We have two threads running for about the same info just in to differnent places. Lets use this one for the 390 Holley tuning.

I am also asking question on the Inovate forum. I am forgeting if I told you guys some stuff, so here is a link to keep us all on the same page.
http://www.innovatemotorsports.com/foru ... php?t=8261

Today I have to acually get some work done, so the car is on hold for today. I will takes some pictures of the metering blocks so someone can point out what needs to be measured.
Thanks guys for you patience.
Brennan

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Changed out the IFR's today from .033 to .029. My idle adjust ment screws could only be turn out 1/4 turn. Now they are between 1/2 and 3/4 turns out from lightly seated. I still need to play with the idle air bleeds (which are 73's now), but I am closer now.
http://tinyurl.com/ynkktz Block pic
http://tinyurl.com/27exk4 Block pic
http://tinyurl.com/23enlg 390 top view
http://tinyurl.com/ywkt7m Throttle blade view

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I'm not impressed with that simplified 570 Avenger metering block.

I would put some restriction in the high speed air bleeds and see what happens to the high load, high speed A/F mixture. Should go richer for sure. Are they the same size as the main jets?

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Joshua

Got a couple of questions.
1. What might be the cause of going somewhat lean during a shift? (904, rapid rpm decrease) When ever the RPMs come down quickly I am going about 1 to 1.5 points leaner for about a full second.
2. What do you think about this lean then rich spike? I am running a pair of white cams and the primary nozzle is a 31 and the rear is a 25. Do you think using a 35 up front would bring enough fuel to cover up the lean spike and be spent sooner and not give me the rich spike?
http://tinyurl.com/2rl8lw
Purple line = O2
Blue= TPS
Red = MAP
Black = RPM
Green = 12.9 AFR

Also what is considered the perfect Air Fuel Ratio? Is it better to be rich or lean when considering power, not safety. Of course rich is safer, but what makes more power if the AFR where to deviate the same amount from ideal?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

bump

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Well, I will tell you my expeirances with this problem. First off no amount of pump tuning will help this.



Evey carb setup I have used on the slant has done this. I could get a nice flat A/F through one gear no matter if it was all the way through first from a launch, or if I was running 60 MPH and pulled back to second gear, the A/F would stay flat ( after some tuning). But as soon as I shifted it woudl lean 1.5 from where it was. I tried everything I cold learn and did not cure this. The Holley 500 two barrel setup I ran for awail I came close and got it to stay within 0.5 (1/2 a piont). I did this through booster mods & emmulsion tuning. I got to the piont I went to far with the carb and need to put new boosters in, and I was going to change to a Keith Dorton metering block to get more ajustability.


I was told at one time this was because my carb was to big, I proved this to be wrong. I have also noticed other peoples dyno charts of /6's that showed the same problem. Other setups like V8's have had this problem and the cure was a open plenium intake, or sometimes just a bigger plenium.


There are other things that can cause it though.

One, pull over from the accel pump system. AT the higher RPM the air just pull fuel out of the squirter and richins the mix. You just about need a camera to prove if this is happening at WOT.

To much timing that cause a brief bit of detination. I cured some off mine because of this. The engine would detinate on the shift. It would not not be enough that I could notice,hear, or find by looking at plugs, but still a few degree of timing helped to flatten the fuel curve.


The O2 sensors will show richer if backpressure builds in the exhaust system. Bosch & NGK have docs about this. I have not tested to see if this is effecting mine, but it something I intend to do when I start tuning again.


As far as A/F goes, 12.8 is where the sweat spot was with my engines
( when I could keep it there). Dont let it go above 13.5, from 13.5 to 14.7 is the danger zone with EGT's.

One thing you could try and that is stacking two 1" spacers. One four hole on top & then a open spacer under it. This will change the signal to the carb and add plenium space. If it helps then maybe a Cliffod intake might help some with its bigger plenium. Droping half of your exhaust (muffler & tail pipe) could help to see if backpressure is causing it.


