I think I need to go to Carter BBD Skool !

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Duggie

Duggie

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Since doing the latest engine mods, there is a hesitation accelerating off of idle (below 1500 RPM) when the choke has opened, and the thermostat is still closed. Stone cold / choke closed - no hesitation. At operating temperature - same smooth pull off of a green traffic light. In between full choke and thermostat open, you wouldn't take the chance at a stop sign trying to cross through heavy traffic.

The car: '64 Dart /6, points and condenser, 4 spd. 8 1/4" - 2.45 rear end out of a '72 Cordova. 205/50 R17 tires. Engine turns at 2K RPM at 60MPH.

Before the mods; It had a Holley 1920 - 1 barrel, and factory exhaust. Timing was 2.5 deg BTDC. Plugs and inside the exhaust tip were a bit sooty looking. It always started at the first bump of the key cold or hot. Mileage was 18MPG and it wouldn't pull a blanket off the bed. Approaching any type of incline on the highway under 70MPH required downshifting to 3rd. No downshift and the car would slowly decelerate.

The mods :D; Tube headers routed via 2" pipe to a 'Y' at the transmission cross member, and 2" exhaust out the back through a Magnaflow type muffler. Shaved the head to a static 8.6:1 compression with multiangle valve job. Modified the stock 1 barrel intake manifold to fit a NOS Carter BBD #6465S for a 1974 318 (It still smelled new!). The choke is an aftermarket electric unit. Also added a water fed, intake heating plate. Timing is now at 11.5 deg BTC. The car pulls GREAT from 2K RPM on about any incline and accelerates like never before (for a /6). First tank of gas came in at 30 MPG. It starts great cold with a couple pumps of the throttle and will fire right off if I turn it off hot and start it right back up. After sitting warm for ten minutes or so, I need to add some throttle and crank on it before it will fire off.

Looking for the cure; I went through the carb twice and adjusted everything to factory specs. The air hole in the butterfly was filled. I've confirmed twice that there are no vacuum leaks. The idle mixture was adjusted lean to a slight RPM drop. Increased richness through max RPM and then slight RPM drop, then back lean half the turns from lean RPM drop to rich RPM drop. With the idle adjustment screw turned all the way off the stop, the engine turns 650 RPM. The plugs are all the prettiest buckskin tan I've seen, and the exhaust smells 'funny' like a bad catalytic converter or something (new exhaust?). With the air cleaner off, the carb has a high pitch whistling sound at idle that I've never heard a carb make before.

I'm guessing I have a lean transition from the idle/low speed circuit to the main metering circuit when the choke is off and the engine still a little cold. Out of desperation I cranked the choke so far closed that at wide open choke and thermostat open, the choke plate was still partially closed. At this constant enriched choke position, there was no hesitation off of idle in the low to mid-engine temperature range.

I'm in need of a lesson. Raise the metering rods? use a bigger hammer? :BangHead:
 
Seems like adding fuel is the answer. The factory settings went out the window when you dropped a 318 carb onto a mildly chooched up slanty. So, adding or removing fuel is one step. Raising the metering rods would be first. Typically factory set,but if they have been moved, then its a crapshoot. A reference point/mark so you can go back if needed. Its been 20 years since i had one apart.
Thick carb mounting gasket? I forgot one once, didnt run very well.
 
Tooljunkie said:
Seems like adding fuel is the answer. The factory settings went out the window when you dropped a 318 carb onto a mildly chooched up slanty. So, adding or removing fuel is one step. Raising the metering rods would be first. Typically factory set,but if they have been moved, then its a crapshoot. A reference point/mark so you can go back if needed. Its been 20 years since i had one apart.
Thick carb mounting gasket? I forgot one once, didnt run very well.
Click to expand...

HA! I found a vacuum leak under the carb after the first install. The return spring on the throttle shaft was riding on the generic gasket, raisin the carb just enough for a leak.

I think I can adjust the metering rods higher incrementally by keeping track of the gap at the top of the rod lifter (piston?). Don't know how much to open the gap per try. I think the factory spec was maybe .040".
 
Replace the carburetor with something that uses the Holley 2300 bolt pattern. Then you can actually adjust the carburetor to match your components. The BBD was a great carburetor, 50 years ago. Not so much now.
 
kesteb said:
Replace the carburetor with something that uses the Holley 2300 bolt pattern. Then you can actually adjust the carburetor to match your components. The BBD was a great carburetor, 50 years ago. Not so much now.
Click to expand...
Boy do I have a lot of frustration to go to get my money's worth out of what I have in this carb. The messiest part of this carb conversion has been paying through the nose for the pleasure of working with a NOS carb and then having a local shop modify the throttle shaft to accept the original '64 Dart throttle linkage. Yeah, waaaay down the rabbit hole.:eek:
 
Intake manifold too cold ,thus less than ideal fuel vaporization,can you lengthen the time the choke stays on?
 
