B4B vs. SP-1 and a quest for mileage..

Discussion in 'Street/strip 400/430/455' started by 436'd Skylark, Aug 3, 2020.

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  1. Marv Marksberry

    Marv Marksberry Well-Known Member

    I will be pulling the water from the front of the Aluminum Heads.
     
  2. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    After another tank I can officially say the mileage is up to 12. This was driving easy with only a few sessions. Up next is the q-jet. Im also considering putting the GS hood back on it..
     
  3. rmstg2

    rmstg2 Gold Level Contributor

    I'm getting a strong 15 MPG with a B4B 800 Q-jet

    Bob H.
     
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  4. hugger

    hugger Well-Known Member

    my 2013 Camaro Zl1 averages 11 mpg if that makes anyone feel better haha
     
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  5. BQUICK

    BQUICK Gold Level Contributor

    A trick I tried on a q-jet on 67 Riv was disconnecting the accelerator pump after warm up. (gas crisis....remember?)
    Carb was plenty rich so hardly needed for cruising. Tried it once on a trip. Seemed like 2 mpg...17 to 19 at 55-60 mph .Didn't have to try to hold throttle like egg. Otherwise every slight movement squirts un-needed fuel.....
     
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  6. Mike B in SC

    Mike B in SC Well-Known Member

    I have been looking at used ZL1's, maybe I need to rethink that! 11mpg! Of course you probably keep your foot in yours!
     
  7. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Actually it does!
     
  8. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Another update...

    I got the Q-jet back on. I had it on and off a couple times thanks to a plugged idle circuit on the left side of the carb. I also had to swap the power valve spring to one size stiffer. Must be the b4b provides a stronger vacuum signal over the sp1.

    The initial seat of the pants comparison is great. The q-jet is much more responsive. The cruise AFR hangs around 13.5-12-5. The Holley was always a touch richer, 12-11. To be fair the last time I changed the jets it was about 40° at the track in October. Leaning the carb back out was on the list of things to do, but so is fixing the drawer in the kitchen... anyway the car drives much nicer.. its even better when its lugged down. I'll update with some mileage numbers when i can.
     
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  9. 70 GMuscle

    70 GMuscle Plan B

    Nice. Been putting some good miles on my Rob Ross tuned q jet.
    He did a heck of a job for me.
    I have another one for him. But waiting on horse power upgrades.

    mr gasket makes a 4 hole q jet 1 inch spacer.
    I have one. Will have to dig out. Still haven’t tried it yet my car runs too gods now w the q jet finally.
     
  10. Jim Weise

    Jim Weise EFI/DIS 482

    Joe, for mileage, get that cruise AF ratio up into the 14's.. your pretty rich right now.. Probably just need a primary rod change.. I would go up about .002-.003 to start with. And don't be afraid to swap in an even stiffer power piston spring.

    Your correct, the dual plane manifold increases signal to the carb fairly dramatically.

    As far as Holley's go, the 1000 HP is superior to something like say a 950.. Those typically cruise in the pig rich 10's for AF ratio.. the 950 is a 750 baseplate with a smoothed out 850 main body.. and the relationship to of the venturi to throttle bore is not good for part throttle operation. The thousand is the same main body, with an 850 baseplate.

    I have seen many 1000 HP's in the mid to high 13's at cruise, might even touch the 14's at some throttle openings. They come out of the box in the 13's typically, but do respond to primary side jetting and air bleed changes.

    If your going to run a Holley DP depending on your combo, and 850 or the 1000 HP are where it's at.

    And stay away from anything but the classic Di-chromated Holley's.. the newer shiny stuff has been nothing but problems for the last few years. Buying one from a vendor that just puts a billet baseplate on it is fine, if you need the extra vacuum outlets.

    JW
     
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  11. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I'm going to drive it some before I make more changes. The quick test runs are really too short to gauge the AFR accurately. It is cruising primarily around 13.5 or so. I want to get on the highway and see where it's at turning 3k first. I'm definitely in the park..

