ida jetting

[loudaddy]

hey guys. i am just second guessing myself here, but i was wondering if my jetting is optimal.
i have: 205 airs, 180 mains on f7 e-tubes w/ 55 idle 0n 120's. -42 venturies 3.0 needle seats 5.0 aux vents
i am 420 feet above sea level.
2276 . 44x38 c/e 's  ported -not hogged out.fk 46 1.4 cb rockers 10 to 1 c/r
thanks - loudaddy

[maui]

I'm at sea level and my street bug has a 2176 with E130x1.25s, SE ported 42x37 at 10+1 comp with IDAs and 42 vents with 165Mx200AxF7 and F10-70s and it runs super nice and cool and pushes a 12.70s with muff and DOTs. Hope that helps. I tried 55, 60, 65 and I think the bigger idles are better at sea level.

[loudaddy]

so maybe i went a little large on main jets? - lou

[Ohio Tom (DdK)]

Yeah, your mains are huge..
Try 165 mains and 175 airs. That should be much closer..
Also, 55 idle sounds kind of small.
I'd go with a 60 or 62.5

[loudaddy]

thanks tom, how should that change my performance? -lou

[Bruce Tweddle]

How does it drive?

[Bloke]

Sorry to jack your thread for a second Lou, but while were on the subject.  I have a 2275, 9.4:1, 44x37, 86c, 1.4, 1 3/4" h, 3" exh, with 48 IDAs.  I had 37 vents in them, but I have some 42s to try now.   Where should I go on my jetting, it ran good with this in the 37s and a 2 1/2" exhaust, just a slight stumble off idle.
145 main
200 air
F-7
55 idles
120 idle holder

I'm at 600ft above sea level.  Try a 165 main???  Any thoughts

[loudaddy]

well, it drives pretty good, it doesnt have quite the snap down low. i'm fresh on the  2276, i came from a torquey 1835.  i am also running the berg 5.0 aux vents( short) and the 3.0 glass balls.  i am getting a little drip on idle from the aux vents, so idle isnt that great. i dont street drive hardly at all so the only other thing to help clue you in would be to look at my video.thanks for your help!!

http://videos.streetfire.net/video/c6226e7b-65a4-4dbe-a476-73d3a85063ec.htm

lou

[1969dragbug]

Some of the jetting could depend on your ignition, MSD dist/blaster coil as opposed to blue coil with 009, points or petronix ignitor?? I run 185 mains and 200 airs in my drag car, so a drop down would be expected for the street.

[Lee G]

Its very difficult to get good information on jetting by asking what other people run unless you are running a virtually identical combination.  The heads play a key role, for those of us that run Steve Tims race heads (2200cc motor, FK-89, 12:1 compression, etc) running a 170-175 main jet with around a 200 air will get you pretty close for decent atmospheric conditions.  Most who jet for performance look at ET and mph from the track and pull spark plugs and read it for color as an indication of rich or lean conditions.

I tried the 3.0 glass ball and had problems with fuel pushing past and flooding the motor.  I know that others have had the same problems but some have had no problems....just giving you my experience. 

Lee G.

[loudaddy]

i have the mallory unilie on a mallory hyfire 685 box, msd wires(8.5). 10.6 to 1 c/r 2276 fk-46 ,comp eliminators
44x38 ported manifolds,93 pump gas. i mixed 50/50 110 citgo @ track last time. i ran better on pump gas i believe. would  a 44 vent benefit me? i read mark herbert's (r.i.p.) post on ssb and he reccomends 44's with my combo type w/ those jets. thanks again.-lou

[Ohio Tom (DdK)]

The 3.0's will start bleeding past if your fuel pressure is above 4 1/2psi... Or, sooner if your float setting adjustment is off (even by 0.5mm).
You must get the float settings just right first. Then check your fuel pressure (with known good guage).
Then (and only then) can you start playing with jetting and have any real data.

