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Discussion Starter #1
I am running a Holley 4165 650cfm spread bore carburetor on my 351W. I have replaced all the gaskets, but would like to know what jets I need to put in to ensure driveability and performance are maintained as best as possible.
Setup:
Edelbrock RPM Air Gap intake
AFR 185 heads, 58cc chamber, 185cc intake, 68cc exhaust.
Hooker Super Comp or Heddman long tubes, havent decided yet.
12cc dished pistons, standard stroke, bore punched .040 over.
Cam- 0.506 intake, 0.542 exhaust. 275/283 duration.
I do not recall what jets it currently has in it, I want to say it has 68 and 108? maybe? I can take it apart and have another look if anyone needs to know.
Just trying to get a ballpark number on jets to get me close so I can start fine tuning and get everything going again.
Thanks
 

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I don't remember what I have in mine at this point either but our specs aren't to far appart. I take it you already own a jet kit? If so the best way to dial it in is to jump about 5 sizes at a time and see where your at. I don't know of any sure fire methods- just trail and error. They do however make a very nice adjust-a-jet kit which makes life a whole lot easier - you don't have to crack it open to make adjustments! If you have the jet kit I wouldn't spend the $ on it though, not really worth it since the jet kit's aren't cheap anyway.
 

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^ plus one. Trial and error. Dial it in, and then check and see if you are rich or lean on the plugs, and jet accordingly..
 

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I have similar setup with my 351C and found with a wideband O2/AF gauge that I run around 12.4:1 AF ratio at anything off idle, way too lean. I was thinking something similar about changing the jets more than the "usual" recommended 2 sizes at a time, but not sure how many sizes it will take to get up to the desired 14.9:1 so unsure of how many sizes to change up. Also, not sure about primary vs. secondary jets. I was figuring to change them in concert, that is change them together going up/down by the same number of sizes from the nominal out of the box sizes. What do you guys think? I have an email dialogue going on with Cougar Bill's dyno guy but he hasn't yet responded with "the skinny" (although he promised to write me something, he says it is complicated (ut oh!)).
 

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Discussion Starter #5
I don't currently have a jet kit, but was looking into what jets I would need to buy in order to get the best results. I will look into the adjustable jets, as that seems like the best and easiest idea. I will probably get a wideband o2 and a/f meter to keep tabs on my ratios instead of having to pull plugs.
 

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X2 on the 2 sizes at a time. It doesn't take much to change the way the fuel will flow at say freeway speed and fuel economy if your to big on the jets.
 

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i'm not familiar with the spreadbore jet sizes but i would recomend NOT using an adjustable set up without the use of an 02 sensor or a smog machine--they run bad when too rich but will burn down if too lean---2 to 3 jet sizes sounds about right---try some new ngk plugs and watch the ground strap after a full on pass---the zinc should be burnt off the tip and down to where it attaches to the threaded portion---if the plating goes away all around the end , you're getting to lean
doctordesoto
 

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bob is on the right track with the wideband o2/af meter.
this is a great tool to have even if your cars have a carb on it.
they cost a bit, but it has been a handy modern day tool.
you get instant results at any position the gas pedal is at.
step up to one that will data log as well. then you could sit
down and look at the data while sitting in the shade sipping on _________.:)
 
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