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post #1 of (permalink) Old 02-23-2002, 10:24 PM Thread Starter
 
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360 Engine Assembly ?\'s

I have a question about rocker arms, rocker pivots and pushrods. I bought all new pushrods. One of the old was bent, the others were really dirty, plus there cheap to replace. When I disassembled the heads, I found one head had already been rebuilt. The pivots appeared to have been put on backwards on the that head. So I bought 8 new pivots. All of the rockers have been completely scrambled. I can't really tell rocker which one came from which stud. Let me add that I've got a new cam and lifters.
Having always heard that the rocker, pivot and pushrods should be kept together and reassembled onto the same stud. This is supposed to account for wear patterns. I've also read (in the same engine manual) that you can flip a pushrod if it has a pivot on both ends. That informatin seems contrary to the earlier 'keep them all the same' theory.
So the question is: Should I replace the rest of the rocker pivots and buy all new rockers? Or I stick with replacing the parts that were obviously bad? I want to follow the appropriate process.

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post #2 of (permalink) Old 02-23-2002, 10:54 PM
 
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Re: 360 Engine Assembly ?\'s

I've never worried about the rockers when I rebuilt motors. I've always made sure the lifters always went in the same holes, but not the push rods or rockers.

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post #3 of (permalink) Old 02-24-2002, 12:30 AM
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Re: 360 Engine Assembly ?\'s

It is better to keep parts that develop wear patterns together (i.e. rockers and pivots, gears) but parts that shouldn't develop wear paterns( i.e. push rods, valve springs) can be mixed and matched.

Glenn

Build what I can, buy only what I must.[img]/wwwthreads_images/icons/crazy.gif[/img]
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post #4 of (permalink) Old 02-24-2002, 10:48 AM
 
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Re: 360 Engine Assembly ?\'s

The wear pattern theory is correct.

You should try to keep the wear patterns together if you can.
If you can't, you've already done the next best thing.... New push rods.
New push rods will help correct a multitude of sins.

Check the socket of the rocker arms for the wear ring where it came into contact with the push rod.
If that wear ring gets into the hole (oil hole) replace the rocker arm.

Check the valve stem end of the rocker arm, if you can catch your fingernail on a groove worn by the valve stem, replace the rocker arm.

Check the fulcrum (pivot 'ball', 'wedge', ect.) If the oiling grooves are worn away, replace the rocker arm and fulcrum.

Make sure the lifter is on the base circle of the camshaft. If it's on the ramps or lobe, this is not going to work.
Use a dial indicator in the plunger of the lifter, and with the rocker tightened down, you are looking for that plunger to be 0.030" to 0.060" off it's seat.

If you have too much (over 0.060") compression of that plunger...
If you have the type of rockers that bolt solid to the heads (rail or singles), and you have had your heads, block deck or 'towers' milled, or are using a thinner head gasket, you may have to shim the rocker fulcrums up to gain that 0.030" to 0.060" tolerance...

Don't forget lots of assembly lube!!!!!

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post #5 of (permalink) Old 02-24-2002, 10:55 AM Thread Starter
 
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Re: 360 Engine Assembly ?\'s

Thanks for the feedback. I'll look at the wear patterns on the rockers. I replaced those 8 pivots because the oil grooves were worn away. The other 8 looked OK.

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post #6 of (permalink) Old 02-24-2002, 03:02 PM
 
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Re: 360 Engine Assembly ?\'s

On the AMC 360 you will be better off if you completely replace all the rockers, pivots, and pushrods. With the weak oil system on the AMC V8 they develop wear and noisy valve train very quickly.
I tried re-using my rocker assemblies on my freshly rebuilt 360 and had to replace everything with new parts in less than a 1000 miles.

Replace the timing cover also. It houses the oil pump and is prone to wear also.
Like I said the oil system is weak so you need every advantage you can get when rebuilding the AMC motors.


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post #7 of (permalink) Old 02-25-2002, 09:33 PM
 
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Re: 360 Engine Assembly ?\'s

I thought I understood this when I talked to you earlier but now I am questioning my understanding.
With the dial indicator, are you essentially measuring the end play of the pushrod between the lifter seat and the rocker seat? I understand shimming the fulcrum if it is too tight, gotta give it some room or it will bee too tight and bend/wear with the heat expansion. But how do you put a dial indicator in line with the pushrod installed? How do you make sure the lifter is off its seat? If you have one, a picture would sure help. As always, thanks.

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post #8 of (permalink) Old 02-25-2002, 11:43 PM
 
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Re: 360 Engine Assembly ?\'s

Let me go through it again...

The lifter has a piston inside it.
That piston moves up and down on a spring actuating a set of valves.
That 'Piston' is referred to as the 'Plunger' in a lifter.

That lifter is full of oil.
The cam starts to push the lifter up against the push rod, and the push rod pushes down on the plunger (or piston, what ever you care to call it).
When the plunger is depressed by the valve spring pressure, it forces oil out of the lifter, up through the push rod to the rockers.

