Wideband AFR tuning a carburetor

[Supercharged111]

No they aren’t

I drilled the low speed air bleeds (0.085”) and drilled new idle feed restrictors (0.035”) to lean out the idle. The originals were 0.078” and 0.038”. Worked out perfectly. I still have some fine tuning to do on cruise and WOT

Sounds like the path I need to go down. This Monte pukes raw fuel out the exhaust at an idle.

 

[64nailhead]

I expected a change in AFRs in the winter, but did not observe any. Also, I do not see a change in MAP from summer to winter on my laptop (for my EFI trucks) either. Doesn't make sense to me, but this is what I've observed.

Winter to summer has little to do with a map reading. The map reading is a reference to the amount of air entering the engine at a given rpm. An intake temp sensor is used to adjust timing and fuel based on temps. As far as air density (barometric pressure), you need to either watch the weatherman or have two map sensors - one for the motor and one reading atmospheric pressure. Most every aftermarket systems handle two map sensors. Humidity is the real challenge, But a street car s 500/600 is referencing it's not that important.

I just spent $200 on some to play with instead of $2200 for something that may disappoint. I’ll see what happens.

Holley Sniper EFI 550-516K Holley Sniper EFI Self-Tuning Master Kit - Classic Gold Finish

Holley just brought EFI within range

www.holley.com

I'm not sure where you're getting the $2200 price, but these are more like $1200 if you shop and $1400 if you don't. These are extremely easy plug and play setups. They do not care about cam size, within reason.

Please don't take my comment the wrong way (sarcastically), if you can handle carb tuning then you will not find much of any gain from EFI other than tuning speed. Also, I'm not a fan of taking reviews as the gospel. Keep in mind some of the people that write them. Practical experience is much more valuable IMO. I've watched two of these systems installed and tuned in a day by a professional. They are definitely a weekend job if you can handle a basic multimeter. I've followed your skill level with rear end setups, the Sniper will be a snap for you. A well built and tuned 850 carb is going to be in the $600+ range, this system will eliminate all of the seasonal tuning adjustments.

My two cents and best of luck-Jim

p.s. - once you have an AFR gauge you'll wonder how you ever lived without one.

 

[500/600]

$2200 covers the 8 injector TB and the fuel system needed to support 10-12 pounds of boost.

 

[64nailhead]

I didn't realize you're at 10-12 psi. Correct me if I'm wrong, this is a 500+ cube Cadillac at 10-12 psi of boost? So a 400hp+ motor plus another 80%, so 700+ HP?

I think the Sniper 650 system will get that done with a small increase in FP. But if you're looking at a multiport system, then I agree - you'll need a custom modified steel stock intake for 8 injectors, runners, TB, and fuel lines/system.

Inj- Deka 80's $400, runners - $200, TB - $200, fuel system $600 (minimum) and ECU + wideband. So $1200 + ECU and wideband. Yup I agree the multiport system will be ALOT more than $1200.

So what are you using for a carb now? A CSU or did you modify it to handle boost? If you say that you modified it, then I would stick with it if you have that skill set - way cheaper and a blowthrough carb is better than meth injection for detonation resistance.

Please elaborate 🙂

 

[500/600]

I didn't realize you're at 10-12 psi. Correct me if I'm wrong, this is a 500+ cube Cadillac at 10-12 psi of boost? So a 400hp+ motor plus another 80%, so 700+ HP?

I think the Sniper 650 system will get that done with a small increase in FP. But if you're looking at a multiport system, then I agree - you'll need a custom modified steel stock intake for 8 injectors, runners, TB, and fuel lines/system.

Inj- Deka 80's $400, runners - $200, TB - $200, fuel system $600 (minimum) and ECU + wideband. So $1200 + ECU and wideband. Yup I agree the multiport system will be ALOT more than $1200.

So what are you using for a carb now? A CSU or did you modify it to handle boost? If you say that you modified it, then I would stick with it if you have that skill set - way cheaper and a blowthrough carb is better than meth injection for detonation resistance.

Please elaborate 🙂

No boost yet. I’m putting miles on it now getting ready. I’ll put a large single turbo on the car. I won’t buy a 650hp setup and then do it again later. I have a new QFT 1050 annular carb which will convert easily if I went that route. There are injector bosses on my intake already so port FI can be done with an engine management system.

The engine is a minimum of 500rwhp and was built with 12psi or 350hp nitrous in mind. 10psi should make well over 800rwhp, 12psi even more. And torque well over 1000lbft. It has a new 1000+hp TH400 and bulletproof rear. Once I’m happy with the engine NA, I will start buying parts.

I have a perfectly driveable 500rwhp car now, and my goal is to use just enough boost to go 9.99 without losing any driveability at all.................and without having an LS.

 

[fleming442]

No boost yet. I’m putting miles on it now getting ready. I’ll put a large single turbo on the car. I won’t buy a 650hp setup and then do it again later. I have a new QFT 1050 annular carb which will convert easily if I went that route. There are injector bosses on my intake already so port FI can be done with an engine management system.

The engine is a minimum of 500rwhp and was built with 12psi or 350hp nitrous in mind. 10psi should make well over 800rwhp, 12psi even more. And torque well over 1000lbft. It has a new 1000+hp TH400 and bulletproof rear. Once I’m happy with the engine NA, I will start buying parts.

I have a perfectly driveable 500rwhp car now, and my goal is to use just enough boost to go 9.99 without losing any driveability at all.................and without having an LS.

PM me your address; I'm sending you a sticker

 

[500/600]

Which address? Email?

 

[64nailhead]

I have a perfectly driveable 500rwhp car now, and my goal is to use just enough boost to go 9.99 without losing any driveability at all.................and without having an LS.

PM me your address; I'm sending you a sticker

Oh no, I'm being outed by the anti LS coalition. 🙂🙂 That fleming is a bad influence hehe.

Would love to see your build sheet and see the Caddy in action. Sounds like a fun build.

 

[500/600]

Oh no, I'm being outed by the anti LS coalition. 🙂🙂 That fleming is a bad influence hehe.

Would love to see your build sheet and see the Caddy in action. Sounds like a fun build.

There is a build thread with all of the info.

 

[pontiacgp]

Update: The 850 vacuum secondary runs well, cruises well, and AFR is good everywhere. It has the tiniest of hesitations at 1900rpm for some reason. I have tried everything and I believe that it is the rpm where the distributor springs start moving.

The QFT 1050 annular carb runs way better. All kidding aside it has to be 30 or 40hp better. AFR was 11.5-12.0 rich at idle and I couldn't lean it out enough. I bought jet blanks and pin drilled them smaller and now it idles well at 13.5-14.0 and 900rpm. I removed the rear power valve and jetted the primary down and secondary up and will tune in the cruise and WOT this weekend. The AFR gauge has been well worth the money and fun. Even though both carbs ran ok, the gauge proves that they were way off of optimum just about everywhere prior to tuning.

I just remembered when we had a hesitation at a certain rpm in a circle track car we had years ago. It was a G body with a built 350 and stock hei distributor. We were stumped after looking at the holley carb, changing plugs, wires, caps and rotors. We changed the ignition module while crossing our fingers and that cured the hesitation