the other direction. Of course, he can shim that to take care of it.

Either measure the channel thickness or compare the channel thickness to a .030 and .060 shim to see if you've got enough to work with. I don't think there's enough thickness in the channel to work with, but I could be mistaken. Furthermore, you have to machine/sand the whole channel which throws the other rocker off too - but it can be shimmed up. My recollection is that a .030" shim removes about a 1/4 turn to torque. So, if you want it to hit your torque target at 1/2 turn, you're gonna need to remove at least .060 + however big the gap is now when you've got it tightened. Removing a little more isn't a problem because you can shim your way back.

If you're willing to wait - I'd measure everything and get another pushrod. If you want to deal with it right now, the rationale above is what led me to conclude that having someone machine the bottom of the one rocker was a reasonable alternative. Obviously, there's a number of ways to skin the poor cat here.
 
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