At some point, the piston bottoms out inside the lifter, and the lifter then starts to move the rocker arm and valve stem against the valve spring pressure.
<hr>
The idea is to pre-load your valve train a little, keeps things from vibrating and adding extra wear.
By judging how much you have depressed the piston in the lifter, you can tell how much pre-load you have on the piston in the lifter.

Most guys just spin the push rod between their fingers, but from the time the piston leaves the seat (a snap ring in the top of the lifter), until it bottoms out on an internal seat, you can't tell how much pre load you have.

Too much pre load, and you won't get adequate oiling to the top end,
The spring pressure will feel the same (and you add lube to both ends of the push rods, and your fingers), but you have lost piston 'stroke' to pump oil, too far down and the piston will cover the incoming oil inlet, and it's a good way to have an already 'tight' top end go into coil bind and wipe out your camshaft...

Not enough pre load, and you will have push rods and rocker arms vibrating loose, and hammering on things every time the cam lobe comes around.
You will also loose lift at the valve (the cam lobe has to take up the slack before anything moves) and that will cost you power.
Not to mention the hideous noise that loose valve train components make!
<hr>
If you have machined the head, Machined the top of the block, used aftermarket head gaskets, or used new rocker mountings, you need to check the 'Stack Up' height of the engine and your lifter requirements.

1. I make sure the lifter I'm working on is on the base circle of the cam, if you are on the ramps or lobe, things aren't going to work out...
2. I assemble the top end, rockers, push rods, lifters in the bores, just don't tighten them down yet...
3. Then I use a dial indicator on the piston in the lifter.
4. I tighten the valve train down until the piston is depressed more than 0.030" but not more than 0.060".
(0.030" is the most common recommendation of the top three lifter manufacturers in the country for stock applications)
5. If you have fixed rockers, ones that bolt to the head directly, like some of the AMC V-8's did, you may have
more depression than 0.060". In that case, you will have to shim the rockers up.
Use proper shim stock so you don't get off a some crazy angle.
Shim the rocker mount up until you are under the 0.060" max.
6. If you find you can't make the piston go down 0.030", you may have to pull the rocker mount, and CAREFULLY file off a little of the mount where it meets the head.

The EASIEST (not the best, but acceptable) way is to buy a sheet of window glass, lay the glass on a flat surface, tape a piece of very fine sand paper to it, and sand away at the bottom of the rocker mount, BEING CAREFUL TO KEEP THE MOUNT FLAT ON THE SANDING BLOCK.
(this same trick works to flatten warped water neck gasket surfaces, oil pump plates, ect...)

Clean the part THOROUGHLY before returning to your engine assembly.
(glass as thick as you can afford. Keep an eye out for a store with a broken plate glass window, and have a piece cut from the scraps, Very cheap, and very good for checking flat...)
<hr>
As for keeping the dial indicator inline with the piston with the push rod in place...
They make a little arm that allows you to inspect at right angles.
You can also just tighten down until you take all of the slack out of the push rod (all up and down movement is restricted) then mount a normal straight run indicator at the top of the rocker arm over the push rod pocket, and tighten the rocker arm down and torque it.
If the total downward movement of the push rod pocket, (and hence push rod and piston) is between 0.030" and 0.060", you win!
If it's more than 0.060", you will have to remove the rocker arm mount and shim it.
If it's less than 0.030" downward movement, you will have to remove the rocker mount and remove a little material where it meets the head.

Any downward movement will be easy to inspect like that.
(that's the only way to do it on some of the tiny lifters put into European engines)

That's the good part about the 'Floating' rockers that Chevy uses, instant adjustment since the rocker mount never bolts solid to the head, you can just tighten the nut until you get 0.030" and forget it...
<hr>
I know this is a hard concept to grasp when so many people have been teaching you to 'Bolt it down and forget it' for so long, but there is Horsepower & Torque to be found here...
And it's FREE!!

Brhino, for you I'll find a picture. I'm getting ready to go through a 360 in my garage, and I'll have to do just what I've described, and I can take some pictures then...



So many cats, so few recipes...
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post #9 of (permalink) Old 02-26-2002, 09:23 AM
 
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Re: 360 Engine Assembly ?\'s

Do not need a picture now-got it. What was confusing me is the use of the 90 degree verses the plunger type dial indicator. We call the 90 degree ones "test indicators" at work so I was thinking only using a plunger one the whole time. Think Newton has a law about two things occuping the same space at once-can't happen. That what was confusing me. The rest of it makes complete sense about the lifter needing room to pump. I can attest to the bolt it on and go thing not working. Did that trick in my younger years, had many head problems. Heads seem simple when you look at them, it is the details that get you. See-even engineers can be taught something with a lot of effort!

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post #10 of (permalink) Old 02-26-2002, 12:18 PM
 
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Re: 360 Engine Assembly ?\'s

All of this comes natural to me...
Gears and wires are easy for me to work with...

Throw me in a room with strangers and I'm ready to wet myself...
I have no concept of how to deal with people...

So many cats, so few recipes...
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