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81 K5 Blazer Engine specificaitons

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TD85, Apr 13, 2003.

  1. TD85

    TD85 Registered Member

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    Just purchased a 81 K5 Blazer. Love it, looks as good as any chevy truck ever made in my mind. However, the 1st thing I notice is that is is definitely underpowered. It has the 5.7 litre motor in it, however I see in the specifications section on this site that is a 165 HP motor.

    Thus, so that I can begin my engine modifications, I would like to know some more in-depth specificaitons such as the:

    Camshaft Lift, duration at .050" Is the cam a hyd flat tappet or hyd roller ?

    What are the specifcations on the heads: Intake runner volume, chamber size, valve size. Are there any decent gains with a little head porting with these heads or is it just smarter to go with a low dollar set of WP SR torque heads ?

    It looks like the 165 HP occurs at a low 3700 rpm.... what is the torque peak and where does it fall in the rpm range ?

    I would like to increase HP up to the 225-250 HP level However with 330-350 ftlbs off torque off idle. What aftermarket intake manifold do you recommend for this. I would also like to keep this motor below a 5000 rpm HP peak and would like to see the torque peak right around 3000 rpm.

    This vehicle will see some lightduty offroading, but will more primarily be a tow vehicle for a 3000 lb car.

    Are there any budget build-up personal webpages I can have a look at ?

    Thanks for any input. /forums/images/graemlins/smile.gif

    Todd
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    A good cam and better breathing really wakes those 350's up. I swapped in a Comp Cams 260HE in my old 350 and was really pleased with the gains. I added headers, and Edlebrock 600cfm carb too. It was quite torquey.

    If I had to do it again I'd probably use one of the newer Comp Cams Extreme Energy cams. They are a dual pattern cam which helps when running stock heads.

    Rene
     
  3. Blue85

    Blue85 Troll Premium Member

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    The stock 350's are pretty wheezy. Some were only 8:1 compression. I think these things were designed to run on 80 octane gas for 1 billion miles with low maintainance. They are reliable powerplants, but in stock form most of their potential is untapped.

    I know there is great variation in the heads over the years and even within each year. You'll probably want to get the casting # of the heads and the block. Then there are some good links in the "links" thread.

    Unless the compression is unusually low, you should be able to get the power you're talking about with cam, intake manifold and headers. You can also get like 20lbs of free torque by changing to lighter springs in the distributor for like $15. Some of the Quadrajets don't open all the way on the secondaries, so a little time with a grinder (remove gas first, of course) might net a few free ponies. The air intake is another place to look for some power. The tall version of the air cleaners flow pretty good, especially when that charcoal ring thing is removed (more free power). You should look at the exhaust because that is probably a bottleneck, too.

    Keep in mind that your goal is not to get big HP, but big torque, so make sure the intake and cam are off-idle to 5000 types and not race-car types, that the headers are good for torque, etc.
     
  4. TD85

    TD85 Registered Member

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    Blue & Renee,

    Thanks for the feedback.... will try to do a little additional research to determine the details of what I currently have.

    thanks,
    Todd
     

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