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The legendary 2.9 Free Floating Rockers

Paulos

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I forgot to mention the gap between the roll pin and the outside rockers. Between 0.0505 and 0.0725 between the spring clip and the rockers, with the spring clip approximately 0.020 thick. So overall, roughly 0.0705 and 0.0925 gap between the roll pin and outside rockers.
 


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Yes I do...

The shafts I've used were drilled and tapped on the ends. They had an aluminum cap with a machined cup for the shaft...and shims to get the rocker where it was needed. Then torque the caps down. I don't remember issue with shim wear anywhere on the shaft... but there was ample oil to keep them lubed.
 

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So the pedestals are free floating on the rocker shafts, believe it or not. They feel pressed on due to the spring pressures and galling issue.

Not sure about the spring clips or outside rockers. I can see the utility of aluminum bushing there, though.

My fear with the spacers and shims would be wear. I need to look into how the V-dub guys do this.

Any suggestions Gump??
I'll have to take apart a rocker arm today, now that you brought this up :). Are you planning on using new shafts, or reusing the old ones? Having the rocker bores enlarged and the wear from the valve stems cleaned up by a machine shop looks necessary, or can the bores be honed that much without taking the rockers to a shop? It would be nice to have a spacer kit with an assortment of shims, and an inexpensive way to polish the old shaft and prep the old rockers at home, in order to bypass the cost of a machine shop.
 

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Yes I do...

The shafts I've used were drilled and tapped on the ends. They had an aluminum cap with a machined cup for the shaft...and shims to get the rocker where it was needed. Then torque the caps down. I don't remember issue with shim wear anywhere on the shaft... but there was ample oil to keep them lubed.
A poster in this thread mentioned that he "milled the sides of the stock cast aluminum rocker shaft pedestals to allow the rocker arms to line up better over the valve tips". But he never said if it weakened the pedestals by doing so. Ford clearly made the contact surface of the rockers more than wide enough to account for the offset, but the poster mentioned that the offset was seen as unacceptable by aftermarket roller rocker manufacturers. I guess Ford decided that the excessive offset was acceptable for the 2.9 valve train.
 

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Ok, I pulled a set off of a junkyard engine to do this free floating mod, actually!
2.0085
2.1525
2.0395
2.1575
I find that those numbers vary by +/- 5 thousandths around the shaft.
I actually had the concern with aluminum being too soft and prone to wear, so I've been trying to find someone who sells bearing grade bronze/brass of the right size. (Still looking!)
 

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I see all you 2.9L guys worried about wear on these aluminum spacers. Now maybe this is a valid concern but... The rockers will be "free floating". There will be no side load created by the springs forcing a wear surface. In all the years I've played with free floating rocker shafts I don't ever remember shim or spacer wear issues. Unless... when the person assembled the shafts to tight and "forced" a wear surface. Something to also remember is the spacers and shims will rotate on the shaft... way different then the rocker rubbing against a stationary surface. An aluminum spacer... steel shims against the moveable surfaces with proper clearance... I honestly think you guys would be golden.
 

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I see all you 2.9L guys worried about wear on these aluminum spacers. Now maybe this is a valid concern but... The rockers will be "free floating". There will be no side load created by the springs forcing a wear surface. In all the years I've played with free floating rocker shafts I don't ever remember shim or spacer wear issues. Unless... when the person assembled the shafts to tight and "forced" a wear surface. Something to also remember is the spacers and shims will rotate on the shaft... way different then the rocker rubbing against a stationary surface. An aluminum spacer... steel shims against the moveable surfaces with proper clearance... I honestly think you guys would be golden.
Good point... especially if we replace that spring-steel clip on the ends... What grade aluminum would be best? 6061?
 

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Quite a number of things. Gump nailed one of them.

They were a cheap and sh*tty design concocted by Ford.

The springs allow the rocker arms to walk slightly. The other thing they cause is metal galling by exerting lateral pressure on the rocker arms between the arm and the pedestals. Constant uneven lateral force eventually wears the arms in a canted pattern (like my old assemblies) and starts cutting off oil flow to the valve train, and leads to the infamous 2.9 tick.

