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Topic Review (Newest First)
10-29-2006 09:55 AM
Mike Britton Yeah, everybody I talked to at Goodguys with heavy engines said they were having no problems with their front ends.
I 'm going to try to get the big motor as far back in the frame as I can to take advantage of that long wheelbase. It means I probably won't be able to run a set of laker style headers, but that's ok, as I have some cast iron truck headers that will probably make for a quieter exhaust note, and give some sanity to the car.
I live about 20 minutes North of Dallas in a little town called Highland Village.
It's cool here, every street you go down has some sort of project covered up on the driveway, and there are at least three buckets that I know of prowling around in the neighborhood.
While I'm on the suject of buckets, I just did the Ft.Worth swap meet. A handfull of buckets for sale there, and I'm biginning to see more ingenuity in design that other open wheeled rods. Lots of times, with an A, or deuce, everybody follows the leader, but buckets show more original thinking in suspension design and frame layout than others.


Quote:
Originally Posted by Choctaw Bob
My front end on the T-Bucket works perfect. I think the original model A spring was above the axel. I had one in '63 and it had a "spring over" axel that had been dropped 6 inches. The stock spring worked fine with a full race flathead, iron bell housing and iron case 39 Ford trans, which is probably nearly as heavy as the Big Block Chevy and modern aluminum case transmission.
Speedway and some of the axel/spring manufacturers might be able to tell you the capacity of the spring. If it is like mine, it can flex a long way before the car bottoms out. With mine, the engine sits far enough back that the weight distribution is about 50/50 so the total is around 950 pounds on the front spring. I think the original Model A Coupe probably weighed around 2800 pounds so we're not getting even close to the stock spring capacity, if that is what you have.
Where in Texas are you?
10-29-2006 08:53 AM
Choctaw Bob I love Q Jets. They are the best street carb by far. Not hard to maintain/repair once you know the common problems. The Q Jet by design is a very economical carb with small primaries that besides being stingey on gas, are very responsive at low speed. The secondaries and and dual accelerators make it be an awesome performance carb. If you can find them and afford them, the latest models were also pretty good on emissions.

Quote:
Originally Posted by onovakind67
My q-jets have manual operated secondaries with an air valve. The air valve is not operated by vacuum but by the actual airflow going through the secondaries. Most people don't realize that the Q-jet also has a secondary accelerator circuit, a double pumper of sorts. I modified one of them to have a 1:1 ratio that makes the secondaries open at the same rate as the primaries. Throttle response is awesome, to say the least.
10-29-2006 05:20 AM
mechanicodell
Thanks for the carb formula

I will also look at the Holley add ons. Thank you.
10-28-2006 11:50 PM
Choctaw Bob My front end on the T-Bucket works perfect. I think the original model A spring was above the axel. I had one in '63 and it had a "spring over" axel that had been dropped 6 inches. The stock spring worked fine with a full race flathead, iron bell housing and iron case 39 Ford trans, which is probably nearly as heavy as the Big Block Chevy and modern aluminum case transmission.
Speedway and some of the axel/spring manufacturers might be able to tell you the capacity of the spring. If it is like mine, it can flex a long way before the car bottoms out. With mine, the engine sits far enough back that the weight distribution is about 50/50 so the total is around 950 pounds on the front spring. I think the original Model A Coupe probably weighed around 2800 pounds so we're not getting even close to the stock spring capacity, if that is what you have.
Where in Texas are you?

Quote:
Originally Posted by Mike Britton
I looked at your pics. How well does that four leaf front spring work with the big motor?
I have the same front end on my '29, only I plan to change hangers to move the spring above the axle. I'm changing mostly for looks, but also to get just a bit more height. I have 114" wheelbase to work in, so I don't have to shove the 454 out over the front crossmember like I would if I had a stock A frame.
10-28-2006 07:42 PM
Mike Britton
Hey big guy, how's yer front end??

I looked at your pics. How well does that four leaf front spring work with the big motor?
I have the same front end on my '29, only I plan to change hangers to move the spring above the axle. I'm changing mostly for looks, but also to get just a bit more height. I have 114" wheelbase to work in, so I don't have to shove the 454 out over the front crossmember like I would if I had a stock A frame.
10-26-2006 11:59 PM
Choctaw Bob Hey Mike, I'm from Texas too and a couple of years older. We probably rubbed some rubber on the same asphalt. Why don't you come by http://www.nationaltbucketalliance.com/bb/. We share the same kind of roadsters and have a big chapter in Texas with lots of guys to help out. You can probably get a antique tag for that track roadster pretty easy without having to pass emissions.
On the smaller carb is usually better, the reason is that a little engine doesn't suck enough air at low speed to maintain enough velocity in a big carb to drag fuel from the idle circuits. You compound that with a big cam with low vacuum and you have an engine that won't idle at all under 1,000 -1,200 RPM. I have that problem somewhat on my T-Bucket. I have a 60 over 402 Big Block Chevy with a tunnel ram and 2 500 CFM Edelbrocks. (check out my photos) The engine idles around 950 RPM with the throttle blades against the venturis and minimal idle air on one carb. There is enough air leakage in the new carbs that I have to richen the mixture to keep it from melting the headers off. Anyway, on the street, smaller is easier to tune, has better throttle response and is more economical. The only reason we would want bigger is if our buddy is smokin us on the track.

