Holley Vacuum Secondary Tuning EXPLAINED | Holley Carb Secrets | Holley 1850 4160 4150

Today I'll be showing you guys how the vacuum secondary system works on a holley carb. This particular carb is a holley 80457S vacuum secondary aluminum main body. This holley carb had a stuck accelerator pump and plugged air bleeds. It made it really hard to keep running so we had to take it off and swap it for a holley 1850. The 1850 is also a 600 cfm carb but it is a zinc body instead of aluminum. Today I'm showing you guys how to tune the vacuum secondaries on a holley. Its not rocket science, and with a little bit of effort, you can get your vacuum secondary carb running like efi.

[NightWrencher]

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[olliehopnoodle]

A couple of points of clarification. The secondaries do not use ported vacuum, they use venturi vacuum. The primary purpose for rod on the linkage is to force the secondaries shut, it makes sure they don't stay open even after the throttle is closed.

[stevenbongiorno]

I’m watching this again. It still makes me think more about using my vacuum secondary carbs. I want to rebuild an old double pumper, and give it a shot after 20 years. Who knows. I’ve changed a lot on my engine, and gear ratio, so it might be what I’m looking for 👍

[charlesoxley]

Thank you for the explanation i am rebuilding an old holley 4160 for my 72 f100 its got a 351w this really helped me understand that system much better thank you for your explanation of the system and the use for the smaller v8 cruisers for the daily driver👍👍

[CadillacZachOffical]

Good video, well explained. I have a 5, 500lb f100 (super cab Longbed w/helper springs) I recently built a 390 for it, went with a Holley vacuum secondary 750 to replace the Edelbrock 660 manual secondary that was on the 360 that blew up... Night and day difference between tuning and drivability. Love my Holley vacuum secondary carbs run them on all the heavy vehicles.

[robpeters]

Thanks for a great explanation! That was on point and makes sense.
I was wondering what the differences are when you change the springs would be? What does it do to the diaphragm? What does the harder springs do the secondaries? Does it hold the secondaries open longer or close them back faster?

[alexconan]

Excelent something tht no one yet explained scruw mixture on secondaries vacum

[b-wingman]

Good video ! On 460 cid, certian years, the secondary stop adjustment screw spec. is 1/4 in.

[loudicanzio]

Just came across your video, great job explaining secondaries. I have a 4150 on a 454, vacuum secondaries, when the secondaries start to open it bogs down and backfires. Could this be a blown power valve. Am I too lean or rich?

[CQBWarfighter]

Definitely going to be going with a vac secondary carb for my heavy 4x4.

[AGClassicCarTuning]

Great video, and answers quite a few questions for me. I've been asked to help set up a supercharged Rover V8, for which we do not know the internal bore and stroke spec if they are none standard to 3500cc (213 cubic inch). No ARP studs is making me think it's relatively standard internally. The carb is a Holley 1850-2 and some have been informing me that this carb at 600cfm is way too big. However from how you have just described it running on the primary's, and will only call on the secondaries 'if and when needed' due to vacuum at the primary. Of course if the primary's can feed the vacuum requirements created without generating vacuum which needs feeding by the secondary's. Hopefully I'm right with this thinking??

[josephfriedrich]

What benefits are there, for a screw to be in the pathway that the secondary linkage/rod travels in. Is it to convert a vacuum secondary to a mechanical? It's on a 1460

[jasonsimone]

What about the check ball? Leave it in or remove it?

[jwjw]

So I drive a 67 ford LTD with a 390 short block all stock I recently put a Holley 600 brawler on it tuned it up runs perfect until the secondaries open when they do open it has a hesitation like it’s going to stall then all at once it comes right back and the only way to get back out of the secondaries is to completely let off the gas I’m not sure if it’s a vaccum issue or something I did wrong but it’s been bothering me so any advice helps

[Cuzntime]

I have a pair of 4160 carbs on my tunnel ram drag car.. Someone told me if I crack open up the secondaries at idle it will act similar to a vacuum leak because the 4160 carbs don't have meterting blocks and idle mixture screws on the secondary side of the carb. Is this true?

[jsbenami]

Great fundamental explanation! I have a 4160 600CFM on a stock-ish 302 and I've been tuning with an AFR. Strong idle vacuum. After a good shot and response, descent power....rich mixture (11-12.0) it leans way out at the top of the power curve (14-16.0). Is this because I'm losing vacuum or because the metering plate is too small, and not delivering enough fuel?

[alanblaikie]

I have a 89 Cobra and it only shows 5" vacuum at idle, vacuum rises to 20" as i open the throttle but when on the road at very light throttle its undrivable as I think its going lean, changed all the normal stuff including power valve, could it have race cam fitted ?

[thehoule]

Question I have a 355 sbc 218/220 cam around 320hp 4 speed with 3.42 I have a 670 jetted or made to be a 750 my secondary’s are only opening at 5000 rpm and on a tiny bit opening up is this carb to big for my application? I don’t want to blow up my motor help please 😮

[coolhandluke]

If I get a rebuild kit for a 4160 is it worth just getting a vac secondary diaphragm for it too, or just see if the old one holds vac?

[colinmertes]

I rebuilt my 750 single pump Holley it started right up and drove alright it fells like the back 2 barrels and blades are not working? It bogs down when u try to step on it hard it’s on a 350