    I drove it to work today and have to go to the body shop and check on the scout. I'll be running all sorts of speeds and driving conditions. I'll have a good idea of what needs done. I'll probably put in a larger primary rod as you suggest.

    I could have done more with the holley but I was only concerned with WOT at the top end of the track with it.
     
    Last edited: Jun 21, 2021
  12. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Another update.

    470 cubic inches, 470 miles!

    I had to make a quick trip home to surprise my mom for her birthday. The wife stayed home with the kid so I took advantage of the opportunity and drove the skylark. The drive is about 50/50 highway and normal roads. The route I take cuts right through the Adirondacks for a couple hundred miles and then its onto the 90 for almost 200 miles. I had been tinkering on the Q-jet and got it lean. Cruising afrs are consistently 14-15. I am going to swap the power piston spring up one more size as it has a slight stumble once in awhile.

    Anyway, I went through some fuel! Crusing 60ish through the Adirondacks I was turning 2500-2700 rpm. The car seemed to like that best and was getting 13.5 mpg. The interstate was a different story. 3000 rpm was about 68 mph. I noticed at 3300-3400 the exhaust was much quieter so I tried to cruise at that rpm. OD be damned.. that netted 11 mpg. Afrs were holding in the 14s so I'd say thats about as good as it will get. It might be time to swap the dynomax bullits. My ears are still ringing.

    I put just under a thousand miles on the car in 3 days.. stopped for gas seven times and used half a quart of oil. Get out there and drive these cars!

    Snapchat-587786010.jpg
     

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  13. wildcatbuick

    wildcatbuick Active Member


    Where did you get the adapter plates from?
     
  14. Marv Marksberry

    Marv Marksberry Well-Known Member

    Many years ago, Charlie Evans spent a lot of time and research to have them made. They are the best anyone has ever produced. You would be very lucky to find a set of “new, un-touched” adaptor plates.
    Recently, Charlie took my plates to a machine shop and asked how much to duplicate them. I think the price was close to $700 for the set. I have had this set for several years. They are for the 440 intake to adapt to the Stage 2 Track Eliminator heads. I have a new set of heads being ported by Charlie and as soon as he and Mike finish the valve job, I will finish assembling and Dino the motor.
     
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  15. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Another update-

    I'm in the beginning days of a week long road trip that should be about 3000 miles by the time I get home.

    The car is still the same setup as before. B4B with the q-jet. AFRs are 13ish to 14, admittedly a tad rich.

    The big change is a gear swap. The car has a 9" ford rear diff. Somewhere along the way I aquired a complete center section with 2.75 gears. I knew most of this trip would be highway driving so I took the time and installed the 2.75 gears in place of the 3.50s, along with a new tru-trac carrier.

    This cut roughly 1000 rpm off the highway rpm. The results are as expected- 15 mpg cruising 60-65. The highway dropped to 14 going 75. I was also up against a 15 mph head wind on the highway, so I expect some improvement there.

    Side note- the q-jet doesn't like the stage II scoop on the highway. It runs fine, but it pushes fuel out the accelerator pump hole. I think I might try routing the carb vent out of the air cleaner.
     
  16. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Update- 1450 miles later and we're in Tennessee. I did manage to route the vent out of the air filter housing. That solved the issue with fuel pushing past the accelerator pump. It also bumped the AFRs up a tad across the board. Fuel must have been splashing around. Either way it no longer smells like gas while driving. Fuel mileage- well were up to 15 mpg going 70-75. Not too shabby.. AFRs are 14.2-15. I don't have a vacuum advance, so there might be some mileage there..

    Either way, get out there and drive your car!
     
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  17. Quick Buick

    Quick Buick Arlington Wa

    Had a 64 HI scout with a 289 or 302 in it...The accelerator pump failed on it.... Had to prime the carb to start when cold, That thing got some great milage then I fixed it....
     
    Last edited: Oct 20, 2023
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