So I finally pulled the engine and trans on the beater for the long awaited 4 speed conversion. My first hiccup is the pilot bushing... iI have 2 bushings- one is the standard size- 1.097 and another one that my clutch guy said was for auto to 4 speed conversions which measures 1.067. The standard size one seems a little too big and the smaller one fits in there loose. And it seems the hole in the crank has a slight lip at the base of the hole thats about .090. So whatever bushing I get, I'll have to either chamfer it or shorten it by .090-.100" I have to get a long reach inside caliper to get an exact measurement of the crank hole and see if my clutch guy can machine the diameter down of the pilot. I have the pilot in the freezer as a hail mary. I want to see how much smaller freezing it with reduce the diameter but it looks like its going to need a custom size
Everyone of them are different size seems like, I gotta get one turned down to size this week myself for my dad's car
Jason, Yes, most of them we have done are in the 1.072 to 1.075 range for size.. and we have seen a few with that step in them. If your guy can't do it, provide me all the dimentions and we can do one for $20, shipped... we have built the tooling here to turn the Od of the bushing down. JW
I had to do the same thing. It would go halfway in then stop. I got a buddy at work that fixed me up.
1.072- 1.075 sounds right on from the way the 1.067 bushing fit. I might take you up on that offer Jim after I get an accurate measurement on it How much bigger should the bushing be from the hole it goes in? .003?
Interference fit is about .0002 to .0005... any more and the bushing ID starts to shrink on you. It's what's known as a "light tap fit". Measure carefully. JW
I measured the crankshaft three times and called my neighbor over who's an engineer and we both came up with the same number- 1.085. So if we add lets say .0005, that's 1.0855. The stock GM bushing is 1.097. That's .0115", so lets say .012 difference. So that's .006 on the radius. I wonder if I could use the right size bolt and nut as an arbor, and use my drill press as a lathe with some emery cloth?
Worst thing that will happen is you will ruin a $5 bushing.. The step will be the hard part. I would actually recommend using a big flat file. Make sure you spin the bushing at it in the correct direction. JW
Jason, I've run into this on a few cranks as well. Try this: http://pitstopusa.com/i-5068605-allstar-performance-pilot-bearing-driver.html This keeps the ID of the bearing at .590 Then, a Dremel with a fine grit sanding drum just fits inside the ID. Shade tree, yes, but it's just a beater.....
This morning I went to an industrial machine shop on a recommendation from a friend of mine. Huge shop floor. A bunch of CNC machines, all kinds of equipment. I was told to see "Dave". Dave wasn't a car guy but it didn't matter. He understood exactly what I needed to have done. Out came the caliper and after a few minutes of discussion, we agreed on the finished diameter. It was so nice talking to someone that just gets it. I explained about the "step" at the base of the hole too. He said no problem. He machined it perfectly to exactly the right size and had it ready for me by 2pm. $20 . Probably wasn't a big deal to him but it was to me. Its the whole lynch pin to the conversion. The rest is easy. Im going to have some time to install it Weds. Dropped the flywheel off today to get match balanced to the old flexplate, Tomorrow Im going to hang the pedals. The goal is to get the engine and trans back in the car and on the mounts by the weekend. Then running and driving my the following weekend
Pressed in the bushing today. I wanted to find a better way that just pounding the thing in with a hammer and socket. What I did was get a FWD hub puller tool from Auto Zone. OEM brand #27037. https://www.amazon.com/OEMTOOLS-27037-3-75-Axle-Puller/dp/B004FDMWE0 This tool fits the crank of a 455 like it was made for it! Unbelievable! I took the arbor out which had a point on it like a pencil and replaced it with the arbor from my harmonic balancer puller that had a larger point. The point on that arbor fit perfectly into the 1/2" square hole in a 1 1/8" socket. Something like this- Pressed in nice and square with just the right amount of resistance. The custom pilot bushing was right on the money. I checked the inner diameter and my .590" tool fit. I should freaking patent this!!
Thanks Jim! I have this attention to detail thing I cant shake. Anyway, while the engine and M-21 are patiently waiting to go back into the engine room of the GS, I turned my attention to the interior over the long weekend and took care of what needed to be changed over in there. I cut the whole out in the tunnel using a section of an original 4 speed tunnel and test fitted my 4 speed hump. That was a big step, now there's no turning back! I swapped the 4 speed speedo, speedo cable, hung the pedals, swapped in a floor shift column, 4 speed steering column floor plate with the hole in it for the upper clutch rod, and swapped in the correct small block gas pedal. Every component Im using is an original GM part even down to the big block clutch fork. No repro parts. I raided my parts inventory and pulled everything out of stock. Im trying to make the conversion look like its always been there so whenever possible, Im using original, rusty hardware. No shiny hardware store bolts or nuts here! Im not even degreasing the engine or transmission. Its going back in dirty!!!
Hi Jason, I have been following your post here.......very interesting and educational for me. Thanks for taking the time to post your process with the conversion. What did you need to bring to the machine shop besides the flywheel and flexplate? Anything? I am would like to have the same balancing done for my engine.
Glad you like the thread! . Thats it. If your replacing one of these parts, just bring the old part and the new part to the machine shop so they can check the new part against the old one. Flywheels and flexplates are balanced to the engine they're on. So when you replace one of these, you have to make sure the new part matches the balance the old one had. Otherwise, you might get a vibration in the engine. The phrase "good vibrations" doesn't apply here
