k so 7 mpg..

Discussion in 'Street/strip 400/430/455' started by snucks, Nov 12, 2012.

  1. sean Buick 76

    sean Buick 76 Buick Nut

    I am glad my suggestion of tuning the idle mixture screws helped! Great work getting double the MPG you were before!!!!
     
  2. doc

    doc Well-Known Member

    YUP.. what Shurkey said, that is the usual cause of plug breakage like that....:Smarty::Smarty:
     
  3. snucks

    snucks Well-Known Member

    Whoever installed these over torqued them I think. In all the years I have been messing with engines I have never seen this sort of thing happen. I am used to aluminum motorcycle engines so am super aware of the proper amount of torque needed. I use a nice Kobalt set of tools I specifically bought for this car since I pretty much only owned metric stuff I came with a pretty good spark plug socket. Well before I swapped out all the plugs and readjusted the carb the mpg was up to 13 and that was about 70% city driving with occasional testing blasts. I only Burned a few gallons of gas with the latest changes and early results were 15 mpg almost all city with a good chunk of the freeway driving being these full throttle shift to 3rd gear runs so yeah im pretty happy right now. I get the feeling this car is going to get better mileage than my 140hp 5spd truck!

    side note. I went with the suggestion from the pertronix guy to put a resistor inline with my tach dwell meter and sure enough it worked. The crazy part is it turns out I had the idle speed set perfectly at 550 rpm just by ear...spooky
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes, lots of people over torque them. 1/16 of a turn past finger tight is all it takes.
     
  5. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Sweet, Snunks,I knew you could make this a daily driver,more than double the initial mpg,you got to love that!! That really makes for a Happy Thanksgiving!! Which I wish to you and everyone else here!!

    Tuning,tuning,tuning,make sure your engine is tuned,and your engine will love you for it!! And you will love how your engine runs.
     
  6. doc

    doc Well-Known Member

    most all old mechanics has learned a certain ''feel'' when a bolt comes up tight....and will give it just a little more and then stop.... but if you are doing many bolts, you will gradually get tired and the tork wont be even.... this is what a tork wrench does...it forces the tech to come to a constant standard of force on each bolt....
     
  7. Babeola

    Babeola Well-Known Member

    Wow, that sounds so much better comparing the first video to the last. Now, I would be finding reasons to go for a drive if it was mine.

    Cheryl :)
     
  8. slimfromnz

    slimfromnz Kiwi Abroad

    Hi Snucks, I have read your whole thread, and cudos to you mate. Persistance pays off. It must feel like a whole different car now:TU:
    Well done, and of course all the guys on this forum for their great advice, experience and knowledge.
    Cheers
     
  9. electraboat

    electraboat Well-Known Member

     
  10. doc

    doc Well-Known Member

    Now, now,,, it aint sht gas,,, it's cat pee gas....:Brow::Brow::laugh::laugh:
     
  11. rmstg2

    rmstg2 Gold Level Contributor

     
  12. snucks

    snucks Well-Known Member

    UPDATE:

    been averaging around 11-12 mpg in mixed driving. If I drive aggressively the mpg dips into single digits very quickly. It runs rich and the mechanical advance is not advancing enough ( advance spring kit should be ready for pick up tonight). The off idle power is not what I feel it should be and there seems to be a bit of overall inconsistency with this car. The engine will bog if I floor it at lower than freeway speeds about half the time. Sometimes the idle will get a bit rough for no particular reason then go back to normal. I can make changes to the timing and Idle speeds after work then the next day it will run different than it did the night before. I did the old flip the air lid cover trick and it actually did make a difference with the top end power (the video I posted a few days ago was with this mod) but economy took a dip I'm guessing because I like the sound of the secondaries opening LOL so I put it back to normal. There is probably 100ft worth of vacuum hose on this thing and maybe there is a leak somewhere...grrrrrrrrrrrrrrrrrrr
     
  13. bammax

    bammax Well-Known Member

    Grab a handheld vacuum guage and connect it directly to a vac source on the manifold and watch the needle. To save money you can get one of those handheld brake bleeding pumps and us that as your guage. If the needle bounces you have a vacuum leak. Test with the engine cold and again with it warmed up. Also try wiggling some of the vacuum hoses while the engine is idling and the gauge is connected. There's a chance you have a leak that's only present when things are warmed up and vibrating.
     
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I think you still have the same problem you had when this thread started. The carburetor is running rich? Why? You need to figure that out. A common problem with Q-jets is when you have the idle speed screw to far in, the throttle blades are open too much, and the engine is actually not running on the idle circuit, but on the mains. Fuel drips out of the nozzles creating a rich condition, and the idle mixture needles are unresponsive. You should be able to stall the engine by bottoming the idle mixture needles. The idle timing has a lot to do with this. With insufficient timing, you need to open the throttle more to maintain the idle speed. That is why I suggested you run manifold vacuum to the distributor advance. More timing at idle lets you back out the idle speed screw.

    Other reasons for rich running is too high a float level, or too high a fuel pressure. Find out why it's running rich.
     
  15. bammax

    bammax Well-Known Member

    Listen to Larry. He was diagnosing my issues better than I could even describe them. If I'd followed his advice at first I'd have saved myself some time and stress. Of course my issue ended up being a bit more involved than anyone had guessed, but the mystery was all cleared up based on what he was telling me to look for.
     
  16. snucks

    snucks Well-Known Member

    the vacuum gauge bounces between 18 and 19" while in park. I have checked every connection in the engine compartment and found a few leaks that I have corrected. The one area I really haven't looked at too much is under the dash.
     
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If you have a vacuum leak under the dash (climate control hoses), you can pinch off the supply hose, and see if the gauge steadies out. The needle wavering between 18 and 19 could simply be from running rich. Like I said, you need to figure that out.
     
  18. snucks

    snucks Well-Known Member

    I will check the mixture screws tonight. I haven't turned them far enough to kill the motor yet but friends have commented on the smell at idle. would a clogged or restricted fuel return line cause a rich running condition? The reason I ask is when I changed the hoses a lot more fuel came out of the return line than the supply line.
     
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    A popular modification is to block off the return line. When you do that, the fuel pump can make a bit more pressure because it doesn't have to pump fuel back to the tank. I don't think that has anything to do with your problem.
     
  20. doc

    doc Well-Known Member

    Do the basics first,,, eliminate vacume leaks.... take a hard look at the distributor operation, check out and lube the mechanical advance, the vacume advance, the basic timing.... and when I say basic, I mean,, is the crank timing mark actually on top dead center... some are not.... ascertain that it is, then proceed from there... go with about 8 deg. basic...check out the vac diaphragm to see if it will hold vacume... yeah , I know some engines call for 0 deg. or 2 deg. ,,, but you are complaining about the engine being lazy and Inefficent.... tighten up the secondary spring on the carb and see what happens....
    listen to Larry,,, he has been there and done it.... what he says is solid....
    then when all the basic stuff is right and you know it is, then turn your attention to the carb and get it right.... clean it , blow the passages out with compressed air, then put a good kit in it.... then check out my list of cheap tricks in the wrenchin secrets section....
     

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