LOL!! When testing is done by a REPUTABLE carb builder that has over 50 years experience in the field, a reputable mag that posts all data and test conditions, and by a competitive manufacturer, the test are considered inaccurate, invalid, or skewed!?! Too funny.... There was way more data to chew onin that article than "We ran a 600 CFM Edelbrock® vs. a 575 Speed Demon™, and averaged the numbers between 3300 RPM & 5500 RPM. Here is what we found.
The Edelbrock® averaged 362.57 HP, and 302.5 Ft/Lbs Torque
The Demon™ averaged 374.80 HP, and 312.98 Ft/lbs Torque".

The whole point of the article was to show the effects of under/over carbing. I am sure that the next step would be to fill out their Custom Calibration FORM to correctly identify the exact carburetor needed for your INTENDED APPLICATION. I am very positive that the recommendations would not be that far off from the conclusion of what carb SIZE that they came up with, more of what boosters, double pumper vs. Vac sec, acc. pump size, etc. for your intended application and what vehicle this engine was going in.

I went so far as to call The Carb Shop, and I spoke with Bob. He reiterated what I just said above, that the carb CFM would not change as far as for THAT PARTICULAR ENGINE, but that dependent of your intended purpose of the vehicle that engine was put in, would determine what boosters, double pumper vs. Vac sec, acc. pump size, pump squirters, main circuits, etc.

This thread is good fodder for the manufacturers, but NONE of them would go so far as to change out the above items in order to taylor/custom tune the carb for your intended purpose. They ALL would pull one off the shelf, according to THEIR guidelines for your intended application. BG Carbs just seem to "ballpark" their suggestion betterYou STILL would have to fine tune the carb.

Don't get me wrong, I think that BG carbs are the finest carbs out there. Again, I wished I would have known more about them when I bought mine, I would have gottebn one just for the superior flow characteristics.

Wildman,

We’re not saying that there was anything done wrong with the testing or that it was inaccurate in anyway. What was said is that this type of test will give you the pros & cons of using different size carburetors on the same engine on an engine dyno. It is not the end all be all answer for what is going to work best on this specific engine in the real world in different applications. We did not, and do not say anything negative about the way the test was performed. Just as in the test we performed was showing the specifics from one size carburetor, and brand to another. It does not say anything more specific than that. We did the comparison to rebutt some things that were being said. Not to say which size carburetor to specifically use.

BG Tech corrected me....I should have written "as a first step" read the Holley basics page (or whatever carb your considering).

He was right.

I'm outa' here...now were gona argue dyno's..!

I'm with BG 150%. I work doing experiments all day long, I do it for a living with government funding. That means I don't get to make an experiment or do tests to prove a theory that's flawed in the first place! Just because a magazine is reputable doesn't mean that all their data are worthwhile or even accurate. In fact, most of these "so called" tests that are run in these magazines are inconclusive for what they are trying to show with those data!

The only thing proved by that article is that if you drive a dyno to work every day with weather that is the same every day, you can use more carb than you thought.

That experiment is inconclusive.

K

Another good laugh....

You have a reputable mag, go to a reputable carb builder, and the results of multiple testing are in your face, and it is "inconclusive". Isn't that how this thread got started, by Tech@BG posting 2 lines of data from a (single) dyno test? Is that not "inconclusive"?

Obviously what I last wrote was not thoroughly read, but oh well. I posted the info because it was requested by Red65mustang. No wonder more people leave this forum or just end up not giving out valuable info due to the playground mentality here. I think that I will just PM whom I think is knowledgable in what areas when I need an answer, stick to reading, and get good laughs....

I have to agree with wildman so some extent. Some people are so ready to discard magazine test on one post and then the next post they are pointing to them to compare dyno pulls for a certain combination. I will agree that the mag tests are sometimes a little misleading, but over all they are about 100% better than any of us have ever done or will ever get to do. The main problem with magazines is the same problem you get here.....OPINIONS. I always enjoy watching the magazines flip flop on turbo stuff since that usually peaks my interest more that another damned 383 buildup. They go from turbos being black majic that noone can afford, understand, or tune to being the best thing going in the power adder department.

I think BG did a service with the dyno pulls as do the magazines. You just have to sort through the opinion and extract the real data.

Chris

You're missing the point while managing to be rude about it too. My point is, just as BG pointed out, the test doesn't take into account very many variables. The fact that the guy who was doing the testing has a bunch of experience has nothing to do with it, its just not real world data.

If you had any research experience you'd know that conclusive results don't come from one experiment. These data have their merits, but I'm not going to take them for gospel just yet, that's what I'm saying. They're a great first step, now maybe people should take the next few steps and see how these data can lead to further findings.

