Tuning a Carter AFB

[DavidBrownlee]

I have taken my 300 engine and removed the 2 barrel intake and replaced it with a 4 barrel from a 1965 340 engine. I have also tracked down a installed the correct Carter AFB 3326S and have it installed. I am looking for suggestions which jet's to use for the reduced airflow I get for a 300 as opposed to the 340 engine. Any other tuning guidance would be helpful. I am handier at doing the work than I am knowledgeable on this.

[66electrafied]

Not sure it's an issue; - in fact, it might be a better idea to leave it just as it is.

The jetting on that carb is tuned for the air it'll take, sure the 300 is a little smaller, but not by much. It might actually like that little extra fuel. The only time that jetting really comes into play is at WOT anyway, and for the most part Buick engines were under-carbureted for economy and not set up for performance.

Just an opinion...

[techg8]

I agree with the above. I would try it out and adjust from there. I bet it will be pretty close.

[64SkyConvert]

x3 on the above.... beware jetting changes on those carbs- the tuning kits you can buy from Edelbrock include the jets and rods to make mostly "large" changes in the mixture. I spent weeks with the AFB on my 300, ordering the kit, extra jets on top of that, only to discover 1 month later that it was as good as it's going to get, right out of the box..... Now the pump stroke I would change to the shortest stroke, however- that is what mine needed anyway. I can see why people go with a Holley:laugh:

[DavidBrownlee]

I will change it to the shortest pump shot position and leave the jets as is. Thanks for the advice

[Jim Cannon]

If you really want to see where your mixture is, install an air-fuel mixture gauge in the exhaust and see what you have. Analog carbs are not that precise; you are probably as good as you are going to get...

[doc]

All of the above advice is good.... all a carb sees is the amount of air being pulled thru it.... and it induces the right amount of gas to come up with the correct fuel/air ratio.... just run it right out of the box....the most critical thing is the accellerator pump shot.... set it to its richest setting for performance.... pay close attention to the air cleaner assembly.... open it up for more and easier air intake... and if you are enclined, fab up a ''cold air'' pick up for a considerable performance/mileage boost....Buick says 8% of the total hp output.... about 20 horses in your case.... well worth it.... ck out my list of cheap tricks in the wrenchin secrets section....

[djonesutah]

Isn't the carb he mentions, 3826S, the right one for a 300. I think the carb for a 340 is a 3443S.

[Bigpig455]

I'm a Q-Jet guy, but cannot knock my Carter on the 65... after I did the Doc mod on my manifold, I went up one jet size on the secondaries (.082 to .086) and changed the .062/.068 rods to .052/.065....

Throttle response is awesome and I can run my finger along the inside of the tailpipe and have it come out perfectly clean... but it does run a little lean in 50 degrees or less weather.

My only complaint is that it will tend to flood when hot and parked - I've never been able to cure that