Idle rpm drops substantially when putting car in gear

[eldubb440]

Possible diaphragm let got in the brake booster
At least that’s what my issue was when I experienced the same symptoms

my brake booster was beat by 1985

 

[Geoff 2]

Basics first would be looking for vacuum leaks/leaking hoses etc:
- disconnect & plug brake booster
- plug ALL vac fittings to the carb or intake manifold
- check spark plugs & cracks in the insulators
- etc. Look for things that age or mileage could cause deterioration.

 

[Michael_]

Thanks for all the replies.

Turns out there are multiple things wrong.

Removing & blocking off the vaccum line from the brake booster results in a noticeable improvement.
Unfortunately still not perfect.

Spraying brake cleaner along the intake manifold (left & right) results in bubbling and idle rpm change.
So the manifold gasket is shoot aswell.

I'm basically sure at least 1 of those 2 problems already existed when i bought the car because it came with a 1000-1100rpm idle.

Looks like i'm in the market for an intake manifold gasket and brake booster and at this point i'm replacing the carburetor gasket and master cylinder aswell.

Questions:

Is it a good idea to buy an NOS brake booster or are there parts inside that degrade over time so that buying new is a better idea?
(We recently replaced the bake booster on my 72 cutlass and while it's a factory repo that looks great it does not perform as good as the original one did before it broke.)

If repro which ones are A factory correct (survivor car) and B best quality?
Of if NOS let me know if you have one or know one for sale. Ideally together with the master cylinder.

PLEASE NOT MY CAR HAS FACTORY CRUISE CONTROL which is connected to the brake booster via. vaccum line. Is the brake booster the same with and without cruise control?

Also which manifold gasket is factory correct for my (stock) car? Are there different ones?
Not too long ago i replaced both valve cover gaskets with factory correct cork and it works great.

1969 Dodge Charger R/T 440, 727, Disc Brakes, Power Brakes, Cruise Control, Stock.

Here are a couple pictures of the brake booster etc.:

Album — Postimages

postimg.cc

 

[Michael_]

So i did a little research and it looks like there is no repro brake booster that is 100% identical. Additional most master cylinders seem to have the connections on the wrong side.
Mine are on the engine side which seems correct given these 2 cars comparable cars:

1969 Dodge Charger R/T SE Sunroof For Sale At Auction - Mecum Auctions

View the 1969 Dodge Charger R/T SE Sunroof for sale at Dallas 2024 in Dallas, Texas as S66.

www.mecum.com

For Sale: 1969 Dodge Charger R/T in Milford City, Connecticut

Find classic cars, collector cars and vintage muscle cars on ClassicCars.com. Search, sell or buy and Drive Your Dream today!

classiccars.com

Also both the mecum car and my car have a support bracket for the line/cable from the cruise control attached to the brake booster.

Furthermore it seems like buying an NOS brake booster would be a bad idea because it most likely will have a vaccum leak aswell due to degradation.

What i found browsing the forum is that getting my original brake booster and master cylinder rebuilt would probably be my best option UNLESS i can find already rebuilt ones.
And the top rebuilders seem to be these:

Vacuum Brake Boosters | Power Brake Booster Exchange, Lynwood

Power Brake Booster Exchange rebuilds vacuum brake boosters and supplies hard-to-find booster parts. Find out more about our services online today.

www.powerbrakebooster.com

Remanufactured Automotive Parts | Rebuilt | Ontario | John Stuart Power Brake Co. Ltd

Maybe i get lucky and find already rebuilt parts because i'm not liking the idea of shipping my booster overseas. But otherwise i guess i have no other choice.

Anything i should watch out for regarding the intake manifold gasket?
i found these fel-pro ones on rockauto.com. Are they good? I had good luck with fel pro cork valve cover gaskets in the past.

More Information for FEL-PRO MS90175

More Information for FEL-PRO MS96000

Also maybe there is the possibility that if i fix the intake manifold leak that the brake booster leak is small enough so i can ignore it?

 

[R413]

How do you know that the master cylinder and booster on there is original?

Drum or disc brakes master on it now? Photos? What is the 7th digit of the VIN?

Brake booster will get worse. You can try just intake gasket first and see.

 

[Michael_]

How do you know that the master cylinder and booster on there is original?

Drum or disc brakes master on it now? Photos? What is the 7th digit of the VIN?

Brake booster will get worse. You can try just intake gasket first and see.