If you're going to complain about a playground mentality, maybe you shouldn't start your posts with LOL and laugh at people just because they don't agree with every word you say. You're scoffing at a guy who works on carbs 8-10 hours a day over a 2 paragraph article you read.

And yes, BG's data are inconclusive too, due to confounding variables. Perhaps my first post wasn't read thoroughly... oh well.

K

Ok so on that exact test yes between those three carbs on that particular engine it didn't show a drastic hp difference on the dyno. Of course it was a 40 hp difference if you dropped to a 390cfm double pumper. But the reality that I still stand by is that a dyno does not cover all the bases when it comes to how any given car will actually perform on the road or track. A dyno does not account for many variables that are present actually driving a car. Overcarbing (especially with a double pumper) will not be as evident on a dyno as on the street. I would like you to run a 750cfm double pumper on a stock 283 small block in a '64 Impala, stock auto trans/converter, and highway gears. Then take that same car and put a 600 vacuum secondary carb on it and run her. I'll tell you right now that car will be dying with that 750 on her, I know I tried almost exactly that as a goof back in high school. We swiped the 750 DP off of my friends Camaro and stuck it on our 4 door boat of a car with a stock powerglide trans and highway gears. If you hit it off the line oh my God a Honda could have beat us. The reverse also applies. Take a car with a decent built 350 but with a stock auto trans, converter, and highway gears. Now add a little tranny work, a 2,800 stall converter, and a set of 4.11 gears and I guarantee it will be able to handle more carb than before those changes were made. Yes maybe on a shop dyno you are not going to 'see' a drastic difference in output between three carbs closely rated (600-750 and all double pumpers also) but in real world application when you mix in all of the variables out there and then also include carb variables (vacuum secondary and double pumper styles) yes proper carb choice is the difference between having a car that can hold it's own or going home with your head between your legs cause you got beat by a Nissan Sentra. Now that's street reality not just some controlled dyno run.

THANK YOU DMORRIS!

why is it other people always say what I'm trying to say better than I manage to spit it out, lol.


K

Well if you stopped spitting it would come out easier.

Whoa, Lots of flaming going on!


Let me throw a wrench in the works of your magic carb formula/ small carb ideas.

Why do tests repeatedly show that a carb needs to be bigger than the formula?

Why does a 350ci engine produce more torque at 3300(440tq vs 424, an increase of16ft/lbs) rpm when using a 750cfm carb vs a 390 cfm carb? Even if we consider 100%VE (very unlikely) the best size carb would be a 334cfm carb. As the article said they picked up 10 HP down low...so the formula is not considering something(and it's not the car or chassis).

Either carb CFM is overrated by the manufactures or
Carb CFM is measured at a different vacuum # than the engine likes(likely)


And just look at a BG vs any other carb on the market. it is so obvious that even a blind man could "see" that size for size the BG will give the cleanest most unrestricted airflow possible of any of the "big three".

And speaking of blind men...
One day this blind man was walking down the sidewalk, tapping his cane along the way and passes a fish market. He pauses, takes a deep breath and says.."Good morning ladies!"

If you had read the basics of carb selection as a first step, from any of the carb mfgr's, you would have known a 750 double pumper is not a wise choice for a stock 283.

Simply swapping carbs (600 to 750) doesn't work. You have to tune a carb to the motor.
"If" (I can't) you could tune the 750 double pumper to a 12-13 WOT A/F ratio (wide open throttle air/ fuel ratio for the newbies) and 14-16 driving, on the stock 283, numbers and performance would have been close(r).

It's already written into this thread, next you phone or email the carb mfgr with the details of your car to make a wiser choice, vacuum secondaries etc. Yes weight/tranny/ gears/heads/cam/etc. is part of selecting the best carb.

This thread is about Demon versus Edelbrock, if you have info to share about either great.
Maybe you should start your own "carb wars" thread?

Sounds a bit contradicting to me. I don't care how well you 'tune' a 750DP it will never perform as well as a nice 600 vac. secondary on that stock boat with a 283 as mentioned. The smaller vacuum secondary carb will be more responsive, perform better, and get better fuel economy. How can you say going from a 600 to a 750 doesn't drastically change anything on a street motor and then say a 750 is too much carb for that set-up? Make up your mind. Either it does make a difference or it doesn't when choosing a carb for your car.

Your question is from a different thread, ask the question on that thread.

And if you want to question my posts with quotes, put in all the info, not excerpts.

I did not say close or applicable on a STOCK motor.
I said "street" motor, which your motor is (rpm intake, cam, on stock 2V heads with headers, Ford 302), which the motor in Chevy article is, which the BG test mule is, .......

This thread was 5 stars, now 4, so no more replies here from me about your question