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383 Piston options

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SnackPack, Jul 24, 2005.

  1. SnackPack

    SnackPack 1/2 ton status

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    Hey guys, This is my first post. I bought a 1987 K5 (TBI 350) a few months ago, and it spun a rod bearing shortly after purchase. I've removed the block and sent it to the machinist. I asked the machinist to do the block modifications for a stroker, so I guess all I need now is the right rotating assembly setup. I'm no expert on the issue, and this is a low-budget project.

    My plan is to get the bottom end rebuilt as a stroker, and leave some of the top end modifications for later, since they don't require removal of the engine. For this reason, I'll probably go with some stock heads with my TBI for now. This is where my question comes in. What kind of pistons (flat top, dished, or a good target compression) should I get that will work well with a stock cylinder head, but leave room for upgrading those and keeping good compression. I'm not big on having to run premium gas, so I guess keeping a low compression is what I need (correct me if I'm wrong?).

    Also related, what would be a good cheap cylinder head solution other than using stock heads?

    Thanks for your help!

    SnackPack
     
  2. ryan22re

    ryan22re 1/2 ton status

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    if you don't mind spending $400 for an intake, vortec heads would be the best bet. best place to find a used set is a gm dealer. find one that sells alot of engines. the 96-99 vortec 5.7's only have a $100 core on them. with tax, i got a set of vortec heads for $105. if you go with a cam less than .420 lift, you can bolt them on with no mods (cept for the intake).

    ryan
     
  3. ryan22re

    ryan22re 1/2 ton status

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    when i say $400 for the intake, i mean that if you buy a tbi intake from gm. keith black sells a set of hyperutectic (spelling?) pistons that will yeild 9.7:1 with 64 cc vortec heads and .030 over and a 3.75 inch crank. and sell for ~$250 from summit. pick the right cam and you will run on 91-93 octane all day long (provided either a carb or aftermarket fuel injection).

    ryan
     
  4. SnackPack

    SnackPack 1/2 ton status

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    Do you know what the compression of those hyperuetectic pistons on stock heads if I must go that route? I do like the vortec option, but how much would I have to change with that intake and heads? Can I keep my TBI and existing wiring?

    I just don't want the cost of this to spiral up before I can even get it running again. I also need to bolt up a new dual exhaust and headers, so after the bottom end is built, I'd like the cheapest route back to the road.

    I'll be sure to looks for some prices on the vortec stuff. Is there any particular year or model of vortec heads I should be looking for?
     
  5. ryan22re

    ryan22re 1/2 ton status

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    the pistons that would yeild 9.7:1 with 64cc vortec heads would be about 8.7:1 with your stock heads (assuming a 76cc stock head). they have an
    18 cc dish with a 5.7 inch rod (stock length).

    to keep the tbi you would probably need to go to an aftermarket prom. turbo city sells a kit that would work with the vortec heads and whatever cam you would want to run. the kit sells four around $1000 plus you would need to buy a tbi vortec intake, which i think scoggin-dickey sells for around $400. so you are looking at $1400 plus the vortec heads (and a set of vortec gaskets ~$40). or you could buy a carb vortec intake and a tbi to 4bbl adapter, or you could convert to carb. not a cheap undertaking anyway you slice it.

    i have an 87 and i plan on the 383, vortec heads, and convert to carb.

    ryan
     
  6. ryan22re

    ryan22re 1/2 ton status

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    dont know the casting #'s but there are certain vortec heads to avoid. something about the 2500 or 3500 trucks having a restictive boss cast into the intake port. be safe and try to find a 1500 series core (shouldnt be hard)

    also, would be nice to convert to a hydraulic roller since you already have the provisions for it, just need the cam, lifters, lifter retainers.

    ryan
     
  7. SnackPack

    SnackPack 1/2 ton status

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    Definitely sounds like the vortec is not an option at this time. I just ordered the rotating assembly with some speed pro dish pistons and 5.7" rods. This stuff and the machinsts bill will leave me with not much cash until I can build the top end anyway.

    How does a 4bbl => TBI converter work? Is there anything else needed besides the intake and converter?
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you try running 9.7:1 compression with iron heads you won't be running pump gas anymore unless you run a large cam but that opens up another can of worms for you.
     
  9. ryan22re

    ryan22re 1/2 ton status

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    since the vortec head is a copy of the LT1 head design (minus the goofy cooling jackets), and the iron head LT1s in the caprices and roadmasters had 10.4:1 with only a .414/.428 inch lift cam, i dont see any problem running 9.7:1 with vortec heads and a decent cam.

    Chevy High Performance buit a 10:1 vortec motor that ran on 93 no problem.

    ryan
     
  10. ryan22re

    ryan22re 1/2 ton status

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    howell (www.howell-efi.com) makes a nice 4bbl intake to tbi adapter. works about the same way as a 4bbl to 2bbl adapter.

    ryan
     
  11. ryan22re

    ryan22re 1/2 ton status

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    oh and the 96-99 vortec trucks have 9.4:1 compression

    ryan
     
  12. SnackPack

    SnackPack 1/2 ton status

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    I checked out those 4bbl -> TBI adapters... about $50. After the 4bbl intake, vortec heads and a decent cam, this adapter is all I would need? If so, that rocks. I may just go that route. Just making sure here since I don't want to buy a vortec 4bbl intake and find out that something the TBI needs won't hook up to it.

    Thanks for your info, man!
     
  13. Thunder

    Thunder 3/4 ton status

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    You are also in for some chip work. The combo you are building will never run right or reach its potential on a stock chip. It may even self desruct depending on the cam. Also(clicky) bigger TBI and injectors (68 lb hr would be nice) and adjustable fuel pressure regulator should be on your list of things to get.
    Your can of worms is officially opend. :D

    Just a little advise. Dont just go slapping parts together on a TBI engine and expect it to run right. Your best course beings you have a stroker bottom end now. Is to call a chip burner and find out what works with what. He will recomend cam, compression ratio, and heads ,that work with chips that they already have programs for. The chip is the brain of your engine. Build you engine around its brain.
    get a hold of http://www.cfm-tech.com/index.htm They have chips for stroker small blocks Vortech heads ECT. They will help you out.

    Might check with http://www.affordable-fuel-injection.com/ They burn chips and are very reasonable.
    He is a vendor here on CK5 and gives a 10% discount to members. They do very good work.
     
    Last edited: Jul 26, 2005
  14. gonecheenin

    gonecheenin 1/2 ton status

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    if your just looking to build torque for towing, could you simply do a stroker bottom end and burn a new prom for the TBI and have it run correctly?

    I don't see it would be nessecary to change the cam, heads, and ETC...

    Maybe upgrade to larger injectors, but you would think the prom could handle increasing the fuel considering that you change nothing but the cylinder volume

    But i've been wrong before, thats why i'm asking
     

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