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Improving 305 Performance

Discussion in 'The Garage' started by prossett, Sep 16, 2006.

  1. prossett

    prossett 1/2 ton status

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    I run a 1983 Jimmy in sand dunes - awesome truck! - but I'd like to get a little more out of my 305 small block.

    I have headers and removed the cat, and I flip my air intake cover to let more air in... but other than that everything is stock, and it runs sweet.

    What can I do to get more power?
     
  2. readymix

    readymix 3/4 ton status

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    change the cam.
     
  3. prossett

    prossett 1/2 ton status

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    Thanks - sounds like a good mod, and cheap (Summit Racing cams start at $50) but what can I expect as a gain?

    I know you can't say exactly, but would you say it's a "Wow!', a 'OK then' or a 'Well, barely felt that'...?
     
  4. rtrotter

    rtrotter Registered Member

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    It depends on the cam setup you get. Some packages are set up for hauling and low-range torque, and some are set up for highway use (better mid-range HP and throttle response). You will normally feel a noticeable difference with throttle response and acceleration, and depending on the cam, up to about a 5% to 8% HP increase on stock heads. Not bad for a $300 cam setup.

    Heads will make a huge difference, but they're pricey.

    BTW, I'm in UAE right now.

    Rob
     
  5. prossett

    prossett 1/2 ton status

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    Really? Come visit our local chapter of 4x4 crazies - Dubai4x4.com, I'm PR there. Not many GMCs, in fact I think I'm the only guy with an old GMC. It sure gets noticed!!! :)

    So the cams I see listed at SummitRacing.com give me a choice of rpm range, duration and lift... I climb amazing long friggin steep dunes, so I reckon I would need the cam designed for high engine screaming - that would be something like this?

    RPM range: 2200-5700
    Duration: 224/234
    Lift: .465/.488

    I don't have a rpm gauge, but basically I floor it and then release a bit, so I've got to be in the 5000rpm range as I start the climb, then it kind of drops until I either stop or make the turn up top.

    The low rpm ones listed start at 1000-3000 rpm, and the highest are 4000-7200 rpm.
     
  6. rtrotter

    rtrotter Registered Member

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    From what I've seen over here with the little pocket cars and luxury cars, I'll bet you stand out! Unfortunately, I'm stuck on the Air Base here, but I'll definately check out your site.

    As for the cam, I've never climbed a sand dune, but I'd imagine you'd need a lot of sustained torque in the low-rpm range, so you would want a cam designed for some serious low-range torque.

    Rob
     
  7. Metrodps

    Metrodps Strange but nice guy Premium Member GMOTM Winner Author

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    hmmm I had a led sled with a 350 4bl that I put a 350 lift with a 292 duration in with roller rockers and a dbl timing chain in and it screamed! I compare a 1974 Chevy impala station wagon to our Blazers. Now if you don't care about mileage ;)
     
  8. obijuan

    obijuan 1/2 ton status GMOTM Winner

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    three words 383
     
  9. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I recomend going for one of Summits packages that gives you a cam, intake, carb, and everything needed to put it together. The best deals and it would greatly improve your power.

    I think the best cams out there are the Lunati Voodoo cams because of the power they make and wide power band they create. But are a little more coin than Summit cams.

    Also think about upgrading your ignition. I have a Pertronix Flame Thrower 50,000 volt coil and ignition module, with a Moroso cap and wires. The throttle responce I got out of was well worth the $$. Also get new spark plugs, stock ones work the best surprisingly.

    Also if you don't want to do a cam you go with 1.6 rocker arms over the 1.5 stock rocker arms. Gives you more lift, gives you more power.
     
  10. 02turbogixxer

    02turbogixxer Registered Member

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    Thats 3 numbers not words. :D
     
  11. broc944

    broc944 1/2 ton status

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    Technically just one number.:doah:
     
  12. prossett

    prossett 1/2 ton status

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    OK, let's settle this so I can work more ponies out of my 305:

    383 can be three or five words if spoken, three digits or one number, and if written on a check it's one word. It can also be interesting to note that it reads the same backwards.

    Now, if we're done with the trivial - a Summit package sounds like a good idea, thanks.

    So, we've got:

    intake manifold + cam and lifters package
    distributor, wires, plugs

    Does anybody know of a complete heads package for 305 similar to http://store.summitracing.com/partdetail.asp?part=EDL%2D2098&N=700+0&autoview=sku Summit told me it wouldn't fit 305 and had no other suggestions, which kind of sucked.

    BTW, here's the dunes I drive: http://www.dubai4x4.com/albums/albuo45/Climb_Resize.jpg

    http://www.dubai4x4.com/albums/albuo45/Along_Resized.jpg

    http://www.dubai4x4.com/albums/albuo45/Turn.jpg

    I know, not the k5's most suitable environment, but my beauty holds its own and often kicks sand up the nose of much younger cars!!
     
  13. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Some answers might presuppose that you are have the average CK5-poster shoestring wallet, which may not be the case. What kind of a budget did you foresee laying out on this power upgrade? Would something like this be do-able for you? This is the same engine at Summit.
     
  14. rtrotter

    rtrotter Registered Member

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  15. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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