Y07_A66,

What is your goal for the light throttle AFR?

Dave

Dave,
My current goal is to see the cruise A/F around 14.7-15.5 range. This is just a guess from the reading that I have done. This goal means that I still need to add about 1.2 to the transition circuit, so it appears that I need to work with the IFR's to make that large of a change.

I do know that I was getting light surging at 17.0 (30mph) and the car still feels a little strange with a 16.0 reading at 30mph too.
If I can get into the low 15's and get rid of the 16+ readings, then I think that would be safe enough to move on to the main jetting.

OOPS,
After all of that, you said light throttle. I have read where light throttle accel should be in the low 13's, so once I get my transition where I need it, then I will tackle the primary pump setup. But the current readings 13.8-14.0 seem fine for casual driving.

Thanks Dave.

""Is there a lean spike when you tip the throttle in?""
When I had the .075 IAB's and my metering screws were not dialed in, the answer was yes.
The 071's (MS dialed in) and the 067's did not show a lean spike at tip in. The light accel from a stop and cruise to light accel both showed 13.8-14.0 on the guage with the red/037 primary pump setup.

""Is there surging/missing at steady cruise below 2700rpms?""
30mph [1700rpms] (.067"=16 / .071"=16.6) there was a slight surge.
40mph [2200rpms] (.067"=16 / .071"=16) there was a slight surge.
50mph [2500rpms] (.067"=15.6 / .071"=15.6) there was no surge felt. It seemed that once the cruise was richer than 15.6 or so, there was no surge at any rpm level. It appears that 15.6 might be my lean limit.

My thoughts are to test .031" IFR's front/back and go back to the .071" IAB's (stock for my carb) and see where the readings go.
Note:
I need the gauge to read about 5-7% richer between 1700rpms and 2700rpms. If I swap out the .028 IFR's to the .031 IFR's, that will give me about 10% more fuel available in the transition circuit.

I called QF and they suggest that I do not go richer than .067" on the IAB's with a gasoline setup. So my current IAB's are .067,.071,.073, and .075 IAB's. I will also have the current .028 IFR's, plus .031 and .033 IFR's to test with.
The next five days show storms, so I won't be able to give any updates for a while. This will give me some time to get the lost .031 IFR's on order.

Since I am going to have the front metering block off, I am thinking of swapping out the 66 jets for some 65's since my reading at 60mph (3100rpms) is down around 14.2 and it goes lower at 65mph (3300rpms) to 13.8.

Thank you very much for your time.

UPDATE:
The weather allowed me to test drive the car again with the following changes:
.028" IFR's to .031" IFR's [lean trasition circuit, 15-16+]
66 main jets to 65 main jets [60mph/65mph was in the mid to upper 13's]
.071 IAB's [back to stock setting]


I started out after a short drive tuning the in D idle A/F ratio and I got it to 13.8-14.2 which made it idle nice at 850rpms. Then I started the test drive.

The following shows the last test drive (first) and todays results second. The 028" to 031" IFR's made a big difference (no more 16+'s) and they put me right about where I am guessing that I need to be for cruise.

64 degrees:
25mph ----------------14.0
30mph 1700rpms (16.2) 14.6
35mph ----------------14.6
40mph 2200rpms (16.0) 14.6
50mph 2500rpms (15.6/15.4) 14.6
55mph 2700rpms (15.0/15.2) 14.0
60mph 3100rpms (14.0/14.2) 13.6
65mph 3300rpms (13.8) 13.8

Then I tested my WOT from a cruising 40mph to WOT and it showed 12.2 and then slowly climbed to 12.5 before it shifted into 3rd.
Then I tested my WOT from a cruising 55mph to WOT and it showed 11.8 and then slowly climbed to 12.5 before it shifted into 3rd.
I am guessing this rich WOT reading immediately at WOT kickdown, might be from my secondary pump cam combo which is a red/031. I am going to retest with a smaller cam, maybe the pink/031 to see if the number keeps from dipping down to the 11.8-12.0 mark. If this does not work then I will look at the secondary jetting. It is currently at 75.
Is 13.6/13.8 too rich for 60/65mph? I could drop another main jet from 65's to 64's and retest. The outside temps are still fairly cool at 64 degrees today, so Summer may have me leaning it out anyway. I am surprised that my 60/65mph A/F ratio did not change since going from 66 to 65 main jets. I am wondering if I am still not on the main jets at these speeds. REF: My only 70mph test showed 3500rpms @ 13.6-13.8.

When I got back from my drive, the in D reading stayed at 14.0 and then I watched my N reading and it richened up to about 13.4 from when I initially left the garage when it was about 14.2. The car did not like the leaner N reading of 14.2 and it showed lean while driving until I got to stop and retune my in D A/F ratio as shown above.

