Does a 67 Duetto have Brake Booser?

[whagan]

I finished (phase 1) restoring a 67 Duetto and have always been disappointed with the braking. I was just talking with Bob at Centerline and he was surprised that I didn't have a booster. There is no evidence of the booster although the car sat for 28 years and farm dust covered everything. I have always been puzzled with the vacuum port on the forward side of the intake manifold and the small pipe protruding out of where the hose from the valve cover vent hose joins the air intake plenum box. Joining these two never seemed right seeing as that would effectively create a nice filtered intake leak! I plugged it instead.

If this car is supposed to have a boost that would explain things. If so could someone post a pic for me of how this looks on a 67 Duetto.
Thanks!
Wayne

[ossodiseppia]

Some do and some don't. I don't think anyone has figured out if those that do have one were retro-fitted with it or if they came from the factory with one. I think it really depends on when your car was manufactured. Those Duettos made later in the production run probably got them at the factory.

[101/105guy]

Never seen a first series Duetto 1600 come with a factory mounted booster. None in any of the factory photos or in the manuals. I have seen some added by owners.
Never missed having one on my Duetto. Different brake pads will change brake feel.

[ossodiseppia]

Table 41/3 from the Spider 1600 Amendment to Spare Parts Catalog, Pubblic. No. 002/1251. Note the sixth part on the list called POWER BRAKE ASSEMBLY. That is a Bonaldi booster. Under the description is state Optional parts added.

[60sRacer]

None of the Duettos I've seen that were made in 1966 had boosters. Same for most of the 67's. BUT... Otto Zipper told me that for most of 1968 alfa was on strike, and US rules for car safety forced alfa to make some changes that we saw result in the 1750 injection cars for 1969. Meanwhile, they did assemble some cars in 1968 that were actually 1967 models. They were sort of "parts bin" cars, made with whatever was on hand. [For example, mine had the bell housing from a Sedan that had several rather large holes cut in it for the column shift mechanics]. A few to a few hundred of these came to the US. Many but not all of these had the single circuit booster system. The 69's (1750) had dual boosters to go with the new dual circuit brakes.

Also remember that the early Duettos had Dunlop brakes, later ones were ATE.

I think the GTs and Sedans (especially the TI Super) around that time had the single circuit booster more often than the Duettos.

So, in answer to your question, yes there were some Duettos with single brake boosters.

There also is a different MC that goes with this by the way. It's larger in diameter, which reduces the line pressure before the booster so you don't get "over-boosted". (Smaller diameter gets higher psi for the same pedal force, used on cars withOUT the booster). I think the two MC's are 20 and 22 mm bore diameter, with the larger one going to the booster cars.

Robert

[whagan]

Thanks for all the info! I think I might see if different pads help before dealing with the expense/hassle of installing a booster, esp. since I just overhauled the brake system. Thanks Robet for explaining the mystery of that gaping hole in the side of my bell housing. It seems strange that Alfa would put a rubber seal on the clutch lever arm where it goes through the bell housing and then leave a gaping hole for all the mice, weather, dirt to enter!

I still am curious where that little hose is supposed to go that exits from the side of the hose from the valve cover to air intake, (small black hose seen in above photo off air intake plenum).
-Wayne

[60sRacer]

I didn't like the big hole in the bell housing either. I used a thin sheet of aluminum and a rubber mallet to make a cover, which I fastened with a few pop rivets. Been in place for a few decades.

The little rubber hose goes to a fitting on the intake manifold. Its a path to take oil vapors into the CC with the throttle closed. BTW - there is a brass fitting on some duettos that goes in the rubber "L" shaped hose (about 1 inch dia) from the valve cover to the intake cover. It's just a thin brass screen
but its purpose is to stop the flame from a backfire (the carbs do pop occassionally) from going into the crankcase. takes a bunch of problems, but it could cause trouble if the crankcase vapors are ignited.

Robert

[whagan]

That's actually were I first placed the hose, but after reflecting on I thought it would effectively create a big vacuum leak in just the 1st cylinder, albeit filtered by the air box, I was experiencing unusual leanness in the number one carb on idle and so I plugged it up thinking hey, this is the only cylinder that has air leaking in (no check valve). This seems a weird design that would effect air mix unevenly at idle?

I wish there were holes like that for every intake barrel so I could hook up my synchronizer gauge for a more accurate carb sync!

[Alex]

A couple of photos if this will help? Just to repeat what Robert said, there is a very fine brass gauze inside.

[whagan]

Thanx Robert and Alex, I wondered what that screen was for. But it's the little black hose off the #1 Intake that I take issue with, seems to function like a big leak for #1 cylinder. At least with my limited understanding of the physics of vacuums. Seen here in crop of previous poster.
-WH

[Bill S]

Did phase 1 of your refurbish include replacing the brake master? You may want to check and see if you or someone before you replaced your MC with the incorrect (for your car) larger one that Robert mentioned. That would definately affect your braking.

[whagan]

I purchased a new one from Centerline, is there a quick way to tell if it's the right one?

[Bill S]

You might just call Centerline and ask which one they stock. I believe that the ID in mm is usually shown in the casting on the outside of the cylinder so you might be able to tell by crawling under the car with a flashlight.

[whagan]

I'll check in on that, thanks!

[alfabecker]

If you plan on installing the booster, the vacuum hose was attached to a one way valve, located on the intake manifold, perpendicular to the left of the #4 intake port. I recently acquired a 67 Duetto that I am restoring, that came with a booster and ATE brakes.