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A bog on acceleration
https://slantsix.org/forum/viewtopic.php?t=5811		 Page 1 of 1
Author:  kesteb [ Wed May 21, 2003 12:55 pm ]
Post subject:  A bog on acceleration
When shifting thru the gears, there is a distinct bog, when first accelerating. This feels like a lack of pump shot from the accelerator pump. How do you adjust this on a BBD?
Author:  87Slant_sickness [ Wed May 21, 2003 1:34 pm ]
Post subject: 
The Accelerator pump on a BBD is right where the metering rods are except on the other side, loosed the screw and bring it up all the way for one nice LONG shot (and a high volume shot) or bring it down for a low volume short shot.

Justin
Author:  kesteb [ Thu May 22, 2003 2:29 pm ]
Post subject: 
Thanks for the tip. I tried it out and it fixed 80% of the bog. With normal upshifts and intial startout the bog is just about gone. From a steady state 3rd or 4th gear drive, foot to the floor, makes a big "gasp" then away we go. To bad there is no "strip kit" available for the BBD. With one, I could fix this problem. As it is now, I need to decide if purchasing a Holley 2300 is worth the money, or to spend that on the ongoing EFI project.
Author:  Al T [ Thu May 22, 2003 6:01 pm ]
Post subject:  I've got a Holley 2300 sitting on the shelf
I had a 2300 on Big Red before I did the EFI/blower setup. Here's it peaking from beneath the cleaner. If you're interested, perhaps we can do a deal.
http://www.projectplato.com/cars/currentsetup.html
Author:  87Slant_sickness [ Thu May 22, 2003 6:36 pm ]
Post subject: 
kesteb,

If you got a day off and a round metal file with some nice sand paper (120 for finishing) and a rebuld kit, i reccomend taking about 2hrs and "porting" the BBD, this can be done really easily (because its aluminum) and while your in there you can yourself drill the jets (with a press but i dont reccomend it unless your experienced) or i can send you aset of jets that are about 2sizes bigger for nothing (i have all the machines at work to properly "bore" the jets out)

I did this and you can really feel (and hear) a difference in flow and all, when you look down the barrels of the BBD you'll see this:

Image

And this is what it looked like with about 20min work or so and i'm 1/2 done (remember when i did this it was an experiment but a good one!)

Image

There is a small steel vaccum fitting that you can either "work" around or or you can file down with the rest of it (makes no difference) In the ports you can make it so its straight down and even take some off "here/there".

Of course you can always swap over to a Holley 2300 or something similar for even more flow.... :)

Justin
Author:  Doctor Dodge [ Thu May 22, 2003 7:56 pm ]
Post subject: 
It could be that the "power valve" (step-up plunger) needs to be adjusted.
This is adjusted by putting a stiffer spring under the plunger. If you have a vacuum guage you can use that to figure-out how much more tension to give it.

Is the distributor's vacuum advance working?
DD
Author:  Dart270 [ Fri May 23, 2003 5:53 am ]
Post subject: 
You might also try decreasing the amount of mech advance by welding up the dist weight slots (similar total advance, more initial).

Lou
Author:  '74 Sport [ Fri May 23, 2003 1:48 pm ]
Post subject: 
Sorry 87SS,
I must be missing something. Those two pictures look like two different carbs (I'm comparing the three screw holes in the body at the top of each photo). What is "porting" on a carburetor, and what should I be looking for in the photos? What is the advantage? I just went through a rebuild of my BBD. What would I gain by boring out the jets?

Thanks,
Jerry
Author:  kesteb [ Fri May 23, 2003 3:45 pm ]
Post subject: 
Porting the BBD will not fix the problem. That would be a solution for the wrong problem. The total fuel flow thru the carb seems to be OK. No lean surges and nice color on the plugs. The distributor works fine, it is set at 8 BTDC, and advances when the engine is reved. Slight pinging when pushed hard. The problem is the amount and duration of the squirt of gas.

Some background on the car: '65 Dart weighs between 2600-2700 lbs, stock '78 OEM SuperSix, 4 speed, 2.45 rear gears. The carb is early '70s BBD for a 318.

After fiddling with the pump shot, that is now maxed out, the car accelerates fine from a dead stop and in the first 2 gears. When accelerating from 3rd or 4th there is still a slight bog. When stomping on it there is a "gasp" then it goes. I suspect the 2.45 gears do not allow the car to accelerate fast enough for the carb to start passing enough gas to fill the "hole" when you stomp on it. I don't see a way to lengthen the duration of the squirt. Maybe somebody has an idea.

With the Holley this would be rather easy to do.

Al, send me a email, I'm a cheap bastard, but maybe we can work something out on the Holley.
Author:  Joug_Fin [ Fri May 23, 2003 4:05 pm ]
Post subject: 
Doc

Would you like to explain, how You use vacuum gauge to at figure out correct spring tension for power valve. I've been thinking that maybe I'll have tired out sping there, because my a/f ratio is fluctuating very much at steady cruising.

Joug
Author:  kesteb [ Mon Sep 01, 2003 5:39 pm ]
Post subject: 
After tolerating the situation for a while, this weekend I tore the carb down. So much for rebult carbs. The floats were set wrong, way wrong, the arms were even bent, one side lower then the other. They were sitting about 5/8" below the bowl top. I adjusted it to the proper 1/4". Runs much better now. It helps when there is gas in the fuel bowls.

I noticed the metering rod hanger is lope sided. The left rod is about 1/8" lower the then right. Not good. Any idea how to fix this? The hanger dosen't want to bend.

I picked this carb up from the "carb pile" at the wrecking yard, it still had the rebuild sticker on it. Its sad to think that an old mopar went to the yard because of a "bad" rebuild on this carb.
Author:  Joug_Fin [ Mon Sep 01, 2003 6:56 pm ]
Post subject: 
Kesteb

Are those plastic arms, which holds metering rods assemply unbroken? And is that powervalve gap set correctly- if that hexsocketbolt is too loose, the hanger might be slanting.
I have set that powervalve gap little bigger than instructions says to at get little richer mix when accelerating.

Joug
Author:  kesteb [ Tue Sep 02, 2003 1:05 pm ]
Post subject: 
The plastic arms are unbroken. The set screw is at the original setting. I didn't change that. I might tear down the spare BBD and see how that arm attaches. It may just be a case of misadjustment when somebody tighten everything up.
Author:  Joug_Fin [ Thu Sep 04, 2003 12:11 am ]
Post subject: 
I have a scanned pic how to adjust powervalve gap, but I don't know how to put it here

Joug
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