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Old 04-17-2006, 11:02 PM
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assembling float pin / rod

I have never worked with bushed, float rods before, just normal pressed-in pin, however I was under the assumption that the pin just slides right into the rod like it slides into the piston. I'm now assuming that I was wrong.

I got a set of Eagle rods today and I wanted to assemble it with the piston to compare this combo (Keith Black pistons) with the stock combo, to compare weight. To my surprise the pin wouldn't slide in and I didn't want to push hard because I was nervous about jarring the bushing. I began to think maybe I was sent the wrong rods so I looked up the measurements online. The pin diameter is .981 and rod hole is .980. so apparently the pin is not supposed to just slide in.

So now Im curious, how exactly does this work? If the hole is smaller than the pin how the heck does it free-float? Also how do I go about assembling it...do I need a shop to heat up the rod like a pressed pin?

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Old 04-17-2006, 11:47 PM
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If you full-float the rods with a bushing, you should be able to drop the pin right through the rod with little or no persuasion. Same for the pin hole in the piston. If you can't get the pin through the rod with little or no effort, then you had better get back with the supplier and discuss your problem. Did the pistons come with lock rings?
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Old 04-17-2006, 11:51 PM
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Maybe this isn't valid, but on all my motorcycles, 2-stroke and 4-stroke, the pin just slides in nice and easy. Internal clip on both sides and they be done. Now the 2-strokes have caged needle bearings but the 4 stroke is just like an auto in that it has a bushing.
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Old 04-18-2006, 12:21 AM
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I dont know what to do now. Like I said, I looked up the sizes for Keith Black float piston pins, and the Eagle pin hole diameter......pin is .981, rod is .980. so I dont even know who to complain to. If anyone is familiar with these parts, they are for an Olds 455, .030 over piston, stock sized H-beam rod.

Could the bronze bushing be too thick? Id compare it to 2 sheets of construction paper thickness.


Alright, this is weird. I expanded my research of sizes by looking at the pin diameter of other brands of pins. Speed-Pro uses .980 but are pressed, and SRP uses .980 also and are float. Is it possible that Keith Black is manufacturing a wrong sized pin? (i doubt that).

Anyone with experience using these parts?
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Old 04-18-2006, 12:31 AM
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If the pins slide in and out of the pistons easily and you have lock rings with the pistons, call Eagle and tell 'em what's going on. Ask if they can send the correct rods or if you should take the rods to a local machine shop and have the pin ends honed.

By the way, pay no attention to any published figures from anybody. Measure everything yourself and re-machine as necessary. That's my best advice.
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Old 04-18-2006, 01:01 AM
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A friend of mine just dropped over my house, he has a set of Speed-Pro's for a 455 too laying around (hes seems to build engines in his head more than in the garage ). We compared pins, but no other noticable differences. So I tried his pin into the Eagles and *presto* slipped right in, almost dropped it out the other end.

So now I thought to try and see if my pin could fit into his piston, and it does, although there is a noticable tightness. His pin goes into my piston, obviously as well, however there is no 'slack'. Even with the pin only through one of the holes there is zero wiggle even applying significant force. So Im thinking of maybe swapping pins with my friend.


BUT, of course there is a problem with this now (maybe). After thinking of this swap, I compared the pins very carefully and noticed the only differnce between the two is that mine is a hair, like 1/32th of an inch longer. I thought this was so that the pin sat tightly between the locks but after putting my pin in my piston, there was visable space between the pin and the lock groove, Id say about another 1/32th. Do you think that would cause major problems, using his shorter pin and having approx 1/16th clearance between pin and spiro-lock groove? I honestly have no idea about float pin lock tolerances, or even the side-to-side stress it may under. Any input is greatly appreciated.
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Old 04-18-2006, 01:17 AM
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Don't worry about pin length. Are the pistons machined for a total of 4 locks per piston or 2 locks per piston? If 2, install the locks with the rough side of the lock (burrs where they were stamped out) toward the pin. If 4 locks per piston, install the rough sides together, with the smooth sides riding toward the aluminum of the pin boss on one side and the pin on the other side of the locks.
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Old 04-18-2006, 01:24 AM
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hmm, are you talking about snap on C-shaped locks? These are a spiro-lock. There is one groove on each side of the piston. The lock is a coil, spring looking thing that you 'screw' into the groove, the coil then compresses and binds in the groove and sits in it. I guess it may be difficult to explain, but either way, I have the directions for the locks. The important thing is that pin length doesnt matter here.

