OEM Rocker Arm Side Play

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12many

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Working on a 360 build and getting around to mocking these new Melling Rocker arms and shafts on a set of Speedmaster heads using the oem shaft hold downs and just checking things over i got to wondering about the side play of the oem rockers:



It’s how it is with these (slop) and we all just bolt em down, maybe ensure equal hold down spacing, but I’d think some custom spacers in between the rocker pairs wouldn’t be a bad idea. The big blocks do, small blocks don’t. I’d assume it’s due to the angularity issues with the small blocks? Any of you more seasoned builders ever put spacers in between, while still allowing some adequate side clearance? Never paid oem setups no mind as far as side to side goes. Seems excessive, very Sloppy!
 
Got any OE rockers to try and see if they’re just as bad?

HS sells shims in various thicknesses you could use to tighten that up.
 
I've seen from very little slop to about as bad as what you have there and nothing ever caused a problem.
 
PRH said:
Got any OE rockers to try and see if they’re just as bad?

HS sells shims in various thicknesses you could use to tighten that up.
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Yes, they are the Same dimensions. I guess it’s just good old oem tolerances. I’ll look into those shims. Obviously some side play is needed just need to settle on how much. Not building a race engine just a fun street performer for my son, could just bolt and roll but..... again, just very sloppy!
 
mopowers said:
Where is the tip on the valve stem at either extreme?
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Rockers butted against hold downs, which are spaced equally, the tips seem to line up pretty centered as shown:

ADDD9CF2-AEC7-4B07-BEE3-C221CA0E416E.jpeg


When any opposing rocker slides over tight to the other (which is butted against the hold down) the tip contacts the valve off center as shown:

CB945662-BF2D-49EF-8547-0949149548DA.jpeg


Both extremes the Contact is pretty consistent for all the rockers
 
PRH said:
“If it were me”, I’d shim that up to have about .020-.030” slop per pair.
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I've got a set of the MP heavy duty ones on my 340, they are dead tight.. actually can see where they " self clearanced" a Lil here and there
 
Ironracer said:
I've got a set of the MP heavy duty ones on my 340, they are dead tight.. actually can see where they " self clearanced" a Lil here and there
Click to expand...

Hmmm. Did some quick measuring and weighing myself of the oem (1978) rockers and these Melling replacements. The widths of both versions I have are all within a similar range as they do vary some but it is small, the Mellings are beefier overall, thicker stampings and therefore weigh a little more. (139g to the oem 121g) How wide are those MP’s on average ? (taking readings with a dial caliper from where they contact each other)
14E0ED0B-B045-4CC4-ACA7-B726B84255B1.jpeg
 
Spacer between like everyone already said. Dykem/pen test them till centered. I think mancini may sell them still...or mod some 273 spacers.
 
Looks like I can slide on some .125” spacers in between the rockers and still have at least .035” clearance per set. Summits got the Harlands in the size I need. Like RRR basically said, no problems either way. I just don’t like slop! Add this to the dressing up of the SM exposed spark plug threads in the chamber......creating more work!:realcrazy:
 
There are rights and left in a set at least on a 340 each valve set will have one right and one left I assume all of that is correct. I have also noticed quite a bit of difference in the nipples on the whole Downs I would find the best combination to true up my spacing on my rockers.
 
check the hold down spacers. I checked a set in the garage, the factory set didnt have that much play.
 
Orientation is correct, stamping uniformity, tolerances are what they are: Inconsistent. When I get to bolting on the heads and measuring for pushrods I’ll see how everything lines up, clearances and so forth. As it stands .125” spacers will work on all 8 sets and still leave adequate side clearance. Obviously this isn’t something most would bother with. The amount of slop caused me to raise an eyebrow though!

B726CDBB-4D15-402B-86C3-96911214B1BF.png
 
12many said:
Hmmm. Did some quick measuring and weighing myself of the oem (1978) rockers and these Melling replacements. The widths of both versions I have are all within a similar range as they do vary some but it is small, the Mellings are beefier overall, thicker stampings and therefore weigh a little more. (139g to the oem 121g) How wide are those MP’s on average ? (taking readings with a dial caliper from where they contact each other) View attachment 1715841719
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I'd have to go out and measure them. I had a Lonnggg thread about a " Diesel Sound".. I caint put a feeler gauge between some of em
 
The 1.6 DC alloy ones I installed had very little clearance. I assumed that was correct.
A few months later at the first scheduled tear-down inspection, it became evident that it was not. The alloys were galling against eachother. I opened it up to .015 per pair.
At the next season's end tear-down, that had proved to be adequate.
 
I’ve got about .160”+/- total clearance for each set of factory style stamped rocker arms, a .125” spacer in between will leave .035” +/- total. Nobody would run any roller rockers (alloy or iron) with that much, they’d add enough spacer to get proper clearance. Makes sense to check the stamped as well and adjust as needed, maybe no big deal on a stock or low reving engine but an upsized cam, stiffer springs with some higher rpm’s why wouldn’t you? Another one of those “attention to detail” practices that takes very little effort to check and sort.

I like PRH’s “I know what I’d do” comment:thumbsup:
 
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12many said:
I’ve got about .160”+/- total clearance for each set of factory style stamped rocker arms, a .125” spacer in between will leave .035” +/- total. Nobody would run any roller rockers (alloy or iron) with that much, they’d add enough spacer to get proper clearance. Makes sense to check the stamped as well and adjust as needed, maybe no big deal on a stock or low reving engine but an upsized cam with some higher rpm’s why wouldn’t you? Another one of those “attention to detail” practices that takes very little effort to check and sort.

I like PRH’s “I know what I’d do” comment:thumbsup:
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Wow. Not meant to hijack, but I'd have to grind the sides off to get that!
 
There is a fundamental difference between a roller rocker & a stamped factory rocker.
The roller tip on the roller rocker is not very wide & there is little leeway for side-to-side clearance before the roller runs off the valve tip.
The contact area of the stamped rocker [ in comparison ] is quite wide & has a lot latitude as far as side clearance goes before excessive side clearance [ on the shaft ] causes a problem.
 
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