Cfm questions
Thread Starter
|
Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
It's a stock roller block out of a 97 and yea I'm aware it's extra but i got it for cheap a while back and figure if it works why buy another one
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
Because it is so large it may not idle too good and the air flow thru the carb would be too slow to pull the fuel right.
The smaller CFM carb has a smaller opening so the air flow is a little faster and that pulls the fuel thru better.
Look at a water hose and sizes to floe say 1 gallon of water per-min.
A 1/2" hose the water will come out with a lot of force / flow.
Now take a 1" hose and the same amount of water / time it will look to just trickle out but it is the same amount of water.
What one would you like to use to wash you truck with?
BTW a 600 CFM and no larger than a 650 CFM is all you need / want on that motor for street.
Dave ----
The smaller CFM carb has a smaller opening so the air flow is a little faster and that pulls the fuel thru better.
Look at a water hose and sizes to floe say 1 gallon of water per-min.
A 1/2" hose the water will come out with a lot of force / flow.
Now take a 1" hose and the same amount of water / time it will look to just trickle out but it is the same amount of water.
What one would you like to use to wash you truck with?
BTW a 600 CFM and no larger than a 650 CFM is all you need / want on that motor for street.
Dave ----
Thread Starter
|
Tuned
Joined: Feb 2022
Posts: 295
Likes: 7
From: Central Montana
Because it is so large it may not idle too good and the air flow thru the carb would be too slow to pull the fuel right.
The smaller CFM carb has a smaller opening so the air flow is a little faster and that pulls the fuel thru better.
Look at a water hose and sizes to floe say 1 gallon of water per-min.
A 1/2" hose the water will come out with a lot of force / flow.
Now take a 1" hose and the same amount of water / time it will look to just trickle out but it is the same amount of water.
What one would you like to use to wash you truck with?
BTW a 600 CFM and no larger than a 650 CFM is all you need / want on that motor for street.
Dave ----
The smaller CFM carb has a smaller opening so the air flow is a little faster and that pulls the fuel thru better.
Look at a water hose and sizes to floe say 1 gallon of water per-min.
A 1/2" hose the water will come out with a lot of force / flow.
Now take a 1" hose and the same amount of water / time it will look to just trickle out but it is the same amount of water.
What one would you like to use to wash you truck with?
BTW a 600 CFM and no larger than a 650 CFM is all you need / want on that motor for street.
Dave ----
Super Moderator
Joined: Apr 2004
Posts: 34,466
Likes: 2,798
Trending Topics
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
X2 and what my point I was trying to make.
You dont need a throttle stop as that only will limit how far open the throttle will go limiting the top speed only.
Dave ----
You dont need a throttle stop as that only will limit how far open the throttle will go limiting the top speed only.
Dave ----
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Moderator
Joined: Jan 2001
Posts: 56,949
Likes: 2,718
From: Virginia
About the cheapest you can go is buy a China knock-off 2100 2bbl off Amazon or Ebay. They are brand new and a little over $100. If you have a 4bbl intake, you can put a adapter on it. I would not use an adapter to put a 4bbl on the 2bbl intake, but the 2bbl on the 4bbl intake seems to work fine.
Lead Driver
Joined: Apr 2002
Posts: 5,240
Likes: 1,222
Could well be. I have no experience with oversized carbs. I see them on other people's rigs. I think I've seen a 4 barrel on a 4.9l before. Perhaps the engine was trick and built? So the issue is throttle response? Like after the accelerator pump delivers a blast? Atomization as in the fuel being delivered too rich?
I have always stuck to stock carbs. I like work trucks with the best fuel mileage I can get, so oversizing is not my thing.
I'm still wondering if there might be tweaks to make the cheap bad boy work. For me, I order or rebuild a stock carb. I don't try to out think the designers.
I have always stuck to stock carbs. I like work trucks with the best fuel mileage I can get, so oversizing is not my thing.
I'm still wondering if there might be tweaks to make the cheap bad boy work. For me, I order or rebuild a stock carb. I don't try to out think the designers.
FTE Community Team
Joined: Dec 2023
Posts: 8,664
Likes: 4,208
From: sussex county, nj
funny you bring up the 4.9 inline, we have built several model a hot rods powered by forklift 3.0l/181 inch gm based 4 bangers,replacing the low rpm cam with a marine 3/4 grind using clifford intakes and what is the smallest holley a 4160 4 barrel which is 390 cfm crazy little motors sound sweet and run just as sweet they are not really over fueled since in true marine trim that same motor's stock 2 barrel is 300 cfm
sad that so many people think bigger is better with carbs when it's totally the opposite,
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
Could well be. I have no experience with oversized carbs. I see them on other people's rigs. I think I've seen a 4 barrel on a 4.9l before. Perhaps the engine was trick and built? So the issue is throttle response? Like after the accelerator pump delivers a blast? Atomization as in the fuel being delivered too rich?
I have always stuck to stock carbs. I like work trucks with the best fuel mileage I can get, so oversizing is not my thing.
I'm still wondering if there might be tweaks to make the cheap bad boy work. For me, I order or rebuild a stock carb. I don't try to out think the designers.
I have always stuck to stock carbs. I like work trucks with the best fuel mileage I can get, so oversizing is not my thing.
I'm still wondering if there might be tweaks to make the cheap bad boy work. For me, I order or rebuild a stock carb. I don't try to out think the designers.
Ha you have a 500 HP motor well I got a 800 HP motor,. You had a 750 cfm carb I got a 850 cfm carb, etc.
All that BIG stuff adds up to a crappy running motor that a much smaller motor could run circles around.
See below on the 390 cfm that is used on most straight six motors that are stock other than the carb, intake and header.
FYI the Holley 2300 v2 carbs (350 & 500 cfm) are flowed at a different HG rating then the v4 carbs so you cant say a 500 cfm of each flow the same as they dont. I forget what the HG rate is for either but changes everything.
funny you bring up the 4.9 inline, we have built several model a hot rods powered by forklift 3.0l/181 inch gm based 4 bangers,replacing the low rpm cam with a marine 3/4 grind using clifford intakes and what is the smallest holley a 4160 4 barrel which is 390 cfm crazy little motors sound sweet and run just as sweet they are not really over fueled since in true marine trim that same motor's stock 2 barrel is 300 cfm
sad that so many people think bigger is better with carbs when it's totally the opposite,
To lazy to look that up but if it is it is half of the GM v8 so it would run half as good right
I think it is cool when walking around at cars & coffee or a show and see something other that the GM / Ford v8 motors that is in everything.
That is what is nice of the 300 six in my truck, most of the time it is the only 6 there unless an old 60's Mustang shows up with a 170 in it.
Dave ----
FTE Community Team
Joined: Dec 2023
Posts: 8,664
Likes: 4,208
From: sussex county, nj
iron duke is a totally different motor , it's what started life in the mid 60's nova,as a 153 ci 2 cylinders hacked off a 230 inline 6, it was made till around 2015 as a 3.0 l/181 inch ,powered forklifts water pumps,generators running propane had 10.25 compression merc omc, and volvo marine used it to power IO boats merc and OMC used it with dished pistons at 8.5 volvo used flat tops at 9.5 , later marine even had port EFI and cats . merc used a rochester 2gc carb at 250 cfm volvo used a holley at 300
flywheel back they used normal small block flywheels,bell housing and clutches clifford still makes the intake and header for them
flywheel back they used normal small block flywheels,bell housing and clutches clifford still makes the intake and header for them