Holley Carburetor Jetting Tuning Guide And Explanation | Holley Carb Secrets |

Lengthy video on tuning the jets on your holley carb. this info can translate to any holley 4150 and 4160 style carbs. Too many people have no idea how jetting even works so this video is to enlighten those people and prevent them from spouting nonsense and giving people bad advice. Once you get the basics of how jetting works in a holley carburetor, the rest is easy as long as you tune in the triangle formula.

#holley #holleycarbs #carbedls

Holley Carburetor Jetting Tuning Guide And Explanation | Holley Carb Secrets |

There's been a raging debate on this topic for as long as I can remember. On one side you have the purists that want everything period correct and on the other you have the hot rodders who will even mill off the choke horns for more CFM. People often ask how to adjust choke on holley carb or holley carb choke removal because they seem to be dealing with a problem that is related to the choke cold start system as a whole. Hopefully this holley carburetor video finds you well and you enjoy this little opinion piece.

Holley Carb Choke Problems And Removal | Holley Carburetor Secrets |

I'm sure most of you have had a flooding issue or a carb running rich and you just don't realize whats going on and even if you do happen to figure out what is happening, sometimes you don't even know what to look for. Holley carbs are some of the most versatile car parts but even they have their own set of issues. holley carburetors depend on a well balanced fuel level in order for them to work correctly. Once the balance is tipped to one side or the other, you can have several problems such and fuel coming out the vent tube, have the holley carb secondaries flood, holley carb running rich, holley carb hard start and even fuel leaks and dripping from boosters. So come by, sit back, relax, and enjoy the show to learn a little bit more about holley carb tuning!

Finally getting around to making this video, everyone loves the HP main bodies because they look super racecar with the adjustable air bleeds on top. What if I was to tell you that you can install custom air bleeds on any holley carb as long as its a squarebore? There is just enough meat on the top of these older holley carbs to allow you to install the adjustable bleeds, but you would be very careful when doing so because you can ruin your main body real quick!

After A long while I have put the most cohesive method of setting up the idle on your holley carb. Setting the idle mixture screws and getting your engine to run clean without having to buy any special tools. In this video I manage to set up the idle in less than 15 mins and also do it quickly and easily. As of right now, the holley carb on the 318 duster is perfectly set up in both idle mixture and idle speed. The carburetor in question is a DEMON 625, an older barry grant holley copy before holley bought out DEMON. It took a little bit of work, but I've got this set up perfectly.

Tuning Holley carbs are probably the most widely used carb is all of automotive history. The Holley 4 barrel is a staple among racers and cruiser a like but too few people really understand what goes on inside their Holley carb and too many decide to ditch the old carb in favor of a new one. I am here to share 5 secrets you can employ TODAY to get that Holley nice and tuned and running better than ever in true DIY fashion. I'm put to work these 5 secretes to get my Carb ls going so these are definitely something you need to keep in mind. Tuning a holley carb is what separates the boys from the racers. Depending on how well this video does, I'll be breaking up and going into full detail of what goes on specifically in the different circuits as well so stay tuned!

[NightWrencher]

Kind of a longer video. It used to be an hour and a half and I trimmed the most that I could I promise!

[mechanknuckle]

I've been wrenching for many many years, but I ALWAYS learn something new on this channel. NEVER stop learning!!

[NewEngland]

I converted a vac secondary 600cfm that had a secondary squirter boss into a true double pumper. Even machined the baseplate for a secondary pump arm and spring pearch. This was a rare opportunity to actually see jetting difference. From being a vac secondary to true double pumper. Jets were identical. 65/65. Front and rear. 28 squirter primary. 31 secondary. Pink pump cams. 351w roller motor. Carb rips. Perfect on wideband. Also had converted it to 4 corner idle. Ps. U can use wire on baseplate to block off front to back transfers slot for 4 corner idle. Or just use epoxy

[rustypanels]

Great video thanks. I have an 850 DP Holley Street HP with manual secondary's on my 434 Corvette. It's running a big cam, alloy heads, MSD ignition and all the gear to make a great noise and up around 500 HP. I've been having issues with it backfiring against the starter and constant strong fuel smell. I reckon it's using way more fuel than it should as well not that I bought it for economy but still it could be better. The Vette is a 78 model and I bought it as a cruiser and show car so it won't be raced. I just want it to be reliable and not self destruct. The previous owner had the engine built and gave the mechanic the green light to build it how he wanted. I'm guessing that the 850 is too big for the intended use but a replacement carb is over $1, 000 Australian so I'm hoping that I can drop jet sizes to help reduce the problem. The standard mains are number 80's in both the primary and secondary's I have ordered 73's to try. I'm wondering if you think I'm on the right track? Thanks again for the great information.

[garyhelms]

Went over my head. I'm going to have to watch again. Question if you're still responding to this video. I purchased a Brawler 750 for my 440 engine. Is this the right choice for my 440 or should I have purchased a 650 CFM?? Any other advice regarding the use of the 750 would be appreciated regarding what might be stock jetting in that 750. Regarding the Brawler, I regret the purchase but I went on the recommendation from someone else. I should have bought a Holley. That's another story. Thanks for your time and the video!!

[calholli]

Damn.. that was a lot bro. lol..
Looks like I'll be sorting through your archives. We have a 383 stroker with 750 double pump, and it's fouling plugs. I was told someone swapped the primary and secondary jets- not sure why; But I'm going to start by reading them to see what we have/ swapping them back to the smaller jet on the secondary and start from there. It seems to run pretty well on the top end, but it's definitely flooding gas while idling, or on the lower end. Another problem is it sat for 10 years and has horrible gas; I'll go search out your videos on getting the idle jets and accelerator pump setup first. cheers.

