I have a Holley 2300 350cfm carb on my 1971 F250 300 inline 6 with a C4 trans. Motor is a 5000 mile fresh stock style rebuild. Carb is mounted on a stock 300 log intake manifold with a 1x2 adapter. With this intake and adapter I feel the CFM is more like 270-275 CFM. Holley factory set the jetting for 350 cfm @ sea level to 1000' with a pair of .062 jets. My AFR gauge shows that I am running on the rich side at 14.1-14.3 level.

Has anyone ran a pair of .057-.059 jets in their 2300 Holley? I really think that with my restricted cfm that the .057 or .059 jets would be a better setting. Comments.

 

AFR gauge is big help here. at what conditions is afr 14.2 ish? sounds lean to me.
General targets, N/A:
idle 13.5
cruise 13.5
WOT 12.5

you will likely need addition timing to run lean in the 14s. Lean is hard to burn, start earlier.

 

smoky_diesel
Idle & cruise mph 45-55 14.2 / WOT 12.4

The motor is definitely running rich. Would like 45-55 cruise to be around 15.0-15.5 on the AFR.

Base timing is 14* BTDC with 34* mechanical advance all in at 2400 RPM.

I really think that the .062 jetting with my restricted 270-275 CFM carb air flow & the to big .062 jets is the main problem.

 

What do your plugs look like?

 

85e150 - Plugs look not bad, more or less normal. Reading plugs with todays fuel ain't like the old days. My AFR gauge will show a rich or lean condition long before you can see it on a plug. To go along with the rich cruise AFR number I have my dual exhaust pipe have a strong gas odor when idling with the motor at normal operating temp.

 

Lean the idle out a little and check again. Running too lean can cause troubles.