got a la roller 360, edelbrock heads, , slapped a 780 v/s holley on that I had froma 440.. any ideas what I should have in it for a baseline jet ? something to start out at? is a 780 vacuum, secondary too much carb for this? eng is a 91 360 roller block, with a custom roller cam grind , don't know specs , I didn't intailly build it. airgap intake, rpm heads, headers, 3000 stall , 4;10 gears,
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360 carb jetting help
- Thread starter 68gtx
- Start date
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Run what it came with as a starting point, usually 72's in primary.
No, it's not too much carb.
No, it's not too much carb.
OldmanRick
Well-Known Member
Most versatile carb Holley ever made for street performance imo. I've probably used close to two dozen on all sized engines before.
Cracked is correct on the #72 primary jet. I'm curious if yours is a 780 or 750? If you could post the list # off the choke horn, it would tell for sure. If it's a 4160 with a secondary plate, it would be a #21 which has a .081 jet orifice.....equivalent to a mid #70's jet. If seen these carbs come with a #25 and #31 accelerator pump nozzle before, and they all came with a plain sec'd spring. It should also have a 6.5" power valve.
Stock jetting is pretty close on moderate small blocks. I have worked with several combo's like yours and found a #28 nozzle was best on a dual plane intake, such as yours, and a #31 worked well on a single plane or dual plane with a spacer. As far as the secondary opening spring, a yellow or short yellow worked best with a 3k converter and a 4.10 gear. The 6.5 power valve should be fine for all but the most radical cams.
Don't forget to get your timing maximized before tweaking the carb, if you choose to do so.
Cracked is correct on the #72 primary jet. I'm curious if yours is a 780 or 750? If you could post the list # off the choke horn, it would tell for sure. If it's a 4160 with a secondary plate, it would be a #21 which has a .081 jet orifice.....equivalent to a mid #70's jet. If seen these carbs come with a #25 and #31 accelerator pump nozzle before, and they all came with a plain sec'd spring. It should also have a 6.5" power valve.
Stock jetting is pretty close on moderate small blocks. I have worked with several combo's like yours and found a #28 nozzle was best on a dual plane intake, such as yours, and a #31 worked well on a single plane or dual plane with a spacer. As far as the secondary opening spring, a yellow or short yellow worked best with a 3k converter and a 4.10 gear. The 6.5 power valve should be fine for all but the most radical cams.
Don't forget to get your timing maximized before tweaking the carb, if you choose to do so.
Most versatile carb Holley ever made for street performance imo. I've probably used close to two dozen on all sized engines before.
Cracked is correct on the #72 primary jet. I'm curious if yours is a 780 or 750? If you could post the list # off the choke horn, it would tell for sure. If it's a 4160 with a secondary plate, it would be a #21 which has a .081 jet orifice.....equivalent to a mid #70's jet. If seen these carbs come with a #25 and #31 accelerator pump nozzle before, and they all came with a plain sec'd spring. It should also have a 6.5" power valve.
Stock jetting is pretty close on moderate small blocks. I have worked with several combo's like yours and found a #28 nozzle was best on a dual plane intake, such as yours, and a #31 worked well on a single plane or dual plane with a spacer. As far as the secondary opening spring, a yellow or short yellow worked best with a 3k converter and a 4.10 gear. The 6.5 power valve should be fine for all but the most radical cams.
Don't forget to get your timing maximized before tweaking the carb, if you choose to do so.
number is 3310-3
OldmanRick
Well-Known Member
number is 3310-3
Out of the box.....
Primary jet...............#72
Secd plate...............#134-21...has a .081" main feed. About a #74 jet size
Power valve..............6.5" vac
Accel pump nozzle.....#25
Secondary spring.......Plain color........Medium tension.
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