Bugman said:
Actual fuel level in carb bowl, if to low will delay start of main circuit. Old bulletin link and picture 78 Volare Super six carb issue. - Slant Six Forum
Click to expand...
Thanks for the link!

I turned the allen head adjustment screw for the metering rods one full turn clockwise (rich). Test drove it from stone cold to full operating temp and it didn't stumble once. Let it completely cool down and drove it again and it stumbled from fast idle off until the thermostat opened. Same thing happened after I re-checked the carb linkages. Ran great on the first run and stumbled on every run after.

Maybe I just need to slam the hood before each drive. :BangHead:
 
Bugman said:
Intake manifold too cold ,thus less than ideal fuel vaporization,can you lengthen the time the choke stays on?
Click to expand...
I installed an intake hot water heating plate where the stock exhaust header attached.

I got ticked and rotated the choke so far closed that at operating temp the choke flap was still partially closed. It didn't stumble at low and mid-engine temps then.
 
Bugman said:
Accelerator pump adjustment, try a higher setting closer to 7/16. Test this on car engine off, make sure throttle does not hang up and this Timing chain? - Slant Six Forum
Click to expand...

Chain was good with the one barrel on it and it only hesitates with the choke off / engine cool. I did wonder about metering rods VS accelerator pump. Looking down the carb, the accelerator pump squirts at the first bump of the throttle shaft. I'm willing to give it a go though!
 
Just went thru similar with the BBD in my 1965 273. I knew it was running lean because it wanted to stall coming off idle. It idled OK cold with the choke closed and liked me closing the choke more as it warmed up. I couldn't test once warm since it wouldn't even idle long enough. I had to keep tapping the throttle to shoot accel pump gas to keep it idling and if I did that and held the throttle down a bit it would die after using up the accel shot. Going out on the idle screws didn't help much. I figured it must be a vacuum leak and suspected my current kludge of using the BBD on a 4 BBL intake w/ adapters, but flowing propane around there didn't help. After checking the booster hose, I thought to check the big PCV hose and found the purty aftermarket cap at the PCV valve off since its rubber gasket had fallen apart, which gave a massive vacuum leak (open hose). Amazing it even ran. Ran great after fixing that. It ran bad last time, but good enough to relocate the car in the driveways, so probably the gasket was partly cracked then. Problem was also confused because I found the brakes were locking up, due to having misadjusted the tip on the booster rod (piston didn't fully retract to open the fill port in the bore). Made same mistake on our 1996 Plymouth, but now have a booster measuring tool.
 
Yep that pcv hose was my vacuum leak on my little Hornet.... again!
I need a L pcv valve, do ya think the little girl at the parts store had one, just one????? No or either she could not find it!! She was the only clerk.
HELP wanted sign there too.
 
I had the same problem you did. Exactly. I ran the car with the top of the carb off. Turns out the floats were set too low starving the power valve of fuel.

reset the float a 1/16 of an inch runs fine.

was neat to get an old schooler to show me this. Was really cool to see how the carb really operates.
 
First open the transfer slot on the carb to a tiny square and NO MORE. Then use the timing to adjust the idle where you want it. Don't follow the factory specs for timing, let the engine tell you what it wants. It knows more than a book does.
Then adjust the mixture screw until you get the highest vacuum.
Voila your done.

If you have the transfer slot too far exposed (throttle too far open), you're already into the transition circuit for fuel. Then when you hit the throttle it's adding more fuel and it's too much, which is why you're seeing the hesitation.
 
I've never claimed to be the brightest bulb in the knife drawer, but this is getting ridiculous, even for me.

I wrote that novel in the first post out of desperation, looking for what I missed. My parts guy says, "It's going to be something really simple." Me, "Is not!" My buddy that helped build my tube headers says, "The only thing that can make a carb whistle is a vacuum leak." Me, "Don't got one. I triple checked."

My buddy takes a can of starting fluid, soaks the throttle shaft where the shop attached the one-barrel linkage and there's the vacuum leak.
Shaft leak.jpg


I triple checked everywhere for vacuum leaks EXCEPT where the highest recommended carb guru did his work. I chat with the carb shop next.

Man, stupid hurts. :BangHead:
 
All BBDs leak there. And I don't think there is any bushings available to fix the problem.
 
kesteb said:
All BBDs leak there. And I don't think there is any bushings available to fix the problem.
Click to expand...

