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BBD and ported vacuum
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Author:  killnine [ Fri Jan 17, 2014 5:15 pm ]
Post subject:  BBD and ported vacuum
OK so I'm fighting an issue where at idle I'm still reading over 10 on the vacuum gauge from the ported vacuum fitting on a Carter BBD. I'm using the port that sticks out the passenger side. I've made sure the throttle is all the way closed when I'm doing this. I've also made sure that the curb idle was backed out all the way (throttle plates closed), and still the same reading. I even put a little pressure on the throttle to make sure it was tight. A reading at manifold vacuum is exactly the same. So I took the whole carb off. Now I traced where this port goes to and it goes from the tube, to a little hole on the bottom of the body. This hole goes directly to another opening on the base plate, and through the gasket. It ends up at a little square opening just below the throttle plates when they are closed. How is it supposed to not read manifold vacuum when the hole it reads from is right there on the manifold side of the throttle plates? Now the egr hole, it's on the other side of the plates, the top side, and it's more of a slot, and there is a notch out of the throttle plate right where it sits. So it would seem to at least have a chance of seeing something other than straight manifold vacuum at curb idle.

Can anyone explain this? Should I just use the egr port instead of this other one?
Author:  Aggressive Ted [ Fri Jan 17, 2014 6:25 pm ]
Post subject: 
Quote:
Now I traced where this port goes to and it goes from the tube, to a little hole on the bottom of the body.
Not good......don't use that one! you can use this one to run the snorkel air dam.
Quote:
Should I just use the egr port instead of this other one?
I would try the EGR port and see how your vacuum advance works since that will come on much more gradually. Hook up your gauge and see what it shows in 500 rpm increments. If you don't like the curve, get a more aggressive vacuum advance can.
Author:  killnine [ Fri Jan 17, 2014 8:41 pm ]
Post subject: 
Quote:
Quote:
Now I traced where this port goes to and it goes from the tube, to a little hole on the bottom of the body.
Not good......don't use that one! you can use this one to run the snorkel air dam.
Quote:
Should I just use the egr port instead of this other one?
I would try the EGR port and see how your vacuum advance works since that will come on much more gradually. Hook up your gauge and see what it shows in 500 rpm increments. If you don't like the curve, get a more aggressive vacuum advance can.
Yeah that's about what I figured would be best. Ted, or anyone, have any information on the flange bolts for the carb. The brass nuts came off easy but they're going on hard, and before they even grip down on the gasket they're getting really hard to turn. Very strange, like the nuts match to a specific stud or something. One of the studs spun out when I took one of the nuts back out. How do I get this stud back in, or do I just spin it in with the nut?
Author:  killnine [ Fri Jan 17, 2014 9:40 pm ]
Post subject: 
So I just torqued down pretty good on the one that wouldn't quite make it and it went in. The rest were harder to put in than take off because of the gasket being a little less than flat.

So, I think I might have found the reason why I was getting vacuum even with the throttle all the way closed. I was making the assumption that the throttle was closed because as far as I could tell by sight it was, and nothing was opening the throttle as far as I could tell, because the curb idle screw was backed out, and I even applied pressure to the throttle linkage. Well, the trouble I think is that the throttle cable was locked down to where it held the plates open just a bit. Here's a pic of where I will have to loosen it and adjust to where it can come fully to rest with the plates closed before reattaching the linkage. Oh PO, you've cost me so much time.

Image
Author:  Reed [ Fri Jan 17, 2014 11:09 pm ]
Post subject: 
I have made that mistake many times. Wondering why the engine won't idle slower than 1k and then remembering the throttle cable adjuster clamp. Good save!
Author:  killnine [ Fri Jan 17, 2014 11:52 pm ]
Post subject: 
Quote:
I have made that mistake many times. Wondering why the engine won't idle slower than 1k and then remembering the throttle cable adjuster clamp. Good save!
In defense of PO, he did rig that fabulous kickdown linkage.
Author:  oldskoolracer [ Sat Jan 18, 2014 8:20 am ]
Post subject: 
Have you checked vacuum at that port since you re-adjusted the cable? I only ask because the old BBD I had on mine did the same, took me forever to realize it too... I did alot of research trying to figure it out because Im used to running ported vac to dizzys and it had me very confused. If I remember correctly some had manifold vac to that port with a different vac pod on the distributor, and other models ran ported (again I may be waay wrong here, just going off random stuff I found while searching).

So after getting sick of all the issues with the old BBD wich had worn out throttle shaft, warped bowl cover, among other "little" issues (turned out to be a reman, found the sticker first time I rebuilt it myself...), I purchased a reman one from VAPEX through my work, checked it all out, set the floats, accel pump, step-up, and verified it was definately a super six carb and not a 318 carb I slapped it on. All the issues I was having are now gone, as well as the fact the one I have now pulls ported vac and not manifold vac from that port... :?:
Author:  killnine [ Sat Jan 18, 2014 1:04 pm ]
Post subject: 
Quote:
Have you checked vacuum at that port since you re-adjusted the cable? I only ask because the old BBD I had on mine did the same, took me forever to realize it too... I did alot of research trying to figure it out because Im used to running ported vac to dizzys and it had me very confused. If I remember correctly some had manifold vac to that port with a different vac pod on the distributor, and other models ran ported (again I may be waay wrong here, just going off random stuff I found while searching).

So after getting sick of all the issues with the old BBD wich had worn out throttle shaft, warped bowl cover, among other "little" issues (turned out to be a reman, found the sticker first time I rebuilt it myself...), I purchased a reman one from VAPEX through my work, checked it all out, set the floats, accel pump, step-up, and verified it was definately a super six carb and not a 318 carb I slapped it on. All the issues I was having are now gone, as well as the fact the one I have now pulls ported vac and not manifold vac from that port... :?:
I just came in the house from running it for about 20 minutes or so.