Quote:
Originally Posted by Mike Britton
I'm listening to you guys, and I'm reminded of when Mike Norris and I were killing our selves in top fuel in the early '70's. We were running a cast iron '92 with the typical 6/71, and an old set of hilborn four port " Laguna lean outs" on top. We would come into stage having to wing the engine 'cuz it was so fat it didn't want to stay lit, and burning the tops of the pistons on the long end. Carbs are alot like injectors in that they work great in a very narrow RPM range, and only adequately any other time.
I did read an article some years back that said "within reason, a too large carb is better than a too small one in that it will only flow as many CFM's as the engine needs at any given time."
However, it only stands to reason that it all hinges around getting close to the correct CFM's for any given engine. The 600 is probably reccomended simply because that's about as small a four barrel as your'e gonna find, and it won't overwhelm the little engine in everyday use.
Did I just stick my foot in my mouth!?!
10-26-2006 10:37 PM
willys36@aol.com Good points Mike. Engines are just a big set of compromises. No engine is good at everything - to get the ultimate top end you give up the bottom end and vice versa. The "smaller is better" mantra applies to 99.99999% of the engines out there 'cause they are mostly run on the street from stop light to stop light. Vac secondaries are a really good compromise 'cause they give you the bottom end you can live with but also give you a lot of the top end that is fun.

And I am honored that an old fueler like you has joined our little chat room here.
10-26-2006 02:41 PM
Mike Britton
Carb too big?

I'm listening to you guys, and I'm reminded of when Mike Norris and I were killing our selves in top fuel in the early '70's. We were running a cast iron '92 with the typical 6/71, and an old set of hilborn four port " Laguna lean outs" on top. We would come into stage having to wing the engine 'cuz it was so fat it didn't want to stay lit, and burning the tops of the pistons on the long end. Carbs are alot like injectors in that they work great in a very narrow RPM range, and only adequately any other time.
I did read an article some years back that said "within reason, a too large carb is better than a too small one in that it will only flow as many CFM's as the engine needs at any given time."
However, it only stands to reason that it all hinges around getting close to the correct CFM's for any given engine. The 600 is probably reccomended simply because that's about as small a four barrel as your'e gonna find, and it won't overwhelm the little engine in everyday use.
Did I just stick my foot in my mouth!?!
02-16-2006 10:22 AM
onovakind67
Quote:
Originally Posted by rifraf

What do you consider a Q-jet to be?

My q-jets have manual operated secondaries with an air valve. The air valve is not operated by vacuum but by the actual airflow going through the secondaries. Most people don't realize that the Q-jet also has a secondary accelerator circuit, a double pumper of sorts. I modified one of them to have a 1:1 ratio that makes the secondaries open at the same rate as the primaries. Throttle response is awesome, to say the least.
02-16-2006 09:40 AM
Choctaw Bob
Q-Jet

The Q-Jet has a small screw and spring that sets tension on the top set of butterflies on the secondary side. You can adjust this to allow the air to flow at a lower or higher RPM. Watch this though because you can really kill your gas mileage by having these open early.

This is a great carb for performance when you take the time to learn to adjust it. When I was in my 20s I had a garage. It got to where most of my business was rebuilding carburators. I learned to tweek the quadrajet because in the earily 70s, the manufacturers first attempt at controlling emissions was to lean out the carbs until they would barely run. I maintained a fleet of Federal Agent cars. They were continually getting outrun by people in older muscle cars. The 396 Impala and 440 Dodge cop cars really woke up with some adjustment on the metering rods and jets and secondaries.
08-17-2004 06:51 PM
Rhansen
Quote:
Originally posted by Terje
My Toyota came that way stock, and shocked the hell out of me quite a few times.
I just read through all this and had to laugh at that. I was trying to track down a bad wire by pulling them one at a time (motor running) and got to experience firsthand what you're talking about. I was amazed how far the spark would jump.
08-17-2004 10:47 AM
jpd37 I want to thank everyone that has contributed to this post.

My motor is finally running smoothly with good steady power on acceleration and at cruise speeds up and down the dial. My settings, after cleaning and rebuilding the Edelbrock 1405 (600 cfm) Performer consist of replacing the metering rods by one stage leaner and using the orange metering rod springs.

My rich living days are over and the motor is much happier now. It starts right away and once it has warmed up for about a minute (manual choke) it settles down to a decent idle. I think I need to work on the cold start settings a little more, but the improvement compared to before in remarkable. I'm no longer embarrassed to sit at a light and have to coax the car to stay running.

Thanks to all of you, especially Terje, for your patience and encouragement. All the additional discussion on related topics has also been very educational for a rookie just beginning to learn the basics to tuning a normally carberated motor. I am truely in your debts. Maybe some day I can return the favor.
08-03-2004 07:33 AM
willys36@aol.com Q-jet is a vacuum secondary carb. Vacuum secondaries are the best of all worlds - only as much venturi open as needed for optimal responsiveness but plenty of flow area @ max load. Can be tuned for superior performance at all speeds and loads. Key word there is 'tuned'. They get bad raps from people who don't tune them properly.
08-03-2004 06:51 AM
rifraf You mean only the lower plates of the secondaries,but the secondaries still don't open(flow air) until they can be accepted by the demands of the motor,right? So to me the secondaries are not open to breath at the demand of your foot like a manual Holley would be. They need vacuum,vacuum operated secondaries. By opening the lower secondary plates you only create an opportunity for the secondaries to open up for flow completely.

What do you consider a Q-jet to be?
08-02-2004 11:39 PM
gcrmcc The secondary throttle plates are opened mechanically on the AFB's and Edels, The Holley's that have vacuum secondaries have a vaccum diaphram chamber that opens the secondaries, as it is slower opening than mechanicals they don't need the air flow valve. As for vaccum ports for the distributor, I call them manifold vaccum and venturi vaccum.
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