One thing I didn't mention in the video is that I made over 400whp on the dyno with 33" tires, on 91 octane, at low boost and conservative timing. I've since turned up the boost, added more timing and am running e85 instead of 91. The engine should be making close to 600hp and I wont know what the wheel hp is until I get back on the dyno.
Great video. Once I get my wideband wires in and the weather gets warmer I'll be going through the whole process from the bottom and this video will make it easier. Thank you
Something that I always wanted to know is. What's going on in the carburetor when you are drag racing and staging and about to take off. When you're on the partial gas for about 8 seconds at 1800 RPMs foot braking it are you on your idle circuit or on the Jets and does that take away from your pump shot when you mash it?
The pedal position does take away from your pump shot which is why carburetors have a "1" and "2" position on the pump cam. the higher number moves the cam further away so that you can take more advantage of the pump shot while racing. As for the first part of your question, depending on where your foot is, that's where you will be pulling fuel from. Ideally you'd want to pull from your main jets but you may not have the throttle open far enough while staging. It all depends on your converter stall speed, weight, etc.
Great video. I get it, as I've been tuning for years, mainly bikes, some cars. Pyramid is great presentation. I think I may have bought the wrong Holley DP'r for my new build though... Reason being, the metering blocks don't have adjustable transition jet sizes, neither are the air bleeds changeable. I bought a 750 Ultra DP'r for a Ford FE stroker 445, moderate cam 282/288 pulling 11 inches at 850rpm idle (4-speed car). Problem is transition, as you mention. I have everything dialed in except I can't get a clean transition (5%) throttle, it hesitates and stumbles showing 15-16 AFR at the 5% throttle position, cruising slowly thru my neighborhood in that 'part throttle' position. I called Holley Tech who really didn't have a good solution, stating to either increase the PV from a 7.5 to a 8.5 or 9.5, or completely removing it and jetting up (kinda stupid for street car). Anyway, looking fwd to your 2nd video explaining how to change the idle transition jets, I imagine 'drilling' is required..? I'm thinking I should have bought a "Track Warrior" version of the DP'r which has adjustable air jets, etc.
Hey man, the Holley is tech doesnt know what hes talking about but they do that on on purpose unfortunately because they dont want you to permanently mess with the circuits and then return the carb if you mess it up. In your case its an easy fix though. You'll need 3 things. 1) A pin gauge set to measure out the hole in your IFR that you have right now. 2) a jewlers drill bit set. 3) a pin vise so you can hold the tiny drill bit. The pin vise then goes into a drill and you can drill out to the size you need. You'll probably need to drill it out by .004" in order to get it dialed in. You could jet up to compensate as well but like you said, it would run too fat at cruise.
This is an older video so its not as clean as my newer videos but the info you need is right there starting at 5:30 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cIUhlHltPpM.html
@@NightWrencher LOL! I already found your linked video after watching this one. Thanks a lot for making these videos! I can't believe Holley didn't even bring this topic up...!! Very simple if you know the circuit is there AND how it works.!! I found many, many people complaining of this exact issue in forums, but no even mentioned the idle transition jet mod. Thanks again.
Its crazy that these circuits change the entire driving experience but finding info on them is next to impossible. That video was from over 2 years ago and all of it still applys even though I'm doing much crazier things
Only asking, in no way disputing, Thank You for all your work getting these on here. How does higher or lower fuel pressure change the fuel curve when fuel in the fuel bowls is no longer under any pressure. If bowl fuel level is maintained, regardless of bowl inlet feed pressure, will not the fuel circuit curves remain the same? For fuel curves to change, float bowl fuel level must change ? If for a lower HP motor, say 300 gross hp, if say 4 psi would maintain fuel bowl fuel level, that 4 psi would still somehow change the fuel curve?
Thats right because you have to remember that there is a bottle neck at the needle and seat so during sudden throttle movement, the level will drop momentarily and it takes a little bit to fill back up to compensate. The pressure reading that you see on a gauge is based off the needle and seat so if the needle is filling as fast as it can, the pressure will read steady even if the bowl is emptying out. Higher pressures allow for faster filling to prevent that.
Hello, Im trying to adjust the rear mixture screws on my 4180. They are on the baseplate like yours. What is a good starting point? 1.5 turns out? Thanks
I originally skipped this comment because I was not sure what you were reffering to, and 4 days later I still am unsure. As far as I know, the 4180 only had a front metering block and could only be adjusted at the front. But maybe you have something different?
im build a fe 360 030 over with 468 compa cam flat tapped it got 390 intake stock trany and rearend auto ma what type carb would yu go with for street ap
For a street set up you wanna go with a smaller carb for better response and efficency. With that being said, a smaller carb on a big engine is harder to tune so if you want something easier, a proform 750 with minimal tuning would be a good choice
Hey NR I'm having a issue with my 4160 600 I'm wondering if there's a trick I'm missing ? The carb is on a 69 F250 with 390 Edelbrock RPM comp 265/275 cam Headers . The stock jetting is 65 main 6.5 PV 74 rear plate. I changed the rear to a block and now has 80 or 82 rear jets 7.5 4 door PV my mid to wot is pretty close I'm at 1170 on the wideband and mid pedal it around mid to low 13 mid 12 . With the 4 spd auto I like to cruise at 70 on the fwy my wideband reads 1320 to 1380 and often hits 14.11or so with the 65 main jet although once I give it throttle up to maybe 1/2 throttle when the PV kicks in it's way lean like high 15 and mid 14 . Common sense says go to a 69 main jet although there goes all my mileage on the fwy . I did it before and at 70 mph I was all 12"s maybe a 1320 occasionally am I asking to much out of this carb ? Not understanding why I can't have everything 😆. I want to try a high flow squirter screw with maybe a 0.35 squirt nozzle I tried other cams they didn't do anything really and maybe go to a 8.5 9.5 PV ? Any thought 🤔. Thanks
Hey man, it all depends on vacuum. What I would do is jet to the speed that you want to cruise at and then move the PV up to where itll kick on once you get into a loaded situation. Typically you circuit will go lean as load increases and then go rich once you pass that load. I would grab a vacuum gauge and watch it to see where the vacuum is in relation to load and then move the PV # up to compensate
@@NightWrencher that's what I was thinking too yeah it's a 7.5 so when the lean load as you say stops and it goes to low 13 mid 12 I'm around 1/2 throttle so I'm thinking trying a 9.5 and doing what you said so I get that x tra fuel around 1/4 throttle
I appreciate the fast response. I should have mentioned that when I'm cruising at any speed and I try to accelerate a good amount it jumps super rich for a short amount of time then the afr goes back to normal. Still think it might be accel pump, cam or squirter? Also my 383 likes to idle at 1k and when I put it into drive it wants to almost die (550 rpm) . Any idea what might cause that? BTW I love your videos!
Also, it does sound like your idle is off. I don't know how much cam you have in it but it shouldnt drop that much and your idle speed shouldnt be that high. How much timing do you have in it?
