This is the best carb video I've ever watched. I've watched plenty. Nobody even comes close to the info you gave in this video. It gave me all the information I needed. Specifically, how to lean out the idle circuit, when and why and how to do it. Thank you sir.
Thanks for the kind words! Just remember Ignition FIRST, then carb and always do only one change at a time. Once you have the concept of leaning the t-slot (if needed) you're off and running! But location matters a lot. What my car liked in flat Florida is way different than the tune in hilly Colorado!
Not sure why you have to go through other videos to get to this man's knowledge and superior knowledge of carbs than what's out there. Thank you sir for doing this for any who want to comprehend circuits
I have been trying to dial in a 50 year old 4165 spread bore double pumper and my afr gauge would tip into 16.6 in the transfer circuit so I just used a jewelers drill bit to open the restrictor up a little.
I've watched 100 Holley carb in depth tuning videos, read DV's book and have been using what I've learned But this video bridged in some seriously good explanations on the RPM's and AFR and reading plugs and relating to what to do to tune that sector. And man, putting the blanks in the drill if far easier than what I have been doing when trying to drill the smaller diameters. Damn nearly wore my fingers out on the pin vice. Simple but brilliant. How'd you get the spark plug bodies exposed like that? You rock and I do believe I picked up some missing parts in my knowledge base. THANK YOU!!! New subscriber here.
Thanks for the kudos! You can cut plugs with a hacksaw, a cutoff wheel or a small diameter deep hole saw. I did a video on it, ( ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-le6MsxAV2tM.html) but the hole saw doesn't work on all plugs, you may have to experiment with that a little. Once you start cutting them you will learn a lot. Do only one change at a time! ;-)
It looks like Holley, an air bled carburetor same as Weber, finally learned that they can allow the users to make their own calibration/adjustments, if they made the bleeds and jets removable and available. Not the same on a Carter/Edelbrock, they're meeting rod carburetors, different animals.
Hey Wolf, sorry to bug. I have a Holley 650 double pumper with 4 corner idle. Im about to drill and tap the IFR's smaller so i can get the mixture screws within the 1 - 1 1/4 range as their only out about 0.3-0.4 turns and still cant get it to idke above 12.4 on the wideband. My question is, on a 4 corner idle carb, do the primary and secondary metering blocks have to mirror eachother? If i put a .24 IFR in the primary and a .48 IAB should i do the same to the secondary side? Thank you in advance (Im reducing the IAB size to try and see if it helps an off idle lean tip in i have that causes me to have to slip the clutch alot more than id like)
Can you help me. I have a street brawler 750 double pump carburetor. Truck can be up to operating temperature but won't idle unless the choke is closed. As soon as you Crack it open it dies. Part # BR-67313 chevy 350 bored .60 out howards cam Part Number: 466-CL110061-08. Stock bottom end flat top pistons. I say around 10:5.1 on compression afr 195 enforcer heads. I just can't get it to idle when engine is at operating temperature. No matter where the floats are set mixture screws idle screw has to be crank up way to far like 4 turns from the seat. It's just a mess. Please help me if you can anyone.
Without all the specs on the carb it is difficult. I'd look at the idle air bleed and the idle feed restriction first. \ Also. What is your timing set at at idle?? Do you run vacuum advance? The formula is: Ignition FIRST then carb.
@Wolf Wengler's - One Car Garage well I bought it with the air bleeds being primary 63-31-31-63 and the vacuum secondary being 78-31-31-78. It calls for primary 70-31-31-70 and secondary 39-31-31-39 if I read the sheet correctly. Well prior to setting the bleeds to what they were supposed to be, I got the carb tuned to the effect of good idle, clean transition, and clean cruise except for when I went WOT in 1st it would shudder, pop and backfire. But it would not do that in 2nd or 3rd. 2nd and 3rd however the afr would show a lean dip then recover to about 12.5-13:1 afr. So I set the airbleeds to what they say is factory and ran into other issues! Looked further to find ifr is 31s and the pvcr are 53s. Other than that I've got it to a 8.5 power valve and jetting being 68/78
@Wolf Wengler's - One Car Garage also its a FE 390 warmed up with performer rpm intake, headers, cam is 218/224 519/525, 600cfm carb, 4 speed (granny low 1st)
@@RockstarRanger01 Have you tried a bigger or faster accelerator pump shot? I'd to that first. Are the power valve jets adjustable? What is your timing curve? What spring is in the secondary? Remember: Only make one change at a time!