The spacers create oil galleys in the valve train, and allow oil to free flow through the top end. Word on the street is that they eliminate lifter tick entirely from the 2.9, and allow the engine to come on faster due to less mechanical resistance on the top end.
I imagine this also contributes to the rocker pedestals breaking. It wasn't nearly as common as the heads cracking, but it was a known issue.
 

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Good point... especially if we replace that spring-steel clip on the ends... What grade aluminum would be best? 6061?
That was actually my next question - what grade of aluminum/brass/bronze/unobtanium to use.

The other idea from seeing these measurements was to look for someone like McMaster Carr / Grainger / Fastenal / Whatever that has tube stock on the shelf that's the right bore diameter, or that can cheaply/easily be made the right diameter.

The idea I have kicking around right now is to design/choose a source so that they are 'modular.' Gump's idea of shims, and the amount of variance in tolerances/wear is suggesting to find a source so that these are a kit composed of a few pieces, something like a 1.500"/1.750"/1.900" main spacer, and one or more spacers of 'whatever' thickness to make up the rest of the gap. Don't quote me on main spacer lengths just yet; I really am just spitballing at this point.

The other question was if there were two "true" lengths that could be used universally. I'm curious if the variances that we're seeing are wear, machine slop, or how much the rockers truly can move on the shafts. Furthermore, how much we can allow the rockers to walk/float around on their own and still be safe to run? The 2.9/4.0 rockers have fat-assed control surfaces, can we take advantage of them? Just develop a 'long' and 'short' spacer, not worry too much about the precision lengths, and just send it?

Actually, does anyone have a set of 4.0ohv rockers that you can measure to see if the spacers would apply to them as well? The set on my 89TM heads look just like 4.0 pedistals. Always wondered if they were interchangeable.

Seems to me that if the main spacer was aluminum and the end shims were steel/whatever, that it would make for a off-the-shelf kit that would require no custom machining. Just pick up a 'main' and whatever shim(s) you would need for each rocker shaft, and go to town.
 

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That was actually my next question - what grade of aluminum/brass/bronze/unobtanium to use.

The other idea from seeing these measurements was to look for someone like McMaster Carr / Grainger / Fastenal / Whatever that has tube stock on the shelf that's the right bore diameter, or that can cheaply/easily be made the right diameter.

The idea I have kicking around right now is to design/choose a source so that they are 'modular.' Gump's idea of shims, and the amount of variance in tolerances/wear is suggesting to find a source so that these are a kit composed of a few pieces, something like a 1.500"/1.750"/1.900" main spacer, and one or more spacers of 'whatever' thickness to make up the rest of the gap. Don't quote me on main spacer lengths just yet; I really am just spitballing at this point.

The other question was if there were two "true" lengths that could be used universally. I'm curious if the variances that we're seeing are wear, machine slop, or how much the rockers truly can move on the shafts. Furthermore, how much we can allow the rockers to walk/float around on their own and still be safe to run? The 2.9/4.0 rockers have fat-assed control surfaces, can we take advantage of them? Just develop a 'long' and 'short' spacer, not worry too much about the precision lengths, and just send it?

Actually, does anyone have a set of 4.0ohv rockers that you can measure to see if the spacers would apply to them as well? The set on my 89TM heads look just like 4.0 pedistals. Always wondered if they were interchangeable.

Seems to me that if the main spacer was aluminum and the end shims were steel/whatever, that it would make for a off-the-shelf kit that would require no custom machining. Just pick up a 'main' and whatever shim(s) you would need for each rocker shaft, and go to town.
Have you tried removing the springs and bolting the rocker assembly to a head, then measuring? If the pedestals are the same thickness, the threads in the heads the same distance center to center, and the rocker arm shafts and rockers have the same dimensions, then maybe the difference in measurements was in a great degree due to the rockers not being bolted down when they were measured. If the rockers are free-floating that may have effected the measurements. I agree that the spacers should be pretty close for nearly all non-thrashed rocker assemblies, with an assortment of shims and maybe a couple new roll pins (you definitely need a thick shim to replace the clip between the roll pins and the outside rockers). If there was a spacer kit available, I'd probably find a local machine shop to have the oil holes chamfered, the shafts polished, the rockers bored (if honing them won't work easy enough), and the rockers cleaned up where they make contact with the valve stems.