The weather is breaking! Everybody's out with their cars. 3 cheers for springtime!

Can I talk you out of changing 3 things at once? It obviously worked, but I'm just sayin...

If you can get a leaner cruise than 13.8 without upsetting the balance (and you're pretty darn close now) sure, go for it! It seems to be going richer as you go faster (14.6 to 13.8). Any way you can safely cruise it faster than 65 MPH and see what happens? (IE, does the curve continue toward rich) You might try a larger MAB, which will lean it out at higher airflow. What size do you have now? (I searched this page for the answer and nothing came up). Hopefully, you have some that aren't a huge jump up from what you have now. As I said, you're close.

Jim,
Now that I have had a few hours to think about it, I don't want to open up the carb just yet. I am currently running the stock .033" MAB's and I "think" that I have a set of .036". I will check tonight. Once I swap out the MAB's, I will test it up to 70-75mph to see what the curve does.

Thank you very much for your help.

Wow great stuff here.

I tried to post fishing for experienced answers about these issues here and got nothing. I'm currently trying to dial in my 750 dp for street driving and the tuning is starting to involve wires in the idle feed restrictions. I already ditched my main body for a HP version for the bleed tuning.

My issues are similar- I have a strong motor with a race carb that is a pain in the butt in traffic. The carb cruises super rich on the t-slots and the transition to the mains is jerky as the proper mix takes over and good power hits

I already switched from a single plane to an air gap and put a four hole spacer (secondary opened up now a three hole) in an uneducated attempt to boost the signal to the carb. I was thinking more vacuum would give me the street performance of a smaller carb but it probably just sucked harder on the rich mix in the t-slots.

Thanks for all the in depth tuning results. It seems like most guys just live with a bad street tune as long as wot is good. I moved close to work in a congested area so I need to get dialed in.

""Thanks for all the in depth tuning results.""

My main reason for posting all of the details is because I ran into the same problem as you. I could not find allot of information or any articles that showed the progression of the tuning with actual results. I could find some reading here or there, but not any from beginning to end. Hopefully this will help others that run into the same questions that I have had trying to tweak in their carb.
So far, I can't think of a better tuning tool for a carb than these A/F kits!!

FOR REFERENCE:
I still can't get over what 1/12 of a turn on the metering screws will do to the A/F ratio.
If I turn all four of mine from 11:00 to 12:00 positions (for reference), this could be .5 difference on my guage. I would have never guessed that before this process started.
.028" IFR's to .031" IFR's showed a 1.4 to a full 2.0 change in my cruising A/F ratio at the same speeds.
.075" IAB's to .071" IAB's showed .4 to .6 change in my cruising A/F at the same speeds.

""There are other guys on this board who know their Holleys but they've not posted.""

Jim,
I do not know why the others have not chimed in but we appreciate your opinions!!

I found my .036" MAB's and they are in. Now I need to wait again for the weather to clear.

Thanks again.

Y07_A66

The MAB experiment will be very interesting to me. I am doubtful that you are moving much fuel thru the main jets at 65MPH, and suspect there will not be much of an impact at cruise. It may have a bigger impact on WOT at high RPM though, so you might want someone running shotgun to keep an eye on the AFR if you run it up to redline.

The IFR change from .028 to .031 is a 22% change in area, which is a pretty big jump. Your current results look pretty good though. A change from .028 to .030 is around 15%. At light throttle you could probably run leaner than 14.6 but going to .030 might make too much of a change (you can always add that jet to a future parts order if you want to try it!).

As JimG said, there were 3 changes at once. With the bigger IFR, you may be able to go a little bigger on the IAB. This could help with the 65MPH+ cruise, since I suspect most of your fuel delivery is still from the transition slot. I think you indicated you only had .075, .071, and .067 IABs. Again, if you are really wanting to fine tune it, getting a set of .073 IABs would give you an intermediate step to try.

If your MAB experiment doesn't bear fruit, then you could try the .075 IAB, and if that is too much then time to consider that parts order! It is a little expensive, but I ended up getting a QF IAB jet kit to let me experiment to my hearts content.

I look forward to your next update!

Dave

Dave:

- MAB .033" to .036" swap: Once I can test drive the .036 MAB's and write down any changes at cruising speeds, then I am going to test the cruise to WOT affects. I did not change any jetting, only the secondary pump cam change from red to pink (due to the rich spike right at WOT kickdown. The pink should lean that spike out). This test should help me decide if I need to make any changes on my secondary jetting.

