To all those people who tell me " carbys are crap cos you just have to live with it being rich in one rpm and lean in another ". As a tuner with over 20 years playing with carbs I want to confirm this man has just passed on the secret to a clean flat air / fuel ratio trace that I achieve with a billet metering block and time on my dyno . I've had ignorant laptop tuners call carbs "No better than a monkey with a bucket".... this is a major part of teaching the monkey to dance.. If you are interested in carby tuning SUBSCRIBE..
With the Billet metering blocks and carb bodies today that have a replaceable jet or air bleed for EVERY part of EVERY circuit, a carburetor is SO easily tuned for every part of the throttle sweep today. A guy just has to know what each part of each circuit does, and then it's simply a matter of replacing the little brass threaded orifices to tune them to perfection for your particular engine combo. Carburetors are MORE alive today, than they've EVER been
@@holleycarbshowtosadvice40y90Nope. Those guys don't even understand how a carb works at all. They think that it's all idle mixture screws and main jets, and you're stuck with how it operates in between those 2 things. How WRONG they are...
And this video right HERE, also solidifes the IMPORTANCE of having the floats adjusted right for the PROPER level of fuel in the bowls!! A too high, or too low, level of fuel in the bowls completely throws the Emulsion tuning right out the window.... Sure, there are other circuits and throttle positions that the bowl levels will affect, but this is a big one right here.
www.grumpysperformance.com/emulsion8.jpg My favorite background. Doesn't have the hockey stick looking "spark timing" channel as the block in this vid does, but all other principles are viewable. I am thankful Bill Jenkins was so prolific in his later years - I learned a ton [I wish I learned earlier], and still wind up reading his posts from time to time. Its funny: at some point in life, we all wind up teaching. At a minimum, our kids & grandkids.
What would be a good emulsion size bleed for a blow though billet metering block carb to start with? As always you one of the easiest to understand videos on the tube out there.
The idle mixture screws can only change the fuel to the round holes . The transfer slot can only be changed by idle air bleed or idle jet change . The transfer slot comes in above the mixture screw. And runs off of the idle jet and idle air bleed .
You set up a holley basically two different ways for the idle circuit, one way if has a racing cam with low vacuum and another way if its stock. Watch my video.
I've been watching your videos to tune my Edlebrock Double Pumper - It's real. They made it. I like the way you describe the circuits in the carb. I just made my own PVCR based on your videos. They seemed to help a bit. I am about to get into tuning the bleeds on the emulsion well of the carb. My truck is limited to 4200RPM for now so I may not even need the high speed circuit.
If your talking about the edelbrock vrs becareful this carb is a 4 circuit carburetor tunes differently than a regular holley. Haven't had a chance to check one out yet. Good luck.
@@holleycarbshowtosadvice40y90 yes thats it! I will be tuning the fuel curves a bit next. I need to find out what emulsion plug relates to 4200 RPM on the metering block and then fine tune all the ones above it. I'm about to make a jet drilling fixture too.
Great video and provides a lot of information that I think has been missing in different internet discussions. Having a problem with a 1000 cfm dp down leg boosters, and hoping to maybe get pointed the right way. 500 cid bbc. Demon body with Holley 5 hole blocks (6 if you count kill bleed). This is in a boat and it’s under load all the time. Idle and transition are okay but once on the mains it continues to lean out. Jets are 91/98 with 070 pvcr primary. Emulsion is: kill bleed 027 then 028/0/028/0/0. Main air bleed is 28. Floats are right. Frustrated with how much jet I’ve needed. Dangerously lean at peak torque (4700 rpm - 14.2). Was going to drop the main air bleed to 025 and work way up. Close up the emulsion too?
Tom are your emulsion 0s are they blocked with screw in bleed plugs? Also give me your high speed bleed size and how high is your float level. I'm guessing your venturi is 1.560 and 1.750 throttle plates. Let me know.