[davenkaren]

Absolutely THE best carb jetting info ever!!!!
SUBSCRIBED!!!!
I wish you had a way to reach you - for recommendations on what I need on my 496 stroker for my jet boat. I have a Weiand tunnel ram and two Brawler 750 double pumpers mounted side saddle….. the primary jets are 74, secondary’s 84 with a 4.5 power valve. I have 10.5:1 compression and my cam is a pretty big Howard’s .640/ .640 lift, 296/ 308 (243/ 255 @ .50) and a 114 centerline. It’s a hydraulic roller retro-fit. I’m most concerned with the carb jetting, so I don’t melt a valve or piston break nag too lean…… other friends have said, I need to be “square “ on my jets for both carbs, but I have no idea where to start! My carbs are brand new out of the box from Holley like I stated, and it starts and idles good- so far.
Can you please help a brother out!!

[bertramlrezenet]

The power output of an engine is directly proportional to the breathing capabilities of the engine. In other words, how much and how easy can an engine get air in and out through the combustion chamber...
For years the rule of thumb for carburetor size was, you can safely use 2X engine displacement to sect the size of your carburetor. As an example we can say that Ford 289/302 cid engines will perform well with 600/650 cfm carburetors. For serious racing you can go 3X engine displacement without any problems. During the 1960's and '70, I raced big block Ford engines with two 600 cfm carburetors. Keep in mind, engine make up, timing and fuel system must be tuned accordingly.
Cheers!

[kenjohnson]

Good job ! Helped me understand some fine points that I never knew before.

[gas_light_garage]

Absolutely LOVE these videos on the holleys great work!

[flinch]

Square jets... depends on secondary linkage. If primary/secondary movement is synced, that's probably achievable. If they are progressive [30, 50% or whatever] then you tend to go away from square. The application [outside of WOT drag racing] is almost irrelevant. The question is if the secondary opens later, what happens to plenum vacuum? If it drops enough, your primaries are asked to play in two worlds, even with increased air demand. So if say... a 76 might work both sides with synced movement, you could wind up something like 72/ 80 where secondaries don't pickup until primaries are open 50%. That, and secondaries having no power valve tilts away from square to begin with the moment part throttle driving is a required mode of operation.

[GregEngelbrecht]

Hello. Love your stuff. I have a 68 bronco with a holley carb that is leaking on the left side there is a brass cirxle that is on the left it is on the top side of the carb. There is a tube on that side on the top horizontally and where the rube foes into the carb there is a brass circle about a size of a centimeter and a half. When you push on the brass circle you can feel it give way and it is not seating well so fuel is leaking out there. If you push on the brass circle more gas comes out and you can tell it is not tight or seating. Not sure how to get it tight or dixed. 6:57 7:01 7:02

[coyoteserranoband]

Stupid question here; are both jets supposed to work at the same time? For a 2 bbl? Or is one a idle jet and the other a main jet.

[bcraiders]

My 1850 doesn’t have a metering plate on the rear of the carb. I can’t seem to wrap my head around the little aluminum plate and secondary jets if I don’t have a full metering plate. Just float and what looks like a block off plate.

[stevecooper]

I'm up against a wall.
I had a 600cmf holley but the back does not have jets.The 351w ran ok at idle but seem to run out at high rpm.Did have a slight hesitation when you first acceleration.Had 66 jets in the front.
I picked up a 750 quick fuel carb with vacuum secondary for cheap.I put 68 in the front and 76 in the back.Came with 72 front 82 back.Runs to rich have fouled plugs.I have installed a air fuel gauge and am running to rich at idle 10.4 - 10.6. Rich cruising 11.5 - 12.4. Not real bad under load on a hill 11.1- 12.1.Run I smash the throttle after that it goes down to 9.5 for a split second then up to 12.5-13.4.
These numbers are after I down sized the jets in the front to 66 the same as the 600.
My next move is the back jets down to ?? 70 maybe . I have a 4.5 power valve have vacuum pressure at 9.5 .The 750 runs better than the 600 hands down.
It's a 87 f150 dual plane gt40 heads I have completely rebuilt motor top to bottom .The best quarter mile was 15.3 but fouled the plugs the second time I went back to the strip.Any advice on the jet sizes would be appreciated thanks for the video really good information.

[jakefriesenjake]

I have a 650 speed demon on my built 383 Chev stroker. Made 511hp and 492 tq on an engine dyno.

74 on primary and 83 in the sec.

[pillypr]

I have a 242 I6 4.0 running a holley 4412 carb... It runs good, even as I know is a big carb for the application... what jets should I use in order to get better milage same or better perfornce.. I know there is a smaller 350 cfm version but just looking to leanr and tune waht I have.. thanks..

[georgenerces]

Great video thanks for sharing! I am currently rebuilding my carb and was wondering if you could help in choosing the right jet and power valve size. The motor is a 440 with a mild comp cams (dont know the specs of the cam). Has edelbrock aluminum heads, headers, 750 double pump 4150 style holley with a stock style fuel pump. Its running rich from what I can tell. black smoke especially at cold start., Spark plugs are covered black all around. Once the engine warms up it runs pretty good and the black smoke clears. The carb has a 6.5 power valve and 72 jets in front and 80 in rear. I read the vacuum at idle to be around 8-9. Please let me know, I literally just took the carb apart and am going to put it back together in a few days after cleaning and replacing all parts. THANKS!

[leinadalan]

So, start with idle circuit, then transfer circuit, primary jets, pv, then secondary jets?

[jamesrobinson]

Another great tuning video thanks for teaching