Thank you very much Inspector, I must say, this forum is 50million times better than an Oldsmobile specific forum I asked this question on as well.
Ill update this if there is a conflict, however Im as happy as can be right now.

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Old 04-18-2006, 05:16 AM
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pins

IMO you need to do a little more checking before changing things around....

What size is the bore in the piston???

What tools are you using to check these sizes...


A few observations,
The eagle's as well as other rods some times come with the bushed end on the small side or .0005" under. You need to hone them out about 50% of the time for the correct fit..Also they have a very sharp edge on them,if they are fitted with only a few tenth's clearance you need to be careful how you start the pin. I will usuall use a 3 sided scraper and put a very small chamfer on the bushing to help get the pin started easyer....

Me personally i would not run the shorter pins... I can-not say for sure what you can "get away with" as far as end play goes becasue i keep mine as tight as i can... The more clearance you have at the end the more the pin is going to beat on the retainers....


Keith
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Old 04-18-2006, 08:24 AM
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I wouldn't swap the pins either. The pins have been fitted to the piston as that's who supplied them. In this case the rod maker didn't have the pins in hand to measure and made them to their tolerances. I would have the rods honed to fit. I find this happens about 25% of the time.
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Old 04-18-2006, 09:05 AM
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It would probably slip in if you left the rod out in the sun for about 20min. The metal will grow. Try not to handle the pin in your hand to long. The absorption of heat will be your detriment.
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Old 04-18-2006, 10:19 AM
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Quote:
Originally Posted by k-star
IMO you need to do a little more checking before changing things around....

What size is the bore in the piston???

What tools are you using to check these sizes...


Same size, they are both for Olds 455, .030 over. Which sizes do you mean? If you are talking about the pin and hole diameters, Im using advertised sizes displayed on Summit and double checked on other similar vendors. If you mean the gap between the pin and the lock groove, that Im going by eye.


Anyway, thanks for the responses, I had no idea it was that common for the rod holes to be a little tight. I will contact my machinist today, have him give it the proper measuring, and if necessary, prepping.

However there still is the question about Keith Black. Is it possible that they are manufacturing an incorrect pin size? I wouldnt have believed it if I didnt see it myself, but they are the only piston maker for Olds 455 that doesnt use .980 pin, and it cant be a coincidence that their .981 pin doesnt fit, but the Speed-Pro .980 pin does. If anyone has experience with KB's in this application, please comment if you encountered a similar problem, or if there was no problem and they worked fine for you.

Thanks for the replies.
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Old 04-18-2006, 11:09 AM
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rods

I was asking about the pin bore in the piston. i would check it's diameter compaired to the rod bushing diameter. Don't use advertised sizes,check the real sizes...

I have used 10 or 12 set of the KB pistons and i have had zero issues in this area with them...

Check the pin bore diameter in the piston and the rod and let use know the sizes....Or take them to your machine shop and have the deal fitted....


keith
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Old 04-18-2006, 11:16 AM
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Not to drag this out but is it not true that the rod will center itself on the crank pin, floating within its 3 thou clearance (its been awhile...is that about right?) between the other rod and the fillet off the counter weight and then at the top the piston will center itself within the bore with its sidewall clearance allowing the small end to "float" from side to side, but not rock on end to end, without really putting much pressure on the locks. All the floating is really done between the bushing and the rod. The clips are there to just keep the pin from flalling out...right....or ? My point being bushing to lock clearnce is not all that critical but bushing to rod is of upmost importance, along with the bushing to piston of course.
Your course of action I think is the best. Let a machinist make the call and hone to fit if necessary. It would then be a perfect fit!
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Old 04-18-2006, 03:06 PM
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I guess I will bring everything to the shop. I wanted to avoid this as much as possible because I dont have a trusted machinist yet. I trust more people on this board than the guy I happen to be using right now (not because he does bad work necessarily, just that I dont really know if he does do good or bad work).


Thanks for the advice.
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