Quickfuel 3-circuit
 

Trying to sort out a Quickfuel 1250 on gas, when running on the stop it's a fat pig and doesn't come off the stop cleanly. Is a 3-circuit carb just wrong for t-stop racing? Currently running a 95 main, .046 idle, .076 intermediate, and unknown HSAB - no digits on it. The O2 shows a big rich spike on the stop and it blubbers it's way through it. Wondering what to do next........ 8) JB

I had one of their 1150's on my car and it was impossible to get a good stop ratio. I went to a Holley hp 2 circuit and its good to go now.

That may be just me though, I dont have good luck with carbs...lol...

I built my own 2 circuit 1250 and love it. Start by taking the intermediate bleeds out, put in .025 HSAB's, and jet up to 98 for starters. As long as you don't get an uncurable lean condition at WOT, you can probably plug the intermediate jets as well, it depends on what you have for metering blocks and what mods were made if any. This is a very common issue with a 3 circuit carb. After plugging the 3rd circuit you can't get WOT rich enough I'll get you more info.

I've heard many complaints on the Quick Fuel carbs. I've heard the 2 circuit is better than the 3 for thottlestop. Check your HSAB with a drill bit, I'd guess its around 35. I don't agree with the 98 jets. Your adjusted air is at 6500ft, 98 jets will be way to much. I would put 93 jets in the main and a 24 to 26 in the HSAB. That will lean out your midrange and still let you have enough fuel on the big end. If you race Hobbs this weekend, I think I have some small air bleeds 24-26.

Thanks for the tips Dean-o, I woke up sick'rn a dog this morn, I'm not going anywhere today. Hope it ain't the swine flu......see ya in a couple weeks.. 8) JB

93 might be OK for a 1050, but we are talking about a 1250. Mine has 128 BLP jets that are equivalent to around 100 Holley, even the factory Holley 1250 comes with 99's.

The quickfuel guys were pretty concerned even with the 94 jet, so I can see your point about the 1250. Probably will start at about 95, since I'll be leaning the int. circuit. Going to call them Monday about changing this to a 2-circuit. 8) JB Edit: It sounds like I should be able to do it no problem.

I would suggest at least 1 jet over what the carb came with when removing the intermediates, you don't want to be too lean at WOT. The idea is to get the low and midranges on the lean side, and the fuel curve in the range you run it WOT in as flat as possible. Pulling the intermediate bleeds may make it manageable enough an should show improvement, an as long as the metering blocks have had the mainwells opened enough you should have no issues getting it rich enough and the fuel curve flat without the intermediate circuit.

Florida has never seen air like we even had today. 6978ft adjusted with 60% humidity. Do you really think 1200ft of air in Florida and your 100 jets is going to take the same jets as 7000ft of air. His O2 sensor is already showing a rich spike in the mid range. I'm sure more fuel going to help his blubbering. I doubt his O2 sensor is showing it way lean on the big end or he would have mentioned it. Even Dan Divinci is usually 10 jet sizes wrong on his advice on jets at this altitude. Maybe you have a magic carb that takes the same jets no matter what the air. Enough for me on jets. My true advice would be to try a APD or Davinci carb. I just don't have to much confidence in Quick Fuel carbs, especially with the quality of parts SC4405 has on his car. It won best appearing car in Dallas(National Event) and has the best of everything other than the CARB.

To change the subject sc4405, you should have come racing today. J.Wenger and Glen the torke convrter guy(Glen) in the finals tonight with Glen winning his 2nd race in a row today. I think Cotham and Callaway went out in the fifth round. With Wenger going to the finals beating my a## in the fifth round also should give him sole possesion of first in the points.

Thanks for the update Parker. I'm not the kinda guy who gets sick much, but this thing has kicked my a s s bigtime! I just laid around all day with a killer sore throat and fever. Sure wanted to go race but just didn't have the getup to go. I'll be there in a couple weeks, I hate missing races! On the carb, I think I'll try it with no airbleeds in the intermediate - I may also get some plugs for the emulsion holes in the metering block? It's definitely the inter. circuit that's causing the problem. I gotta get this sorted out soon, Great Bend and Denver are coming up and I need some more laps. I bought that carb off RJ only because I had one on the SBC and it worked perfect, in fact Frank is still winning races with it. I just didn't know about the 3-circuit deal on the stop. 8) JB

I agree, I just don't know about changing a 3 circuit over to a 2 circuit. As good a racer as you are you'll probably pay for a 2 circuit before you fix the 3 circuit like you want. And Frank got a whole lot tougher when he quit using his thottle stop with that carb and started running it all out. Hell he got plum deadly. Did he run Roswell this weekend?
cowboy up and kick that cold.lol.

I'll probably dink with the gas carb thing for a while longer, even with the stumble it's better on the stop than the Terminator was. I might just put the alky setup back on later in the fall, just have to wait and see. Just have to move the SLE cylinder to the throttle body instead of down on the pedal. You mentioned Davinci, the Satterfields swear by 'em, but @ $2k I'm gonna try this a while longer. Frank said he was going to the mountains this weekend. I dunno who, if anyone, ran @ Roswell this wknd. 8) JB

You can figure about 1 jet size per 2000 ft. My whole point is that leaning the intermediates will lean it at WOT as well, I would rather have him start rich at WOT and lean it to suit. You can be pretty lean at part throttle an not hurt anything, just don't want to be too lean at WOT. MPH and plugs will tell you where it wants to be with the final jetting.

As far as the 2 circuit, I think by far it is the best way to go and is not as difficult as you might think to make the change. If you get to that point I can lead you to the info to take it on yourself as long as you can handle a tap. Let me know how it goes.

Thanks for the info Mark, I just might do that. I was looking at these billet metering blocks and the inter. jets appear to just screw in.......why couldn't you just put a blank in that hole? Must be more to it than that so enlighten me if you can...... 8) JB

Sent PM.

UPDATE: After several frustrating weekends I think I have finally tamed the beast. Looks like the liquid-filled pressure gauge on the fuel log was no good, hence the pressure was WAY higher than the needle/seats could handle. New gauge, slowed the pump to 40% crank speed, and voila! instantly cured! Car is rock steady on the stop and comes off clean with no rich spike etc. etc. Lost a close double-breakout 3rd rd. Sat. in S/C but not the car's fault this time! Just a caveat - fuel pressure and float levels are critical! 8) JB

Glad you got it figured out JB. Are you coming to the big race on the 4th. I guess you'll have to spot me now. Hopefully see you Sat.