someone teach me how to tune my carb.
- Thread starter woodyy24
- Start date
See http://www.amazon.com/exec/obidos/s...eld-keywords=tuning+carburetors&Go.x=9&Go.y=8 for a long list of books on how to tune carburetors
352Ford2
New Member
crazypete
All my crevices are greased.
Get a 1 wire o2 sensor (the old cadillacs have them, $20) and a mixture guage from summit, $35. Take all the guesswork out.
Black1987Stang
Active Member
crazypete said:
i guess ill say it before someone else does...in order to tune it like this you need a Wideband 02 sensor and meter...normal kind is narrow band...most people here like to say its just good for a light show and about the tuning...do alot of reading and research...internet, holley book, etc.
crazypete
All my crevices are greased.
87stangdiddle said:
No the o2 sensor reads high/low and bounce. Bounce is what you want because you are right around stoich. A narrowband costs like $20 and a wideband $300 so this is why I say use narrowband and add a little guesswork.
It lets you have 2 inputs: reading plugs and the lightshow. Lets you get closer.
Tonys96Cobra
professional deer "mounter"
What is it that you are trying to tune? I can help you with the basics live what power valve to run, float adjustments, etc. Tell me what you need
79lxSBF said:
That's so true.
Start with the basic's- Adjust the float's, ensure that both primary and secondary's are fully open at WOT, set the idle speed and mixture, etc.
From Holley, your carb came with a few different Jet combo's depending on the generation you have.
They are: List # 4776- F: 69 R: 71
4776-1 and 2 F: 66 R: 76
4776-3 and 4 F: 66 R: 73
All versions came with a 6.5"hg Power valve.
Post you're combo and we can give you a better idea, but in most applications, the 6.5 PV is just about right for the street.
You need to go for a short drive and use only light acceleration, and just cruise at a steady 30-35 MPH, don't get on it at all. Shut the ignition off at speed and coast onto your street or into your driveway, then pull the plugs and read them. You want a nice light tan colour on the electrode, grey or white indicates you are too lean, and dark brown or black indicates too rich. Jet the primary's up or down in 2 size increments if needed, then re-test. Keep doing this until you get that light tan colour on the plugs.
Example: If it's lean, you would go up from the stock 66's to '68's and then retest. If it's rich, you would go down from the 66's to 64's.
As for the secondary's, the procedure is almost the same, except you floor it to WOT, then shutdown and read the plugs. Jet up or down if neccesary and retest.
Once you have it jetted, then you can work on the accelerator pumps. If you have a flat spot or hesitation during light acceleration, you need more of a pump shot. To adjust the pump shot on the primary's- Just move the leaver to the next hole on the pump cam and retry. If you run out of adjustment, you need to try a different colour pump cam.
If you get a bog- It falls flat on it's face, then picks up, you need a smaller pump shot. Again, if you run out of adjustment, you will need a different pump cam.
On the seconddary's, the same thing apply's, except this time you are looking for the hesitation or bog when you mash the throttle to WOT. Curing the issue ids the same.
Definately pick up a book on Holley Carbs- Your local parts store should have one, or at least be able to get it. They are invaluable.
95GTAODE said:
That's so true.
Start with the basic's- Adjust the float's, ensure that both primary and secondary's are fully open at WOT, set the idle speed and mixture, etc.
From Holley, your carb came with a few different Jet combo's depending on the generation you have.
They are: List # 4776- F: 69 R: 71
4776-1 and 2 F: 66 R: 76
4776-3 and 4 F: 66 R: 73
All versions came with a 6.5"hg Power valve.
Post you're combo and we can give you a better idea, but in most applications, the 6.5 PV is just about right for the street.
You need to go for a short drive and use only light acceleration, and just cruise at a steady 30-35 MPH, don't get on it at all. Shut the ignition off at speed and coast onto your street or into your driveway, then pull the plugs and read them. You want a nice light tan colour on the electrode, grey or white indicates you are too lean, and dark brown or black indicates too rich. Jet the primary's up or down in 2 size increments if needed, then re-test. Keep doing this until you get that light tan colour on the plugs.
Example: If it's lean, you would go up from the stock 66's to '68's and then retest. If it's rich, you would go down from the 66's to 64's.
As for the secondary's, the procedure is almost the same, except you floor it to WOT, then shutdown and read the plugs. Jet up or down if neccesary and retest.
Once you have it jetted, then you can work on the accelerator pumps. If you have a flat spot or hesitation during light acceleration, you need more of a pump shot. To adjust the pump shot on the primary's- Just move the leaver to the next hole on the pump cam and retry. If you run out of adjustment, you need to try a different colour pump cam.
If you get a bog- It falls flat on it's face, then picks up, you need a smaller pump shot. Again, if you run out of adjustment, you will need a different pump cam.
On the seconddary's, the same thing apply's, except this time you are looking for the hesitation or bog when you mash the throttle to WOT. Curing the issue ids the same.
Definately pick up a book on Holley Carbs- Your local parts store should have one, or at least be able to get it. They are invaluable.
thanks that a lot of good info
95GTAODE said:
E7TE heads with all the goodies. performer RPM intake, Clevite version of the E cam, BBK equal length shorty headers, BBK x-pipe, MSD dizzy and box, i also have a holley Blue fuel pump and i set the psi to about 5-6. and the carb has a PV block off
i usaully set the timing to 13 or 14.
recently ive been starting it and itll run fine for about 30 seconds and then start to bog and itll die out if i dont give it a lot of gas (air actually cause it seems like its way too rich, the exhaust burns my eyes). and i set the idle screws and that didnt make any difference.
The PV block off is in the secondary side correct? If it's in the Primary, get a PV in there! Also, the secondary's will have to be jetted 6 or 7 sizes over stock to compensate for the lack of a PV. Also, be sure that the Primary power valve isn't blown, because that will cause an excessive rich condition you can't cure.
its in the primary, i bought a rebuild kit and changed the power valve which seemed to be blown and cleaned all the ports and changed the gaskets, it stopped the bogging.... for a while. and it started again a few weeks later when i went to start it up (car is being garaged kept over winter) so i thought id try a power valve block off because a lot of people i know said they can blow real easy with the slightest backfire. and it fixed the problem again...for a while. i cant figure out why it keeps bogging after a few seconds after start up. i still have a spare new PV though along with all the other stuff the rebuild kit comes with.
Part of the problem is that you HAVE to jet up when running without a PV. Besides, running without one is more of a dedicated drag race deal anyway.
If the carb is newer than 1992 it should have PV blowout protection, but if it's older, the kit is ony $5-$10 and easy to install.
I would put the PV back in(stock replacement should be a 6.5, perfect for the street), return the jetting in both sides to factory specs, and scoop up an accelerator pump cam assortment($15 or so), and tune from there.
Idle with the Ecam is going to be around 800-900 RPM, if u run out of idle adjustment, you're going to have to pull the carb and open the secondary idle screw a bit.
To be absolutely honest, you would be better off with a VS carb for you're combo anyway, but the DP can be tuned to work almost as well on the street.
If the carb is newer than 1992 it should have PV blowout protection, but if it's older, the kit is ony $5-$10 and easy to install.
I would put the PV back in(stock replacement should be a 6.5, perfect for the street), return the jetting in both sides to factory specs, and scoop up an accelerator pump cam assortment($15 or so), and tune from there.
Idle with the Ecam is going to be around 800-900 RPM, if u run out of idle adjustment, you're going to have to pull the carb and open the secondary idle screw a bit.
To be absolutely honest, you would be better off with a VS carb for you're combo anyway, but the DP can be tuned to work almost as well on the street.
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