Carburetor tuning

[Bewy]

Dan,
I will explain the 3 points in post #15.
[1] Insufficient fuel delivery means that the carb is using more fuel than the pump can deliver to the carb. Fix would be bigger pump/less restriction to flow.
[2] n/s. Means needle & seat. Fuel bowl in carb refill as fuel gets used in a similar way that your toilet bowl refills. There is a valve [ n/s ] that shuts off when the fuel level has reached the correct level in the carb. The hole size in the seat is a determinant factor in the flow rate into the carb. If the hole size is too small, the carb can run dry. A lot of people fit larger jets to fix a lean condition when the real problem is restriction in fuel delivery. n/s come in different sizes to accommodate the expected hp.
[3] Carter/Edel carbs have removable boosters. They have a brass tube about 3/16-1/4" hanging out of the mounting pad. This is the emulsion [ E ] tube. I have seen pics [ Edel only ] of these tubes having a bullet end [ instead of being open ] with a small hole in it. If the hole is smaller than the main jet, the hole becomes the de-facto MJ & the MJ no longer controls flow. If you type in 'Tuner' on the net, you will find some of his info & pictures on this.

 

[Hysteric]

Most likely the poster will be using a solid fuel meter carb (Thermoquad) so most of what is posted about Holley's and Carters AFB's is not transferable especially about air bleeding.

 

[Dan the man]

It ran high 13's with stock exhaust manifolds, 2.45 gears, and factory torque converter. It did have a 750 DP on a eddy rpm (not air gap). 2.94's and headers brought it to 13.3's. 3.23's and OOTB speedmaster heads it ran 12.9's. Speedmaster heads were worth about 2.5 tenths over the factory cast due to the small cam not utilizing the heads (we knew this when we did the swap).

What cam specs did your cam have? I'm wanting to have a fun car without breaking the bank and I see that you have done this. I don't mind spending time reading, researching as I understand that no 2 engines are a like

 

[318willrun]

What cam specs did your cam have? I'm wanting to have a fun car without breaking the bank and I see that you have done this. I don't mind spending time reading, researching as I understand that no 2 engines are a like

cam is .427 lift and 204 @ 050 on the intake. exhaust is .455 and 212 (? if it remember correctly). It's a little bit smaller than a stock 340 cam. It's still in the car, but it will be getting replaced as we are going to make some changes to the car.

 

[Dan the man]

It ran high 13's with stock exhaust manifolds, 2.45 gears, and factory torque converter. It did have a 750 DP on a eddy rpm (not air gap). 2.94's and headers brought it to 13.3's. 3.23's and OOTB speedmaster heads it ran 12.9's. Speedmaster heads were worth about 2.5 tenths over the factory cast due to the small cam not utilizing the heads (we knew this when we did the swap).

I'd like to get similar results, what cam would you recommend?

 

[318willrun]

I'd like to get similar results, what cam would you recommend?

The rest of your combo will matter. Combo means entire car. To me, there are no isolation parts. IF your build is very similar, I'd use a 340 size cam. My cam works well because I have no converter (factory stock) and highway gears. So low end torque is very important and key to a good ET.

 

[Dan the man]

cam is .427 lift and 204 @ 050 on the intake. exhaust is .455 and 212 (? if it remember correctly). It's a little bit smaller than a stock 340 cam. It's still in the car, but it will be getting replaced as we are going to make some changes to the car.

I'm thinking of a compression ratio of around

The rest of your combo will matter. Combo means entire car. To me, there are no isolation parts. IF your build is very similar, I'd use a 340 size cam. My cam works well because I have no converter (factory stock) and highway gears. So low end torque is very important and key to a good ET.

I don't remember the spec's, but lunati has a cam that is listed as having very strong torque, would that be something that I should consider

 

[318willrun]

And I cannot emphasize enough on "knowing what your plan is on the entire car" before ordering parts. More cam would "hurt" my cars performance if it killed the low end torque. But with more gear and converter, my cam becomes "wrong" for the combo. Again, no isolation parts. You have to plan around your intended purpose, then every part will be purposefully picked.

 

[Dan the man]

And I cannot emphasize enough on "knowing what your plan is on the entire car" before ordering parts. More cam would "hurt" my cars performance if it killed the low end torque. But with more gear and converter, my cam becomes "wrong" for the combo. Again, no isolation parts. You have to plan around your intended purpose, then every part will be purposefully picked.

My car is going to be a daily driver, something for cruising, and have decent performance too. Here's the cam I mentioned earlier,.454/.454 × 250* / 256* duration at 0.050 208* / 213* LSA/ICL 112*/108* idle to 5,000. Says will work with stock converter. Should I look for a cam that has a split lift too?

 

[318willrun]

My car is going to be a daily driver, something for cruising, and have decent performance too. Here's the cam I mentioned earlier,.454/.454 × 250* / 256* duration at 0.050 208* / 213* LSA/ICL 112*/108* idle to 5,000. Says will work with stock converter. Should I look for a cam that has a split lift too?

What are we building now, 318 or 360? Headers? Gear ratio? Converter? In general, yes, the cam you listed looks tame for a daily driver.

 

[RustyRatRod]

The thing's that you mentioned here I have no idea what it means. I'm wanting / trying to learn how to tune a carburetor in order to get maximum performance from it as I'm thinking about building a engine to run in pure stock, so the carburetor has to be of the same cfm and secondary operation as it came from the factory when new. I'm sure that it's going to take a lot of reading,etc. I've always liked to see how good a car can be made to run with what it came with.

What particular carburetor are we talking about here?

 

[furrystump]

Furrystump,
I can think of 3 reasons that your engine could be fuel starved, not air starved because of carb cfm.
- insufficient fuel volume delivery to the carb
- n/s too small. All the Edel carbs I have seen come with piddling 0.093" n/seats. In contrast the original AFB 500 cfm came with 0.101" n/seats. I would be using 0.110" for any performance application with an 800 cfm carb
- some Edel carbs had restricted secondary E tube holes in the base that acted like the MJ. For reasons known only by Edel....

I’m running the big needles and seats, I have a large mechanical pump and a holley red back at the tank. Rock steady 5 lbs throughout the run and the sec main emulsion well tube is totally open on the bottom. The sec air bleeds are known to be pretty big and without a secondary enrichment system on the AVS like the AFB. The fuel is pretty slow to respond in the booster. I played with copper wire in the bleeds to speed up the fuel movement in the sec. No appreciable effect. I have an air horn that picks up 10 HP on similar combo on the dyno, but it organizes the air so well it just slams the air door open and goes LEAN. You can only tighten the door so much until you risk breaking the spring. Two of us have tried to get it to work and both of us have had to shelve it for now. The horn was designed for an AFB, but trim here, trim there and it fits like a glove. Just doesn’t like the air door.

 

[furrystump]

I thought about creating a secondary accel pump. It looks like Carter made the casting with the dream of it, but it just was too much a PITA. Modify the sec well to work. Plum a small external tube to feed a nozzle in between the secondaries Then just design a linkage. All to find out it no likey! It would not need much. Easier to just steal a bit of the primary pump shot somehow.