rebuilt Carter BBD, won't idle

[oldandintheway]

I rebuilt the Carter BBD on my 318, but it won't idle. It runs strong with the choke on, pulls 20" vacuum @ high idle. As soon as I kick it down, it sputters and seems like it is out of gas and dies. Mixture screws are 1 1/4 turns out. I have tried looking for a vacuum leak but I can't keep it running once it comes off the high idle cam. The rebuild kit had most of the proper gaskets with some spares, and the throttle body to main bowl gasket was slightly questionable. It was a 1/8 thick gasket, and most of the holes were the same except the new one had a triangle opening where the vacuum ports went instead of 2 separate holes. There was a thinner gasket with separate holes, maybe I should have used it? I went with the same thickness. This was pretty much what it was doing before I rebuilt it, so this may not be the problem.

Any ideas?

I tried spraying barymans carb cleaner on the throttle shaft to see if there was a vacuum leak, but just couldn't tell @ high idle (didn't stutter even when sprayed in the bore)

[Daddiojoe]

Carter BBDs are pretty notorious for throttle shaft leaks. I ended up having to suck it up and buy a new one from some place in TN. I went through six used ones trying to find a carb w/o the throttle shaft problem.

Good luck,

Joe

[oldandintheway]

Thanks for the reply Joe. From your experience, do these symptoms sound like what you were dealing with? It seems to run fine on fast idle.

[indianajoel]

I think it could be a throttle shaft leak. It might work when it's on high idle and the throttle plate is cracked open, because more air is coming through than at idle so less air sucked in the throttle bores compared to total airflow into the engine. In other words, the vacuum leak is a smaller percentage of all the air drawn in at high idle or open throttle, and then it doesn't change the air/fuel ratio as much.

Anyway, just grab the shaft and see if it wiggles in the bore.

This winter I made my own bushings with washers and JB weld, but haven't had a chance to test out the carb yet.

good luck,
-Joel

[oldandintheway]

How much have you guys seen the re-bush and rebuilds go for? I have one quote for $83 to rebush and a rebuild including re-bush for $203, another rebuild inc re-bush for $170.

[JimE]

Stay away from the $83 price, as you will get what you pay for. The $170-200 mark sounds about right. Jim

[F6866]

If you have power brakes check your booster. I had the same problem, unhooked and plugged the vacuum line to the booster and the problem stopped. Had to have the booster rebuilt.

[oldandintheway]

If you have power brakes check your booster. I had the same problem, unhooked and plugged the vacuum line to the booster and the problem stopped. Had to have the booster rebuilt.

This is my next step. I talked to a rebuild shop and he said it was highly unlikely that a worn shaft bushing would keep it from idling at all, most likely another larger vacuum leak is the problem. I may still have a throttle shaft issue, but i need to eliminate all other leaks first.