Carter BBD w/Idle Enrichment & EGR Dump

[Leizurtime]

Okay, new thread. I don't suppose anyone can explain to me why....occasionally on cold mornings (which really isn't that cold, because I live in the OC Socal, its like constant 72 degrees almost year round) why my car idles at this high of rpm during warm up? In the picture, basically almost too normal op temp and revving so high, even after pumping throttle a few times to try and kick it down. It usually does kick, sometimes right after I start the thing. Occasionally, it will only kick down after I rev above 4,000 rpm Lol, thing has a mind of its own. The carb is brand new from Rockauto. Carter BBD with Idle enrichment and the EGR dump, what the car originally came with. I've tuned the thing with a vacuum gauge and rpm settings are set to factory spec. Choke coil is a brand new G.P. Sorenson. Have a NOS Mopar on standby.

 

[kkritsilas]

When somebody says a carbed car is cold, it is not only due to outside temperature. The engine is "cold" (as in below normal operating temperature of the engine) even when it feels warm outside to humans. The determinant of how "cold" an engine is the temperature of the exhaust gas going by the bimetallic strip that controls the choke lever on the carb. Only when the exhaust temperature has gone over the temperature at which the bimetallic strip begins to move to the point where the choke lever on the carb will the choke "kick off". That temperature may be reached quickly, if the car was in use just moments ago, it may take a longer time, if the outside air is cold and the car has been sitting around in those cold air temperatures.

Of course, this all depends on the choke working properly. If you don't have cold start issues, or driveability issues, and the choke does kick off, it should be fine.

 

[Leizurtime]

When the car warms up, it runs perfectly. Almost like a hot rod. Nonetheless, until it reaches 195 degrees, I experience all kinds of issues. If I fire it up and try to drive it right away, it won't go over 2,000 rpm, as if it has a governor. In neutral it will rev to 6,000 cold. It tends to stall unless I feather the pedal when driving during this time. Its not a typical thing, I always try to let it warm up at least 5 min. Even so, I just can't understand why the car would ever need to warm up at 2,500 rpm, that just seems way too high. Supposably the idle enrichment is supposed to aid the driveability during warm up. I don't see it happening though.

 

[BudW]

There is a pair of screws on front of driver’s side of carburetor.
One is for idle speed and other is for fast idle. I suspect the fast idle screw needs to be adjusted a couple of turns.

Personally, I like my fast idle speed to be a tad higher than normal – but that is my preference. Regular idle speed, I like to be normal.

I can’t take pictures at this time to show you.
The fast idle speed can be adjusted with engine warm – but you need to move the link first, to do so (and it helps to have a photo to look at to do so.
BudW

 

[Aspen500]

One thing to keep in mind also is, cars of the era (especially CA emission) tended to stall on cold starts, cut out on acceleration until warmed up, etc............. If everything is stock and adjusted to stock specs is what I mean.
That said, 2,500 rpm is way too high for the fast idle. It should be around 1,600 rpm. Like Bud mentioned, you'll need to adjust the fast idle stop screw.

Not sure if your choke t-stat is electrically heated but if it is, make sure the heater is being supplied with battery voltage with the key on or engine running.

 

[Leizurtime]

It has a duralast choke coil on it now with the warm up wire. The wire connection was always loose and prone to falling off. I crimped it harder with a pair of plyers and it seems to work fine. I just don't trust that duralast for some reason though. So, I purchased a Ma Mopar choke thermostat, which I been meaning to install. I get a feeling though that its something with the carb, even though its brand new from RockAuto.

I have gone through the proper procedure, as it is, both idle screws are where they are supposed to be. The entire speel has been performed at least three times. I do set the fast idle @ 1500 rpm while the engine is at normal operating temp. My Haynes Instruction manual says to place the the fast idle cam on the second notch and adjust to spec. Now, some mornings it idles @ 2500 and others @ 1400. It can't decide.

In the past, I've actually tuned it down to 1500 while it was fast idling at 2500 during warm up. This didn't work out very well. Afterward, some mornings it would idle at @ 500 rpm and others @ 1500.

I wonder if I have a vacuum leak somewhere still. Perhaps a bad power heat valve vacuum diaphram or vaccum line? Or maybe one of the vacuum switches on the manifold. Something in the warm up circuit, but which is shut off once the engine reaches operating temperature. When I used the vacuum gauge during warm up, it was right on the cusp of being too low about 17 in. After the engine warmed up the vacuum was right about 19-20 in. During this time the engine runs fine. But before operating temp it suffers a severe loss of power, cruising down the road car won't rev above 2,000 rpm, like something is holding it back. After it warms up though, I can push it to 3,000 and it runs and drives normal.

