I have had my 70 Cutlass for 20 years. From day one. when I press on the brake in quick pumping action, I get a very slight rough idle. This must be a result of a vacuum leak, but I have not been abel to find a leak on the hose line from the power booster to the manifold. Could there be a slight internal vacuum leak on the power booster.? Any idea what would case this…(the engine is a stock 350 #6 heads etc)
Second question I still have the original Delco booster. I am thinking about replacing, to improve under hood appearance, but I notice restoration parts suppliers carry new reproduction boosters that appear be gold cadmium plated. From what I have see on original cars, GM power boosters looked like they had a silver cadmium like plating. One survivor cars, this plating oxidized to a silver gray color. I have removed the cover on the Delco relay switch and found this same silver cadmium plating, in like new condition, not that bright gold plating. What was the factory plating on the power boosters? Thanks in advance

 

I believe it could be the booster leaking although it could also be a leak someplace else causing the same indication. If you have thoroughly inspected all other locations where a leak may occur (don't forget the advance canister), then it may be the booster. As to the color of the plating, I will leave that to others more experienced in restoration. You should go ahead and start posting in appropriate forums now as you will get more readership of your questions. Some members don't read this newbie forum and it may be one of them that has the answer you need. Moving thread accordingly.

 

The leak could very well be in the booster, as it is just a big rubber diaphram in there.
However, a constant pumping of the brakes could mimick a vacuum leak, since you are releasing the vacuum and replenishing it over and over.
Therefore you could still have another vacuum leak somewhere or the car is running a bit lean.

In 1972 it was the gold plating, and I ~thought~ 70 and 71 were also.
The experts will chime in shortly...
Is this the Delco Morraine one?

 

this is me, changing plugs in my 6 month old SS in August, 1970. Something I had to do every 2,000 miles. the 10.75 to 1 CR ate them up.

note "gold" brake booster. the scan doesn't reproduce the color real well but it is gold


70SS-1.jpg

 

Yes it is the Delco Morraine booster? commenting on the Chevelle pic..Very cool..but this does look silver to me.... I am thinking there maybe different degrees of the plating applied, which makes sence..maybe some are very gold and other are less... just my theory..thanks for the feeback

 

trust me, it's gold. that's a scan of a 40 year old photo.

the booster, mc top and bail should be gold

but, it's your car. do what you wanna do


004.jpg

 

I highly recommend Steve Gregori

www.brakeboosters.com

Top notch quality and a great guy.

He does all kinds of plating too.

 

yep

 

as far as i know, this would be normal. if you pump the brakes it will use up the vacuum reserve and act like a vacuum leak till it rebuilds the vacuum reserve. should only take a couple seconds to build up after you quit pumping.

 

X3

He will rebuild and replate your original brake booster, and replate your original master cylinder cover for about $145.00.

Your original brake booster will have a julian date code stamped on the front side of the top retaining tab with the last 4 digits of the GM p/n stamped on the backside of this same tab (9391 I beleive).

Also the Delco stamp on most original brake boosters are stamped upside down.

This is if you want originality.

 

I have seen this photo somewhere before

Do you post this same photo on Team Chevelle a month or two ago???

These vintage photos are very, very cool!

 

Now that we're on the subject - we just experienced a vacuum leak on our 1972 Cutlass Supreme and traced it back to a tear in the booster CUP seal that is immediately in behind the master cylinder...does anybody have any ideas on where to get a replacement seal without having to buy a whole new booster? Thanks.....

 

It looks gold to me. 145 to rebuild and replate that is pretty damn good. Considering it costs more to buy the repop.
________
BALD ***** LIVE

 

nope. I might have posted it the Corvette Forum some time back. someone probably ripped it off

another view

scan0001-1.jpg