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Scratch the 400, now it's 383, desktop dyno anyone?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Low76K5, Apr 20, 2006.

  1. Low76K5

    Low76K5 Registered Member

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    I went to my mechanic today to put money down on a 400 build. We got nervous about the durability of the stock 400 short block I could afford and decided to go 383.

    Thoughts on this combo? I want an easy driver that will smoke the tires and run 13s.

    4 Bolt 350
    Scat balanced rotating assembly, 5.7 rods/Hyper pistons
    Edelbrock perfomer intake and heads (64/170)
    9.5 Comp
    Crane Z Cam 218/230 459/486 - Rev to 5800ish
    1.5 Roller Rockers
    Stock Q-Jet
    Milodon Water Pump
    Heddmann Headers, 2.5 Duals, Quiet Turbos
    TH 350, built w/ 2200 Stall Sat Night Special, shift kit
    3.07 Gears
    26.7" Tires

    What do you suppose a 76 2WD Blazer weighs and any bets on 1/4 mile times? Anybody out there with a desktop dyno?

    Thanks,
    Scott
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Not much into drag racing, but 13's in a truck with that assembly, I'd have to say probably not going to happen. Especially not with 3.07's. I know there are some here that have better "guesstimates" than I about quarter mile times. You said gears later, get a posi diff at the same time.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    You won't get anywhere near 13's with that engine/convertor/gear combo in that heavy of a vehicle. I ran a 350 with 11:1 compression with a .573" lift solid cam with a TH350/3500 stall and 3.08's in a 66 nova, (lightest production car built) with a 25" tire open rear and had a best of 14.1 @ 99mph. This was shifting at 7800 rpm. I shifted earlier and ran slower yet.
     
  4. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I would think more like 15s you gotta have cubic inches to move cubic pounds and you gotta have cubic dollars to get two other cubic thingys
     
  5. Low76K5

    Low76K5 Registered Member

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    What a negative vibe :). You would make a poor support group. How about "Here's what you can do to hit 13s."

    I had a '67 Firebird with a mild 400 and TH400 with 11" conv, ran fine but felt like a monster after we added 4.11s. That car only hit 13.90 even after gears, with slicks and open exhaust.

    My point being I don't expect 13s without 4.11s (which will be in before I hit the track), but then I think it will be doable. I will have 1/8 mile times in a month or so. So we'll see.

    Scott
     
  6. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    How much money do you want to spend?
     
  7. Low76K5

    Low76K5 Registered Member

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    I pretty much have the plan of my motor, trans, 4.11s, and next year maybe and overdrive unit. I will/have spent anything that seems worthwhile. What is your idea? My 383 is being assembled and it is too late to change direction on it.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    You are pushing probably at least 1000lbs more than your firebird...think about that. (old adage being a tenth per 100lbs, and I'm having to assume a Firebird is down around 3200)

    Stock GM midsize car from the 80's weigh in between 3200-3800lbs (Monte, Regal, Cutlass) and the absolute lowest you are going to get on a full size Blazer in stock trim I'd say is 4500lbs for a 2WD. 4wd, no less than 5000, from experience.

    Not trying to be negative, just realistic. Come back and throw it in our faces when you do it though. :)

    I'd say a mild 454 would do it and still be streetable, but a NA 383 to push a K5 into 13's? Streetable is in the eyes of the beholder I guess.
     
    Last edited: Apr 24, 2006
  9. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Sorry about the vibe bro build it for nitrous and go into the 13s with a 200 shot and the bawls to use it as soon as you get hooked up all the way to the end. There used to be a s-10 we would race against that had a "mild 350" yah right anyway this guy was a genuis getting the truck to hook up he could leave at about 4200 RPM on I think some 31x14.5 drag slick. Anyway my point is you have to look at the whole track if you are getting into the 13s with something that heavy build the motor and then build rear and front suspensions at the same time I would love to see the vid good luck
     
  10. AussieK5

    AussieK5 1/2 ton status

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    To pull 13's you'll need at a minimum 350hp at the back wheel with a trap speed around 100mph. They're perfect world figures and don't account for poor gearing, drag etc

    Good luck
     
  11. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Another thing to remember is that in addition to accelerating the vehicle's mass, these big steel boxes have a terrible drag coefficient, and you (and specifically your engine) willl be fighting that as well. Even without a study of Wong's Theory of Ground Vehicles (an excellent book for any car nut's collection, highly recommended), and hanging numbers on the problem, instinct tells us that wind resistance at higher speeds will be one of the major obstacles in lowering 1/4-mile times in a big box on wheels. In your C6 Vette, for example, the problem is still there, but it's a lot smoother package to push at speed.

    On another note, getting one of these to have a very snappy 0-40 or 0-50 time (for the stoplight gran prix, or win that race to the 2-into-1 merge) is not so hard, especially with the low gearing that is usually already there.
     