 

[lowbudget]

To check for a vacuum leak get a can of starting fluid or carb cleaner and start spraying. I was having hell with the idle on my 5th Avenue last days off and found a leaking carb base gasket. Which I will address in 3 days when I get home.....

 

[BudW]

To check for a vacuum leak get a can of starting fluid or carb cleaner and start spraying. I was having hell with the idle on my 5th Avenue last days off and found a leaking carb base gasket.

Carburetor cleaner will make RPM spike if it finds a vacuum leak – so good for finding vacuum leaks. I have seen what Lowbudget has, a few times.
For whatever reason, the fasteners that attach carburetor to intake will loosen. I suspect as gasket gets saturated with fuel, they seal off the vacuum leak – but when cold (ie: dry) it will leak air, thereby increasing engine idle speed.

Leasuretime, did you purchased a NEW carburetor from RockAuto?
I checked and the only ones I saw were reman’s (re-manufactured), which is not new.

On eBay, there are some new BBD’s out there, for less $ than reman’s are. They are Chinese knock-offs. I have been using one for 5 years now without any problems and I think others are here as well.


I wrote up a piece about reman carburetors some time back – went to look for it and couldn’t find it – but something that people need to know about.

To recap, carburetor remanufacting companies will “process” about 30-50 carburetors at a time. It would be, for example, a batch of 30 BBD’s, a batch of 50 QuadraJets, then a batch of 40 Holley’s, etc. What happens is they grab, say 30 BBD’s off of the shelf and strip then down – tossing all of the contents of that batch (all 30 units), into piles (Jets in one pile, linkages into another pile, etc.).
All parts get cleaned. Metal items get re-plated, defective parts get tossed, and so forth. When re-assembling the units, they grab one of each part and go back to re-assembling them. This is where problems arise. Linkages change over the years, jets change on engine sizes, and so forth. You would not want /6 jets in a 360 engine (or vice versa). What comes out – is a very clean unit – but nothing like the original unit. It would be very unlikely that finished unit had the same exact parts on it, as it went in – which is one of the reasons I do not like reman carburetors. If the rebuild companies would keep all parts together – I would have a different opinion on the matter – but the way that business is structured – this is best for them.

I cannot tell you how many reman carburetors – I had to “rebuild” to get it back to specifications for it to be roadworthy again.

Now with that said, if a person rebuilds a carburetor (self, friend or even taking it to a rebuilder), then all original parts are re-used, except for defective ones, and you are back to where it should be. If part is marked “reman” then that is not the case.
Carburetors and distributers are the two items I run across being problems. Most everything else (alternators, starters, transmissions, etc.) I don’t have much problems with. Carburetors (and distributers) were not meant to be remanufactured – because of the calibration factor and there is just SO MANY variations of parts used on them.

I suspect you might be a victim of mis-matched parts – this case linkages and/or fast idle cams, etc. – possibly – and those are hard to fix (and diagnosis) – without having an original close by to compare to.

That said, get some carburetor cleaner and with engine running, spray some at the carburetor base, and around intake, etc. – and make note of any engine RPM spikes – before doing anything else.
BudW

 

[lowbudget]

On the subject of carb mounting nuts coming loose at the base. My Aspen was notorious for this. I put in new studs and it hasn't done it again. It might be the gasket but I had replaced it several times to no avail of fixing the problem.

 

[Leizurtime]

Its is a Reman BudW. The new ones I came across were just too expensive. Luckily, the core charge was only $5.00, not enough to even cover the shipping of the old one back to RockAuto, so I kept the original. I was thinking of having it rebuilt. Thanks for the great info on carbs.

When I replaced the carb, I of course used the new base gasket. Upon removing the original, I noticed the bolts seemed too long and a few were loose. I think somebody used two gaskets to mount the original at some point. So I got spectre carb studs and they do work great. Pretty sure the seat of the carb isn't leaking.

There could be a leak at the manifold where it bolts to the heads. One time while throttling the carb from under the hood, I notice a small patch of gases hovering above where the exhaust crossover is. I suspected an exhaust leak. I wonder if the gasket on the intake ports in this area are affected as well. Trying to eliminate most of the simpler considerations first before ripping apart the top of my engine. Its so much work and a dirty job, especially on my car. lol.