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383 choices?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Apr 3, 2002.

  1. Sparky

    Sparky 1/2 ton status

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    I have decided to build a 383 starting in a couple of months, but I need help deciding what to use. Here is what I know so far... I will be using a 96 350 block and getting it machined then throwing a set of vortec heads on top of it. I want to run around 9.1:1 compression so that I can still get by on 87 if I have to. My goal is over 300 hp. and over 400lb*ft. My questions are...

    1.What crank setup should I use and what are the advantages and disadvantages of the various options? I know you can use a 400 crank and get the block/bearing caps machined to work or you can by a crank with the same stroke as the 400 made to fit the 350. Which way do you recomend? Should I get a forged crank or will i be able to get by on a cast crank for that kind of power? (I want to get 100,000+ miles out of it)

    2. What kind of rods should I use? Again, forged or cast? What length rod works best and why? What length rods require the block to be clearenced?

    3. What pistons should I use? Its obviously dependent on which rods I choose right?

    Just some things to keep in mind to help you help me. The block is a 4 bolt main from 96 or 97, the heads will be purchased new (vortec) and complete, i will probably use the biggest cam I can find that is under .5 inch lift w/ the shortest duration and it will have hydraulic roller lifters. This right here is basicly what I want to build, but without the price tag http://www.sdpc2000.com/cart.asp?action=prod_detail&catid=120&pid=465 I already have the block wich allows me to build my 383 and still drive my truck. It will be in my daily driver that i like to use on trails, rocks, hill climbs, and sometimes some mud or towing. For the mean time it will have a edelbrock performer intake and a q-jet, but fuel injection is not out of the picture in the future.

    I know this is kind of alot to ask so feel free to answer any or all of my questions or reffer me to a good online article or something. Thanks

    Sparky
     
  2. Swanson52

    Swanson52 1/2 ton status

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    SCAT makes a cast steel crank with a 3.75 stroke that has the correct journal size to fit a 350 for around 230 bucks. Eagle also makes the same crank that sells through Jegs for 240 bucks. Eagle also makes a rotating assembly with their cast steel crank, new I beam rods, pistons, etc. for around 800 bills. A complete rotating assembly from a reputable manufacturer is the best way to go. They are (generally) already balanced and matched components, and it's usually cheaper than piecing the parts together yourself. Cast steel is strong and affordable for crank and rods. Hypereutectic pistons can take some abuse and are durable for lots of miles, and try to get this combo with a 5.7 rod. If you are pinched for cash, you can use a 400 crank and rods with stock (pin height) 350 pistions, but it's not the most desireable way to go in terms of rod/stroke ratio. Hope I helped you out.
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    From what I hear, Vortec heads are only good to about .480" lift with stock springs.

    If 300 HP and 400 lb ft are your goals, you can do that with a 350. I bet you'll make even more than that with a well-built 383.

    I think you will find that the Vortecs are not as good of a value as the look like they are. $400 heads, $200 intake, special rocker arms, ($200) plus they'll need some porting to make optimum power on the top end with the additional cubes/stroke of the 383, possibly valve springs, centerbolt valve covers, etc.

    I'm not saying that the Vortecs aren't a great set of heads, I'm simply saying that it might end up cheaper to use a regular set of aftermarket SBC heads for your truck. World Products, Dart, and even a set of aluminum heads such as Edelbrock or Trick Flow come to mind. The Darts or World Products heads can be had for $800-1000 for an assembled pair that will already have the valve springs you want in them. Also, Vortecs come in 64 cc only, so you may find it more difficult to get the compression ratio you want. This makes other heads look even better.

    That said, Vortecs are great heads, but sometimes other heads are a better value when you look at it that way.

    1. Cast crank is fine, use one made for a 383. Get your rotating assembly balanced!!!

    2. Forged rods are not necessary. Use a good set of connecting rods and ARP bolts. You're not turning extreme RPM in a truck so you don't need overly expensive connecting rods. I'd use 6" rods if you can fit them in your budget. Since you've got a roller motor, I can't see why you'd cut corners there. I would not use 5.565" rods under any circumstances, but you can choose to use 5.7" rods if you can't find the pistons you want in a 6" size or they're out of your budget. Longer rods are generally thought to be desireable as the piston will spend more time at TDC (giving the mixture more time to burn) and will give you a better rod/stroke ratio, which will keep the block from tapering so much (my dream motor is a 400 SBC and the 5.565" rod is rough on cylinders so it's hard to find a good block).

    3. Cast pistons are fine. I would NOT use forged as you don't need them and they've been known to make noise on cold start up and they require more piston to wall clearance.

    I'd suggest a Performer RPM intake over a Performer. I don't think you'll lose any torque with it, and you've got quite a bit more motor to feed than the 350 that the Edelbrock packages are basically designed for.

    Camshaft choice will ultimately depend on your gears, tire size, how much towing you're going to do, transmission, cruise RPM, etc. I'd say 210-220* duration @ .050" is what you're going to be looking at, but hold off on that decision until you select everything else.

    Also, when you send the block to the machine shop, I recommend you get it, "Zero decked". That way, you can use a .041" composite head gasket and still say within your optimum quench distance of .041-.045". Quench is very important. Keep that distance as a given and use head combustion chamber size and piston dish to get your compression ratio. Don't use a thicker head gasket. A properly quenched motor is less likely to detonate, even if it does have a higher compression ratio.
     
  4. shaggyk5

    shaggyk5 1/2 ton status

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    im going with the eagle kit from jegsfor my 383 this summer, it runs $899. looks to be a good solid bottom end.
     
  5. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

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    dont fool with the vortec heads !! as in dont get them ported or anything itll mess em up , they are good like they are.
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Hey Tim, I agree with you on everything you have said except that it is not a good idea to use a 6" rod on a 383 that is a street version because it puts the piston pin into the oil ring. Also I would say to buy a set of AFR 180cc heads they are better than the vortecs.
     
