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post #1 of 9 (permalink) Old 11-06-2006, 10:04 AM Thread Starter
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air bleed authority?

After some reading on here I do undrstand how the IAB interacts with the circuit in regards to being emulsified, but does it effect the "autority" in which the booster will function?
The reason I ask is after I finally got my timing all worked out (oops) I ended up dialing my IFR's all the way back down to 34's for idle and part cruise. Very crisp throttle and cruise. If I stand on her hard after the squirter dies off it feels like it bogs untill I hit around 3000 rpm then it takes off. I realize some of this is because of the cam (232/232 @.050, 108 LSA). If I pull the aircleaner and slowly rev the engine (not the best technique) you can actually see the booster start spraying fuel around 3000 rpm.
If I was to use a smaller IAB would my boosters want to come on sooner? Would I be better off tinkering with the PVCR? Or should I just get more converter?
Thanks
Tracy

1964 Comet, 302, Isky 232/232 @ .050 with 108 LSA, Vic Jr, 650 DP HP, Hooker super comps, Ported early 289 heads, C4 with 3200 stall, 9" w/ 3:89's & detroit
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post #2 of 9 (permalink) Old 11-06-2006, 11:23 AM
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air bleed authority?

Go to the Innovate Motorsport's forum. This is the company that sells the LM1 wideband oxygen meter that is one of this site's sponsors. Do a LOT of reading in the 'general tuning' forum, and you'll learn a lot.

http://www.innovatemotorsports.com/forums/index.php

Good Luck!
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post #3 of 9 (permalink) Old 11-06-2006, 01:30 PM
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air bleed authority?

If you can see the fuel coming out of the venturi boosters while out of gear, this means you have low airspeed through the venturi's. Ideal airspeed through the venturies should be 400 MPH or better for a good fuel atomization. Lower then that you will see the fuel not mixing properly right out of the boosters.

This is caused by large lift and big valves, and/or large intake runner volume.

I bet your fuel milage is very poor. Am I correct? Your car is very light, you should be getting 14 - 17 MPG. ( when your not racing or ripping the tires off it) Just driving around at cruise. Regaurdless of your engine setup. I bet your getting under 10 MPG even though you think the engine is very well tuned and your ripping through the quarter mile.... right?

If so, there is a fix if your interested in hearing it.

Michael


What is life worth, if everything comes easy...?
66 Stang 385+ HP 306 .494 /.520 225 durr @.05, 200cc Windsor Sr's, Edle RPM, C4, 3.00 posi, 575 Annular Mighty Demon, 22 MPG,
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post #4 of 9 (permalink) Old 11-06-2006, 03:06 PM Thread Starter
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air bleed authority?

I'm always ready to listen, and welcome your help. Your right about the milage. It has gotten better though since I dialed back the IFR's.
I look at any gain is a gain not only in economy but performance.
It's a 650 DP with a Proform center body and QF metering blocks with the base converted for 4-corner idle.
Thanks
Tracy

1964 Comet, 302, Isky 232/232 @ .050 with 108 LSA, Vic Jr, 650 DP HP, Hooker super comps, Ported early 289 heads, C4 with 3200 stall, 9" w/ 3:89's & detroit
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post #5 of 9 (permalink) Old 11-06-2006, 03:37 PM
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air bleed authority?

Anular Booter Venturies. Check the 67 Project 302 on this website and they had the same exact problem and the same exact solution... but they sent thier carb out to JET to have anulars installed in a holley body.

Helps the final emulisification. The anular has 8 tiny fuel outlets into the booster, making it easier for the low airspeed to pull out the fuel and mix it properly for a superior mixture.

I have purchased my 4th carb of the year. A 750 Edlebrock, a 650 DBP then an upgrade to a 750 DBP with down leg boosters. So I learned this lesson this hard way. I had to go with a 575 Mighty Demon to fix my proplem... the exact same as yours... It is an off the self with 4 anulars boosters, exactly for our problem....talk to Barry Grant techs on the phone and they will say the same thing.

I had a 750 main body with adjustable airbleeds. I got that sucker tuned really well, and had some great 60 foot times... but it was not consisant. Bet yours is the same way too....right????

Also sometimes the sucker would burp and fart for no reason, then take off like a bat outa- double hockey sticks.

When I had my edlebrock on it, I was getting 15 MPG. Then as I tuned my 750 DBP better and better for the 1/4 runs, my milage went down as the tuning got better.

The poor milage occurs when you take your foot of the gas.... Yes, I wrote that correctly. For some reason the gas was being pulled from the transfer slots when decelerating, and you can hear all the mini explosions of gas in the header.... I am sure everyone has heard that poping sound wen taking the foot off the gas... well that is from the transfer slot pulling fuel when it should not be. Caused by having the primaries opened too far... but that was the only way I could get it to idle even with all the airbleed tuning. ( this is a whole nother story to solve this problem if your interested)

The anulars and the smaller carb solves this problem... and man this sucker is even faster now with better low end tourque.

To prove this point, try a 4 hole 1 inch spacer under the carb, and you will get a slightly better throttle responce from the start. The 4 hole spacer slightly increases the airspeed over the booster venturies....