@Wolf Wengler's - One Car Garage yes I went from 31 squirter to 35, and from the factory pink can to a white cam. Also this carb does have adjustable power valve jets and out the box it has 51s. It has the adjustable set screw type vacuum secondaries with a purple spring to that note I have it about half turn out from seated to try to slow them down enough to prevent a bog. If I'm doing it correct that is. As it sits, I have 69 primary idle bleeds, 31 primary high speed air bleeds, 33 idle fuel jets, 53 power valve jets, 39 secondary idle air bleed, 31 secondary high speed bleeds, with 68/78 for jets. At 2 turns out of the mix screws I have a 14:1 afr. If ibhad a way to send you a video of a highway on ramp from 2nd gear roll, I mash the throttle, the engine hesitates pops and spits and backfires then shift to 3rd and I can hold it pinned with little engine coughing or popping. Maybe an email?
Great video! Glad I stumbled upon it. I've never seen anyone use a 5-hole emulsion metering block for 2 emulsion jets, but yeah, keep it simple. These 5 hole blocks are just overkill! It'd be nice to see a video on HOLLEY emulsion tuning. I've messed with it quite a bit, but it never seems to do what it should. For example, using a 4-hole metering block, all jets being .028. If I change just the top emulsion to a .031 it should lean out cruise - when the booster first comes online, correct? It just doesn't seem to happen. Maybe the hi-speed air jets need tuning when the emulsion stack is played with..? Hmmmm?
Thanks! Some blocks with 5 holes want the top hole plugged and the first jet below it, some want the first jet on top. Gotta experiment. It's all a balance. and it depends on the application. For my street hot rod, I like the Idle air bleed big and the high speed bleed small, like .077 and .025 or even .024 on the High Speed. All your gaskets need to be good so there is no leakage inside. And then you want a power valve that comes on close to the same vacuum your vacuum advance drops off at. Gotta have the ignition right before you can get the carb right.
@@wolfwengler Everything you're stating makes a lot of sense. Your video's are great! I've been working with a Ford FE stroker 445, which has been the hardest car I've ever tuned, but your BB videos are relating very well, so thank you! One question... I have the primary transfer slots set square (.020) and the secondary throttle plates set to the same opening which end up just covering the secondary transfer slots. My engine only idles at 600rpm with the blades set in this position, I need to be around 800rpm for the engine to be happy (4-speed car). If I open the blades up anymore the engine start acting funny at low throttle positions. I've thought about drilling holes in the primary blades like so many people do, but am hesitant. Is drilling the way to go? I noticed your car is a 4-speed also and doesn't have drilled blades. I'm working with a new Quick Fuel Q-750-AN carb. Thank you, Sir.
@@huskynox1 Could be any number of things. I like the secondary T-slot to be just about covered, at idle. The t-slots on that carb are big, so you could be getting too much fuel no matter what. There is an adjustment screw for the secondary throttle idle speed, you have to remove the carb and turn it over to see it. You could close the secondary throttle a little and open the primary a little more than the same amount. That would get your idle up a little. Remember where it was so you can go back if necessary. Too much secondary throttle will make it bog on light acceleration. Have you got the timing dialed in? Ignition FIRST, THEN CARB is the sequence for tuning.
Wolf - this and your other carburetor videos are the best. Has helped me tremendously. Have my car humming at all RPM & driving & performance conditions. Thank you sir.
Like what? I'm running the same size orifices on both blocks but I am running a slightly bigger T-slot restriction on the secondary side of the throttle body.
I think McMaster Carr hardware (online) has what you need. Y0u can get them in sets from Amazon or eBay but the quality may be questionable. If you're doing carbs you dont need a full set. I but several of the .020-24 sizes!