  12. Low76K5

    Low76K5 Registered Member

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    I appreciate the input and I will update on the progress/results. I agree 13s are a reach.

    A big block was an option. With all of the swap stuff required the expense went beyond what I thought I should be spending on a toy. I even had a complete BB parts truck lined up, but the 383 fit the budget better.

    In the end the goal is a fun cruiser for me, the wife, and our three kids.

    This whole Blazer thing started out with me looking for anything with room for 5 with rear windows that would roll down. I looked at Fairlanes, a Merc Monterey, a Lemans, and I REALLY wanted a Dart. Then I started thinking maybe a convertible. Then I see a 2WD Blazer in the paper for $1400...I think "removeable 1/2 top, fits 5, looks cool, 2WDs are uncommon, unmolested, good shape, A/C." The rest is recent history.

    Regardless of 1/4 mile this Blazer will be IMHO the BEST family cruiser I could have. Honey, I have fallen love with another, she's in the garage.

    1/8 mile times to follow...
     
  13. moturbopar

    moturbopar 1/2 ton status

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    why not build a 350 with a steel crank forged rods, and turbo it? The turbo would love the 3.07 gears and the auto trans. As for weight and cubic inches, I had a 83 ford turbocoupe 3400lbs with me in it, with a 2.3 4cyl. With a stock short block few mods and alot of tuning, I went 13.2 at 103mph on street tires, and 12.00 at 112mph on a 75shot and slicks. Just imagine what a turbo would do on 350 cid compared to 140!
     
  14. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    My car weighs 3110 with me in it (250) and with a desktop dyno of 428 hp, I run 12.70 @109. 4.11 gears, 2800 stall convertor, and a rpm range of 2500-6500. I can only get a 225/55 tire in the wheelwell (26" tall). They are Firehawks with no slip to them, giving a 1.95 60 ft. time. I'm at 6500 going through the lights, I could use a little bigger tire.
    I suggest you get some idea of what the rig will weigh. Get it to some scales if you can, title weights can be misleading. Build your engine from there.
     
  15. Low76K5

    Low76K5 Registered Member

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    383/700R4 1st day out

    Hi All,

    I went with everything in my orginal buildup except switched to a TCI Streetfighter 700R4, Performer RPM intake, and Flowtech Headers. I took it out last night and was VERY happy with the power. Like my mechanic said-"That motor likes RPMs." With the 3.07s and preloading the tranny I get mostly tirespin with my 295/50s in 1st. It feels like an easy 14 second rig to me right now. It's back in the body shop for a few weeks so I won't get to the track until mid/late June.

    A couple questions

    Flowtech ceramic headers-within 2 hours of driving the shiny finish is replaced with a frosty look on about 1/2 of the surface. Bad headers or normal for ceramic coats?

    Streetfighter 700R4-At full throttle it's great. At low throttle the upshifts and downshifts are unbeleivably harsh, the whole vehicle surges violently. Is this normal?

    Thanks,
    Scott
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Did you break the engine in on manifolds or the headers?

    I know my coated headers (Hedman) stated not to break the engine in with them, I put them on *shortly* after breaking it in and the finish "tarnished" a bit out from the head.
     
    Last edited: May 26, 2006
  17. Low76K5

    Low76K5 Registered Member

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    It was broken in with headers...I just read the sheet that came with them and don't see anything. I thought I had told my builder that I wanted the Hedman's but either I didn't say or he didn't hear it.
    I remember reading the specs in Summit and the Flowtech's were an 18 ga and the Hed's were 14 ga. I am one unhappy dude.
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    God my memory sucks, luckily there are pictures. :)
    [​IMG]

    They "tarnished" further out from the head than closer...this picture clearly shows it...whatever is used to coat the headers is obviously sprayed on, as the overspray on the inside is why they didn't discolor until after that section. The section coated on the inside did not get red hot, but it did after that. I'm a big believer in the internally coated headers, even more so *after* seeing everything past the inner coated spot glowing red.
     
    Last edited: May 26, 2006
  19. Hossbaby50

    Hossbaby50 3/4 ton status

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    Make sure you have a good external cooler and a temp gauge for that 700R4. If you plan on beating on it and having it last you must know what the temp is and keep that temp low.

    If the 700R4 is a performance build then yes harsh shifts are somewhat normal. You want a 700R4 to shift quickly and firmly. It will help keep the slip of the TC down and therefore keep the temps lower. Lower temps = longer life.

    I don't know how heavy the truck it but if there is anything you can strip out that you don't need it will = more speed.

    Harley
     
  20. Low76K5

    Low76K5 Registered Member

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    Thanks D, I feel better because mine look better than that-so far anyway. I expected that shiny finish to last. Should have got the Thorley's.

    Scott
     

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