I posted some photos in one of my replies:

Album — Postimages

postimg.cc

Comparing it with a very similar car on mecum it looks stock to me:

1969 Dodge Charger R/T SE Sunroof For Sale At Auction - Mecum Auctions

View the 1969 Dodge Charger R/T SE Sunroof for sale at Dallas 2024 in Dallas, Texas as S66.

www.mecum.com

I just found a company about 80 miles away from me that claims to rebuild both brake boosters and master cylinders. But of course i'm in germany and idk. if they can rebuild my american parts. But asking doesn't hurt.

 

[RemCharger]

Need to verify if it's the booster leaking.. or the cruise control unit.

 

[Michael_]

Need to verify if it's the booster leaking.. or the cruise control unit.

Agreed.

I think the first thing will be replacing the intake manifold gasket and then go from there.

Speaking of which should i just order these or get something else?

More Information for FEL-PRO MS90175

More Information for FEL-PRO MS96000

Never did this before.

 

[RemCharger]

Agreed.

I think the first thing will be replacing the intake manifold gasket and then go from there.

Speaking of which should i just order these or get something else?

http://[URL]https://www.rockauto.com/en/moreinfo.php?pk=125143&cc=1078961&pt=5424

[/URL]

http://[URL]https://www.rockauto.com/en/moreinfo.php?pk=125718&cc=1078961&pt=5424

[/URL]

Never did this before.

There's basically 2 different gaskets. With, or without the exhaust crossover blocked. If you have a stock carb with choke, get the open one.
The 96000 is the one. I wouldn't bother getting the extra paper ones.. it's all stock correct

 

[Cranky]

There's basically 2 different gaskets. With, or without the exhaust crossover blocked. If you have a stock carb with choke, get the open one.
The 96000 is the one. I wouldn't bother getting the extra paper ones.. it's all stock correct

IIRC, Michael was told it was all original survivor but it's not always easy to tell just by looking at the externals.....imo. I have a 64 Dart that's supposed to be a survivor and most of the signs point to that it is but so far, I cannot verify if the engine has never been opened up.

 

[RemCharger]

IIRC, Michael was told it was all original survivor but it's not always easy to tell just by looking at the externals.....imo. I have a 64 Dart that's supposed to be a survivor and most of the signs point to that it is but so far, I cannot verify if the engine has never been opened up.

Sorry, I was referring to the intake mainly. If it's original etc as believed, I would 1000% NOT use the shitty paper gaskets. Maybe I should have put that in bold.

 

[Michael_]

There's basically 2 different gaskets. With, or without the exhaust crossover blocked. If you have a stock carb with choke, get the open one.
The 96000 is the one. I wouldn't bother getting the extra paper ones.. it's all stock correct

Thanks than i will order 2 of these just in case i screw up...

More Information for FEL-PRO MS96000

Also would you guys paint the manifold while off or not?
Of course it would make sense to protect it from rust etc. but on the other hand it would take away from the original look and also i do not want to remove and paint the valve covers because i put on new gaskets not too long ago and they are not leaking.
So i'm leaning towards NOT painting the manifold.

Edit:

But in case i change my mind. What kinda paint should i use for the original orange?

 

[R413]

Don't paint anything. Unless your going to paint everything.

 

[Orig69]

I agree with post number 7 and do the brake booster or cruise control first.

It looks like it has a 1968 carburetor.

 

[Michael_]

It looks like it has a 1968 carburetor.

I actually did never check but i know the car is one of the very first built in late 68.

 

[Orig69]

I looked at the other pictures it does look it has the original 4640S carburetor the early version is kind of unique.

 

[V_TastyTacos_V]

Sometimes people keep turning screws, not knowing where they're going, then you step in, not knowing what is going on. I've gotten cars with the timing retarded, and the idle speed screw turned up so high that the throttle plate was above the idle fuel transfer ports, and it would do what you describe. Check timing with vacuum advance disconnected. Should have no vacuum at idle, but could have some if the idle is turned up too high. Look down the carb and see how far open it actually is with the choke open. Should look almost closed. You may want to close it all the way, then open it a couple turns. Do the same with the idle mixture screws. Try that and see what direction it takes you. Check for vacuum leaks, too. Spray some carb cleaner down the carb when it's running. It will rise a lot if there is. You can spray tiny amounts around the carb and intake looking for an RPM rise if you spray near the leak.

 

[Geoff 2]

In case you don't know......
The idle screw in the centre of the carb near the air cleaner flange. That is a reverse idle screw.....gets richer when you screw it in.

 

[Michael_]

So i watched a couple videos and these people seem to use RTV together with the gasket:


Is this necessary/good?
If necessary also if you use the additional paper gaskets or is this basically the alternative to using the additional paper gaskets?

 

[Billccm]

YouTube Nick's garage claims paper gasket with aluminum intake as the torque specification is different from cast iron.