If I have some time this weekend I'll try bolting the four rocker assemblies that I have to my new heads and see if the measurements are any different.
 

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Have you tried removing the springs and bolting the rocker assembly to a head, then measuring? If the pedestals are the same thickness, the threads in the heads the same distance center to center, and the rocker arm shafts and rockers have the same dimensions, then maybe the difference in measurements was in a great degree due to the rockers not being bolted down when they were measured. If the rockers are free-floating that may have effected the measurements. I agree that the spacers should be pretty close for nearly all non-thrashed rocker assemblies, with an assortment of shims and maybe a couple new roll pins (you definitely need a thick shim to replace the clip between the roll pins and the outside rockers). If there was a spacer kit available, I'd probably find a local machine shop to have the oil holes chamfered, the shafts polished, the rockers bored (if honing them won't work easy enough), and the rockers cleaned up where they make contact with the valve stems.

If I have some time this weekend I'll try bolting the four rocker assemblies that I have to my new heads and see if the measurements are any different.

Springs were on when I bolted one of.my extra sets down. I really need to get a measurement off of of my.current heads, as they're brand new sets of rockers, shafts, and the 89tm style pedestals to see if there's any obvious differences.

Oil hole chamfering is easy. Did mine on my drill press with a Milwaukee relief cutter bit. Took a few minutes at most. Honestly could have freehanded them.

That would be awesome if you'd be willing to bolt down some sets for measurements. I have one additional extra set that I can do that with. I will as well.

A kit setup would make the most sense to me. I'll do some.research on tube stock to see what McMaster has, as well as a ball/flex hone. I may not hone out my rocker arms, but the spacers seem too good to pass up.
 

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I haven't had much time to check measurements this weekend. But I did dismantle an old rocker arm, and discovered why this particular engine was apparently noisy.

20190902_151642.jpg


The four lower oil galleries in the rocker arm shaft that supply oil to the lower side of the rockers (where the tension is) were plugged up, like the second hole on the right of the shaft. I had to stick a piece of wire through each one to break up the deposits. The deposits were thick enough that I don't think any type of oil treatment would have dissolved it. It's probably a good idea to change the oil once in a while to avoid this :unsure:. An occasional can of Sea Foam or equivalent wouldn't hurt.

The top side of the rocker shaft is not worn at all, so I suppose it may be possible to flip the shaft 180°. The pedestals are not pressed on, but they were pretty snug on the shaft.

20190902_151818.jpg


I did bolt the rocker to the head first though, and with the rocker assembly slightly loose there was side-to-side movement between approximately 0.005"and 0.010". So, it appears that it would be a good idea to re-assemble the rocker assembly without the springs (roll pins installed without clips), center and tighten each pedestal, and then measure for the spacers. Using old pedestals and rocker arms is where the shim kit will come in handy due to different wear on different engines. I'll get some measurements without the springs and clips in the next day or so.
 

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Last set I have on hand, polished and reground 86tm rockers and shafts mounted on 86tm heads:

2.129
2.044
2.016
2.151

Shafts measure 0.880 diameter.

OK. I think we're getting somewhere.

I need to nerd out and put a spreadsheet together of all of these. I think we won't be able to have a generic set made that would fit all engines, but I should be able to run some averages and either get a shop to turn out a generic kit, or find a industrial bushing supplier / performance parts shop that will turn them out. Would be nice to be able to just "get a set", even if it's a TRS exclusive thing.

I really should pop my valve covers to check if my 89tm rocker assemblies have different gaps, but /lazy.
 

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