Tip for drilling. If you have access to a small lathe, hobby lathe or professional machinists lathe, take a piece of 6061 aluminum rod of any diameter, say 1/2" and cut off a section that is equal to the length of the lathe chuck jaws plus a little extra to make this simple drilling jig. Drill the aluminum with a #27 drill no more than 1/4" deep. Now thread the hole with a sharp tap for 10-32x16. I prefer high speed steel over the average hardware and tool truck carbon steel taps. Carbon steel taps are brittle compared to HSS. Use some WD40 as a lubricant for both drilling and tapping. The lathe should not be powered for the threading - it is easy to break the tap since the hole is blind - turn the chuck by hand and if needed use a crescent wrench on on jaw to turn the chuck. Start with a taper tap and follow up with a bottom tap. This will prevent the set screw from tightening in the jig with straight threads all the way to the bottom. Now you have a fixture to hold set screws and it will be easy to install and remove while not doing any damage to the threads and the orifice hole will be centered and to size. Use a light feed when drilling brass. Slow and let the chips clear by stopping momentarily. A drill bit this small at the wrong speed can easily break off in brass. Brass is a weird material to drill at times and it can bite you. It drills nice then ll of a sudden the drill catches, the chips do not clear and the drill bit breaks. This fixture could also be mounted in a drill press vise using one small v-block to get it perpendicular. I believe most DIY guys know someone that has an operational lathe. If you only have a drill at home, this jig will be a benefit to holding the set screw, no slippage in the drill chuck and no flat spots on the threads from tightening. You gotta work with what you have and I hope you find this helpful.
I got a 500 Holley 2-barrel 44 12-8 can't get it to idle down to set my mixture screws it sucks once I do about 2,200 sucks fuel out of the boosters the only way I can get it to idle down as put toothpicks in the outside idol bleeds please help brand new carburetor
Great video, but the idle mixture screw does not do anything to the transition slot. It controls only the idle fuel. The t slot is only controlled by the ifr and the bleed and of course the slot size. Also the idle well is affected minimally by jet size if you look at a diagram of the complete routing of fuel.
Greetings Wolf, Great video on carb tuning. Been fighting a rich idle on a pontiac 400 with a mild cam (12 inches mercury at idle) with Holley 670 street avenger with msd ignition 30degrees @ idle 39 all in at 2800. You talk about addressing lean/rich idle by varying the size of idle restrictors and watching your AFR numbers. What are your thoughts on drilling air bleed holes in the butterflys that so many people recommend as a way to get more air in to address rich idle? I am really reluctant to drill holes in the butterflys. I am chasing my tail trying to fix this issue though. Maybe first step is to pick up and install AFR gauge. I have watched this video several times now. Maybe you could do a video specificly addressing how to tune out rich idle on holley 4 barrel. Thanks for your time sharing your wisdom with us.
Hey James. How far out are the idle mixture screws? Rarely (very rarely) is it necessary to drill holes in the butterflies. Getting an AFR gauge will help you immensely, especially if you log your changes and do one change at a time. I'd take the car out, warm it up on the highway and record the AFR numbers at idle, 1000, 1200, 1500, 2000 rpms and see where you are rich. The idle feed restriction meters fuel to the idle circuit - that is made up of the idle port and the transition slot (T-slot). That idle fuel can be made richer or leaner by the idle mixture screw and by changing the Idle Feed Restriction, which is the outside brass bleed hole at the top of the carb, on each Venturi. Being able to change those little brass bleed holes is a feature of some higher end carbs, but not a feature of the 670. It can be done but you have to be careful. The other thing is metering the fuel that goes to the T-slot by installing a jet in the main body - I dont know how mechanical you are so that could or could not also be easy. There are videos on all that stuff one my channel. Let me know what you want to do, I'll help if I can.
