Just want a good replacement carb for my 69 F250 360
#16
03-24-2018, 10:21 AM
When I read about flow and CFM and the rest of it, they always seem to be talking about 6000 RPM, stuff like that. Those are drag racing calculations. It will likely run like **** at anything other than ***** to the wall pedal to the metal. If you plug in your average RPM in high gear at 50 or 60 mph, see what it suggests. Most likely something close to 350 CFM or even a bit smaller. Just what was provided as OEM. Hm, maybe those Ford engineers were on to something!
Trucks were designed to haul heavy loads, starting from a dead stop a smaller carburetor atomizes fuel better, and offers crisp throttle response with lots of torque in the low range where most people do their driving. Carburetor flow differences (mostly) show up at the high end, at high speed anyway. When it comes to carburetors and camshafts, I've read "pick the one you think you want, and go one step smaller."
Trucks were designed to haul heavy loads, starting from a dead stop a smaller carburetor atomizes fuel better, and offers crisp throttle response with lots of torque in the low range where most people do their driving. Carburetor flow differences (mostly) show up at the high end, at high speed anyway. When it comes to carburetors and camshafts, I've read "pick the one you think you want, and go one step smaller."
#18
03-24-2018, 11:41 AM
Back when I was young and into trying weird stuff, I happened upon a free 750 Holley and a 2-4bbl adapter. Bolting it onto my completely stock 360, it did improve the high end, which with that stock 360 was about 4500RPM. It didn't hurt the low-end either.
Your Mileage May Vary.
The moral of this story: The stock 350 CFM carb was definitely limiting the engine. It wasn't a huge gain or anything, but it was different.
HOWEVER - going from a 350 CFM 2bbl to a 500 CFM 2bbl might make idle and low-end WORSE, as the venturis are larger, and the air flow at idle and low RPM will be slower through the carb making jetting a possible issue.
Your Mileage May Vary.
The moral of this story: The stock 350 CFM carb was definitely limiting the engine. It wasn't a huge gain or anything, but it was different.
HOWEVER - going from a 350 CFM 2bbl to a 500 CFM 2bbl might make idle and low-end WORSE, as the venturis are larger, and the air flow at idle and low RPM will be slower through the carb making jetting a possible issue.
#19
03-24-2018, 12:11 PM
Back when I was young and into trying weird stuff, I happened upon a free 750 Holley and a 2-4bbl adapter. Bolting it onto my completely stock 360, it did improve the high end, which with that stock 360 was about 4500RPM. It didn't hurt the low-end either.
Your Mileage May Vary.
The moral of this story: The stock 350 CFM carb was definitely limiting the engine. It wasn't a huge gain or anything, but it was different.
HOWEVER - going from a 350 CFM 2bbl to a 500 CFM 2bbl might make idle and low-end WORSE, as the venturis are larger, and the air flow at idle and low RPM will be slower through the carb making jetting a possible issue.
Your Mileage May Vary.
The moral of this story: The stock 350 CFM carb was definitely limiting the engine. It wasn't a huge gain or anything, but it was different.
HOWEVER - going from a 350 CFM 2bbl to a 500 CFM 2bbl might make idle and low-end WORSE, as the venturis are larger, and the air flow at idle and low RPM will be slower through the carb making jetting a possible issue.
#20
03-24-2018, 12:28 PM
Did that years ago, when I was in high school, to my dads 53 Ford flat head. It was a dog out of the hole but the engine wouldn't quit winding out. In the course of app. a month, burned out 11 of the 16 valves. Dad was not impressed with my foray into the world of auto mechanics.
Probably ran lean?
#21
03-24-2018, 12:39 PM
Carburetion is weird sometimes. AFR can change in ways that are not necessarily intuitive. Increased air velocity due to smaller venturi can also increase the amount of fuel flowing through a carburetor.
This is actually how a carburetor choke works in fact. It's not so much the air flow is decreased, but it pulls far more fuel.
This is actually how a carburetor choke works in fact. It's not so much the air flow is decreased, but it pulls far more fuel.
#22
03-24-2018, 05:45 PM
Carburetion is weird sometimes. AFR can change in ways that are not necessarily intuitive. Increased air velocity due to smaller venturi can also increase the amount of fuel flowing through a carburetor.
This is actually how a carburetor choke works in fact. It's not so much the air flow is decreased, but it pulls far more fuel.
This is actually how a carburetor choke works in fact. It's not so much the air flow is decreased, but it pulls far more fuel.
I ran a 3310 750 on an Exploder 5.0 on a Ford A321 intake for a time, never had issues in the lower rpms there either. The response was pretty clean off idle too. Surprised me that one did. It probably never pulled the secondaries fully open at WOT to use all the flow. I replaced it with a 570 Street Avenger later on. Didn't see a whole lot of difference in the lower rpms after the switch.
#23
03-27-2018, 12:27 AM
#24
03-30-2018, 08:01 AM
#25
03-30-2018, 08:29 AM
#27
06-20-2018, 01:38 AM
Holly 500 cfm 4412s
I have Both fresh rebuilt 350 in the box and running the 500 cfm on my 69 CS 390 C6 comp 265 dual energy cam I was a little ticked at Holly tech they told me at first not to use the 500 I was in the process of rebuilding the motor first V8 project in 20 some years I was rusty it had the 500 on it so I sold it and bought the 350 after lots of research like here I bought the new 4412,s 500 with a 1" spacer under it man I won't even need a 4bbl that things kicks rear gear I smoked the tires !!!!!! 374 rear gears posi rear for the CS smoked em ....easy to tune I'm happy
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