The bog and backfire when I hit the throttle fast is now gone, thank god. However, yes that port still pulls manifold vacuum. The other port might work, what I think is for EGR, but it is way too small for the vacuum line to the dizzy, so without some kind of rigged setup I can't try it right now.

Now the problem however is that it will run, and at a pretty high idle (I don't have a tach yet), I think around 600-800, with the curb idle and fast idle backed completely off. So making sure the throttle plate was completely closed didn't help anything. It's not whistling or sucking a ton of air and the manifold vacuum is around 15 at idle, so vacuum all seems normal. I'm pretty sure it's not supposed to do this though. I really want to go drive it around for the first time since it's running pretty good but this scares me because it's abnormal.
Author:  oldskoolracer [ Sat Jan 18, 2014 1:38 pm ]
Post subject: 
Idle speed screw backed out will lower idle, turning the mixture screw(s) "out" (counter clockwise) however will increase the idle, and turning the mixture screws "in" (clockwise) will lower the idle. (out is richer, in is leaner)

In the mean time you CAN safely drive it, either run the manifold vacuum to the dizzy and run the timing slightly lower with the vacuum disconnected OR, cap the port on the carb and run no vacuum to the dizzy. Either way, your not going to get any advance while accelerating without having a true ported vacuum. The EGR port you talk about may not EVER pull enough vacuum to move the advance properly, it provides "venturi" vacuum wich tends to be quite less than "manifold" or "ported".
Author:  killnine [ Sat Jan 18, 2014 2:26 pm ]
Post subject: 
Well, I figured out the won't die conundrum. The carb wasn't down tight enough. It was able to be tightened quite a bit more to the manifold once it was warm. It died while I tightened it down and I could hear the vacuum leak getting closed. Only problem now is I can't get it to start up and idle again. Sigh. What an adventure. Maybe I ran out of gas. Oh well, one more problem down I guess.
Author:  oldskoolracer [ Sat Jan 18, 2014 2:45 pm ]
Post subject: 
Now that you did that, get to a base setting... Turn both mixture screws all the way in, then turn them both out about 2-2 1/2 turns, and screw the curb speed screw in about 1/2 to 1 full turn after it contacts its stop. If you have fuel, this should get it fired back up. If not, turn it over to TDC again and see where the distributor is pointing... Could have the timing way off trying to get it to run with the vacuum leak. Once started and warmed you can move on to setting the idle speed and base timing again...

Sounds like your making progress, even if you did take a step or two backwards :D
Author:  killnine [ Sat Jan 18, 2014 3:23 pm ]
Post subject: 
Quote:
Now that you did that, get to a base setting... Turn both mixture screws all the way in, then turn them both out about 2-2 1/2 turns, and screw the curb speed screw in about 1/2 to 1 full turn after it contacts its stop. If you have fuel, this should get it fired back up. If not, turn it over to TDC again and see where the distributor is pointing... Could have the timing way off trying to get it to run with the vacuum leak. Once started and warmed you can move on to setting the idle speed and base timing again...

Sounds like your making progress, even if you did take a step or two backwards :D
Definitely. I think it's low on gas. I only had about 3 gallons or so in it and when it gets low in the new tank I think it doesn't pick it up very well. When the wife gets home I'll go get some more and give it another go. I think I'm so close!
Author:  killnine [ Sun Jan 19, 2014 3:05 pm ]
Post subject: 
Still have manifold vacuum at the ported vacuum fitting, but I hooked it up for now. I put gas in it today and had a long adventure with the timing. I'm pretty sure the balancer has slipped, but even just trying to go by compression or putting it where it should have been based on the valves being closed wasn't putting it where it wanted to be to start and run. I basically set the dizzy in and out until it was clunking when trying to start it, and then kept backing it off (retarding it) until it started and ran pretty well. I got it to the point where I could loosen the dizzy and retard it some and watch the vacuum drop so I figured I was about where I should be. I gave it as much advance as the bracket would allow. According to the notch in the balancer (which isn't too far off since it is in the right valvetrain phase at least), I'm at about 15-20 BTDC or so, hard to tell. That's initial. If I back it off much more it just doesn't run well though, so I think the notch is actually off a bit. I'll have to figure out as close as I can to TDC and mark it, but I did that before and I guess I didn't get it right. Maybe time to buy a piston stop.

So anyhow it was still running a bit rough, but eventually I figured out that AGAIN I had to tighten the carb nuts down. I have to put a lot of torque on em with a 1/2 open end wrench. But they do still move somewhat. I was really afraid of breaking something but when I tightened it yet again it had less of a vacuum leak, and purrs like a kitten.

Then, I actually DROVE THE CAR. I put it in gear, and moved it, and drove it to the end of the RV park, and turned around and came back!

I have a lot of brake and suspension work to do.

And now I remember why I hate the power steering on these old beasts. It's like a damn pirate ship. The waves were choppy and she wasn't turning quick.

I have everything brake wise except new drums, but I'm hoping they aren't bad. I'll be farming out the suspension work after I buy some parts. The important thing is that I CAN DRIVE IT TO THE SHOP!
Author:  matv91 [ Mon Jan 20, 2014 4:03 am ]
Post subject: 
Holes in throtle plate? Looks like 318 carb.
Author:  killnine [ Mon Jan 20, 2014 6:48 am ]
Post subject: 
Quote:
Holes in throtle plate? Looks like 318 carb.
It is a 318 carb, but there are no holes in the throttle plate. I think it's a 76 V8 carb. There is a small notch in one throttle plate right where the egr passage is.
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