Hello

Just installed a NOS Carter BBD on Super Six conversion to replace a rebuilt unit that I could not get to idle right. Carb was taken out of the original Carter package and installed on Sunday. It is NOS not rebuilt.

Runs well, starts cold, accelerates ok, no hesitation —-but after a warm shut down—seems to be leaking gas from the bowl into the engine. Garage smells of gas and after 5 min of sitting car is very hard to start. No visible wet fuel externally.

Fuel pump is new.

Love the two barrel power, have not been loving the BBD.

Thoughts/suggestions on best way to correct this ?

Thanks.

This what you describe is called percolation, and it is exactly what it sounds like: the carburetor is boiling like a teakettle, and the boiling gasoline is foaming up through the nozzles and into the throat, from there down into the intake, and because the manifold is still hot, it vapourises and fills the garage. Also makes the car hard to start until the flooding is cleared.

Check and make sure the float level is correct, not too high. Do the fuel line mod and make sure you've got the correct (3/8" thick insulator type) carburetor base gasket installed. Make sure your manifold heat control "heat riser" valve is working correctly.

(What exact BBD did you install? What's the 4-digit number with the "s" after it?)

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Aren't you the guy who had like 10 NOS carbs for sale a while back? Whoever it was I got 2 of em and they've been great.
That said I have had AFBs and Edelbrock versions of the same carb (same as each other not same as a BBD except for who made them) and have had all kinds of problems with that issue on those carbs. Can't ever remember having a BBD do that.
There is a member here that makes and sells a plastic carb spacer for those carbs. (Phenolic?)--- type of plastic I think is what they're made of. Most BBDs ran with a pretty thick gasket/ though the 2 NOS BBDs I got came with a pretty thin gasket which I didn't use with either of mine. The thickness of the gasket can mess with the chole working right, too.

Is your engine running hot? Exhaust partly plugged?

Thanks for the responses.


Carb is a BBD 6537

Fuel Line Mod is done--all rubber hose that is routed well.

Heat Riser is free and working.

Engine is not running hot. Exhaust is clear and free

I was not the guy with the carbs for sale...I was a guy that bought one of those carbs for sale...this is one of them…not unhappy with the carb—just trying to make it work right.

I was using the gasket that was supplied with the carb--defiantly not 3/8 thick. Maybe 1/8?

Found a thick gasket and swapped it out. Went for a drive, came back pulled into the garage—fuel smell and hard start 15 min later.

Gasket did not change anything.

Why else would the fuel be leaking down on a new carb?

I'm not the guy who had that collection of 1974 heavy-duty Dodge truck 318 V8 BBDs (is what that is) for sale awhile back, either.

Your engine doesn't have to be overheating or running hot for percolation to occur. You do want the thick insulating base gasket, and a careful check on the float level. Make certain the carb bowl vents (indicated in the attached pic) are not blocked off by the air cleaner or its gasket.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Bowl Vents do not appear blocked by the gasket or air cleaner housing.

Thin gasket I took off appears stained?

I bought 2 of those exact carbs out of that same lot, and so far couldn't be happier with how they're working. Same BBD-6537

Tighten the screws accessible from the underside of the carb before you put it back on.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I bought a NOS 318 V8 BBD for my super six at 1999. It was running right out of box but leaked fuel all around like this. Mostly after engine shut down. In that carburetor the problem came with casting quality. The gasket surface was not complete and there was opening outside of the carb. I parted that carb and hey'd the casting with sandpaper over a flat glass. With new gasket it was fine then. Have you opened yours to see there is everything well inside?

And my caburetor was also in unopened Carter box and plastics.

_________________
1966 Dart. 170 cu.in. 200 rwhp.

It would truly be a shame if it was a bad cast…but it would not surprise me.

Before I go into the carb…

Could excessive fuel pressure or a bad needle & seat have any role here?

The fuel pump is new….but just did notice a difference in the part number for a 1bbl (1971) vs a 2bbl (1979) on a slant six.

I am using a Delphi fuel pump listed for a 1971–the year of the engine, but I am running a 2bbl intake from a 78 aspen with this carb intended for a 1974 318. Confusing yes.

The specs on Rock auto show slightly less fuel pressure on the later 1979 carb (4psi vs 5psi). The Carter fuel pump shows 2.7 min PSI I believe.

Would a 1979 fuel pump work on a stock 1971 engine?

Or is this completely irrelevant to the leak down issue ?

That's because the '71 cars had a third nipple on the fuel pump body for the primitive evaporative emission control used only in '71 (50-state/Canada) plus '70 (California). Read about it [url]here[/url] if you like. The factory fuel pump pressure specs are the same for all Slant-6 engines: 3 to 5 psi.



Doesn't matter whose name is on the box any more; they're all Chinese junk. Read this (and links) and you might decide to re-replace the fuel pump.

A fuel pump issue is probably not as likely as other causes already mentioned, but it's certainly a possible cause.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Warm start/long crank with strong fuel smell problem still exists.

Here is what I’ve done so far based on recommendations:

-New 5/16 mounting gasket installed
-All rubber fuel line from pump mounted away from excessive heat
-Stock 1970s era Carter fuel pump re-installed
-Bowl vents free and clear
-New needle and seat installed.
-Carb assembly screws tightened.
-No indication of excessive engine temperatures

Looking down the throat of the carb after shutdown—you cannot see fuel dripping but you can see white vapor filling the carb

It would seem at this point the carb will need to be opened and gone through.

I’ve not checked the float level as suggested. First time messing with a BBD. Does someone a good guide for the best way to check float level on this carb ?

Thanks

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. See here about float gauges.

If you check and find it's right on the spec, try dropping it by 1/16" and see if that fixes the problem without creating new ones. If adjusting the float level doesn't do the trick, the next step is to fabricate a heat shield. You'll kind of be on your own; see here and here to get the brain-juice flowing.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.