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Canadian Poncho Homepage -> Canadian Poncho -> 65-70 Full Size Power Train Tech Forum -> Engineering help please.
Post Info TOPIC: Engineering help please.
4SPEED427


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Engineering help please.
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I need an engineer! I am looking for a crank pulley for a big block. I was sitting here looking at pulley pictures and remembered I have the identical pulley except it's for a small block and the pilot hole is wrong to centre it on the balancer.

I have access to a press. How can I change the hole in the black pulley to be the right size like the orange pulley has? In case you've never looked at one, the back of that hole has about 1/16" lip sticking out  that fits into the centre hole in the balancer.

I have access to tapered dies that fit into bearing cups on a brake lathe. I was thinking I could use that to press in to the hole. I could slowly press and measure until the hole is the correct size, or.....?

DSCF0390.JPG



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
73SC


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I think I would be inclined to broaden my search for the proper part Carl. That's a critical piece and I know you would be meticulous in drilling the small block one however it could be out ever so slightly.  



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dualquadpete


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Carl, do the 3 bolt holes line up the same as B/B??? if so they will centre it on balancer as long as it sits flush to bal. I personally don't think the small "lip" does anything but make it eastier to line up. If Dia. is same, pulley "belt" groove is the same??? I'd go for it if you can't find one or really want that lip!!!

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4SPEED427


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Yes, it bolts right on. I just am not comfortable enough with using just the bolt holes. The small lip on the back of the centre hole makes it sit perfectly in the middle of the balancer. I don't think the bolt holes are precise enough. I guess I could put it on the balancer and use a dial gauge to measure it while I rotate the balancer.

But the other thing is, I like little challenges like this!

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
Fake68


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1) Drill it out until it is approx. 3/16-1/4" under the balancer opening size. Carefully align and bolt it to a spare balancer (dial if you like). Use a body hammer to lightly form the overlap into the hole.
or
2) Carefully align and bolt it to a spare balancer (dial if you like). Use a bolt through the assembly small washer on pully side large on back side. Tighten bolt until it "pulls" the pully flange into the balancer. Trim pulley center on lathe afterward.

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Beaumont4008


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I think if you enlarge that hole on that small block one it would make it very weak indeed. You have around 12 holes in that small block one and that would not leave much material around the new larger hole.



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Fake68


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All of the applied load to the pulley is between the belt (outside edge) and the bolts. Any material inside of the bolt holes is just along for the ride (or in this case for centering the pulley onto the balancer).

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72 Nova SS - Minitubbed
70 Nova SS - #'s L-78 Bench Stick
68 Acadian SS clone - factory air
67 Chevelle rag - SS 427 clone

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Beaumont4008


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Fake68 wrote:

All of the applied load to the pulley is between the belt (outside edge) and the bolts. Any material inside of the bolt holes is just along for the ride (or in this case for centering the pulley onto the balancer).

 yes I see what you mean , good point.  (now that I got my glasses on and had my medication) its all clear now.



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4SPEED427


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No lathe, sorry.

I think I will try opening up the hole as you and Fake68 suggest though. Then maybe bolt it down to a balancer and tap tap tap.

I see I can buy a new one for about 40 bucks but now I'm to the point I want to try this just because!

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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