PS... I do not work for Barry Grant....I think thier quality control sucks too... so really go through the whole carb if you pick one up.....$550.00




What is life worth, if everything comes easy...?
66 Stang 385+ HP 306 .494 /.520 225 durr @.05, 200cc Windsor Sr's, Edle RPM, C4, 3.00 posi, 575 Annular Mighty Demon, 22 MPG,
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post #6 of 9 (permalink) Old 11-06-2006, 04:10 PM Thread Starter
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air bleed authority?

Man, you hit the nails right on the head!
I will look into the anular thing. Ironcally this morning I was searching the web for info on booster design
I had the idle problem until I figured out that too much transfer slot was uncovered. I bought the holley bracket so you can adjust the secondary butterfies. Once I got the transfer slot exposure where I wanted it I used the secondaries to bring the idle up a touch more.
I'll let you know how it turns out.
I have to wait a day to tear it apart again for a older friend of mine at the local tire shop I like is going to do the shelby drop and realign it tomorrow for an hours labor. I know he has done more than a few!
Thanks again
Tracy

1964 Comet, 302, Isky 232/232 @ .050 with 108 LSA, Vic Jr, 650 DP HP, Hooker super comps, Ported early 289 heads, C4 with 3200 stall, 9" w/ 3:89's & detroit
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post #7 of 9 (permalink) Old 11-06-2006, 05:03 PM
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air bleed authority?

The idle air bleeds dont affect booster operation. It only affects the idle and transition circuits.

You may have fixed it, let us know, if not raise your float level slightly, if that doesnt work, get a power valve that opens a bit sooner

70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/reprogrammed A9L/CnC ported Victor.
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post #8 of 9 (permalink) Old 11-07-2006, 03:28 AM
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air bleed authority?

Like I said, I learned all this the hard way, and no one really had answers for me... I had to do a lot of research myself. The hard way..... meaning $$$$$$.$$$$$

If your taking the carb off, this is how you adjust the Idle....
( I now think the only way to set idle is with the carb off the car)

The transfer slots should look like squares from the bottom of the carb when they are adjusted properly. ( Period) Anything other then squares, then you will start to loose gas milage... and you will forever be trying to figure out why the outside ring on your spark plugs are always black no mater what you do to jetting, or IFR's or any other fixes.

The rear idle set screw adjustment should be between 1/2 a turn from fully closed to 3/4 turn from fully closed when your finished doing all your adjustments. You use the secondaries to fine tune how much air you need to mix with your idle circuit from the front. In reality, the secondary throttle plate position at idle will be adjusting your idle RPM's. Did the way I wrote this make sense?

The front throttle position should not be used to adjust your idle RPM's. If you do, you will go back to the bad gas milage.

Man Law...
Set the front idle screw to have a perfect square on the transfer slots and use the secondaries to adjust your idle RPM's.

Man Law...
Your 4 corner idle adjustments should be in a perfect ratio. 2: 1
Example: If the front mixture screws are 2 turns out, then the rear mixture screws should be 1 turn out ( from fully closed) Your final mix screw position will be different based on a lot of factors. But if the fronts are more then 3.5 turns out... you have a different problem that I can explain too.

It may take up to 1 hour to get this set correctly. Please take your time, and write down exactly what you do as you go along, incase you take a beer break...(wink)

All of the above will help your fuel milage and some off idle responce. It may not solve all your off idle responce....

Leave the fuel level in the bowls alone. It should be set per the way it should be set... just at the bottom of the site hole... and rock the car a little bit to make it spill out... then it is perfect. Anything else you are putting your carb out of balance, and will have to re-calibrate all your airbleeds again... we all know how fun that is....

I have even more info if you want to hear...( read....)





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66 Stang 385 HP 302 .494 /.520 Roller, Edle RPM , Windsor Sr. C4, 750 DBP 74/84 jets, 34 Deg



[ This Message was edited by: Mikes66 on 11/7/06 6:46pm ]
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post #9 of 9 (permalink) Old 11-07-2006, 03:58 AM
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air bleed authority?

I got a private message asking what that poping sound is when de-accelerating.

The answer is... When taking your foot off the throttle at anything higher then 2000 RPM's you will create a lot of vacuum in your engine. 20 - 30 HG's of vacuum. This is a lot of vacuum and it truely lives up to it's name... Vacuum.

The vacuum sucks the fuel out of the transfer slots.

Since the throttle plates are closed, the vacuum is trying to get as much air as possible and the only way it can do it is by pulling air/fuel out of the transfer slots.

Since the throttle plates are closed, your air/ fuel mixture is very far out of balance. Near 10 parts air to 5 parts fuel. As dictated from your IFR setting vs your idle airbleed settings.

Since this mixture is too rich to burn completly, a lot of the fuel is not being burned, because it is not fuel that burns... it is the air that burns when fuel vapors are in the correct ratio.

So, when the exhaust valve opens, the mixture of burnt and unburt air/fuel enters the headers where it mixes with more air that is in the headers... once the mixture reaches the proper ratio, it will ignite in the headers causing the back-fire or poping sound on de-acceleration.... (just like deisiling)

Hope this answers that question too....



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[ This Message was edited by: Mikes66 on 11/7/06 7:01pm ]
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