PICKING THE RIGHT CARBURETOR SIZE FOR YOUR MOTOR

[moes]

check this video out about how to choose a carburetor for your motor from BAD *** Racing. I just posted it on FABO to

http://www.badasscars.com/index.cfm...ct_id=450/category_id=13/mode=prod/prd450.htm

 

[Montclaire]

I believe that most people buy a bigger carb than they need. You also have to look at the type of carb you are buying - thermoquads had crazy high numbers (like 1000+), but being a spread bore you could get away with it.

 

[65-440]

Very good watch !

 

[rumblefish360]

Good video. The math (typically seen at Holley.com) used is for min. size to use on a average vehicle motoring down the road with good results.

Going larger is OK within reason, or for a reason, as the host says. I noticed the formula chart for sizing a carb on a given engine & rpm. IMO, while there is science behind the math, you can go up in size just a little bit and be OK. Engine size dependent, as well as what your doing with the engine/car, 50 - 70 cfm is OK.

 

[rumblefish360]

I believe that most people buy a bigger carb than they need. You also have to look at the type of carb you are buying - thermoquads had crazy high numbers (like 1000+), but being a spread bore you could get away with it.

The biggest “Race TQ” went there. The smaller “Race TQ” was an actual 910cfm unit I was told.
(IIRC that is... LOL!)

I was told... The small OE unit flowed in the 760/770 range.

I like the flexibility of the spreadbore on the street. Fun street strip carbs they are.

 

[33 IMP]

High tens with a 327 in a chevelle at 8000 at 110mph.
Riiiiiggght. B.s.

 

[ddpsnake]

dont need a vid to tell me what carb i should get lol

 

[451Mopar]

The video on re-curving the dist is pretty good too

 

[moes]

there is alot of good information on The BAD *** website

 

[65-440]

I'm tempted to go down in carb on my 340 and see how it does.... having too much trouble with this AED 750, I think I have a 600 sitting around

 

[Cranky]

High tens with a 327 in a chevelle at 8000 at 110mph.
Riiiiiggght. B.s.

I know a guy that went 11.40's with a 265 in an all steel and factory glass 56 Chevy launching at 9500 and shifting at 9000 in SS/O. Back in the 80's you could only run 3 gears but it didn't matter what trans you used so as long as you only shifted twice, you were good.

 

[33 IMP]

I know a guy that went 11.40's with a 265 in an all steel and factory glass 56 Chevy launching at 9500 and shifting at 9000 in SS/O. Back in the 80's you could only run 3 gears but it didn't matter what trans you used so as long as you only shifted twice, you were good.

I don't doubt that for a minute. I've been attending drag racing and racing my own cars for 40 years and never seen a 10 second car run 110 mph unless something was wrong with the car, or it ran out of gear and rpm at 1000 ft or less, or it was ridiculously light and had no top end power.
8000 rpm at 110mph implies something like 6.50 gears ( which is likely what the 56 had). Did he race people on the street for 200 feet, beat them, and quit?

 

[Ranger16]

VERY informative. I've always suspected my 383 was a bit "over carbed" with a 750, but that was probably due to the radical cam the PO had installed. I haven't tried the bog test he talked about, but will. The good thing is I don't race it and I can't say it has caused me any problems, but if I could trade it for an Edelbrock 650, I'd probably do it.

 

[rumblefish360]

VERY informative. I've always suspected my 383 was a bit "over carbed" with a 750, but that was probably due to the radical cam the PO had installed. I haven't tried the bog test he talked about, but will. The good thing is I don't race it and I can't say it has caused me any problems, but if I could trade it for an Edelbrock 650, I'd probably do it.

But what is the rest of the package like? A 750 up top a 383 with a cam ( of unknown specs) could be a disaster or excellent depending on the supporting parts.

 

[Cranky]

I don't doubt that for a minute. I've been attending drag racing and racing my own cars for 40 years and never seen a 10 second car run 110 mph unless something was wrong with the car, or it ran out of gear and rpm at 1000 ft or less, or it was ridiculously light and had no top end power.
8000 rpm at 110mph implies something like 6.50 gears ( which is likely what the 56 had). Did he race people on the street for 200 feet, beat them, and quit?

I've seen a few cars that were set up mainly to run 1/8 mile do that sort of stuff.....and this guy was probably maxed out by 3/4 track lol.

 

[Ranger16]

But what is the rest of the package like? A 750 up top a 383 with a cam ( of unknown specs) could be a disaster or excellent depending on the supporting parts.

Well, the cam was a very aggressive one when I purchased the car in '14. So much so that it was no fun to drive. I forget the exact specs, but it was more for strip than street and I'm not even sure if the PO raced it, but I seriously doubt it. That cam has been replaced for a much milder street cam. It sits atop an Edelbrock Performer RPM manifold. As I said, I have no problems with it, especially since I leaned it out a bit. I mentioned it more as a commentary than a complaint.

 

[67440chrg]

Good video I guess my wanting to go from a 750 to 850 is not needed.

 

[BSB67]

Good video I guess my wanting to go from a 750 to 850 is not needed.

It depends. If you follow the formula that has been around forever, more often than not, you will be leaving power on the table.

 

[oldbee]

IMHO, almost everyone goes too high on CFM, especially on the street. If ur honest with volumetric efficiency of ur engine, it’s never as high as you hope/wish.

 

[BSB67]

IMHO, almost everyone goes too high on CFM, especially on the street. If ur honest with volumetric efficiency of ur engine, it’s never as high as you hope/wish.

You can do the formula thing, throw in what ever VE you want, but at the end of the day, a bigger carb than that will make the car faster and quicker in most cases.