Locked-Out Bosch Big Cap Distributor for CB Black Box/MegaSquirt

[jpaull]

I wanted to give some ideas for anyone else using a CB Blackbox or any other Megasquirt/Programmable timing setup and wanting to keep a vintage look.

1. 61-64 Bosch Big Cap distributors are still pretty common, and can be bought for about $50 used.
2. Since they are Vacuum only, they have solid shaft, with no advance mechanism so they are perfect for the most accurate distributor choice.
3. Super easy to lock, as you can simply pull the vacuum diaphragm, and screw in a 3/8 brass plug. (simply advance the timing plate some, and screw in the plug and the plate will rest against it)
4. Since its a "big cap" it has larger gaps to discourage timing scatter.
5. Incredibly strong, and most of these have zero shaft play. After taking some of these apart, I can really appreciate the German quality in fit, and metal.
6. Cap, Rotor, Points, condenser, and paint will run you another $50. ( got Bosch everything off ebay)
7. For $100 and some rebuild time, you will have a super accurate distributor that will last forever.

This idea Came from Glenn(Mr. 010). Somewhere we were talking about blackboxes and he mentioned the big cap would be a great candidate with its solid shaft).
I went looking for a big cap and ran into a guy closing his shop and he made me a deal on 50 of them.(might as well build some more in the future right). This guy had these in his parts storage for 40+ years.

Pulled apart, stripped everything off. only left tag on. wired brushed then polished the distributor shaft.

Painted carefully in Satin Black VHT Engine Paint (resists chemicals and gas)

Everything is wire brushed, greased, shimmed, and put back together. New Bosch Points/condenser, and lubed with Super Lube.

You can see the brass plug, and the timing plate is resting against it with spring tension.

You can get Resister or Non-resistor rotors. One Non-resister is Standard GB-311 for example.

This is how it looks with no vacuum canister, and brass plug filling the hole:

All finished, spent a full day, but its my first one so wanted to take my time.

Black Caps are readily available too:

_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[74 Thing]

Yeah, racers have been using that for years with the benefit of the larger cap and locked out.

Good to see you posting to remind people to use it with the Black Box.

How do you like the Black Box so far?

[Glenn]

Looks nice, here's a vintage race car with a similar setup. but he's using a crank trigger and not points.

It would look for a more solid way to lock it. Maybe drill and tap a hold on the sleeve under the breaker plate and use a Allen set screw to lock it down.

Still very cool.

BTW... it will take 50 years to sell those cores. They are not very popular.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[Dan Ruddock]

Two issues for me, will the big body clear my dds center pull and does this distributor retard #3.

Dan

[jpaull]

[jpaull]

[Dan Ruddock]

Anyone know if these distributors retards #3 ?

Would consider running one with my black box

[jpaull]

[chrisflstf]

[Glenn]

[motomwo]

[chrisflstf]

I dont know if the black box can recognize #3 being retarded, but I believe it would compensate as if all 4 lobes were equal.

Its not going to get "confused"

[chrisflstf]

[jpaull]

If anyone else doesnt want to use the vacuum adapter plates for their CB Black box, here is a idea. Yesterday I drilled and tapped the manifolds for 1/8-27 pipe thread and used 1/4 hose X 1/8 -90 degree brass elbows.

Then used 1/4 brass tee with the tight fitting German fuel line

_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[74 Thing]

How do you like the Black Box?

[Dan Ruddock]

[chrisflstf]

[Glenn]

I tested the one I have in stock and 3 were exactly 90* apart and one was 1.5* retarded.

1.5* (distributor speed) = 3* (engine speed).

The degree lines are close so 1-1/2 lines is a bit hard to see.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[jpaull]

[norris]

Really looking forward to your findings Jeff!