Projects Building My 34 B'Ville Coupe With a Potvin

Stovebolt Chevy's of that era had a ball in the perimeter of the flywheel and timing Mark's with a hole in the front side of the block. So it's old technology and been from the factory for decades.

 

I think the flywheel marking would be the most accurate. I thought about a timing mark on the v belt pulley on the back bearing plate but I think there would be too much fluctuation given the gear play in the drive.

 

I think that is a smart decision and your reasoning is spot on. I agree!

 

You guys are way out of my league and pay grade with your work, but this is really interesting. I'm lurking to see the progress and learn a thing or two.

 

So here’s a question. As the rad will need to be in the back and there will be a track nose. Put a grill in the track nose anyways? OR A track nose with a grill painted on? OR A track nose with some cool stripping on it or a graphic? I’m leaning towards a graphic. Fire Away

 

Gotta have a grill OR a killer aluminum insert in place of the grill with striping

 

People expect a grille on a car. It would also let in cool air to intake.

 

Don't suppose the blower can stick out where the grille would be, or maybe just barely behind it, so's people can choke a bit when they see it... ? .
Marcus...

 

So here is what it looks like without the expensive chunk of iron attached. The hub part is what I'm working on now. In the end, it will be quite a bit shorter. As in the pic the gear on the hub will drive the top outer gear which is bolted to the top rotor gear. My idea is now I can tighten the hub on the crank with the 3/4" bolt just like a balancer then the gear will bolt to it. This will remove the perceived slop of the slip on hub that Potvin designed. I feel there is nothing wrong with the Potvin design for very short periods of use like drag racing or Bonneville, but I plan on putting lots of miles on it.

 

Wonder how the long term pressure on the crank snout will affect the mains?

 

I thought, if the marine and some industrials had gear drives, it can't be much worse.

ted

 

You are probably right, I don't know thats why I was curious

 

I did consider it but couldn’t come up with any solutions so looked at some engines that used gear drives. I found even the large truck and industrial engines use a gear case full of gear drives on the front of the engines that drive in a similar fashion. I think I’ll be checking the bearings until I’m satisfied there isn’t a problem just the same

 

Sounds like a good plan. Keep us posted.

 

I think you're headed in the right direction, looks great so far!

I wonder how those helical gears are going to effect the thrust of the crank? Probably won't be too bad as the crank is only spinning the blower and there shouldn't be any more thrust than when the engine sees a load applied/removed. A top-mounted 6-71 with two v-belt pulleys behind a blower belt pulley and all that tension has got to be loads worse in terms of stress on the snout.

What's drive ratio and final boost are you after? Just curious.

 

I am worried about thrust load on top rotor brgs forward from the gear tooth angle and radial load upwards from the gears normal reaction to move apart, the blower bearing isn't all that big. The overall length of the crank drive gear and hub it bolts to makes me think there is room for a chain coupler, [no side load or thrust] and not have a loose hub on crank snout. But would require an assembling hole in the bottom or either side of the potvin adapter in line with the coupler chain for final connection.May have to shorten the crank a tad more.

 

The drive ratio will be 1:1 and I'm hoping for 6-8 psi

ted

 

The crank hub still needs to be machined far shorter. It will end up in the 1.5 inch length with 1 inch cut off the crank. If you check out the 12 71 hi helix blowers used today, they make 30+ lbs. boost and still use the same bearings with much more load. I think these should be ok.
Yes, the chain coupler would fit but i want to get away from the slip fit on the crank. I'm not a fan of machining a access hole in the adapter for assembly but that's just me.

ted

 

Thank You all for your info and ideas. it's nice to have a place to throw ideas out and get input.
Ted

 

The standard chain coupler used on Potvin setups don't require an "assembling hole" in the timing cover. The assembled coupler is bolted to the blower rotor and then the blower is bolted to the timing cover/adapter. The coupler slips over the crank snout and is located using two keyways.

 

Here is the crank hub and gear installed. It all worked out great with .005 backlash on the drive gears. Now on to building the engine then dyno time to see what all this trouble produces.

 

My biggest concern for street use would be the the long term effects of torsional vibration on both the crank and the drive gears. If there is any way you could adapt a good damper onto the hub (I'm guessing there isn't room, but??) it would be well worth doing.

 

I thought of that too but I only have enough room for a 4.50 dia. damper to go right behind the drive gear. I've checked every site I can find and nobody makes anything close. Because of the oil I could not use a bonded type balancer. I've thought of building a viscous fluid type. Maybe give Fluid Damper tech a call

ted

 

Just saw this.

I guess having the World's Fastest Roadster Pickup isn't enuf for you.

Chico's running 180" Chevy V-8. And you're not. But you're going to street run this. I'm on your side. I know shit about what's going back and forth here – but I'm hoping you can do this sucessfully.

Stan

 

STAN How you doin man. Wish we could have made it to the salt but. We were all dressed up for the prom and Dad said we couldn't go. how did you make out?
Looks like i'll just have to build my own Fluid damper. Chico is running some special OD unit made back in the day. I got my front cover from him, a real good guy to talk to.

 

I just stumbled upon this, I'm building a potvin also. I better start taking notes.

 

Cool....

 

OOOoooo. i'll take one of these and one of those and