good morning from the other side of the pond.

just wanna ask the professional guys here about my little issue with my Carter BBD

last autumn i pruchased a remanufactured Carter BBD from Rockauto and i fairly runs good and does it´s job.

but i still have an little issue with setting the idle speed with gear engaged (D,R,2,1)

my problem: i can´t get the RPM above 480-500 RPM it´s okay, but it´s a bit shaky then

current status:

ignition: 24° BTDC
cold idle after starting - choke fully closed 800-1000 climbs up fast to 1500 -1800 RPM (depends on temperature)
after first touch of the pedal it drops to 900-1000 RPM

idle when warmed up and choke fully opened 750 RPM vacuum reads 19 inch HG

when putting the lever in gear it drops to 480-500 RPM, vacuum drops to 15 inch HG

idle screws are backed out 3,5 times, screwing them in a full turn will let the vacumm drop about 1- 1,5 inches and RPM will also drop to 420 - 450 RPM

turning them out more doesn´t have an effect on vacuum or RPM

my former experience (with 4 BBL Holleys) was: idle screw adjustment is somewhat about 0,5 -1,5 turns

if i try 1,5 turns on that Carter the engine will not start

Cld this be an issue coming from floatlevel beeing to low ? (i did not touch that, it´s the way it was set from whow ever have done it during "remanufacturing")

also it was delivered with a "thick" gasket with slots like this one



any suggestions are welcome

Thanks
Cheers from Germany

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fun is just a straight line.. and it´s approximatly 402 Meters long

Idle speed is set with the transmission in neutral or park. Not in any other gear.



That is far too advanced. A much more reasonable setting for a street driven car is 8-12 BTDC.



Those RPMs sound a touch high. Fast idle is set by warming the engine up fully, placing the fast idle speed screw on the second highest step of the fast idle cam, and using the fast idle speed screw to set the fast idle to about 1200 RPM.



That sounds about right.



That idle speed sounds a touch low, but it sounds like you have other issues such as timing and idle mixture, so that idle speed may change after to you do some adjustments.



The general consensus is when setting the idle mixture you start with the engine fully warmed up, the timing set correctly, the vacuum advance hose disconnected from the distributor and plugged, the curb idle speed set to 700-750 RPM, and the idle mixture screws set to about two turns out from lightly seated.

The first thing you need to do is to get your base timing sorted out. You need to verify that the timing mark on the vibration damper is still accurately indicating top dead center on the compression stroke of cylinder number 1. The outer ring on the damper can slip and give an inaccurate reading. Once you are sure your base timing is set correctly to a more reasonable 8-12 degrees BTDC, then you can start dealing with the carburetor settings.

First, are you sure you have a Carter BBD designed for a slant six? There are differences between the 318 BBD and the 225 BBD. One of the more noticeable is the presence of holes in the throttle plates on the 318 BBDs that affect idle mixture. People have reported mixed results using a 318 BBD on a 225, but that is a factor you must consider.

Second, you may have the idle speed screw turned too far in to compensate for grossly incorrect timing. If the idle speed screw is turned too far in the carburetor may be running on the transfer and/or main metering circuits rather than just the idle circuit. When setting the curb idle speed and mixture the carb must be operating on the idle circuit only.

Can you post some pictures of your carburetor? Specifically the PCV hose fitting and a closeup of the idle speed and fast idle screws so we can see where they are set at hot idle?

I think Reed's got you on the right track. Your severely over-advanced ignition timing means the idle speed screw has to be backed way off from its correct position to get the curb idle speed down to around 750 rpm in park/neutral, which messes up the position of the throttle plates relative to the idle transfer and spark advance ports. "Remanufactured" carburetors like you bought typically don't work very well, but try putting the timing at between 5° and 7° BTDC (with the vacuum hose pulled off the distributor and plugged, engine hot, transmission in Park or Neutral) and rework all your adjustments (idle mixture, idle speed) and see where that gets you. Also, Reed's right again, let's make sure all the hoses are hooked up correctly.

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

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

Thank you both...

Guess i have some homework to do now

Btw. Throttle blades do not have those small holes like mentioned above.

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fun is just a straight line.. and it´s approximatly 402 Meters long

good morning,

last weekend i got time to play around with that carb thing

btw.. here is a pic showing the old idle screw setting you asked for




i started with seating the mixing screws and turning them out 2 full revs and setting the ignition to 10° BTDC

had to turn in the idle screw some turns to get it started und running with 740 -760 RPM - Vacuum was 15 in/hg.

then i started to adjust the mixing screws and ended up with 2 3/4 turns and 18 in/hg vacuum. That was the best i can get

test driving the truck it now has an idle about 500 RPM in D (e.g. waiting at a Stop light) but it´s not so shaky anymore like before with the nearly the same RPM. Overall it feels a bit more sluggish compared to the setting with the more advanced idle

maybe i will try to give it a bit more advance like 12 or 14 degrees

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fun is just a straight line.. and it´s approximatly 402 Meters long