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Whats the best carb/CFM for a 351w?

MartyG

Bronco Guru
Joined
Jun 2, 2010
Messages
1,124
I'm having some issues w/ my carb...Holly 4b (650cfm) and I'm thinking I might want to replace it. Already been rebuilt once.
Hoping there is something that will give me better mpg around town (it's my DD). Is there a lower cfm I can get away with that would make a big difference? Not too worried about power loss...it's just for in town mainly.
Carter? Eddlebrock?
Any suggestions?
And...anyone have one for sale?
Thanks!
 

TwoDalesDad

Bronco Guru
Joined
Jul 19, 2011
Messages
1,515
You may want to Clic it over to Fuel injection..if you are going for mileage. The Holley 450 jetted correctly would be my guess..but may not be cheap to find......
 

wildbill

Old Bronco Guy
Joined
Jun 29, 2001
Messages
6,885
;D;D;D With the 351W I have had the best luck with a 625 carter.:cool::cool::cool: Bill ;D:cool::D
 

tasker

Contributor
all knowing of nothing
Joined
Jun 2, 2006
Messages
20,729
Loc.
NH
run an autolite 4100....very happy with it
 

bronconut73

Bronco Guru
Joined
Aug 7, 2012
Messages
9,916
Holley 670 TA is what I am using. I have to agree with our bronco brother above, fuel injection is king for mileage especially if you want to install it and forget it. A carb can be tuned to get nearly as good of mpg as fuel injection but would require more maintenance to maintain that good mpg. Greater mpg with a carb usually means a little less power but this is usually not the case with fuel injection, infact it can mean more power as you increase efficiency with better/performance parts.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
650 Holley, is that a double pumper?
Most out of the box carbs are set up to run a little rich, safer for the engine. So anything new will require tuning to get it dialed in. Even used carbs will need tuning to match your engine.

A good MAF EFI will be a choice that shouldn't need tuning. Trick is to keep all the stuff matched; MAF, ECM, injectors. The MAF has a specific voltage out for a specific airflow through it. Alter that relationship (change housing size, different sensor then the computer is programmed for, etc.) and you just lost your tune. For a stock 351 you can use a truck lower, BC adaptor for a 5.0 upper, stock mustang 19Lb injectors and have a nice clean efficient running engine.
 
OP
OP
MartyG

MartyG

Bronco Guru
Joined
Jun 2, 2010
Messages
1,124
Great... I'll check these out, thanks guys! By the way, how hard/expensive is it to switch over to you inject shin?
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
With a properly tuned carb you are not likely to see much if any increase in mileage by swapping to EFI.
A smaller carb will increase lowend throttle response but wont always be more effiecent. I would suggest going with a 600 cfm carb and tuning it then going from there.

EFI swap prices are all over the board they can be done for next to nothing if you can score the parts or it can run into the thousands if you went all new. but IMO a basic stock for setup will probably cost you around $500 unless you go with a new wiring harness which will raise the price up about another $500
 

ugly74

Bronco abuser
Joined
Apr 17, 2006
Messages
2,847
That carb may have been rebuilt, but never really tuned right. I love my Holleys. Ive had people jump in and go for a ride in my 74, and then ask if its fuel injected!
 
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