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How much HP and Torque for Daily Driver

Discussion in 'TBI & EFI Conversions' started by Clayton Clark, Jun 15, 2021.

  1. 82TwoHeadlight

    82TwoHeadlight Junior Member

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    Go get a vortec 350 from the salvage yard for $200. Put a quadrajet intake and long tube headers on it when you swap it into your truck. All accessories and water pump from your current set up will bolt right on. It will he 300-310 horsepower and 400 lbs ft at the flywheel. You'll have more compression, better head flow, and a roller cam. Plus stock driveability. This is cheap, dead reliable, relatively easy, and meets all your requirements.
     
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  2. peats

    peats Full Access Member

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    i know it's like a broken record on my part, but from my experience a 400sbc with an rv type cam ,intake and long tube hedders can't be beat for low end grunt and daily driving. don't expect HP beyond 4,500rpm. this setup is especially suited for heavier 4x4"s with the low cost of a smallblock. your tires and gears are just right for that setup.
     
  3. K5ride

    K5ride Full Access Member

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    I'm going through this right now on my 75 Stepside. The previous owner slapped on 305 heads. The engine seems to run great and has good bottom end torque but it falls on it's face about 1/2 way through the rpm range. I just purchased the Summit Racing vortec heads and Edelbrock vortec intake. I'm hoping for a big improvement.
     
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  4. Octane

    Octane Full Access Member

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    The 305 with the 2 bbl had smaller chamber heads as it had dish pistons.This is the heads we put on 350 to raise compression.The 305 with the 4 bbl had larger chambers and flat top pistons in the engine.Use the wrong heads dont work good.Saturday nite racers use to do these 2 bbl heads for a weekend bump in power.
     
  5. Bextreme04

    Bextreme04 Full Access Member

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    ALL 305 heads will have much smaller chambers than 350 truck heads. They could be anywhere from 52-58cc, but the real issue is the port and valve size. Going from a truck 350 head to ANY stock 305 head will almost always have a huge bump in compression combined with a reduction in flow. If you rework the 305 heads with bigger valves and do some mild bowl blending and porting work, you can get the best of both worlds and have a great runner, but you still need to pay attention to static compression ratio and pick a cam that will pull your dynamic compression ratio down into the pump gas range, otherwise you are going to have a bad day all the way around.
     
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  6. Rusty Nail

    Rusty Nail Victim of Culture

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    It's really not hard to get a pair of #416s to kick major ass for a few bucks...:shrug: lol
    "for the love of god" :cool: but you gotta run 91 octane in my experience, if you want any kind of real timing curve.
     
    Last edited: Jun 22, 2021
  7. cstew47

    cstew47 Member

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    You fail to say what engine you currently have. The TQ and HP are just one part of the equation. What rear gear do you have? What diameter tires? What tranny? Just as a general comment, a 383 is a nice mill with a 4l60 or 700r4 (they are the same). The rear gear ratio will be determined by your tire size. Mine, for example, is 4.56 with 35" tires. My 383 make 400hp and about the same TQ. The K5 is made for TQ not high end RPMS. I kept the cam at about 220 duration and .480 lift. It's very streetable and a stump puller.
     
  8. RecklessWOT

    RecklessWOT Full Access Member

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    In the post that you quoted OP already said he has 3.73 gears and 33x12.5 tires. Under his profile pic it says his truck has a 350 and is a 1985 GMC K1500 (which I have to assume he means K15), so it's a 1/2 ton 4x4. He does not specifically list what transmission he has, but in '85 it is safe to assume it's a 700R4. 3.73s and 33" tires with a 700R4 are a horrible combination even on my mostly stock '87 TBI which came with at least 30 more HP than a stock carbed '85. To get back to the equivalent of stock gearing with that tire size 4.27s would be almost perfect. But that is a harder ratio to find, and if you're gonna swap them might as well go a tad shorter and get some 4.56s. With that super tall OD the 700R4 has it will still cruise nicely on the highway but will have more power around town, the extreme lack of power in 2nd gear will be a little less painful
     
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  9. Rusty Nail

    Rusty Nail Victim of Culture

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    4.56 fixes most problems, I concur. :waytogo: :)

    Dude. Screw them 33s.
    Run ya some 28s like a 275/60/15, swap gears with 4.56 and pimp some 305 heads...that's way more than you'll need to smoke the piss out of most mothers riding truck at the light. Sure as hell old trucks - much less other Squares.

    Yeah it sounds silly but
     
    Last edited: Jun 22, 2021
  10. Octane

    Octane Full Access Member

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    That pump gas didnt cut it with that bump in compression.I remember Barnetts Racing telling me to leave those 305 heads alone.lol
     
  11. Bextreme04

    Bextreme04 Full Access Member

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    I ran the numbers for a stock truck 350 as I measured the one I took apart. The stock truck 350 has a static compression of 7.91:1. Dynamic compression with a comp Magnum 270H grind is an anemic 6.88:1. Switching ONLY the heads to the 305 heads will get you a wild 9.66:1 static and 8.36:1 dynamic compression, which is WAY too hot for pump gas. You would need to go to a very aggressive cam to get the compression ratio down to a reasonable number that will work for pump gas(~8:1 with iron heads). I spent a long time mixing and matching parts and machine work to get what I thought will be a decent runner on my replacement 350. I had the shop mill .020" off the deck and switched to flat top pistons to reduce deck clearance from a measured .038" stock to .015" now. Chevrolet performance .028" compressed thickness head gasket and stock 882 heads with bowl blending and mild port/polish with a summit k1102 cam. I should have 8.81 or a bit less static compression and 8:1 dynamic, which is right at the edge of pump gas with a mild towing cam. If I have issues with detonation I can always go to a sportier cam like the 270H it had in it before that would pull the dynamic compression down near 7.64:1 and give it a lumpier idle.
     
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  12. Octane

    Octane Full Access Member

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    Sounds like you are a man with a plan!
     
  13. cstew47

    cstew47 Member

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    Yeah, I didn't read his post very well. I agree with what you are saying. Too often people only focus on the engine and not the rest of the drive train.
     
  14. bucket

    bucket Super Moderator Staff Member

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    Pump gas can work fine in that 9.0-9.6:1 scenario, but it's application specific. Steeper gearing helps a bunch and a lighter weight vehicle obviously would help too.
     
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