Dyno Results Are In! 1971 All Iron 350

Discussion in 'Small Block Tech' started by MrSony, Jun 26, 2020.

  1. MrSony

    MrSony Well-Known Member


    1971 2 Barrel 350, apparently only 63,000 miles. Car it was from looked pretty nice, so it's believable.

    Stock Bore

    3.0/181 v6 pistons, about .094 in the hole, .042 head gasket. I believe it's about 9.6:1.

    stock rods, reconditioned

    stock crank, .010/.010

    .002 clearances on the dot

    Underdog 350 timing cover, still doing great

    stock heads, surfaced/valve job

    TA DP intake

    EverydayPerformance 17057241 800cfm Qjet, further tweaked by me.

    Hooker 1103hkr headers

    TA HEI, 34* all in by 2700rpm

    TA 310 cam

    2.5" dual exhaust, straight out the back, no mufflers.

    Relatively mild build.

    Made 247hp/274ftlbs to the tire on a mustang dyno. That's within 3hp and 1ftlb of my personal guess, so I'm pretty content with that. This was mainly just a curiosity run, wasn't chasing any particular number.

    Secondaries were opening pretty late, according to the dyno guy as he was standing there watching the carb they didn't open fully until 4300rpm. And I can tell they need to open sooner as well, given the gasoline stains on the air doors. I believe that is the cause for the sharp dip in AFR reading (purple line) that the graph shows.
    dyno2.jpg dyno1.jpg
    Last edited: Jun 26, 2020
    patwhac, Mark Demko, Houmark and 4 others like this.
  2. MrSony

    MrSony Well-Known Member

    And, for comparison, my previous engine (rip) was a very high mileage 3x reringed '70 SP 350 that was bone stock at the time of it's dyno run besides a crower level 3 cam, .042 head gaskets, and that same TA HEI but only 30* of timing, factory intake, manifolds, terrible exhaust with chambered mufflers, etc.

    That combo made 211hp@5003rpm and 263ftlbs@2700rpm.
    patwhac likes this.
  3. johnriv67

    johnriv67 Well-Known Member

    This is very interesting to see. Thank you!
  4. alec296

    alec296 i need another buick

    Imagine what big valves would do. And figure static loss thru drivetrain. Of 30-40 hp . So easy 280-290 hp.
  5. MrSony

    MrSony Well-Known Member

    Video from the test:

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  6. knucklebusted

    knucklebusted Well-Known Member

    Aren't dyno plots supposed to cross HP and torque at 5250? Why is this one crossing at 4600?
  7. Mart

    Mart Gold level member

    I'd take the dyno money and put it into go fast parts.....:D
    Mark Demko likes this.
  8. MrSony

    MrSony Well-Known Member

    I think its all 3 variables layered on an incorrect scale, or a glitch. i dont really know. the last run i did 2 years ago the graph was normal.
  9. Reidk

    Reidk Well-Known Member

    I see iowa plates on the car. Wheres the dyno located?
    MrSony likes this.
  10. MrSony

    MrSony Well-Known Member

    Midstate machine. East side of dsm. In between the fairgrounds and firestone plant. That general area.
    Reidk likes this.
  11. MrSony

    MrSony Well-Known Member

    I can confirm this combo is faster than a 2020ish v6 challenger. :D
    I'd post the video but itd be considered exhibit A.
    patwhac likes this.
  12. Reidk

    Reidk Well-Known Member

    Sweet man I know the area pretty well. My wife's from des Moines. What's it cost to use it?
  13. MrSony

    MrSony Well-Known Member

    80 for a one and done but both times I went they Tbh were just curious because it's a sbb so they did a few. Normally its $100 plus more per hour if actually dping some tuning
    I can confirm that a single snorkel air cleaner made less than 3hp in difference in power vs no air cleaner.
    Last edited: Feb 25, 2021
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  14. Waterboy

    Waterboy Mullet Mafia since 6/20

    Very cool!!!
    MrSony likes this.
  15. MrSony

    MrSony Well-Known Member

    Reviving this old thread.

    Put more timing in it for 36 total, leaned out and loosened the secondaries, added some thrush welded chambered mufflers.

    Made 217hp/250ftlbs. Loss of 30hp and 24 ftlbs from last time.

    Pics are overlays from last time plus this time and the second is just the most recent one by itself.
    20240410_134513.jpg 20240410_134543.jpg
    Last edited: Apr 10, 2024
  16. Fox's Den

    Fox's Den 355Xrs

    Go back to 34* timing then
    Mart likes this.
  17. Stevem

    Stevem Well-Known Member

    Referring back to the dyno power graph in your post from 2020, that dip in the torque band at around 4000, I have seen that many times before.

    It's caused by the valve springs loosing control of not only the valvetrain, but themselves also.
    During times in the rpm band where such takes neither end of the valve spring is in contact with anything!

    While the additional timing may be responsible for some of your drop in power your Exh system is having a effect also.
    Dano and Mart like this.
  18. Mark Demko

    Mark Demko Well-Known Member

    WOW .094 in the hole?
    If you believe it “about” 9.6 to 1 its probably “about” 8 to 1
    There nearly bottom of the bore:confused:
    Did you do any calculations using the flat top pistons?
    What is your rear gear in your Regal?

    Or track time.
  19. MrSony

    MrSony Well-Known Member

    3.42 gears, 2500 Hughes off the shelf converter. Every compression calculator I use puts me about 9.2-9.5:1. I'm using the flat top 3.0 pistons.
  20. MrSony

    MrSony Well-Known Member

    My quickest run in the local 1/8th mile was 9.3. I'll dig out the time slips later today.
    Mark Demko likes this.

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