Until I do some more testing & tuning I cant say 100% sure what I think causes it. Extreme carb tuning did help me, but really should not have been needed. I will be setting up some Webers for mine this week, it will be interesting to see if I have the same problem with the Offy duel carb intake and two 32/36 webers. So far every intake & carb combo I have used has, even the factory one barrel & intake.

I was hoping that the heated intake may be causing some of it, but I know you are running headers now and that should have taken the heat away. It may infact be a intake problem as it turned out to be on some that I seen cure it. But I have my thoughts about exhuast causing it also. If it is the intake, plenium volume I feel is the key. A flat A/F curve should be able to be held, atleast to 0.5 piont.


Jess

lean spike on RPM drop can easily be explained: poor signal boost from the main boosters. That's why I suggested you should run annular boosters. If you're already on annular boosters and this keeps on happening, it's time to go custom on those boosters. This is the only way in wich you can aproximate things to perfect. (you'll see a little leaning on RPM drop but if power valve is OK for your setup as soon as rpm drops vacuum will drop and you'll get more fuel while you're building vacuum and signal strenght while going out of the power circuit.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Jess supports my claim that the 500 2bbl is really hard to beat. Signal seems like a good explanation to me, Juan.

12.5 is safest, but may give up a little power. I would try to stay between 12.5 and 13.0. Keep in mind I've never had a WB O2, so I'm just referring other experts' info.

Lou

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Home of Slant6-powered fun machines since 1988

Jess,
What did you have to do for the one barrel set up?
Was it with a 1920 Holley? or?

Thanks,

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

It was the 1920, and I didnt do a whole lot for it. I mostly just jetted and worked with the power valve and air bleeds. The truth is I just didnt try to cure it as much with this setup because I was going bigger and to diff setup. But the thing that stood out to me was even with this small a carb the effect was still there, leading me to believe it didnt have anything to do with carb size.

Also with the super six intake I used, BBD, Holley 500, and a Motorcraft two barrel that was a take off of a 302 ford truck. I believe it has the 1.21 veture size (sweet carb for daily driving). The MC carb has factory annular boosters and it has the effect as bad as the Holley 500 did.


Even with the BBD which was one of the small ones that came on a slant six it did exactly the same.



It was booster mods (incressing booster signal) , and metering block air bleeds ( emmulsion holes) that helped the Holley 500. The emmulsion tuning did the most help. To date it turned out the best out of all setups, including the most power. But the truth is it was the worst with the A/F swing lean drop on a shift thing out of all of them before mods. But believe me my poor metering block went through it and the best way to approach this would be with a Keith Dorton block, or a Billet after market that has full tunability. Things like the fuel feed to the boosters and main well size & shape effect these things alot and I am just starting to learn the tricks of this kinda tuning. I was doing very good, but then got some things to big and need to start over.



With the BBD & the 1920 doing the same thing, I have kinda feel away from thinking venture size and velocity being the cause. Although it does seem to be a signal thing and may be caused from all the cross talk between cylinders with reflecting waves, because of a poor intake design, and to small of a plenium. Its not that there is not enough signal, its the signal gets so out of control and effects other signals that should be reaching the carb ( this cylinder bouncing over and effecting the waves/air from that cylinder, so the signal doesnt make it to the carb).


Some of the cars I seen give results from this problem where V8 Chevy's that where running duel plane intakes and going to a more open single plan intake totally cured the problem. They also tried smaller carbs, carbs with annular booster and other such tuning tricks before fixing it with the intake change.


The accell pump pull over, and the exhaust backpressure things need to be confirmed to not be causing any problems. Although the BBD's and the 1920 Holley never have such problems with pullover, so this leads me to believe other areas are the cause.

I have been tuning for quite a bit now with my Inovative O2 setup. Getting the exhuast backpressure problem out of the way and verified that it is, or is not cuasing any effect is one of the next things I intend to approach. Right now its snowing here so I am waiting for warm weather, I am to old to be out there is this stuff.


When it comes to A/F and best power, no matter where your at there will be a timing level that will work best with it. It want be the same level for 12.0, as it will for 12.8. Leaner mixtures will need more timing, but detination can show up. Rich mixtures will like less and its intersting how it effects the torque, but I have made my best power on the lean side.
Each engine will be differnt. The engine I am running right now is about as close to pure stock as you can get, but that will be changing soon.



