The slant six specific BBD I was running on the stock 225 in my 76 D100 finally died this weekend. Off idle it is OK, but it will not stay idling. There is obviously something wrong witht the idle circuit but i took it apart and blew all the passageways out and it still dies. Right now I think the throttle shaft finally wore a big enough hole in the base ;plate to make a vacuum leak big enough to be fatal.

I dug through my carb stash and found a 1982 318 BBD. I plopped it on the motor and it idles OK, but it won't idle below about 850 RPM. I think the holes in both throttle blades are allowing too much air to bypass. This is irrelevant anyway because there is something else wrong with the internals of the 318 BBD where it just dies off idle. I don't really want to mess with it since it isn't a slant six carb.

Digging further in my stash revealed another older 318 BBD which doesn't look complete and a Holley 2280 that (A) I know is for a 318 and (B) looks too crusty to trust without a thorough and complete disassembly.

My last option is not really one I wanted to do, but I need to get my truck up and running. I do have a good condition Carter AFB 9501 and a new four barrel carb to two barrel intake adapter. Yes, I am going there. However, I am attempting to do what David Frieburger used to say he did on Roadkill garage- "Do the wrong thing, the right way."

Looking past the problems inherent with running a four barrel carb on a two barrel intake via an adapter, and looking past the problems with running a big open element air cleaner (all I have for a four barrel), the good news is the carb is a 500 CFM AFB inteded for use on Chrysler products. I have a kickdown adapter and gasket kit coming next week.

My concern is calibration. The modenr Edelbrock equivalent carb would be a #1403- electric choke 500 CFM unit. Can I assume the rods and jets and springs in an old Carter AFB 9501 will be the same as a new 1403? My gut tells me no. Unfortunately, I have not yet installed a wideband O2 sensor in the truck (on my list).

What do people recommend for jets, rods, and springs for a stock 1976 225 slant six, 500 CFM AFB/Performer carb, 727 trans, 3.9 rear gear truck? The motor will spin up to 3600-3800 on the highway, but not much more than that. There is a possibility that if I can get this motor running decent I will swap in a hotter cam and higher compression head at a later date, but right now I just need to know what I should order to get the calibration in the ballpark.

Any recommendations are appreciated.

Thanks matv91! That really helps. My Carter book doesn't have those specs. I can do some part number cross referencing and see how close my current setup is and what I need to get it close to stock Edelbrock 1403 calibration.

Looks like there might be a typo in the specifications. One says the secondary jet is 120 - 377 the other one says secondary jet is 120 383. Primary metering Rod 120 - 398, and nice thick metering Rod to go along with it, 076 x 055 , that's the biggest rod I ever heard of. So if leaning is necessary you'd have to drop down one jet size.

Thanks. Those tips help. This will be my first foray into the world of truly fine-tuning a carb. Everything I have done before has been just stock calibrations. I ordered a calibration kit for an Edelbrock 1403 carb, so I will have some rods, jets, and step-up springs to play with after I get a wideband O2 sensor installed and can really fine tune it.

Be aware that fuel has changed since that carburetor was made. 9/32 float height for 9501. Modern-day Edelbrock float 7/16. Internet rumors say that the old elderbrock spec was 11/32 seconds. https://www.corvetteforum.com/forums/c1 ... level.html

Awesome, thanks!

Keep in mind that the main system air bleeds maybe different from edelbrock. The number of the size of and the placement of Emulsion holes in the main well might well be different in a real carter. Edelbrock usually just has one big hole at the very bottom of the Main well. Just a suggestion take the Springs out from under the Step Up Pistons go for a test run. This way you'll be able to tell what the main system is doing by itself. When the main system starts to function a little bit rich okay. When the emulsion part of the main well starts putting air into the mixture things will lean out quickly. The main Wells function is to deliver an economical Cruise mixture. Somewhere between 15.5 and 17 to 1. This should not change much regardless of throttle position or engine speed. Power enrichment should come from the Step Up piston and spring. If the mixture gets richer with speed, fuel level too high. If mixture gets leaner and leaner with speed fuel level too low

More great info! Thank you!

Fuel has changed, but in energy density. The point at which the main circuit comes in shouldn't change. And that's what the float level will affect.

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Joshua

So, leave the float setting at factory specs?

Follow the Carter specifications.

Matv91's description of the main metering function is solid. Too high a float level will also cause the main circuit to come in too soon which will show as richness in transition.

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Joshua

just one big hole at bottom