How much CFM?
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Thanks Jim, I appreciate your opinion. I guess the default is normally, they are open whenever the engine is at operating temperature so it shouldn't hurt anything, now that I think about it.
I agree with your carburetor theory. I installed the stock size (1.02" venturi, 243 CFM) on my Y block and it's never run better. I had a Holley 500 CFM on there and it was like a firehose on that thing, I managed eventually to jet it down and such and get it to run pretty good, but it was still a little on the large size. I'm running stock 2v intake and small heads, so it never breathed very well. With the dual exhaust it runs pretty good and idles nice and runs great. I haven't noticed much, if any, performance between the two except to my wallet, at the pump.
I agree with your carburetor theory. I installed the stock size (1.02" venturi, 243 CFM) on my Y block and it's never run better. I had a Holley 500 CFM on there and it was like a firehose on that thing, I managed eventually to jet it down and such and get it to run pretty good, but it was still a little on the large size. I'm running stock 2v intake and small heads, so it never breathed very well. With the dual exhaust it runs pretty good and idles nice and runs great. I haven't noticed much, if any, performance between the two except to my wallet, at the pump.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
Likes: 80
From: tujunga, calif
Thanks Jim, I appreciate your opinion. I guess the default is normally, they are open whenever the engine is at operating temperature so it shouldn't hurt anything, now that I think about it.
I agree with your carburetor theory. I installed the stock size (1.02" venturi, 243 CFM) on my Y block and it's never run better. I had a Holley 500 CFM on there and it was like a firehose on that thing, I managed eventually to jet it down and such and get it to run pretty good, but it was still a little on the large size. I'm running stock 2v intake and small heads, so it never breathed very well. With the dual exhaust it runs pretty good and idles nice and runs great. I haven't noticed much, if any, performance between the two except to my wallet, at the pump.
I agree with your carburetor theory. I installed the stock size (1.02" venturi, 243 CFM) on my Y block and it's never run better. I had a Holley 500 CFM on there and it was like a firehose on that thing, I managed eventually to jet it down and such and get it to run pretty good, but it was still a little on the large size. I'm running stock 2v intake and small heads, so it never breathed very well. With the dual exhaust it runs pretty good and idles nice and runs great. I haven't noticed much, if any, performance between the two except to my wallet, at the pump.
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Senior User
Joined: Oct 2015
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Okay. With all that said, I shall be on the hunt for a junk carb from which I can rob a bowl. That will solve the original problem on the other truck. As stated before, I am more than content with the performance of my 2 bbl. So, I'll list my intake on eBay and let 'er rip. They bring some pretty nice coin on there.
You guys have helped a lot.
You guys have helped a lot.
Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
My 2 cents, a smaller carb will generally perform better at the lower rpms, which is where we usually drive. Part of the reason for that is port velocitys. Same with the smaller heads, better port velocitys at lower rpm. The higher rpm you want to run, the bigger heads and carb it takes to optimize that performance. I think ideally that a small cfm quadrajet from say a 305, would be an ideal carb. Run most of the time on the puny primarys and have the big secondarys on tap for passing semis and such. A well tuned 3x2 would do the same thing and look a lot better.
I used to argue that with the chevy guys. They all thought they needed 2.02 heads on their 4x4 plow truck and it was like driving a spike into a rock to convince them the engine and the driver would both be a lot happier with smaller heads.
I used to argue that with the chevy guys. They all thought they needed 2.02 heads on their 4x4 plow truck and it was like driving a spike into a rock to convince them the engine and the driver would both be a lot happier with smaller heads.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
The CFM calculators (I think) are setup for drag racers. They want you to plug in the maximum RPM to get the proper size carb for that. Except most of us don't spend all of our time at 5900 RPM.
On the other hand if you plug instead the typical 60 mph, in high gear, cruise RPM then the results offered look a lot different in fact, they are almost exactly what Ford provided as OEM equipment. Maybe a little on the smallish side, but it will be a very efficient carb and have good low end torque and driveability for hauling heavy loads. Surprise surprise.
On the other hand if you plug instead the typical 60 mph, in high gear, cruise RPM then the results offered look a lot different in fact, they are almost exactly what Ford provided as OEM equipment. Maybe a little on the smallish side, but it will be a very efficient carb and have good low end torque and driveability for hauling heavy loads. Surprise surprise.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
Likes: 80
From: tujunga, calif
Okay. With all that said, I shall be on the hunt for a junk carb from which I can rob a bowl. That will solve the original problem on the other truck. As stated before, I am more than content with the performance of my 2 bbl. So, I'll list my intake on eBay and let 'er rip. They bring some pretty nice coin on there.
You guys have helped a lot.
You guys have helped a lot.
. Another option would be a 2100 Autolite, great carbs..
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Before I forget are you familiar with Ed's Carburetor forum? It doesn't have a real fast turnover but you might get some more eyeballs on your carb needs. Can't hurt to try.
http://www.network54.com/Forum/88781
http://www.network54.com/Forum/88781
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Logistics Pro
Joined: Mar 2005
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From: tujunga, calif
I have a 1904 Holley with a glass bowl on my 223, I've had a few other early Fords with them..
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The older I get, the smarter he gets!
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