That is the opposite side from the original linkage set up where the idle and choke cam are located, yes?
 
Duggie said:
Since doing the latest engine mods, there is a hesitation accelerating off of idle (below 1500 RPM) when the choke has opened, and the thermostat is still closed. Stone cold / choke closed - no hesitation. At operating temperature - same smooth pull off of a green traffic light. In between full choke and thermostat open, you wouldn't take the chance at a stop sign trying to cross through heavy traffic.

The car: '64 Dart /6, points and condenser, 4 spd. 8 1/4" - 2.45 rear end out of a '72 Cordova. 205/50 R17 tires. Engine turns at 2K RPM at 60MPH.

Before the mods; It had a Holley 1920 - 1 barrel, and factory exhaust. Timing was 2.5 deg BTDC. Plugs and inside the exhaust tip were a bit sooty looking. It always started at the first bump of the key cold or hot. Mileage was 18MPG and it wouldn't pull a blanket off the bed. Approaching any type of incline on the highway under 70MPH required downshifting to 3rd. No downshift and the car would slowly decelerate.

The mods :D; Tube headers routed via 2" pipe to a 'Y' at the transmission cross member, and 2" exhaust out the back through a Magnaflow type muffler. Shaved the head to a static 8.6:1 compression with multiangle valve job. Modified the stock 1 barrel intake manifold to fit a NOS Carter BBD #6465S for a 1974 318 (It still smelled new!). The choke is an aftermarket electric unit. Also added a water fed, intake heating plate. Timing is now at 11.5 deg BTC. The car pulls GREAT from 2K RPM on about any incline and accelerates like never before (for a /6). First tank of gas came in at 30 MPG. It starts great cold with a couple pumps of the throttle and will fire right off if I turn it off hot and start it right back up. After sitting warm for ten minutes or so, I need to add some throttle and crank on it before it will fire off.

Looking for the cure; I went through the carb twice and adjusted everything to factory specs. The air hole in the butterfly was filled. I've confirmed twice that there are no vacuum leaks. The idle mixture was adjusted lean to a slight RPM drop. Increased richness through max RPM and then slight RPM drop, then back lean half the turns from lean RPM drop to rich RPM drop. With the idle adjustment screw turned all the way off the stop, the engine turns 650 RPM. The plugs are all the prettiest buckskin tan I've seen, and the exhaust smells 'funny' like a bad catalytic converter or something (new exhaust?). With the air cleaner off, the carb has a high pitch whistling sound at idle that I've never heard a carb make before.

I'm guessing I have a lean transition from the idle/low speed circuit to the main metering circuit when the choke is off and the engine still a little cold. Out of desperation I cranked the choke so far closed that at wide open choke and thermostat open, the choke plate was still partially closed. At this constant enriched choke position, there was no hesitation off of idle in the low to mid-engine temperature range.

I'm in need of a lesson. Raise the metering rods? use a bigger hammer? :BangHead:
Click to expand...
Your description or descriptive post is kind of hard to really read or understand, so... you're saying that it runs bad when the choke is half on and the engine hasn't fully warmed up?
It shouldn't run bad or cack out/hesitate half warmed...I'd think it may even run better at that temp, but not with it partially choked of course. Could be cured with timing, in other words.. compensated for a rich mix.
Depending on where you are Buckskin tan is not what you want but again that's depending on where you are and what gas do you use Where You Are.
2brl on an adapter plate?
If it's a two barrel there is an adjustment that will pull the rods up or put them down into the Jets a little bit more from the get-go another words or stationary position you can have them stabbed into the jet a little deeper or you can have them a little bit up out of the jet basically giving you full jet sooner or a little later depending on how you set them. I believe they have arm and it's not a spring n vac type of activation.
Funny I was just talking about my tinkerines with my belt slant 6 and a Carter 2 barrel and another thread.
The biggest leak/air source..is where it will draw air from. Econo valve has been known to contribute a whistle when blown out.
.could be the lack of enrichening that's your hesitation gremlin. Who knows
 
Duggie said:
And is there a fix for the shaft leaking on this side?
Click to expand...

The standard practice is to ream out the base plate and install bronze bushings. There are 2 things against this. Not enough room in the base plate to ream it out, and nobody makes bushings to do so.

And yes, you can make bushings. But at some point, there is diminishing returns on the costs involved. And just how NOS was that carburetor? NOS can mean that the carburetor had bad throttle shafts and was replaced with something better. And somebody just picked it up out of the discard pile and sold it online.

The BBD has always had this problem, that is why it was a great carburetor 50 years ago, not so much now.
 
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