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Thread: First dyno pull

  1. #1
    FEP Senior Member dtmilsap's Avatar
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    Default First dyno pull

    Did my first ever dyno pull, I knew going in that carb was running rich. 306 rwhp, 368 tq. Afr was 10.5 around peak hp. I know it needs smaller jets. Carb is quick fuel 750 slayer, engine is 363. Has 1inch spacer 4 hole. Just looking for suggestions

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    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by dtmilsap View Post
    Did my first ever dyno pull, I knew going in that carb was running rich. 306 rwhp, 368 tq. Afr was 10.5 around peak hp. I know it needs smaller jets. Carb is quick fuel 750 slayer, engine is 363. Has 1inch spacer 4 hole. Just looking for suggestions

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    Quote Originally Posted by dtmilsap View Post
    I wouldn't chance it, spending more up front for a quality block might save you more money in the long run.

    Sent from my SAMSUNG-SM-G900A using Tapatalk
    Well done. Iron block for the win!

    No matter what you do, your investment is safe with that block!

  3. #3
    Venomous Moderator Hissing Cobra's Avatar
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    What's the rest of the combination? For a 363 cubic inch motor, that hp level seems low but the torque seems to be ok.
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  4. #4
    FEP Super Member xctasy's Avatar
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    Block is dart 302 shp/363, heads are brodix circle track 1 20 degree,2.055/1.60, Edelbrock 7521 dual plane intake. Intake port match to heads and heads are ported.

    Quote Originally Posted by dtmilsap View Post
    My engine builder couldn't find correct sleeve to repair one of the cylinders so he going buy a new block. He is replacing everything from the valves down. He is doing what is right. I know this not cheap for him.

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    Plimary update of engine failure. After running scope through hole it looks like spot weld on windage tray let loose and hit rod which then punctured oil pan. Rods are intact. Engine coming back out and to builder.


    Quote Originally Posted by dtmilsap View Post
    I have a dart shp block 363, cost about 2000. Can handle around 800hp. With my set up looking for around 475 to 500 carb. With room to grow.

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  5. #5
    Venomous Moderator Hissing Cobra's Avatar
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    Did dtmilsap delete some of his posts? I didn't see any information on this until you posted his quotes.
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  6. #6
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by Hissing Cobra View Post
    Did dtmilsap delete some of his posts? I didn't see any information on this until you posted his quotes.
    No, he's been very careful to work in with his engine builder, and made separate posts with no build list on purpose.

    You've been in that situation too, so As you will appreciate, his builder has done the right thing, and has helped him out with the total engine rebuild, which was probably caused by the sumps Foreign Object Ejection , which then made a brand spankers 363 SHP block a liability.

    Quote Originally Posted by dtmilsap View Post
    Finally installed

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  7. #7
    FEP Power Member Ethyl Cat's Avatar
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    That low of output for me I would be verifying timing. Somewhere in the 18* range base and 36 or so total.

    Slayer carbs come with 72 pri and 82 secondary jets. I calculate 78 square for 7000 rpm so depending on the PVCR size I would think around 72 primary would be close and I would jet down the rear.

    Carb might be a tad small for this application but not the cause of the lack of HP.

    More engine data would be helpful to verify the combination is correct.
    BBD PERFORMANCE
    HIGH PERFORMANCE PARTS
    CUSTOM ENGINE BUILDS
    CUSTOM CAM DESIGNS
    1983 CRIMSON CAT OWNER

  8. #8
    FEP Senior Member dtmilsap's Avatar
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    Quote Originally Posted by Ethyl Cat View Post
    That low of output for me I would be verifying timing. Somewhere in the 18* range base and 36 or so total.

    Slayer carbs come with 72 pri and 82 secondary jets. I calculate 78 square for 7000 rpm so depending on the PVCR size I would think around 72 primary would be close and I would jet down the rear.

    Carb might be a tad small for this application but not the cause of the lack of HP.

    More engine data would be helpful to verify the combination is correct.
    If things go according to plan will have car dyno tuned 12 3 20. The first dyno was on roller, this shop connects to the rear hubs. I am guessing it is more accurate.

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  9. #9
    FEP Power Member Ethyl Cat's Avatar
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    It would be nice to see it make about 30-40 more hp to the tire
    BBD PERFORMANCE
    HIGH PERFORMANCE PARTS
    CUSTOM ENGINE BUILDS
    CUSTOM CAM DESIGNS
    1983 CRIMSON CAT OWNER

  10. #10
    FEP Senior Member dtmilsap's Avatar
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    Quote Originally Posted by Ethyl Cat View Post
    It would be nice to see it make about 30-40 more hp to the tire
    First dyno, no tune, said I was leaving about 50hp because of carb running rich, 10.5 afr around peak hp.

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  11. #11
    Venomous Moderator Hissing Cobra's Avatar
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    Quote Originally Posted by dtmilsap View Post
    First dyno, no tune, said I was leaving about 50hp because of carb running rich, 10.5 afr around peak hp.

    Sent from my SM-G960U using Tapatalk
    What's the rest of your combo and what's your cam spec's?

