‘78 360 dizzy bushing bad?

[Sonny]

I’ve had an issue with the timing mark jumping a few degrees, hearing a rattle below the dizzy, etc. dizzy and timing chain are new.

My intake is off and l noticed the dizzy gear seems loose. What is too loose? Is it an easy replacement and how is it done? Tools needed? Parts? Thanks!

 

[PurpleBeeper]

Hey Sonny, small block or big block? I believe in both cases it's similar, but I will be describing a big block (I know them better). The distributor/oil pump gear rides inside a bushing in the block & is turned by a gear on the front of the camshaft. Maybe you need so see "which way the distributor gear wiggles"? For a big block it could be:
1. Distributor/oil pump drive gear worn (pretty common)
2. Gear on cam worn
3. Busing in block worn
4. the shaft itself on the distributor/oil pump gear worn (not very likely)
5. Hex end of the distributor/oil pump gear that goes into the oil pump (common, but now that I think about it, this wouldn't cause the distributor to bounce around).

If you have a big block, I'd suggest changing that distributor/oil pump gear. "up" options would be a brass gear and/or a hardened "hex" tip (2 possible upgrades) & I would suggest at least the hardened hex tip. To replace it:
a. look at what direction the slot in the gear is facing (where distributor fits) and mark its direction somehow (e.g. masking tape on block above distributor hole)
b. reach down in there with some LONG needle nose pliers and pull upwards with a twisting motion to get it out.
c. the replacement gear just drops down in with a twist, but you may need a try or two to line it up with your tape mark. Either direction is OK, meaning the slot in the gear can be "north-south" or "south-north"
d. all of these steps will let you drop the distributor right back in and fire it up immediately (assuming you also marked the distributor/rotor when you took them out).
e. NOTE --> if you don't get the distributor/oil pump drive gear lines up with the slot in the same direction it was before your timing will be WAY off. That "slot" dictates which direction your rotor points.

 

[Sonny]

Hey Sonny, small block or big block? I believe in both cases it's similar, but I will be describing a big block (I know them better). The distributor/oil pump gear rides inside a bushing in the block & is turned by a gear on the front of the camshaft. Maybe you need so see "which way the distributor gear wiggles"? For a big block it could be:
1. Distributor/oil pump drive gear worn (pretty common)
2. Gear on cam worn
3. Busing in block worn
4. the shaft itself on the distributor/oil pump gear worn (not very likely)
5. Hex end of the distributor/oil pump gear that goes into the oil pump (common, but now that I think about it, this wouldn't cause the distributor to bounce around).

If you have a big block, I'd suggest changing that distributor/oil pump gear. "up" options would be a brass gear and/or a hardened "hex" tip (2 possible upgrades) & I would suggest at least the hardened hex tip. To replace it:
a. look at what direction the slot in the gear is facing (where distributor fits) and mark its direction somehow (e.g. masking tape on block above distributor hole)
b. reach down in there with some LONG needle nose pliers and pull upwards with a twisting motion to get it out.
c. the replacement gear just drops down in with a twist, but you may need a try or two to line it up with your tape mark. Either direction is OK, meaning the slot in the gear can be "north-south" or "south-north"
d. all of these steps will let you drop the distributor right back in and fire it up immediately (assuming you also marked the distributor/rotor when you took them out).
e. NOTE --> if you don't get the distributor/oil pump drive gear lines up with the slot in the same direction it was before your timing will be WAY off. That "slot" dictates which direction your rotor points.

Thanks! It’s a small block. The slack is within the gears as I️ twist it. l don’t see gear play side to side so hopefully the bushing is good. I’ll replace the gear first.
Sonny

 

[Sonny]

Hey Sonny, small block or big block? I believe in both cases it's similar, but I will be describing a big block (I know them better). The distributor/oil pump gear rides inside a bushing in the block & is turned by a gear on the front of the camshaft. Maybe you need so see "which way the distributor gear wiggles"? For a big block it could be:
1. Distributor/oil pump drive gear worn (pretty common)
2. Gear on cam worn
3. Busing in block worn
4. the shaft itself on the distributor/oil pump gear worn (not very likely)
5. Hex end of the distributor/oil pump gear that goes into the oil pump (common, but now that I think about it, this wouldn't cause the distributor to bounce around).

If you have a big block, I'd suggest changing that distributor/oil pump gear. "up" options would be a brass gear and/or a hardened "hex" tip (2 possible upgrades) & I would suggest at least the hardened hex tip. To replace it:
a. look at what direction the slot in the gear is facing (where distributor fits) and mark its direction somehow (e.g. masking tape on block above distributor hole)
b. reach down in there with some LONG needle nose pliers and pull upwards with a twisting motion to get it out.
c. the replacement gear just drops down in with a twist, but you may need a try or two to line it up with your tape mark. Either direction is OK, meaning the slot in the gear can be "north-south" or "south-north"
d. all of these steps will let you drop the distributor right back in and fire it up immediately (assuming you also marked the distributor/rotor when you took them out).
e. NOTE --> if you don't get the distributor/oil pump drive gear lines up with the slot in the same direction it was before your timing will be WAY off. That "slot" dictates which direction your rotor points.

l got a new gear and shaft. The bushing is worn. Where to l get a burnishing tool from? What size?

 

[493 Mike]

The burnishing tool (factory service) is still available new (not cheap). Google it. Or buy one and rent it out (with a deposit) to fellow members.
Mike

 

[moper]

Or buy an aftermarket bushing - no burnishing needed.

 

[493 Mike]

Or buy an aftermarket bushing - no burnishing needed.

I believe the burnishing operation was designed to size and press the bushing into the machined cavity for retention. I do know that I have installed several in my life and never burnished any of them but, some required honing to provide needed clearance.
Mike

 

[HALIFAXHOPS]

I have a new one if needed, think it is a mopar one.

 

[miller]

I’ve had an issue with the timing mark jumping a few degrees, hearing a rattle below the dizzy, etc. dizzy and timing chain are new.

That sounds more like slack in the timing chain. Say it's new?
Cam drive gear all steel? Or, other...?

 

[HALIFAXHOPS]

Hey is the retention bushing on the distributor shaft still there? The have a tendency to crack and the shaft will go up and down and the timing usually jumps. Worth a look.

 

[Sonny]

Or buy an aftermarket bushing - no burnishing needed.

l bought a bushing from summit. It fits nicely on the new gear shaft right now prior to hammering it in. Does that mean it’s “aftermarket “ and doesn’t need burnishing?

 

[493 Mike]

l bought a bushing from summit. It fits nicely on the new gear shaft right now prior to hammering it in. Does that mean it’s “aftermarket “ and doesn’t need burnishing?

The clearance you now have may disappear after driving it into the block. Time will tell.
Mike

 

[moper]

Yup. Time will tell...lol. I use an old not-very-worn oil pump drive to install them.

 

[Sonny]

Yup. Time will tell...lol. I use an old not-very-worn oil pump drive to install them.

That’s what l used. Oiled both new shaft and inside bushing good and after it seated it spun the same as before install.