So Randy, if I understand corrrectly: we use the Main Jets to tune the W.O.T. AFR to be where we want it, but use the air bleeds to dial in everything below that?
No alot of times you will be close but your fuel curve might be rich at wot and you would change your lowest emulsion bleed hole on your metering block by 4 or 5 thousandths larger and lean it out. Now this is if your close with your tune.
@@holleycarbshowtosadvice40y90 doing very well, God is good. Hope you guys are doing great. Helping many friends with the knowledge that you give. Thank you brother 🍻
hey Randy, great ved as usual, but I was surprised you advised us to go get a m.b. with 4 or 5 treaded holes instead of pulling out the drill and fixing the stock block. oh well after watching all your other vedios' I guess i can figure that one out
You can modify a stock block but only to a certain extent, most are two hole emulsion. Billet blocks have up to 5 holes and I usually use 4 holes. Some tuners use three. Hope this helps.
Emulsions... 2 works, sometimes 3. But on the issue of billet metering blocks, never use all 4: gotta play with combinations, and that goes well with an AFR gauge to test across load conditions. One of the funny things about emulsions is by introducing more air, fuel drawn to the booster can increase [to a point] because for the same vacuum signal there is less mass to lift - velocity of fuel delivered increases. The air bleed is the baseline for this function: it determines the minimum signal booster has to develop for fuel to be drawn. Generally, main air bleed is the dead last thing I fool with because most the time... I got something wrong somewhere else.
Hello Randy! I've watched several of your videos and have enjoyed all of them. I always reminded my students that carburetors many times take the blame for other engine problems, two common being engine timing and vacuum leaks. You're doing an excellent job. Keep up the good work! By the way, where in the south is your home base? I come and stay in central Alabama from Houston, TX several times during the year. May be I can stop by and visit sometime. Regards!
Great video i currently have an ATM 750 dp im tuning in my 428 Fe ive got the jets to give me 12-13 afr cruise now but it goes very lean when i left off the gas for a second before it goes back to the idle circuit 4 hole billet metering block has 4 holes the top 2 are wide open the bottom 2 are .020 from factory..
I'm trying to run an AVS2 on my 350 sbc and it its just a pig. I cant get this stupid thing to run right and i am going to go to my 750 holley carb and to my single plane intake. The Avs2 is just backfiring from the low idle on 1 cylinder and it is driving me nuts.
The air bleeds work backwards the smaller the bleed hole it will richen the fuel mixtture . And just the opposite within .a bigger bleed hole the leaner it will be. Hope this helps.
What if your metering block has ports for emulsion air bleeds but it was installed without air bleeds and left exposed? Mine is currently setup like that and im and trying to understand why Im running rich when the engine pulls more vacuum.
Alright the high speed air bleeds , the two closest bleeds to the vent at the air horn control how much air is induced into the emulsion holes so it can't draw but so much air, so its not being emulsified the air & fuel correctly now i don't know if this is a aftermarket block they can have 3 to 6 emulsion holes. Usually 3 to 4 emulsion holes is all you need they usually range from .027 to .030 for instance hole1.027 , hole2 .027 hole3 029 this is an example and mabe a hsab of .030 . This isn't set in stone just an example. Hope this helps.
Well now. I have been struggling to visualize the mail well action as rpm rises, and how the air enters. As rpm rises, the level in the main starts to drop, as it drops it uncovers and air bleed, and air is drawn in. I think I got it.
hey Randy, love your videos. Is there a way I could contact you about my Holley issue that I’ve been chasing for a year now. I have rebuilt it 3 times and still same problem! Thank you
Excellent descriptions I´ve seen. On my carb I have 4 threaded holes so I can fiddle with them. They don´t have any bleeds in them though but they are all open and drilled to 28 thousands from the manufaturer. One thing I´de like to know is if I open one to say 35 thousands, will the lean effect be the same in all positions albeit in a different area och the fuel curve? Is there any kind of typical reference how much effect on AFR a certain change in hole size make? E.g a change in 5 thousands will result in x.xx i AFR?
