I'm putting together a mild street engine... 383 block with 440 crank, Stealth heads, block deck squared to crank centerline so I can build a quench engine. Camshaft is Comp CL21-223-4, which is fairly close to a stock HP camshaft.

I had some almost new MP stamped rockers and shafts (repackaged stockers, I believe) that I thought I'd use since I had them, and since I figured this engine didn't need an adjustable valve train. I'm beginning to think I was wrong.

The camshaft instructions said valve lifter preload should be .030" - .040". I checked #1 exhaust and it was .032". Perfect. With the same pushrod in #7 exhaust, I had .085". I stopped at that point to try to figure out what's going on.

I have not swapped rocker arms from position to position to see if that's where the difference is, but it is probably what I should do next, to at least find out if I need some different rockers. I also wonder how precise this setting was on new engines back in the day. In theory, since my deck has been squared, I should be better off than if I hadn't.

What gives? Am I fighting a losing battle? Is it time to cave and buy some adjustable rockers? Would it be acceptable to file/grind them at the bottom, where they contact the shaft, to get the preload right, or are the hardened/coated there?

Thanks!

If I were where you are now, with those rocker parts already on hand, I'd just call Smith brothers and order up some adjustable pushrods.
Set the preload where you want it, and forget about it.

yes, first to ID what part is different/causing the problem. could it be a buildup of JB weld? (old habits die hard). what part were you considering grinding?

Robert:

I was wondering about filing/grinding the part that wears out anyway, as highlighted in red.

Somehow I knew JB Weld would come up here if you saw that it was me asking!

Do not grind on them anywhere, that is a time bomb waiting to go off Take the time now to swap them around and check all of them for how much preload they have
Stock rocker arms are not hitech pieces, not racing quality by any means, just like most stock OEM parts
I've seen .030 lift variences at the retainers on the best race rocker arms out there
On your deal adjustable rockers or pushrods are probally going to be the best solution to reach your goals

Thanks Cab and Fast68. That's what I was thinking but I didn't want to leave any options on the table.

Jimmy what I would do is swap em around & get the preload as even across the board as you can & call it good. I think you will be fine as is. I absolutely would not grind the rocker arm shaft holes oblong (if I am reading that right). PS has the JB weld come loose from the dist slots yet? could happen any time now. EDIT if the rockers are the only thing that ain't "square" in this equation (& good possibility that is the case), you might not get em very much closer to equal by swapping em but I don't see a problem & it is worth the try

Do it right...... Or do it over.

Ha! I think I'm safe from that happening. That distributor is in a box in my basement. Here's what the engine looks like now, except for the fact that the loose wiring has been cleaned up.

put it up on the wall to cover my modded metering rod caps. that sure looks like more than a "mild" engine.

That's the engine in the Coronet; same engine that's been in it, I just added the FI over the winter. The "mild" engine I'm working on now is for my Adam-12 squad car.

PM me about the metering rod caps. I think your inbox is full.

Another thought is if you really want to use the stamp steel rockers is to check them all and if you have eight that are close to each other and the other eight have more or less are close to each other on the preload than you want put them both on shafts and then shim the shaft that has the most preload to make it taller to lessen the preload
Many different ways to skin the kitty when you really want to
One other input, adjustable pushrods are a pain in the butt to adjust, especially on the center two cylinders on both heads on wedge motors with the motor assembled, it takes three wrenches and almost three hands

Good idea Cab, thanks! It is supposed to rain here tomorrow, so I'll be back on that project. I'll post back after I swap rockers around and compare them.

What you're describing is exactly why Stock racers would spend their winters going through boxes and boxes of stock rockers finding the highest ratio pieces.

R.

This is what I did on the last 2 builds I did for others, cost for the pushrods was about $225 , I had a couple of extras made as spares.

It's a lot easier, and less time consuming, than swapping rockers around THINKING you are going to magically find .050 preload difference. That only happens if you are certain valve stem heights are the same from valve to valve.

Check all the valve stem ends to see if they're at the same level.

Good point. Because the heads are brand new, I "ASS"umed they were. I will check.

Thanks!

Jimmy post how it turns out

Another thing, I'd use the same pair of rockers to check each cylinder, log the measurements and see if that indicates anything, Head or block might be machined at an angle.

Here's the Readers Digest condensed update.

I was apparently full of hooey when I said #1 Exhaust preload was .030'-ish. I rigged up a much more stable and accurate mount for the dial indicator and did the process multiple times. The entire engine actually has between .095" and .125" using the same pushrod on all 16 valves. This is a Melling pushrod, and is 8.550" long, according to the Melling catalog.

On one side of the engine, I checked all four pairs of rocker arms on #1 cylinder. The variation was .005" or less.

I don't have a machinist quality straight edge, but I took a piece of aluminum flat bar and laid it across the valve stems... it was apparent that a few were lower than the rest. I slid the bar along the valve stems looking for the gap to change visibly and it did not, telling me that my straight edge was reasonably straight. With a feeler gauge, I measured .008" gap at the lowest valve stem.

Here's what I came up with:

1E - .100"
1I - .120"
3I - .120"
3E - .125"
5E - .110"
5I - .125"
7I - .118"
7E - .100"

2E - .105"
2I - .110"
4I - .115"
4E - .095"
6E - .110"
6I - .100"
8I - .105"
8E - .100"


It appears that I need some shorter pushrods, although if the're all the same length some of the lifters will have too much preload.