Interesting carb dilema

AnthonyG

AnthonyG

Well-known member
Haven't run the car for a few weeks ( 8BA slightly modified also with tunnel ram 3X2's only center connected the other two fuel blocked and block out gaskets so no vacuum or gas leaks ) ) as I've been waiting and researching a new distributor. Went through the normal cold weather startup with it running with the choke on and stalling a few times. In between feathering the throttle to try to keep it running til it warmed up a bit. 3rd time it started with choke on and with foot off throttle engine wound up quickly and I had to shut it of at the ig. switch before too many RPM's? Went into the engine compartment checked all throttle linkage and throttle at carb and looked to be in the zero throttle position? Tried again same issue. Shut down and while off worked the throttle from the peddle and watched the linkage and throttle on carb looked OK? Tried one more time had to shut down again. Three strikes I'm out.
Getting ready to remove the carb but thought I'd post for some ideas first?
 
I'm not the best mechanic but I'd look down the carb to see if there is a problem with the throttle plate.The linkage might be in the idle position but the butterfly may not be (loose,broken or missing).It's hard to imagine that you could get high RPM's with the throttle closed.Just a guess.
 
Well, it's getting fuel and air from somewhere! It would take a fairly large air leak to rev the engine to very high RPMs.
 
Flatjack9 nailed it. You kind of got it too JSeary. The vacuum is so high from the tunnel ram trip set up that it sucked a square hole into the blocking gasket I made to stop any vacuum leaks on the rear carb. I was Sooooo lucky the square piece from the tear out was in tact and sitting under the center carb. I grabbed it with a needle nose doubled the thickness of the blocking gaskets on 1 and 3 and am back in bus. Scared the sh__ out of me for a bit.
Thx Flatjack9 & JSeary
 
Martin ( scooder ), I changed it before reading your last post and used a double thickness of 1/16 gasket material this time. That puts it at 1/8", do you think it can still suck a hole in them? Assuming if yes I have to make the plates right? No one makes them do they?
What if I run regular gaskets and spring load the throttle plates shut and not linking them to the pedal linkage so they s/b like a progressive setup when 1 and 3 aren't throttled up?
 
C'mon, it's not difficult to make a couple of solid plates using a gasket as a pattern. Using gasket material as a block-off medium doesn't work well for a couple of reasons, but the main reason being that the gasket material is subject to becoming damp and spongy (and weak) from gasoline in the manifold. You've proven that there's enough vacuum force to suck a hole in it under the right conditions.

Your solid block-off plates should be sandwiched by a gasket on EACH side of each plate. DD
 
AnthonyG said:
Martin ( scooder ), I changed it before reading your last post and used a double thickness of 1/16 gasket material this time. That puts it at 1/8", do you think it can still suck a hole in them? Assuming if yes I have to make the plates right? No one makes them do they?
What if I run regular gaskets and spring load the throttle plates shut and not linking them to the pedal linkage so they s/b like a progressive setup when 1 and 3 aren't throttled up?
Click to expand...


Yes, it will probably break and leak again. You have two 1/16" thick gaskets, and not really a one piece 1/8" thick gasket. It will just take longer to break through.
Use a metal shim with a thin gasket on each side.

I also don't understand what you mean by the vacuum being higher because of a tunnel ram ? The engine and camshaft determine how much vacuum you will have, not the intake manifold.

Sal
 
Tony, the guys have already said, and I agree, you need the metal plate.
If there's no gas delivered to the blocked carbs, I'd think you only need a gasket twix the metal plate and the manifold. Unless my just in from work head ismissing something guys?
And yes, you gota make um.
Martin.
 
DD, OK, guess I'm getting wrapped around the axle. A bit of over load, LOL, keeping a sense of humor while using the expletives as well. While I agree and may make them as it's not that big a deal to make a couple of blocking plates, it almost seems as much effort as just running all three and getting the Uni-Syn Carburetor Synchronizing Tool to set up. Question, just to get it running without the progressive linkage can't I springload the 1 and 3 carb throttles shut and just run on the middle carb. as though the progressive never kicked in for now? Then when it's running fine with the one - 2 brl. go back and set the linkage and use the Uni-Syn Carburetor Synchronizing Tool for the other to get the three in sync? Sorry, first shot at 3 X 2's. 2 X 2's were easier but I love the look of the 3 X 2's .
 

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Tony,
The throttle plates won't fully seal the end carbs, you'll still have open idle circuits, aswell. If no fuel is being delivered to the end carbs, and your just using the throttle plates to sit them off, you will have a vacuum leak.
This will upset tuning the center carb.
If you want to run just the center carb, use metal plates to seal the end carbs.
This is the way that it's done, because it works.
Not telling you off here, if you spent the time thinking of other ways to do this simple job, with a drill and cutting some thin steel plates, it would be done and you'd be up and running.
Martin.
 
Thx for the good advice. The whole thing started because the carbs I rebuilt (without new modern throttle plate shafts which could accommodate progressive linkage ) then I realized how much vacuum leak there was on all three. Probably some from the original old throttle shafts. While I loved the look I pulled the trips of and went with my old Edelbrock 500cfm for now to get ready for the season which is on top of us in the northeast. Will revisit next season after selling my Holley 94's and getting new Dennis Carpenter 94's and go with the fulluse trip setup as it s/b and progressive linkage.
Thx for all the good info. With trial and error comes experience and knowledge.
 
Uncle Max makes a nice carb block off plate, thin and really hard to tell its there unless you're looking for it.
 
Thx Ralph, Max was great, total for 2 with shipping was $31. Well worth it not to have the hassle of making two. Max was great to deal with. Waiting to receive them and I'll put the trip setup back on.
 
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