@@wolfwengler Hey Wolf, Thank you so much for responding. Yeah, I pretty much decided on getting a ARF gauge and am now trying to select one. Your recommendation in this regard would be well received. I have a 1975 Trans Am I have owned since about 1980. I have completely redone it. I disassembled the entire car, starting with the frame getting powder coated and going back.together with everything new. It came automatic I changed it to 5 speed tremec. Now has disc brakes all the way around had the 400 built by a self-acclaimed Pontiac engine builder geru (Rock & Roll Engineering) Have since found out he has screwed a lot of people over). I believe the engine is pretty solid but i have never been able to get it to idle without making your eyes burn from richness of exhaust. I have wasted a ton of time on timing and carb adjustment. To address the richness issue, I have adjusted the primary side throttle stop to barley show any transfer slot (less than a square) and adjusted the secondary butterflies to where its transfer slot looks about the same as the primary side. I adjust engine idle rpm by adjusting the secondary butterfly opening which is no easy task while on the engine because the butterfly stop screw is hidden in the base plate. I also backed timing back from where it was before:39 degrees at 1200rpm and 50 degrees at 2800 rpm. Pontiacs like a lot of initial timing but i know 50degrees at final is way too much. The engine started easy with 39degrees initial. I have the pro billet MSD distributor with mechanical advance. . Adjusting the transfer slots to be almost completely hidden has helped lean it up but now am getting random pops thru the exhaust. This started yesterday after adjusting the transfer slots and backing 10 degrees out of the initial timing. I do not know the cause, maybe too rich or too lean or maybe fouled plugs from idling too much with over rich mixture. idle mixture screws are now at 1-1/4 turns out. When i started trying to address richness issue with car running in the garage, your eyes would be watering. Anyway, I am ready to try anything you recommend including a different carb if you think the 670 is junk. I am not looking to race, just cruise and play around sorta like you. I thought about going to EFI as a way to address the richness issue but that has its own bag of worms. I also would like to stay with a carb. I love what you have done with your tempest. Your air cleaner is incredible. Never in my life have i considered a vacuum pump set up to control crankcase pressure like you did. I really like your old school approach all the way down to how you explain things. There are shit loads of self- proclaimed experts on the net now making it difficult to find people that really know their stuff. You are definitely one. I enjoy your episodes. Let me know about AFR gauge set up you like and what you think i should do to get this 400 running like it should. I wish you were not so far away I would swing by and let you look at my car. I am in Wasilla, Alaska. Thanks again Wolf.
@@jameskoecher6036 OK James, here goes... There are a few things to start with. First comes ignition, until that is right the carb can't be tuned. So, does your distributor have vacuum advance?> You need that! If not, let me know, if it does, warm up the car on the highway or open road - it always must be at operating temp to work on it. Then hook up your timing light and tell me what the timing is at idle with the vacuum hooked up and then what it is with the line removed and the vacuum port plugged. Also tell me what port the vacuum is coming from (the manifold the carb base or someplace else.) Then take the cap off and remove the advance springs completely, put it back together without the springs, start it and tell me what the timing light says at about 2500 rpm. That will show his what the total timing the distributor is capable of. Then put the springs back in, start it up, make sure nothing has changed, and then turn the idle mixture screws in 1/16 of a turn and see if that helps the eye-burning richness. As a related question: are you OK with drilling and tapping holes? And as for AFR gauges, I'd look for something with a digital readout. I mounted mine in the glove box. The Bosch probe is what I have used.
Hi Wolf, No vacuum advance on my distributor. It is MSD pro billet mechanical advance only. That is why my initial timing setting of 30 degrees,might seem high. Full advance is 39degrees and maybe all in at 2500rpm. Yes,i have no problem drilling and tapping. In fact I am ordering set screws and a tap set from Mc Masters like you recommend. Do I need both 6/32 and 8/32 set screws?Does McMaster also sell the number drill bits? I have the standard American sizes 1/64,1/32.... but no numbered drill bits nor pin vices to hold them. Do have a drill press. I was watching your spring fire up specifically looking for your AFR gauge and never saw it. I figured that you used it to get carb right then took it off and plugged the bung hole. Seems O2 sensors don't last too long. I will order a ARF gauge today. I agree I am blind as far as tuning without it. Keeping primary butterfly totally closed and cracking the secondary butterfly until transfer slot starts to appear in throttle bore has helped a lot in introducing extra air. Problem is the tiny set screw used to adjust the secondary butterfly has become the idle rpm stop screw and it is inside the base plate and a bitch to adjust on the engine to set engine idle rpm. Tell me about the set screws and pin drills and I will get this stuff ordered. If you think I have to have vacumn advance distributor too, let me know. I was looking at the Msd vacumn advance distributors. Seems to me they just add in another 10 degrees or so as soon as you hook them up to engine vacumn and with a mechancal advance only distributor like I have, you just dial in the extra at your initial setting. Thank you Wolf for taking the time to help me. It is finally Spring here in AK. Time to be driving and enjoying the Classic.
Trying to put together shopping list for McMaster so I only pay shipping once.I know I will need set screws for the idle air hole in top of Venturi and the idle feed restrictor in the primary metering block and maybe later the other air bleed hole in the top of the Venturi(the inside air bleed holes)Maybe you need the hole IDs to tell me which set screws to get. Let me know when you can . Thanks Wolf.