There is so many factors, not just changing emulsion bleeds but also you have to figure in hsab size and then the type of booster your using. I can tell you the holley xp ultra 750 has a great fuel curve. Hope this helps
Normally you are right but it is possible with the right combination. A lot of things come into play like the engine breathing capability, the right size carb and the right carb modifications, this can be the difference in winning and loosing.hope this helps
I have a quickfuel 650 brawler dp and i have set the fuel curve flat on half throtlle. When i ooen the secondaries(full throtlle) my fuel curve goes from 2000-2500 rpm starts at 10 afr and only goes to 12.7 at 3500 rpm to max rpm and stays in 12.7 afr. I wanna change the low rom 10afr to 12.7 afr . Can i do this with just putting bigger emulsion jets in on the lower place? Do i have to do this on the primary and secondary metering block or can i just do it only on the secondary metering block? Do i need to go bigger on emulsiin jet to lean out this rpm range? Thanks for the vid
When you open the secondaries your afr is going to be rich with a dp then it goes to 12.7 through max rpm, if you want a more flat fuel curve you may want to go with a vacuum secondary but you can lean your carb but don't use your emulsion, when you have steady afr from 3500 to max rpm your emulsion is working properly. Maybe try .002 larger secondary high speed air bleed or jetting secondary leaner. Hope this helps
@@holleycarbshowtosadvice40y90 Can I adresse this low rpm rich mixture a little bit with putting my total timing from 3000rpm to 2500 rpm? Will it clean it out a little bit?
When you go to wot it'll go rich from the accel pump and popping open the secondaries until you gain some rpms the 12.7 is the fuel ratio, a holley vacuum secondary has no rear accelerator pump and the secondaries come in slow, so the mixture curve is much more flat. Hope this helps
@@holleycarbshowtosadvice40y90 yes i tested this and so i put full throtlle at 1500 rpms and so the pumpshot is burned and afr is 11.5 but when i come back at 2500 rpm the afr goes back to 10 and lower
Was hoping to hear more about the highspeed air bleeds. In a nutshell, having an issue on my 680qft 4160 where theres not enough overlap between the transition and the mains, goes dead lean from about 1800-2500. Hearing conflicting info on which way to go with the bleeds.. bigger / more air flow helps lift the fuel and bring mains in sooner but will lean it, but also hear smaller will give stronger signal and bring mains in sooner. Currently with 61 idle bleeds it fills the gap enough to run, but the transition is rich untill 1500 where it will lean out to 15-16:1 until 2500 it will start richening up again. 28s in the high speed, with 68 jets, fully on the mains - 3k rpm- im back to 12-13 but starts gradually leaning back out as rpms climb.
Ok the smaller air bleed will pull more fuel and earlier. Now there is ways to help your problem, try raising your float level slightly and install a smaller high speed air bleed , you could try annular boosters which has a better signal but they are expensive. Hope this helps. One other thing that can cause this problem is if your idle fuel restrictor is to small it can feed the idle mixture circuit and starve the transfer slot .
Ive already been playing with the IFRs and wasnt doing anything for me other than making the transition even richer and the idle mixtures a pita to set. Currently i have .034 IFRs and im 5/8 out on the idle mixtures (4corner). Going from 71 to 61 idle bleeds really helped as far as drivability, but now have weirdness at idle with cascading idle and the whole transition being rich. Will drop the high speeds from 28s to i think i bought 23s@@holleycarbshowtosadvice40y90
I sent you a message about my 950 HP running too rich at cruise 2300 to 3200 RPM big duration cam would l benefit from the billet plate, l have a 73 primary jet and a 3.5 PV. The engine is a 455 Buick it made 656 hp 600 ft lb torque
Do you have a video which addresses baseline jetting specs for typical builds. Examples: Say mild 350 with a Holley 600 VS Street/Strip Set Up 350 Holley 750 VS Street/STRIP 383 Holley 750DP ?