I have found with IDA carbs that on most motors, the jetting combo will land real close for each application.
Vent size (and E-tube selection) play the biggest role in Primary jet selection. Only minor tweaks (up or down a size or 2) should be needed for a particular motor.
For 42mm vents and F-7 tube (and working needle/seats properly set). Usually 160-170 main jet will be right and a 165-180 air corrector does it.
Doesn't seem to matter what motor as long as it's "Hi Po" and not some mild low compression pig.
I have landed on the same Vent/ jet combos for both my main (2276) and backup (2095) motors.
I change nothing when swapping the carbs over.
44mm vents/F-7's, 175main/175air (race gas only).
My buddy Jacob's 2110cc hot street motor likes 42mm vents, 165main/175air.
Trust me, we have played with jetting combos on all these motors.
For each level of tune and different motor combos, the jets always seem to be more depenent on the vent size (and E-tube).

For driving around. They seem to like 60-65 idle jets. Adding the 3rd progression hole makes them drive wonderful.
This is my findings and opinions only...
 

[loudaddy]

great info tom.  i do have the third progression hole and enlarged float bowls. the carbs were worked by costello some time ago. on thing i havent mentioned, is that my mallory is the older version, and the spring setup is allowing it to come on full advance off of idle.(12 idle and 32 full). as of now i have the 42 vents would 44's allow for better track results?

[Ohio Tom (DdK)]

44 vents?? Maybe...
Depends on the power curve of your motor. Switchin to 44 vents will give up a little bottom/mid range and gain some on top end.
If your motor is wanting of this kind of change, then it will work well.
If your gears are spaced far apart, then it may acutally make you slower...
Give it a try. ..

[Tom Simon]

Its very difficult to get good information on jetting by asking what other people run unless you are running a virtually identical combination. .... Most who jet for performance look at ET and mph from the track and pull spark plugs and read it for color as an indication of rich or lean conditions.....just giving you my experience.    Lee G.

finally the voice of reason within a "what jets do I use" post LOL

I jet pretty dam good these days but it certainly wasn't always like that...  Worse, I took some advice on jetting a few times and things got worse instead of better. It wasn't the other guys fault, I was too uneducated to know the difference. I'll just say that there is no magic jet combination that works. There are some generalities that will get you close, but ask your doctor whay you should do after telling hime "I have this pain in my side". Any doc worth his salt needs to test, look at the results, then try something. I went several years with pulling a spark plug after every pass, noting the air temp change and plug color. It's pretty easy to see the cause and effect after a few times of doing that, especially day versus night racing, Sac, sac winter versus Sac in summer which could easily be a 40 degree spread, Palmdale/Vegas then mile high "no air" Denver.

a few truths about tuning and jetting:

* Jetting will not fix another problem, in fact other problems might seem like a jet problem.
     chasing the idle tune when you have two tight valves is almost a complete waste of time
* the plugs don't lie, unless you are trying to get the mains right and you drive at low speeds after making a top end blast
     make a blast, shut it off and coast to the side of the road. pull a plug and read it.
* air temperture AND altutude need to be taken into consideration.
* Jetting starts with zero vacuum leaks, synchronized carbs and linkage, adjusted float levels, adjusted valves, set timing
     adjusting your idle mixture while the engine has two tight valves is almost a waste of time
* To evaluate weather or not the jetting is right, you need to read the spark plugs (there is a real good NGK site that will help)
     there is nothing like an experienced guy showing you a real sparkplug  and what to look for, though
* A street car tune and a racecar tune are different... it maybe the same engine but a street car needs more fuel to stay cool.
     A fat racecar is not consistant, and usually blubbers throught he mid-rpm range, then 'comes on' at higher rpm.

[loudaddy]

alright, here's the update,i switched to a 180 air and a 165 main jet and i ran an alltime best run of 7.90 at 86 mph!  i still think theresmore in it, any suggestions for the next trial?? thanks for the help guys.  i also broke my spidergears later on last night. if anyone has a good deal  let me know.  lou

[loudaddy]

alright, here's the update,i switched to a 180 air and a 165 main jet and i ran an alltime best run of 7.90 at 86 mph! down from a 8.29 @ 82.  i still think theresmore in it, any suggestions for the next trial?? thanks for the help guys.  i also broke my spidergears later on last night. if anyone has a good deal  on an irs superdiff, let me know.  lou