I've got some dwell variation, about 8 degrees when I rev up the engine. I have some minor bushing wear in the distributor. Has anyone ever found a source for new distributor bushings? It's a 69 390.

 

Not sure if this helps but I copied and pasted the info below that was originally posted in another thread of mine by Jefffafa. They may have them, I haven't had a chance to call any of them yet.

Also just wondering if you have recently changed points or not. If there is not enough spring tension on them the points can float, maybe even fling open too far possibly giving you the variation. Just a thought.



There never was a rebuild "kit". Ford used to sell the housing bushing separate. Was part number B7A12120A. Replaced by B8QH12120A. And the points breaker plate was D2PZ12151A. Give me a minute and I'll post who has them left. This computer always jumbles up when I paste results. So after posting I have to go back in and edit it to look right.
B8QH12120A:

HUDIBURG PARTS DEPOT
(MIDWEST CITY, OK) shows 1
(800) 800-5963
Morrow Brothers Ford, Inc.
(Greenfield, IL)Sales final on all obsolete parts.
shows 1
(217) 368-3037T
ri City Auto Warehouse
(Fort Wayne, IN)Mastercard/Visa/Discover/Sorry no C.O.D.
shows 1
(260) 471-1649





Dennis Carpenter Ford Restoration Parts

Recently Updated
Part Number:B8QH-12120-A
Seller Dennis Carpenter Ford Restoration Parts
Description:NOS** BUSHING
Phone (800) 476-9653
Price:Request PricingEmail:Send Seller Email Inquiry
Quantity:102
Location:Concord, North Carolina




Miller Obsolete Parts

Recently Updated
Part Number:B8QH-12120-A
Seller:Miller Obsolete Parts
Description DISTRIBUTOR BASE UPPER BUSHING
Phone (607) 722-5371
Price:Request PricingEmail:Send Seller Email Inquiry
Quantity:2
Location:Binghamton, New York




The Lincoln/Mercury Old Parts Store

Part Number:B8QH-12120-A
Seller:The Lincoln/Mercury Old Parts Store
Phone (727) 445-7551
Price:Request PricingEmail:Send Seller Email Inquiry
Quantity:1
Location:Clearwater, Florida




Mark II Enterprises

Part Number:B8QH-12120-A
Seller:Mark II Enterprises
-Description:BUSHING DISTRIBUTOR
Phone (800) 576-2752
Price:Request PricingEmail:Send Seller Email Inquiry
Quantity:5
Location:Apple Valley, California




Mustangs, Etc.

Part Number:B8QH-12120-A
Seller:Mustangs, Etc.
Phone (818) 787-7634
Price:Request PricingEmail:Send Seller Email Inquiry
Quantity:55
Location:Van Nuys, California

 

I'd think finding a source for a fully rebuilt one would be better then trying to patch up one that may need more then just bushings.

And what tooling is needed to remove old bushing and press in new ones and possibly needing to ream the bushing to correct size ect.

This another good reason going to a pointless setup

I'd also make sure it's not a sloppy timing chain that causing the timing to float around.
Orich

 

Thanks for the info. I just rebuilt the engine and it runs great, just the dwell is at 30 degrees at idle and as I rev it to 1500 the dwell decreases to 22 or so. It also may be partially in the breaker plate because even at idle if I apply vacuum on the advance diaphragm, the dwell decreases. So for some reason the distributor shaft is moving away from the points or the breaker plate is rotating in an arc that is slightly away from the distributor shaft. The breaker plate seemed tight when I cleaned up the weights etc.
I'm debating your Pertronix recommendation, I just like things stock.

 

Well, I used Echlin points so I have faith in the quality, also the issue occurs just off idle, not fast enough to float the points.

 

Your problem is most likely in the breaker plate. If it is shot, as the vacuum advance pulls on it the plate will "tip" along with pivoting like it is supposed to. Tipping the points in to the Dizzy's cam. I bet if you disconnect the vacuum hose to the vacuum advance and plug it the dwell will stay closer to 30*. The sheer RPM and the spring on the points might make it still tip a tiny bit. The dwell shouldn't change any more than 2* which is normal. You can buy the breaker plate or a rebuilt Dizzy as Orich suggested. The D2PZ12151A breaker plate is discontinued. There is a company in Wisconsin that carries discontinued parts that your local Ford Dealer can buy it from. Or there is a Motorcraft warehouse in town here that I can buy it from to sell to you. PM me for price if interested.

 

Originally, the point breaker plates were two pieces: B9AF-12151-A lower & B9AF-12151-B upper. In 1972, Ford replaced them w/a one piece breaker plate: D2PZ-12151-A

B8QH-12120-A .. Distributor Bushing (Motorcraft MC-148) / Obsolete

MILLER OBSOLETE PARTS in Binghamton NY has 2 = 607-722-5371.

MARK II ENTERPRISES in Apple Valley CA has 5 = 800-576-2752.

MUSTANG'S ETC. in Van Nuys CA has 55 = 818-787-7634.

CARPENTER NOS OBSOLETE PARTS in Concord NC has 102 = 800-476-9653.

 

I think some people just enjoy making old things work well, the way they were intended to. Buy a new truck if you want electronic ignition and garbage hahaha

 

Exactly right Classic Driver. I have both ends covered with a 67, 69, and a 2016 F-150.

 

Well I ended up buying a new billet distributor from Rock Auto for 71.00.

 

Good deal. I'd be curious to know how you set it up. Timing, curve and dwell. Good luck with it

 

That's a good price too.

 

Well, it'll be setup however it comes out of the box I suppose. I might try to dial in some additional vacuum advance if this one is adjustable like the originals back in the day with an allen wrench. Every mpg is important with a 390 F-250 with 4.10 gears!

 

Good price MPH. Save the working condenser out of your old Dizzy just in case. Or buy a Motorcraft C9AZ12300A (DC13A). There's also been a ton of China condensers going out on new/rebuilt Dizzys.