- I am content with the .031 IFR swap. I think that it puts me right on the richer limit for the cooler Spring and Fall temps. I would like to lean out the 14.6 cruising readings from 25mph to 50mph just a tad, so I might try swapping out my .071 IAB's to some .073's after my MAB test. But the combo of .031" IFR's and the .071" IAB's might be my cool weather ticket. (I currently have .067's, .068's, .071's, .073's and .075's to play with.)

Thank you for your reply and I will post my results once the weather breaks.

Next Update:
Issue: Lean out the rpms above 55mph.
Changes: .033 HSAB's (MAB's) to .036
Weather: Was 66 now 72 degrees.

The 036 swap leaned out the A/F ratio above 55mph. I added the new A/F ratio at the end (/). My 35 & 40mph A/F leaned out some but that might be from the temp change. But I am now aiming for 14.5-15.5 cruise and I am as close as I think that I can get.

64 degrees:
25mph ----------------14.0/ 14.0
30mph 1700rpms (16.2) 14.6
35mph ----------------14.6/ 15.4
40mph 2200rpms (16.0) 14.6/ 15.4
50mph 2500rpms (15.6/15.4) 14.6/ 14.6
55mph 2700rpms (15.0/15.2) 14.0/ 14.4
60mph 3100rpms (14.0/14.2) 13.6/ 14.4
65mph 3300rpms (13.8) 13.8 ----------
The following was a 2nd gear test to see what the A/F ratio was doing at higher rpms:
3000rpms @ 14.4 (same as above 60mph)
3500rpms @ 13.6 (not sure why richer)
4000rpms @ 14.6

The above was with the carb setup: 65/75 jets, .071 IAB's, .036" HSAB's, 8.5 high flow pv, .031 IFR's, red/037 primary cam and pink/.031 secondary cam, 40% secondary linkage delay.



I was able to get my cruising a/f raio into the 15's by leaning out the four metering screws but I was not comfortable with the 15-15.8 readings so I richened them back up. Plus I found that my in D/brake applied A/F ratio needs to be about 13.6-14.0 or my cruise A/F numbers start to change.
I made one WOT run from 50mph and it shows the same as before with an A/F reading at 12.5 then it leans out slowly to 13.0 at the shift point. I am assuming that this 12.5 reading right at WOT is due to the pumps dumping the fuel (DP carb) and then the leaning out to 13.0 is the engine using the extra fuel. Is this a good number for the WOT stab?
Note: I swapped my red secondary cam for the pink cam and found no difference in the A/F ratio.

Thanks to all. The car is running great!!!

Y07_A66,

Your fuel curve is looking sweet! Looks like JimG's recommendations were right on the money.

I haven't tinkered with MABs yet, and your results provide encouragement that this may be viable approach to cure some of my street tuning issues as well.

Your WOT numbers look pretty good to me as well but the final authority on what the motor wants best would be chassis dyno or drag strip MPH numbers.

Thanks again for sharing all your details. This has been a very educational thread.

Dave

Dave,
When you change your MAB's, let us know the results.

I am going to test some more WOT runs but from a stop and from lower speeds to see what the pump cams are doing. I also want to see how lean it goes from the lower speeds up to my shift points istead of cruise speeds to WOT.

Thanks for the reply.

INTERESTING read guyz...... It is my intent to join the 02 crowd when I get motorhome project on-the-road. A couple of Q's .....

How many choices are there for a wide-band 02 combo-kit? Anyone tried to add water-injection to enable going HIGHER UP on the A/F numbers? I knew a guy who worked at Ford who said that either Ford or Mazda tried WI ...and were able to get the A/F #'s out to 25 to 1. IIRC ... but if you ran the car out of water ... the motor was toast.

What are your combo's ....stock type or mild HP?

Doc, I'm partial to the Innovate stuff. You can datalog multiple discreet and analog inputs (TPS is especially helpful, RPM, manifold vacuum, etc.) with their auxbox and a laptop. You don't have to buy everything at first, either. You can buy the basic LM2 kit (or used LM1) and add the auxbox later if you so desire. This setup is something you probably wouldn't want to leave in your vehicle permanently. The basic kit will allow you to read (or datalog) the AFR; the addition of an auxbox will allow you to add other data to the graph.

In your case, you might want to permanently mount an O2 gauge in the cockpit of your motorhome. An Innovate LC1 along with a gauge of your choice would be good in that application.

I look at it this way - the LM2 (or LM1) lives in your toolbox, much like a scan tool or dwell tach. An LC1 lives in your vehicle as an add-on gauge, such as a tach or oil pressure gauge. The first thing to decide is if you want a tool for diagnosing multiple vehicles or an O2 gauge for your motorhome.

The guys here are also having good results with other brands of equipment.

I hope that helps.

J