IDA pump jet tuning question

[Brianatapg]

According to the A/F data from my LM-1 I need to enrich my accellarator pump shot.  I have a slight lean curve that lasts about one second after each shift.  It's not lean enough to cause any flat spots but being that it's there I feel the need to correct it.

The carbs are the new IDA's with the push in .50 nozels. I was told that the bypass valve pump bleeds at the bottom of the float bowls could be closed off or changed to help increase the fuel shot. Then I was told by another that the "NEW" IDA's already have the bleed ports closed so there is no adjusting these. True?

Maybe someone could explain the best way to enrich my pump shot. Drill the nozels to .55 ?

F11 etubes
165 mains
180 airs
55 idles
40 vents

Thanks,  Brian

[RACECRAF]

I hear Shawn Geers or Jack S. has different sizes of new style pump jets, may want to give them a call.

[Bruce Tweddle]

I was told that the bypass valve pump bleeds at the bottom of the float bowls could be closed off or changed to help increase the fuel shot. Then I was told by another that the "NEW" IDA's already have the bleed ports closed so there is no adjusting these. True?

The check valve at the bottom of the float bowl should have no bleed hole for use in IDAs.  Most IDAs are like this.  You must take them out and check them.  I just went through a pair that had one with a 50 bleed hole and the other with no hole.

[Brianatapg]

I was hoping someone would know what the new IDA's had for a check valve. Really dont want to take the carb apart if they already have no bleed hole from the factory. 

[Art Thraen]

I was hoping someone would know what the new IDA's had for a check valve. Really dont want to take the carb apart if they already have no bleed hole from the factory.

They are .000 ( no hole,   you might try a f-7 tube?. or your float height is set wrong, if the carbs are out of the box, I will bet my best hat that the floats are set wrong from the factory.. I reset every set and I have not found two carb set the same.
first, set the floats.
2nd, put in a .65 idle jet
last, start changing emol tubes and acc. valves.,  The engine is going to want a .60 or .65 idle jet.

[Brianatapg]

They are .000 ( no hole, you might try a f-7 tube?. or your float height is set wrong, if the carbs are out of the box, I will bet my best hat that the floats are set wrong from the factory.. I reset every set and I have not found two carb set the same.
first, set the floats.
2nd, put in a .65 idle jet
last, start changing emol tubes and acc. valves., The engine is going to want a .60 or .65 idle jet.

Art, I had gone through the carbs completly before install. Floats were checked with a guage and suprisingly both were set correctly. I could recheck. 

I've played with both F7 and F11 e tubes and like the F11's best. This is based on the fuel curve data from my LM-1 and the around town feel.

As far as the idles go, I started with a .60 idle and it was a little fat so went to a .55 and it runs great. The A/F ratio is correct with the .55's based on the LM-1 data and drivability is good, why would I need a .60 or .65 jet ?

I'm trying to get rid of a lean curve just after shifts. It lasts for about a second (LM-1 data) and then settles. Should I increase the size of the squirter nozels or the acc. valves ?

On another note, does your shop do the 3rd prog hole mod? If so how much?

Thanks for the help, Brian

[Bruce Tweddle]

I was hoping someone would know what the new IDA's had for a check valve. Really dont want to take the carb apart if they already have no bleed hole from the factory.

They are supposed to come with no bleed hole.  You should take them apart since it is very possible for the wrong one to get installed even at the factory.  I have seen such errors.  Also, it is possible the little plastic ball in that check valve is stuck, preventing a good shot.  Remember that one Lanny?

Art does that upgrade, as well as other mods.

[Art Thraen]

Art, I had gone through the carbs completly before install. Floats were checked with a guage and suprisingly both were set correctly. I could recheck.

I've played with both F7 and F11 e tubes and like the F11's best. This is based on the fuel curve data from my LM-1 and the around town feel.

As far as the idles go, I started with a .60 idle and it was a little fat so went to a .55 and it runs great. The A/F ratio is correct with the .55's based on the LM-1 data and drivability is good, why would I need a .60 or .65 jet ?

I'm trying to get rid of a lean curve just after shifts. It lasts for about a second (LM-1 data) and then settles. Should I increase the size of the squirter nozels or the acc. valves ?

On another note, does your shop do the 3rd prog hole mod? If so how much?

Thanks for the help, Brian

Yes, I do the third Hole,  That alone may cure the problem. are you tring to get 12.5:1 A/F ratio?
Thats what I try for.

It sounds like your on the correct path.. keep playing with it , not only will you learn alot, you will become a good tuner. nice to see ya try to profect the tune up.

[Brianatapg]

Yes, I do the third Hole,  That alone may cure the problem. are you tring to get 12.5:1 A/F ratio?
Thats what I try for.

It sounds like your on the correct path.. keep playing with it , not only will you learn alot, you will become a good tuner. nice to see ya try to profect the tune up.

Art, I'll give you a call and get some pricing on that 3rd hole mod.  It's interesting what you can "SEE" with the LM-1, great tool. The recorded data really takes the "seat of the pants" guessing out of the A/F equation and replaces it with fact. I was able to get my 48 Dells tuned to near perfect but these IDA's are a different story. Miss the dells but wanted the ida "look", absolutley no difference in et's for me at the track between the two.

Once the A/F ratio settles in at the top of the gear I'm in the 12.5 + or - a few points. Just after each shift it's 13.9 or higher for about one second and then settles down to around 12.5 to 12.2 until the next shift.

Does going from a .50 to a .55 pump jet sound off base?  Larger initial squirt to richen up the bottom end of the gear.