AFB and MPG (or is it GPM?)

[Yardpilot]

1973 351 C Carter AFB

Plugs say she is running rich. MPG sucks, but I'm not sure that isn't normal. Power feels off. Not much low end, but it is what it is. Comes on 1800-2000, then hammers about 2800-3000. Jets? Metering rods?

[Ron Ward]

Check and make sure you have proper ignition timing, both at idle and at full advance. Once properly set, go from there. Rich will cause the sogginess you have described, but so will retarded timing.

[68scott385]

Is it like the Edelbrock remakes? Here's a link to the owner's manual for the Eddy carbs, it includes a tuning graph for each of the cfm variances. IMO it's easy to get the rods & jets rich in cruise mode but takes some t&e to get the off idle and transitional tuning spot-on.

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

[Scott Liggett]

Make sure it isn't leaking into the intake first. Then make sure the floats are set correctly. Then the air bleeds are clean.

[BigBlockMopar]

Best tool for a tuning job like this is an AFR-gauge.
Then you can see exactly when the carb is rich/lean at around which rpm ranges.

This could be timing related, and maybe even cam-timing.
A worn timingchain-set with quite some play will move the engine's power band to higher rpms, loosing low end torque.

[NewEnglandRaceFan]

Arnt 351c's dogs down low anyways. with those huge ports and low compression

[Yardpilot]

Timing and dwell are spang on the money across the board.

[Yardpilot]

Is it like the Edelbrock remakes? Here's a link to the owner's manual for the Eddy carbs, it includes a tuning graph for each of the cfm variances. IMO it's easy to get the rods & jets rich in cruise mode but takes some t&e to get the off idle and transitional tuning spot-on.

http://www.edelbrock.com/automotive_...ers_manual.pdf

Yup, same-same. Thanks for the link.

[Yardpilot]

Make sure it isn't leaking into the intake first. Then make sure the floats are set correctly. Then the air bleeds are clean.

First two are right. How to check the bleeds?

[Yardpilot]

Best tool for a tuning job like this is an AFR-gauge.
Then you can see exactly when the carb is rich/lean at around which rpm ranges.

Isn't an AFR gauge associated with an O2 sensor? Nothing like that on this old girl.

[Yardpilot]

Arnt 351c's dogs down low anyways. with those huge ports and low compression

I've heard that, but I don't know. Compression is not low on this engine. As near as I can make out, it's somewhere between 10 and 11 to 1. Even if power output at low speed is way down because of airflow through the big ports/valves, shouldn't it be smooth?

[SpiderGearsMan]

3PSI is max fuel pressure in a AFB
start there Yardbird

[68scott385]

3PSI is max fuel pressure in a AFB
start there Yardbird

I don't know that I'd go 3psi, they are very pressure sensitive, but anything over 6psi is too much. I've supplied my afb with a factory/stock replacement fuel pump with no problems.

Use a vacuum gauge to set the idle air bleeds to highest vacuum setting, the rest is rod, jet, pump tuning.

FWIW I don't care much for Edelbrock's tuning graphs. I plugged the part sizes into Excel and calculated difference in area of jet opening in relation to area of rod, it makes more sense to me than percentage rich/lean of base setting.

[SpiderGearsMan]

as stated before , an AFB is a cruiser carb
3-4 psi MAX
my Nova 4500 dominator had carb shop needle valves for 17 psi FP ///now the hot setup for pro stock holleys

[Scott Liggett]

First two are right. How to check the bleeds?

They stick up through the lid beside the choke tower. Right where grease and dirt build up. Just use carb clean to make sure they are not filthy.