Update: As recommended, I took the booster out of the loop w/ a rubber plug and a plastic cap (noticed no difference in pedal pressure—brakes good). The booster was the culprit. I’ll open it up to see what I can fiddle with at a later).

Coop: Your detailed description of the intake manifold miss-match was fascinating. So much so I sent you a personal email thanking you. It didn’t bounce, but I kinda thought you never saw it.

 [Hi Steve. My bad for not posting a follow-up and for not thanking you in particular for your efforts in locating my vacuum leak. That intake manifold & gasket mismatch thing is interesting. It’s amazing you figured it out. Unfortunately, I think the culprit in my case is a misbehaving booster. I plugged both ends and put it aside in favor a couple of more pressing issues—and the brakes are working fine. Seems like there’s always just a couple more issues… Actually, I’m having a great time wrenching again after a long hiatus—careers, family etc. 

Thanks for your interest. I’m sure we’ll talk again. See you on the board!]

Does anyone know what happened here? A hot topic for several days and now nothing. Steve (CTR)

Thank you ZIP, upper left you can just see the upper manifold has been welded. The upper right you can see the gasket issue the pic cropped so you cant see the other side of manifold. If you open the to full screen you can see. Lower left more of the same. Lower right if lined up ( this is the unwelded manifold ) and lifted just a little you can see what's happening. Other pic is some of my 1 1/2 and 1 3/4 intakes. The steel tube is a personal favorite. Calver went to the place and hand picked that one for me and sent it over. False chrome powder coat. Steve (CTR)

PS want to play what's that car?

And, one more pic

Image Gallery

Steve asked me to post some pictures. He'll have to fill you in as to what he's trying to show....

Also you can use a 2 foot or so piece of tubing up to your ear and just poke around the gasket if it is leaking you will hear a hissing sound.

THAT'S what I've been waiting to hear! Starter fluid—I'm on it! BTW: On my early morning test drive after plugging off my booster late last night I discovered that my booster wasn't boosting. Not even a little bit. On one hand, I'm impressed with my unboosted stopping power. On the other hand, "What up, booster?"

You would need to look at the very lowest point where the intake meets the head. Hard to see but I'll try and get some pics. If you have a can of starter fluid with a straw spray below intake while running. I have to weld all mine. Nick and I were talking about this at the track back in 08. Steve (CTR)

Coop:  In the above situation, where exactly would my vacuum leak be coming from? Good idea on the spring-in-hose tip.

I didn't look at all your pictures till now. Looks like you are using a MSC twin 1 1/2 SU intake. From the sounds of things you did not assemble this monster youself. Contact your builder and ask what intake/exhaust gasket he used. If the big bore compitition type the intake has to be welded up along the lower edge adding about 1/8 to 3/16th material as there is not enough material to cover the intake ports in the gasket on the bottom. I have run into this twice with that set up. The last time I ordered a second manifold and had two welded at the same time and put one on the shelf. Maybe I can remember to take a pic of my spare and get Zip to post for me. As for the kink, it would not cause a problem but a short coil spring couple of inches inserted in hose will stop that. Let me know if this info turns out good. Steve (CTR)

I sidelined the booster today by pluging the vacuum bung on the intk manifold. After jiggling the booster around and tighting the medal strap, I hoped my vacuum leak would vanish. Alas, if anything, it's gotten worse. Not only do the revs increase, now it coughs and sputters—I'm assuming from on overlean mixture. Am I on the right track? Once the bung was plugged, mashing on the brake pedal had no effect on the revs.

Regarding that kink in the hose near the booster; wouldn't a kink simpliy reduce the effectiveness of the of the booster by reducing vacuum? Anyway, it looks like I'll be yanking my booster and poking around looking for something amiss. Will advise.

I'm a no booster fan, but each to their own. One thing I would suggest doing if you leave the booster where it is would be to shield the booter pipes and the hose.

My booster is supposed to be a high quality repro of the original long nose booster. I'm definitely getting boost, but not "through the windshield" boost. Then again, I have a vacuum leak.

Russ,

a properly working booster from my experience with my brother's S back in the 70's will put the passenger through the windshield with 1/8" deflection. It was so sensitive that you had to learn to drive with the power brakes.  This was your typical long nose MK 1/2 booster.

It is a split master (Girling). And I am boosting the front circuit only. I didn't even notice. I did notice the kink in the vacuum line. I am suspicious of it too. Re: flakey, white crud. It might have started out as grease, but now it looks like that kind of stuff you'd want to keep far away from a vacuum seal. I'm pretty sure my cam is an Elgin 268/278. It's plenty torquey down low, so I'm assuming the vacuum comes on early as well.

Re: Pedal pressure vs. stopping power. My pedal seems pretty light and I can lock 'em up easily. The rears lock first, but not by much. If I can just find that vacuum leak...

Thanks for your input. Do my master cylinders look undersize? Don't remember what the old one looked like.

Cup: I would call it a remote simply because the booster is located away from the master brake cylinders. Yes? No?

It could be your culprit and the band should be tight. A while back i was trying to diagnose a lumpy idle and stalling on a late Mini with a factory servo and after going through all the usual things i was running out of ideas. While standing in front of the car with it idling i leant on the master cylinder and the idle changed, it turned out the master cylinder was loose and when the brakes were applied it had a massive vacuum leak.

Just so I know, are you using a KAD split master assembly? And if using a a booster are you only boosting the front? I notice a kink in the vacuum line going to the booster. I have only taken a few late boosters apart and they have some kind of white flakey grease around the daiphragm where it meet the halves. I think the kit comes with a tube of the stuff. What cam are you using? I'm thinking about mounting a vacuum gauge as I feel my cam makes little or no vacuum at low rpm. I don't feel the advantage of the booster at low speeds. I brake hard from 70/80 every day with no problems, but moving along in bumper to bumper, pedal pressure seem way high. Steve (CTR)

Thanks everyone for the vacuum leak diagnosis. I'll take the booster off line, use the brakes a bit and see if that's it.

As an aside, I was poking around the left wing (where my booster is located) and discovered the metal band that runs around the circumference of the booster was finger tight. At first I thought the band was simply a mounting strap or something. I backed the nut all the way out and slid the band around a bit. Turns out the band actually clamps the two halves of the booster together. Is the main diaphragm located between the two halves?

When I jiggled the band, white, crusty oxidized cad plating fell in my face (and the booster is new!—but that's another story). If the band is supposed to make an air tight seal between the halves and the diaphragm, it sure looks like it wouldn't seal very well even under the best of conditions. Is this my likely culprit, esp. since all my hoses and fitting are 100%. Can I shoot it with a bit of starter fluid? Here's a better pic of my booster.