    Your power level is what 302's make when modded but your torque is a lot higher. I don't think you're gonna see 50 more horsepower by simply re-jetting the carb.
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  12. #12
    FEP Power Member Ethyl Cat's Avatar
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    What Hissing said...

    The only way you are going to make significantly more power is to increase cylinder pressure a bunch. AFR will not do that, that's why I questioned timing and why he/we are asking for cam/engine specs.
    BBD PERFORMANCE
    HIGH PERFORMANCE PARTS
    CUSTOM ENGINE BUILDS
    CUSTOM CAM DESIGNS
    1983 CRIMSON CAT OWNER

  13. #13

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    You sure it's a "Slayer"? I don't see a mechanical secondary 750 "Slayer" available... HR? Q?... regardless of which... 1-3/8" throats and 1-11/16" throttle bores... the jets in QFT "carburetors" aren't usually really the problem (2 #'s bigger each in your case than an equivalent Holley 750 DP)... everything else, calibration-wise, are all sizeable, oil-diluting, cylinders/rings de-oiling, misfire-causing, plug-fouling (mal)functional problems... including "emulsion" gone wild, IFR's (idle feed restrictions) located up high, MAB's (main air bleeds) too big, typically a double whopper dose of idle air:fuel contributed by the secondary idle circuits (which have an effect, when they reverse and flow, on main circuit function too), and transfer slots that are too wide/long...

    They need (in order to FUNCTION correctly and probably generate all kinds more power than you're seeing):
    - a stable, steady, non-fluctuating, consistent air:fuel ratio... whether idling, cruising, or at WOT...
    - much more than a "dyno tune" will normally get you... unless the dyno-tuning technician in 2020 is actually aware (rare) of what these things need...
    - 0.081" (for starters) TSR's (transfer slot restrictions) added to the main body passages for the too wide/long transfer slots...
    - small (though not small enough if necessary (2-corner idle)) secondary constant idle feeds directly below secondary transfer slots blocked, if present and it's "4-corner idle"...
    - IFR's (idle feed restrictions) removed from the supposed superior upper locations...
    - traditional (Holley) down low locations tapped for new threaded IFR inserts... sized according to camshaft (0.031" for stock/mild - up a thou or two with more camshaft)... like the other fellas have asked - what's the combo, specifically the camshaft?...
    - 0.028" kill bleeds, primary only...
    - TWO traditionally (old school Holley) located "emulsion" bleeds per barrel, sized at 0.028"...
    - Regarding ^ , there are usually 3 (or more), sometimes drilled, sometimes threaded inserts... always too big...
    - 0.027" PMAB's (primary main air bleeds)...
    - 0.025" SMAB's (secondary main air bleeds)...
    - 0.070" PIAB's (primary idle air bleeds) for starters...
    - 0.027" (*) SIAB's (secondary idle air bleeds) for starters if "2-corner idle" (idle mixture screws only up front)...
    - (*) 0.070" SIAB's (secondary idle air bleeds) for starters if "4-corner idle" (idle mixture screws front and rear)...
    - ... and after all of the above... #70 primary jets, 0.063" PVCR's (power valve channel restrictions), and #80 secondary jets will be excellent starting points, and probably not far from perfection for WOT...

    Dunno how often/long you've run it, but not a bad idea to change the oil and spark plugs... ask me how I know all these things, lol!
    Best of luck with it
    Last edited by Walking-Tall; 11-25-2020 at 07:07 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  14. #14

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    Some better explanations of my post above...

    TSR's (transfer slot restrictions - primary and secondary):
    10-32x3/16" brass cup point socket set screws, with 0.081" restrictions drilled in them, drilled (#21 tap drill bit) and tapped 10-32 so that set screws sit flush with the body's metering block face, and installed at main body location numbers 8 and 17 shown in the image below...




    Secondary constant idle feeds:
    The image below shows them, at 0.027"... common QFT, too big... 0.022-0.025" better...
    If 2-corner idle, leave them be, or epoxy-block and redrill for smaller size...
    If 4-corner idle, block them...
    Larger discharge holes seen beside them in the image are from a secondary idle mixture screw...




    Idle Feed Restrictions and Booster Air Correction ("emulsion") Bleeds:
    - First image shows common QFT arrangement of these and sizing...
    - Second image that I created should be self-explanatory for IFR's and "emulsion" bleeds locations...
    - Though notice in the 3rd and 4th images of a traditional Holley metering block, that the uppermost bleeds should be at (or very close to) the level of bottom of accelerator pump passage hole in the metering block, and the lower of TWO at ~7/16" below that... all others blocked... and also where threads have been tapped for down-low location of IFR's (6-32x1/8" brass (#36 tap drill)), and where PVCR's are tapped for (8-32x1/8" brass (#29 tap drill)) adjust-ability...










    * Correction to my post above:
    The primary jets best to initially install (with 0.063" PVCR's) are #72's.


    Then fasten your seat belt, as to how an engine and vehicle with a carburetor is supposed to function.
    Thumbs up
    Last edited by Walking-Tall; 11-26-2020 at 12:45 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

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