Carter BBD High Altitude Jetting

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mammlouk

mammlouk

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Anybody have a some friendly recommendations? I've read on a few Jeep forums that Edelbrock jets will fit into the BBD just fine. I'm currently running stock 2BBL intake manifold and Carter BBD on my 65 Dart 273. I've done the best I can to tune this thing and I just can't get it right. My next step is to attempt to fix the jetting. This was originally a California car and I am running it in Colorado Springs at ~6,000ft above sea level.

Does anybody have recommendations for jets and metering rods? I tried asking the Edelbrock tech line, but they said they didn't have the necessary specs and flow characteristics on the BBD to calculate and give me part suggestions. Eventually I will be installing an Edelbrock D4B intake and I will probably top it with an Edelbrock 500CFM carb using their recommendations. For now I just want to get things running as well as I can without spending $300 on a new carb.
 
I believe that you need to go a couple of steps down on the jets for each xxxx feet of elevation to account for the thinner air... I'm not sure of the correct ratio...
 
edelbrock tech line, what a joke. lol. they say that you should go up to 3 steps down, or 12%. i've found that a little too much and will lean it out. what rods and jets are you running right now? i would start at 1 or 2 steps down and go from there. a 500 edelbrock has a .086 main jet with a .065x.052 metering rod stock. if you want to start 1 step down you need a .086 jet and a .067x.055 metering rod. if you want to go 2 steps down you'll need a .083 jet, and a .65x.052 metering rod. hope that helps...........
higgs
 
Higgs,
Right now everything is stock spec for a Carter BBD. I don't know what those specs are. If anyone knows that would probably help! ;)

Edelbrock actually gave me some recommendations for if I move to a performer 500. They told me to go 8% lean using a main of .098, rods .073 x .052, and secondary .089

As mentioned. Right now I need to work with the stock BBD. Any idea what that would look like?
 
mammlouk said:
Higgs,
Right now everything is stock spec for a Carter BBD. I don't know what those specs are. If anyone knows that would probably help! ;)

Edelbrock actually gave me some recommendations for if I move to a performer 500. They told me to go 8% lean using a main of .098, rods .073 x .052, and secondary .089

As mentioned. Right now I need to work with the stock BBD. Any idea what that would look like?
Click to expand...
No idea with your current carb but I had to go way lower than I thought with a Carter 625 Cfm. I'm at 5800 ft and tuned with an air/fuel meter in my 340 with a 625 cfm Carter on it
.92 main .89 seconday and .070 X .060 rod was dead on at my elevation but I ended up at .095 and .092 with a 70x37 rod because our elevation could drop 1500 ft cruising into the city.
 
A few weeks ago I drove my Chinese-BBD-clone-powered slanty from sea level to 7000ft and up and down all weekend, and never really noticed any difference in the way it ran. The fact it was 100 degrees the whole time may have had something to do with it. But who knows how it is jetted—what's the altitude in Beijing?
 
Well changing the MJs only affects the 'Main circuit". It has nothing whatsoever to do with the low-speed or idle circuits. So, If you never floor it, then, there will be little to no change in the operating characteristics, with an MJ swap.
And depending on the year of the carb,it might already be on the lean side.
And depending on the engine's current specs,or how far it is from the factory tune, the carb may already be perfect.
And yes, temperature does play a big roll in power delivery. That info was enough impetus for me to cut a big ol' hole in my hood and deliver fresh non-superheated underhood air, into my carb. Of course,now, I am at the mercy of barometric pressure and humidity,lol
 
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