Vacuum Advance / Boost Retard unit

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player1up

player1up

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Is there anything out there like the corvair vac/boost can that might be easy to retrofit to a standard dizzy, I've been doing a little research and have found someone that makes one for the turbo corvair, but I'm not spending $125 to hack it up and try it...

I'd like to not have to replace the ignition and buy a boost timing module just to retard the timing a couple of degrees...

Just thinkin out loud, ALL thoughts welcome..well almost ;) I don't want ppl to tell me to suck it up and buy the MSD unit...that's the fallback plan, but I'm still saving...
 
You run SB or BB? Ford used to use a retard/ advance can on their distributors, I'd think one of those would be easy to fit into a BB/ RB Who knows? you might be able to hack one of those cans into a Mopar dist.

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I'm running a /6 :)

I was just checking back in...found that volvo used one on the 81-84 240 turbo as well..
What year furds did those come on?
hmmm, maybe we're onto something
 
Ferds used the dual diaphragm units on just about everything from 68 (start of Fed. smog) onwards for a few years. Donnooooo whether a Ferd 6 dist. would do you any good or not.
 
From what I'm reading the dual diaphragm units are a little different than a vac-advance / boost-retard unit.
Dual diaphram: base port uses manifold vacuum to retard the timing at idle ( not pressure )
and the top port uses ported vacuum to advance at throttle...

vac-advance/ boost retard unit: top port uses vac to advance and the bottom port uses boost to retard the timing...

Apparently porche used the vac-advance/ boost retard unit in turbo 911 models around the mid 80's and ford used the same unit on the turbo pinto :lol:

RockAuto lists a distributor for a 71 pinto "w/Vac retard system" Autoline part# D461 and the can looks the same as the volvo/porche unit
 
player1up said:
From what I'm reading the dual diaphragm units are a little different than a vac-advance / boost-retard unit.
Dual diaphram: base port uses manifold vacuum to retard the timing at idle ( not pressure )
and the top port uses ported vacuum to advance at throttle...

vac-advance/ boost retard unit: top port uses vac to advance and the bottom port uses boost to retard the timing...

Apparently porche used the vac-advance/ boost retard unit in turbo 911 models around the mid 80's and ford used the same unit on the turbo pinto :lol:
Click to expand...

Piddle pooo, you are correct of course.
 
what I'm wondering is if your running power brakes and are into the boost how does your booster work? how about the things that require vacuum that are now getting presurized?
 
66plyValiant said:
what I'm wondering is if your running power brakes and are into the boost how does your booster work? how about the things that require vacuum that are now getting presurized?
Click to expand...

Diesels run either a pump driven off the alternator, or electric vacuum pump, hydro boost brakes
 
I have read that you can use the vacuum advance pot but under boost conditions you need to have a check valve installed between the source and the dizzy. If you are boosted its is best to use a mechanical dizzy and something like a MSD BTM to retard per # of boost that way you won't risk detonation! I can't seem to find anyone that times the curves on dizzies anymore. I guess everyone junked their Sun machines???

There are some threads on TTF about this exact issue.
 
67Dart273 said:
Diesels run either a pump driven off the alternator, or electric vacuum pump, hydro boost brakes
Click to expand...

I know what diesel vehicles do, what do factory gas turbo cars do? how does the carburator work with boost insted of vacuum?
 
ok so I've found a couple of part numbers...

vc1309 / CV1867 - VW / audi unit

Preliminary investigation is interesting, but today at lunch I had a productive junk yard run.
I pulled a stock mopar unit in the first 5 min, and after exhausting almost all of the rows, a set of volvo headlights caught my eye. The volvo gave up the goods in short order and upon arriving at the checkout counter, the gentleman said "what are those?" I replied, "vacuum canisters"...So he says "have a nice day".... :D

It probably helps that I go there all of the time "looking" but don't seem to find anything very often

So now I have a stock mopar one to hack up and a working vac-advance / boost-retard unit....for FREE!!!! ( well, it cost me $2 to get in ) I even pulled the vac line with check valve too.
 
66plyValiant said:
I know what diesel vehicles do, what do factory gas turbo cars do? how does the carburator work with boost insted of vacuum?
Click to expand...

Carbs work on pressure differential, the carb "sees" roughly the same thing as it did before the turbo the air is just more dense.
If the float bowl is getting the same boost pressure as the air flowing through the venturi's , it's all good , the air flowing is moving faster so the pressure is lower, fuel will still flow from high(er) to low(er) pressure. ( at least that's how I understand it )
 
welp, last night was pretty interesting.
I got the unit mounted up to my test dizzy.
1. I cut the arm off the stock mopar unit at the step down ( the junk yard unit ).
2. Drilled 2 new holes in the retard unit and bent the mount plate as to match as close as possible to the outer housing of the mopar distributor. Removed retard stop plug because it wouldn't allow the can to sit flush against the dizzy body.
3. Installed the piece of mopar arm into the distributor and slid the retard unit into place ( verifying that nothing was hitting throughout the travel of the vac advance arm)
4. Tack welded the mopar arm to the retard unit arm. Removed and welded and cleaned up...
5. Reinstalled the unit and bench tested... :D

Oh, I did test the unit before going through all of the trouble and the unit works just like the dual diaphragm unit as far as vacuum is concerned.
--bottom port: vac = retard / boost = nothing ( no movement )
--top port: Vac = advance / boost = retard

I'm going to try to get it added to the distributor that's in the car sometime soon, but I still need to check how much advance / retard is at what amount of vac / boost
 
Initial testing is underway.
I've installed the bosch advance can and set base timing to 10°.
The retard is about 10° and vac advance is about 10° as well.
No pinging at 6psi and pulls good throughout the RPM range.
Now onto adding back in some mech advance or maybe add some boost to see what boost level it starts pinging :D

...but of course I didn't think to get any pics of the setup :banghead:
 
I'll be doing a Vac retard system in the next couple of weeks.I'll post some pics of it while I make it.
 
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