Jess

Jess,

Your analysis of the pulses not getting to the carb for a good signal is a very interesting concept. I understand that the larger plenum will average discrete signals out and may make the spikes less intense. This is a good bit of analysis. I wonder how the dual Offy/Weber set up will respond?

I would like to optimize and master the air bleeds on the 1920. Right now my idle bleed is potted over from the Holley rebuilder but my high speed is still stock. High end and pump shot are awesome but the low end bog when you lightly accelerate is a pain. If I mash the throttle you don't feel it, but I don't want to drive that aggressively all the time. It will go sideways just fine when I stomp on it but my wife is not to thrilled.....

Any suggestions as to what you did with yours that I might try on mine?
I am recovering from eye surgery right now and am waiting to for better weather. I am running a #58 at the moment.

I have the drill bits ready! Send me a PM if you can.

Thanks!

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I've been studying some passed logs and my question is this. Is it a NO NO to run two different size power valves?
I am getting a lean area (15.2) around 20%-40% throttle with a 6.5PV which is gone with the use of a 8.5PV front and rear. My AFR is pretty flat with the 6.5PVs and not so flat with the 8.5PVs.(at WOT) I was thinking about keeping the 8.5PV in the primaries and moving down to a 6.5 or maybe even a 4.5 in the secondaries. I haven't tried it yet to see if it better, but was wondering if mismatching is just not a good idea or not?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

There is no problem with missmatching as long as it works. Although it does seem like the other way around is more common. BUt if it works, it cant be wrong.



Jess

Ted, I dont think I have even seen IAB's blocked off before. I am not sure if this could be contributing to your problem or not. But my guess is your carb builder was trying to cover up the big lean spot these carbs have.


Depending at what throttle level & load this happens at it could be a few things. Two things that really helped me in this area was working with the accel pump becuase it would not work good with very light movement. Drilling out the pump squirter orfice helped me some, working wiht the linkage was a lot of it, and going to a lot heaver spring under the the pump rubber made a big differnce and helped it be more possitive acting to linkage movement. The linkage just releases it and the spring is what pushes it so the orfice size & spring tension really what dictates how quick it acts. Plus if I am remembering right it has a check ball that has to seat and seal real good.


The power valve is real touchy to get working right and if going up a hill and giving light throttle it comes in and effects it. Thats one of the worst power valve designs I have seen. Working with the spring on really helped this alot and changed when it came in. Having a good metering block with this part working right was a must though. I have been meaning to build a redesigned block for these carbs and have a pretty good layout ready to try this, but other things have been getting it the way. I was going to convert it to where you could use Holley IFR & PVCR jets with a Weber power valve that worked off the origanal power valve accuator the 1920 came with. The IFR restrictor in the 1920 is bad for getting restricted and can cause this lean spot real bad also and its very hard to do anything about it without drilling the block aparts.

It feeds off the main jet (IFR) so the main jet can effect this circuit. you can use the main jet & the IAB to get this circuit in line and then use the MAB to help get the main circuit back inline. I hit a very good tune with mine that I was getting 20 plus MPG, had great WOT power and no bogs at all after I learned how the carb worked. But I didnt put much time into it because I had other setups I wanted to try. I do want ot go back to it and come up with some things to really help this carb because many people still try and run them. Plus I was getting great power with it and I feel it can feed most mild slants on a budget pretty darn good with some help. I am hoping I can get a Weber booster assy to work with it also, but out side of looking and saying it looked possible thats all I have done.

This weather should break soon and I will get back at it. When I do I will check all the calibrations of mine and post them for you. This week should be warming up so I can get out in my building. I do most of my work at night and its been close to being warm enough for me to get out there, but just not warm enough. One thing, I need a good camera and I just dont have one, or really wish to spend the money on one. I have family I can barrow one from but I hate to do that and take the chance of something happening to it, then I would have to buy them and me one.



Jess