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Working on MPG

No. So today I drove it to the farm on my usual test strip, at cruise it was 13.5. I worried it was too lean since this set screw drilling may act more like a edge orifice instead of a a regular orifice. I went back to a .031 (original size ifr). On the way back to town it was closer to 13.3 avg. So doing a little math looks like I need a .027 orifice to get close to 15.5. We will see how it does. Ordered a set of carbide drill bits from .05mm-1.55mm. Also ordered measuring pins to better check original restrictor sizes. I have a 1050 dominator to mess with this coming spring.
 
The new .02756 drilled set screw has put the a/f at 15.5 crusing. It is a little richer at lower speeds but this carb seems odd. It has no emulsion holes nor a find able high speed air bleed. I built a latch for tcc lockup and with a bit of tuning I think this will help. I also need to work more on the timing again.
 
I haven't rechecked it again. To keep everything as close as possible I was always making the same trip to school and back. I am sure if I drive around at 55-60 it would be better than my trip that has a 60 mile strech at 70.
 
Take a pic of the carb from the top Ill point out the HSAB and the LSAB orifices.
 
How many of you have been on this board long enough to remember the great acetone debate? Seems like it was back around 2007. Premise was that acetone is a wetting agent. This means that it reduces the surface tension of of liquid such as gasoline. This promotes better atomization of the fuel as it flows from the carb or injector nozzle into the combustion chamber. I for one tried it and got noticeable increase in mpg. Search on 'acetone'.
 
Ah, no. Mpg increase at what loss. I will bet it degrades plastic, rubber and other fuel system components.
 
I tried it when fuel was 4.88 a gallon. I saw a noticable increase as well, I think there was a specified mixture ratio but I carried around a glass measuring cup.. My s10 was an 03 and at 5$ a gallon I was willing to try anything!
 
80' 427 said:
I know where it should be, it is not drilled.
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Toss that carb then, you are working with a fixed emulsion circuit.. which means you end up taking from one side to give to another. which is probably why the variance is so dramatic from one size to the next.. a box standard 600 or a quick fuel or something tune-able will net much better results imho..
 
I would rather cut my dick off and throw it in the river to hear the splash than go LS. If I spent any money on a engine swap it would be a tight quench vortec 355 with a qjet. I think I will finish what I am doing and sell it.
 
80' 427 said:
I would rather cut my dick off and throw it in the river to hear the splash than go LS. If I spent any money on a engine swap it would be a tight quench vortec 355 with a qjet. I think I will finish what I am doing and sell it.
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Aww...c'mon. Tell us how you really feel. :pimp:


:haha:


Does that mean this thread will be ending soon? I've been enjoying it (though I don't typically have anything to add on the technical side)
 
80' 427 said:
I would rather cut my dick off and throw it in the river to hear the splash than go LS. If I spent any money on a engine swap it would be a tight quench vortec 355 with a qjet. I think I will finish what I am doing and sell it.
Click to expand...

Haha, I hear ya. Actually the q-jet can be nice when set up right. Sips fuel when you're not on it, but all the power you could want when the secondaries open up. I always liked the sound when they opened...
 
No, I don't have any reason to sell it besides I have 4 trucks, this being one of 3 73-87. I was thinking of installing a 1850, just to mess with it and see the difference. Really this carb is working ok, I was just going to see if it will change stuff.
 
There are very nice LS swaps and smart owners. I just don't want want to be limped with the other mouth breathing idiots that couldn't change oil with out help telling me what I should do.
 
So here we start iteration 2. I have reduced the ifr in my truck avenger to .0256 and still the crusing a/f is fat. Since drilling the ifr out instead of adding wires to reduce the area I have been working my way back to the a/f I achieved the 13.75 mpg at. I kept reducing the ifr and the mixture stayed about the same. So I plugged the rear air feed to see if there was an effect, it changed the cruise a/f some so I decided to increase the rear air bleed, this it where it all fell apart since the tungsten drill bit broke off in the restrictor. Neat! So after over coming the disappointment and the questioning of "why did you mess with it" I regrouped. Seeing as this carb doesn't have idle feed restrictors I decided that maybe I should change metering blocks and drill and tap it for air bleeds. I like the annualar boosters and if I am just using a body and will be modifying it anyway it looks like a good start. So I wrote the experts on this holley carb, the company. Here is the reply to my question about what metering blocks to buy to modify it for better mpg and street manners.

Thank you for contacting Holley performance. The Holley truck avengers are meant for off road use only. It was not intended for highway of high speed use. There is no High speed air bleed circuits so drilling the ports will accomplish anything. The emulsion system has check needles to shut fuel off to certain passages at different cambers for off road use. We are not saying modifying this carb for daily usage is impossible but we do not recommend it nor have information of guidance in performing this. IT would be best to contact a Carb modifier to modify this carb to your application, or consider another carb meant for daily usage.
Thanks,
Alex

So being a collector I decided for the time being to switch carbs. I have a 4777 650 double pumper. It is a old one, a 71. So knowing they are built extra fat I am considering swapping the primary metering block with one with larger power valve feeds which will allow smaller jets. I had a spare metering block from a marine carb that has a huge pvrc that I can modify for later. I also have a 750 dominator, its primary pvrc is .051 which is a little big but gets us into the ball park. I am going to put it back together with 64 jets and a wire in the .036 ifr.

So I don't know where this leaves us but I think I will go to the swap meet in an attempt to buy a cheap 1850 or other 4150 for parts to convert my truck avenger to a "normal" carb.
 
You would think the "not for highway use" would be part of the carb description.
 
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