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Engine Power

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 77JimmyMan, Feb 25, 2002.

  1. 77JimmyMan

    77JimmyMan Registered Member

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    Ok I got the motor in my 77 Jimmy finally completed, but was disappointed going out for a ride. Its a standard bore 350 with newer casting heads, not vortecs but 350 truck heads from the mid 90's that I ported and polished (it was an interesting experience),. The heads have 64cc chambers vs. the 76cc on the old heads not to mention the larger intake valves, 1.94 now were 1.86? (something smaller atleast). Compression should be up around 9.5:1, was 8.5:1 (as stated in a Motors manual) cause of the smaller chambers (going from 76 to 64cc bumps compression up 1 point as I recall.) The camshaft is the same grind as a Eddlebrock Performer: intake .420, exhaust .442 @.050 with 204 degrees duration (intake). Im running an aluminun intake off of a mid 80's Pontiac Firebird, the GM design is supposed to be better for low end torque, (so Im told) with a Carter 600 cfm carb. The carb adapter plate was also smoothed out and port matched to the intake. Initial ignition timing is set at 8 degrees BTDC. The motor doesnt seem to have any more power than it did before. I was looking for around 300 horse, but it still doesnt seem to have more power than the stock 160 horse. The gearing is all stock and Im running 33's. A guy I know was running 35's with stock gearing and had a GM crate 350 350 horse motor and would leave 20ft strips behind him, Im lucking if I get a chirp. Any pointers or hints or any feedback would be great. Also any ideas on how much power my engine combo should be making, Im still think it should make atleast 300hp. Oh and it has ported exhaust manifolds with dual 2 1/4 mandrel bent pipes going to hooker super comp mufflers. Thanks all. Mark 77 GMC Jimmy
     
  2. shawnboy

    shawnboy 1/2 ton status

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    Hi Mark, I'd check all the usual things like timing, air fuel ratio, vacuum leaks, firing order, plug gap, valve adjustment etc... The gears will kill you with the 33s but I am wondering that with all the porting you did you are not in your power band for making the hp you want. Not enough turbulence to mix the air fuel properly. Just a thought.
    Shawnboy.

    <font color=red>If you are having too much fun it's probably illegal.</font color=red>
    <font color=red>Because I, Am, Canadian!!!</font color=red>
     
  3. ben794X4

    ben794X4 Registered Member

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    I have 33's now on my truck and have an older 350 with 194 heads and the edelbrock performer package cam carb and manifold which is advertised as a huge increase over stock (I also am running higher compression etc) without a noticable increase in the seat. the only real way to more power in a 4x4 is a big block built for bottom end torque. Also swapping gears can also give big results but is also time consuming and expensive just my .02

    79 4x4 k5 stock
    3spd granny stock 350
    12 bolt open rear
    10 bolt open front
    Subvert the accepted paradigm.
     
  4. smartpatrol

    smartpatrol Registered Member

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    I agree i have been told that nothing makes up for pure cubic inches. Thats why i went with a Cadillac 500 for my blazer. Even a stock caddy is at least 400hp. i picked one up at the junk yard out of a 75 cadillac for $125 all i am doing to it is having it bored .030 over new pistons etc.. adding a edelbrock perfomer intake mainfold, crane cam and block hugger headers. Slap on a q jet, a custom flywheel , bell housing adapter plate from www.cad500parts.com and a new exhaust and bingo! more torque that my tranfer case can handle..anyone selling a NP205 in colorado? Cheap?

    I thought my Computer hobby was expensive......
     
  5. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    I had 33"s on my truck and 3.73 gears.. ran nice.. nice highway gear and could spin the tires easilly... but with 4.56's I could light them up so much easier.. also took a mustang 5.0 off the line for about 10' till he whoooped me...
    :)
    my .02

    <a target="_blank" href=http://community.webshots.com/user/rootbreaker>Pics of buildup</a>78 Chevy 3/4 - 14" on 40"x17x16.5 Ground Hawgs
     
  6. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    oh yeah...
    also did they ever make a 350 with less than 200hp?
    I just picked up a 1991 caprice 9C1 police 350 for $500 and is a estimated 260+hp and 300 ft. lb of torque... nothing special just hydrollic roller cam/lifter setup but a vortec block. I hear going to vortec heads... which can be had on ebay for $300 can add 20-40hp... so it says in Jegs which they are about $300 each there....
    Figure out the hp for what each extra component that you are looking to do then you know you have that as a minimum... example....
    Vortec heads =&gt;30hp (play it safe)
    Headers =&gt;15hp ($200 In Jegs)
    Intake =&gt;10hp (Jegs)
    New Q-jet 850 =&gt;5hp ( hope something )
    Flowmasters =&gt;25hp (Jegs dual flowmasters)
    ___________________________________________
    so 85+/- hp in extras on your 160hp motor is roughly 245hp
    as on mine is 345hp +/- and not including the cam I will change to... so it is all in the extra parts.....
    my .01 ( gave you my other .02.... )
    Hope I helped somewhat....
    :)

    <a target="_blank" href=http://community.webshots.com/user/rootbreaker>Pics of buildup</a>78 Chevy 3/4 - 14" on 40"x17x16.5 Ground Hawgs
     
  7. Nrose07

    Nrose07 1/2 ton status

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    Well I'm going to say timing will wake it up to where it should be. You kept your cam conservative, which is good but I'd think more like mid to high 20's advanced would be better. Just keep advancing till it pings then back off a few degrees. Never heard a thing about that intake, which dosen't add alot of confidence. Hope that helps, and spending the money to have a good mechanic tune it would be good if your not comfortable with it.

    Displacement, cubes, and did you say you drive a riceburner???
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm going to say its your rear axle gears. I mean the whole combination is going to be improtant, but "stock '77 gears" to me means either 2.73 or 3.08 (not the optional gears) and even with 27" tires and a 350, 2.73's are not going to give you a lot of power.

    FWIW, I had 2.56 gears (posi) in a 3800lb car, and a 415cubic inch motor, with about 350+ ft lbs of torque. Relatively conservative cam, single exhaust. That thing wouldn't spin the tires at all. I guarantee you that with better gearing, and better exhuast, I would have had no problem spinning them, and acceleration would have been much greater.

    Find out what your axle ratio is first, then go from there.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     

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