Is ther a particular a/f% ratio guage ,that u prefer personallly... Also,when your reading the plugs,do you ,have A particular procedure,that assures ur reading the data,that I've targeted ,
I'd suggest something with a Bosch sensor and a digital readout. You'll be looking over at it a lot while you are driving. The plan is to start a notebook with a page for each test drive. I wrote out the rpms and left a blank space to fill in the observed data while I was driving idle_________ 1000_________ 1500___________ 2000___________ 2400__________ 2800_____________ 3500__________ 4500_________ 5500________ WOT____________ The area between idle and where the main jets begin to work ( through the Venturi) is the tricky part of tuning. For plugs, you have to cut them apart. The bottom is WOT, the middle is cruise and the top, near the electrode is the idle. Your timing will be evident by looking at the electrode strap. Read up on it! ;-)
Awesome video. I have a 16 year old Barry Grant speed demon 650 double pumper, and I was wondering if you know of an adjustable metering block that will work for it? I did a quick test (half throttle, the secondaries were blocked off) with my car and a new afr gauge. Looks like I'm a pretty rich on cruise, but leans out a tad to 11.5 to 1, at half throttle (still too rich, I want to be at 12 to 12.5). Looks like I need smaller prim jets and drill out my pvcr holes. Going to do full throttle tests soon! The engine has been dynoed before so full throttle should be staying at around 11.5 We'll see what happens
I like the metering blocks from BLP. They are in Orlando FL. I also like their red bowl/metering block gaskets and PV gasket. Whatever blocks you get, get ones where the idle feed restriction is down low - the flow is more consistent. If you mess with the emulsion holes, remember: less is usually better. I have some videos on the channel about this..
@@wolfwengler ok thanks. I called aem and Proform about their blocks, and they said that they probably wouldn't work out. I'll either call blp or just buy little Brass set screws, little drills and some taps.
@@wolfwengler I ended up getting some drills and taps and put in a ifr Brass set screw. The ifr was between 0.030" and 0 034", so I drilled out the set screw I installed to 0.026". It leaned it out, but now if I gently get on the gas (1500 to 2000 rpm), it has a massive lean stumble (afr pings 19:1), but then goes richer. If I get on the gas quicker, it does not have that stumble. My cruise is 3000 rpm (62 mph) with 4.11 gears, and it's reading around 12.8 to 13:1, still rich with 70 primary jets and 0.059" pvcr and a 4.5" pv. Thinking about going with 66 jets in the primaries, and 0.028" with the ifr set screw holes. What if I went 66 jets, and a richer idle, raise the float bowl (just a hair below the middle of the sight glass right now) but leave the ifr at 0.026"? It feels like the idle is nice, but then goes lean into the slots, the slots get the fuel, but then once the richer boosters start flowing, it goes to being still slightly rich at 3000 cruise. Wot is around 12.2:1, Secondaries still wired shut. What would you recommend?
@@jakefriesenjake I am running a 750 BG on my car. The IFR should be close. How are you measuring? .026 is very small for the IFR. .031 or .032 might be better. a thousandth of an inch is a lot. First you have to know what you had, then you calculate the area of the jet and increase it 10% at a time.it's a tiny bit that makes a difference. The idle air screw is used for the idle mixture, then you restrict the transition slot with a jet in the main body (I have a video on this) The t-slot is the 1500 -1800-2000 rpm area you are trying to lean out. The BG carb needs a T-slot jet. When that's all correct, For the mains, take out the power valve and block it. You make the mains stupid lean and then start adding back fuel. until the lean surge is just gone. You should have an AFR in the 15s at that point. When you get it right, then you calculate the Power Valve Restriction, put there PV back in, and make the mains perportionallyt smaller to get the balance right at wot. Then unwire the secondaries and match the secondary jet you had for the primaries before you put the PV back in. Do only ONE CHANGE AT A TIME. and BTW: the credo is: Ignition first, then carb. What ignition? How much advance do you have at idle? Are you using vacuum advance?
@@wolfwengler I'm running a pertronix digital hp, multi spark box, and msd pro billet distributor. 24 initial, 38 total timing. On the dyno we brought it all the way up to 40 total, made best power. I backed it down a tad. 381 Cid, 9.5:1 compression, comp cams big Mutha thumpr cam. I would guess the ifr was 0.032", but didn't have an actual drill bit to measure (I then measure it with a Mitutoyo digital caliper.) So I drilled out the restrictor, (set screw) to 0.026", probably a tad small. I just bought 66 front jets, will see where I'm at with those, cruising aiming for (15:1), and Wot I'm aiming for 13:1
