Carburetor tuning information source.

Detroit Bill · #1 (**permalink**) 11-21-2015, 11:32 AM

Over the winter I am going to put O2 bungs in my side pipes and wideband O2 sensor setup. I am pretty sure my car is running rich and I would like to dial it in. Can anyone recommend a good source, internet or book for tuning a Carb. Mine happens to be Quick Fuel.

Thanks
Bill

Jim Vander Wal · #2 (**permalink**) 11-21-2015, 03:36 PM

Bill,

Having done that and since removed the o2 sensor I'll comment.

Did what you are doing in an attempt to calibrate or adjust the carb as you've indicated. All I really managed to do was chase numbers and mess with a carb.

I still have the bungs in the pipes but gave the FAST dual channel meter to a friend that has a dyno.
FAST Wideband Digital Air/Fuel Meters | FAST

I've also played with 4 different carbs ranging from 670 to 940 and can attest to the fact that to big is just as much trouble as too small. But too small is usually easier to drive than too big.

My suggestion is to find a good dyno and carb tuning guy and have the engine tuned properly. This will be a combination of carb, ignition & timing and valves. Then drive it. Certainly there are times when corrections need to be made but generally a good tuner should be able to get it dialed in. I do believe that good tuners are far more unique than bad ones.

But at the same time we buy these little gems, these black holes for all available cash, to have fun with and build to our liking and heart's content so have at it if you are so inclined.

PM if you want more.

Jim
SPO 1855 RDI AL427W & 2584 PE 421W

Detroit Bill · #3 (**permalink**) 11-21-2015, 03:56 PM

Thanks for the advise. Sometimes I am in it for the chase and the learning experience. What bothers me about taking it to a tuner it that it may need to be tweaked after every change.

I may take it to Lingenfelter in the spring to have them tune it. Having bungs in the pipes is a big bonus.

*13* · #4 (**permalink**) 11-21-2015, 04:08 PM

Edelbrock 4barrel carbs ship with a tuning tutorial book which was my guide to learning, years ago. I'm sure they/or someone has it posted online. It was a thorough learning on the theory of carburetors & how to tune them. Edelbrock carbs are more difficult to tune than Holley so... You should be able to grasp either if you can grasp the booklet. Hell, I'm tinkering with webers now....
Here it is
http://www.edelbrock.com/automotive/...ers-manual.pdf

*13* · #5 (**permalink**) 11-21-2015, 04:20 PM

As posted above, smaller runs better in every day driving. Larger cfm carbs really help at higher rpm's, where you are pulling enough air to need those big barrels. The lower rpm's & response suffer for it. I ran a 600cfm on a built 454 chebby(with big gears). That carb noticeably out performed the 750 & 800cfm carbs 99 percent of the time. The one or two times it really had the motor opened up, I needed more carb. So, you really need to decide where you want your power. Accurately sizing the carb will, obviously, give you decent drivability & performance.

sea2jet · #6 (**permalink**) 11-21-2015, 04:30 PM

I had a QuickFuel carb on mine. 3 different tuners tried their hand in it. Couldn't get rid of a slight hesitation at 1800 rpm. I brought it to Jannetti Racing in Waterbury, CT. Instead of chasing our tails on it, trying to figure out the different changes each tuner did, they suggested a new carb. They recommended a Holley 750 HP. The car has never been better. Hesitations gone, more power and the idle smoothed out. My Genesis 427 Is now a happy camper😁

Bobcat · #7 (**permalink**) 11-22-2015, 11:49 AM

My go to site for anything carb related is racingfuelsystems.myfunforum . Moderated by some of the best carb men in the country and full of stickies on theory and practical stuff . Do you understand Holley emulsion circuit tuning and it effects the rest of the circuits ? They do and can explain it .... and are willing to answer your questions as long as you give them the info they ask for .
Spend some time there , you`ll be better off for it .

Ace23 · #8 (**permalink**) 11-22-2015, 09:48 PM

Not that my two cents mean anything but here is my experience. A dyno tune with a tuner who knows what they are doing is a GREAT thing. I'm looking at going to 3" exhaust and I've asked for a 02 bung to be welded in. I would like to have the wideband to check my part throttle AFR. Personally I would spend my money on having my car tuned and then if you want to use a wideband you use it to double check your tune. If you can get your car to a tuner that knows what they are doing it will be the best $300-$400 you can spend. If you want to take a go at tuning it with a wideband then go for it just be prepared for the learning curve.

LoBelly · #9 (**permalink**) 11-23-2015, 01:22 AM

Holley has some good resources - including videos
surf around the site is worthwhile

https://www.holley.com/blog/carburet..._and_tuning/1/

MOTORHEAD · #10 (**permalink**) 11-23-2015, 06:09 AM

Here's a site I found useful : Carburetor Tuning the Scientific Way

Detroit Bill · #11 (**permalink**) 11-23-2015, 06:32 AM

Quote:

Originally Posted by Bobcat

My go to site for anything carb related is racingfuelsystems.myfunforum . Moderated by some of the best carb men in the country and full of stickies on theory and practical stuff . Do you understand Holley emulsion circuit tuning and it effects the rest of the circuits ? They do and can explain it .... and are willing to answer your questions as long as you give them the info they ask for .
Spend some time there , you`ll be better off for it .

I don't see any stickies?

Detroit Bill · #12 (**permalink**) 11-23-2015, 06:35 AM

Quote:

Originally Posted by LoBelly

Holley has some good resources - including videos
surf around the site is worthwhile

https://www.holley.com/blog/carburet..._and_tuning/1/

Awesome thanks for that!

Bobcat · #13 (**permalink**) 11-23-2015, 09:51 AM

They don`t really call them stickies . Just look for various topics under the forum you are on .... i.e. Holley forum has subjects on Emulsion Tuning , Transfer Slot Tuning , Bowl Vents etc . Keep digging and you will find a thread about tuning a QF 850 with a broadband A/F unit .
Mark is the moderator there and Tuner used to be the guy that ran the Innovate forum before they dropped it . Catherder is another one that really knows his stuff , as do a bunch of others .
These guys will answer your questions , but will also make you dig so you understand the theory and why something works .... or doesn`t .

SwiftDB4 · #14 (**permalink**) 11-23-2015, 04:08 PM

I've used an older Powerdex AFX system to tune my 750 Quickfuel. Newer systems with recording capability are better, but it still worked well. I'm amazed how the idle circuit is ignored with a lot of tuning. Up to about 1800 rpm you're still on idles and they factor in transition above that too. Ditched my Holley because it had no idle jet adjustability. Quickfuel changeable idle fuel and air jets are invaluable in tuning. Out of the box carbs routinely have rich idles.