  7. m j

    m j 1/2 ton status

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    isnt a 96 one piece rear seal?
    this limits stroker crank options to aftermarket IIRC
     
  8. TX Mudder

    TX Mudder 1/2 ton status

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    TO elaborate a little more on your piston choice, remember that all piston even with the same specs (say, dished -12cc) ae not the same design. Since running on 87 is important to you, you will be considering quench and also you need to make sure the piston top has a flat portion on one side of the top and the dished area is just a continuation of the combustion chamber.
    Some pistons have little bumps over the quench area to further create turbulence.
    MJy plans for a 383 include the Vortecs and with a 64cc chamber, you really need to think about CR and quench.
    Thee are other forums (mayvbe a Corvette/Camaro board) where there are lots more engine guys.
    -- Mike
     
  9. Sparky

    Sparky 1/2 ton status

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    Thanks for all the information everyone. I appreciate all the responses. It sounds like I will save some money by buying cast parts and the entire rotating assembly instead of buying piece by piece forged stuff. Maybe i will use some of that money on a different set of heads, but i was really stuck on the vortecs. They are cheap, and make alot of power for the money, but the valve spring thing worries me a bit. I thought they were supposed to be good up to .5 in. lift of the cam. As far as the center bolt valve covers go, i already have some so thats not a problem, and i will have to buy a new intake no matter what heads I get. Right now i guess i am leaning toward the vortec heads with some good valve springs or something.

    Sparky
     
  10. MudFrog

    MudFrog 1/2 ton status

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    Check out speedomotive if you want to get a kit. They have everything from budget kits to the high dollar kits. http://www.speedomotive.com/
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    That's a matter of choice. Either 5.7 or 6" are both good...just don't use 5.565. I said I'd leave it up to piston choice and budget.

    I would not use Vortec heads on a 383, especially unported. They just don't flow enough. They were designed for a 350.

    As for not porting the Vortecs, without it, they're no good for a 383. A Vortec 350's HP peaks at 4500 RPM. To make max HP on your 383 build, I'd say you're going to want the HP peak in the 5000-5500 range. And since it's a bigger engine, you're going to need more flow.

    Don't mess with the ports in the Vortecs, but some pocket porting has been proven to add quite a bit of flow/HP.

    Vortecs look like a great deal, but they're really not the best value in my opinion.
     
  12. m j

    m j 1/2 ton status

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    the 5.56 were good enough for chev
    I would run them without question, bonus is then you can use 350 off the shelf pistons IIRC
    though i think aftermarket cranks are set up for the longer rods
    why would you want peak HP at 5000 for a heavy 4x4?
    if you arent running a really high stall auto it will be a dead dog.
    build for torque
     
  13. NorthernRedNeck

    NorthernRedNeck Registered Member

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    the vortecs are a good value...but seriously consider scrougin bone-yards for a set just so u can get them complete with the rockers and valve covers, i forget what issue or which magazine even lol(i think it mitta been CHP in the past year or so), but in all they did was a 5 angle valve job on the stock valves and the flow increase was really impressive-all of which alleviates alot of the "hidden costs". The lift is a concern but all depends on your cam choice-measusre twice and cut once, right? E-bay is stocked full of these heads all across the U.S. so shippin might not even b a big deal dependin on your time-frame.
     
  14. NorthernRedNeck

    NorthernRedNeck Registered Member

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    oh yeah...as far as yer r/s angle i do understand it, but have never really seen a definitive test to back up the expense especially if u don't plan on spinnin it to the moon which i m assumin torque is yer goal in a nearly 6000lb truck, although there is a trick for usin the late 80's carprice rods outta the tiny V-8 that gives u a 5.9 rod length with the already correct journal diameter- just more food for thought!!!
     
  15. NorthernRedNeck

    NorthernRedNeck Registered Member

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    hmmm..wunder if i have opened Pandoras box up here lol
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    As long as you aren't going to be turning extreme RPM's, I agree with most things being cast. Seriously look into hypereutectic pistons though...if you aren't beating the motor hard enough to break cast, you won't have a problem with the hyper's either. Dirt cheap at around $100/set for Speed Pro .030 over 350 pistons. Not only do they have less expansion/contraction than cast or forged, they weigh less...at least thats what I remember anyways.

    As to Vortec heads, its not all in the flow. Flow is a major part of head design and operation, but you must not, and can't, neglect the improvements in combustion chamber design. Since no one suggested older stock heads, thats not going to be much of an issue, but it is something to alwaysd consider.

    When "desigining" my motor, I was torn on two things really, Aluminum heads (weight reduction, less prone to detonation) and the fact that the "complete" Vortec heads have pressed in studs. I got a killer deal on the Vortecs complete though, so my mind was made up for me.

    Again, think of how you are going to be using it, and what RPM's it's going to see. I'd almost guarantee you that running a .480 lift cam (yes, thats what a guy is running his stock vortecs at) and mud-bogging your truck will result in broken or pulled studs. BUT, if like me, you realize that all of your power is going to be made at the low end anyways, press in studs really aren't going to be an issue.

    With my motor combo (roller 204/214 .429/.452, 350 .030 over, TPI, Vortec heads and "high performance manifolds) I will be turning out (according to desktop dyno 2k) 276hp@4000 RPM, and 422ftlbs@2000RPM. That exact combo, but with 383CID, the numbers are 280hp@4000, and 460ftlbs@2000.

    I think with a slightly "better" cam, and some headers, (which an engine that size NEEDS IMO, above 383 combo works out to 311HP and 495 ft lbs with small tube headers)

    I don't think the Vortec Q-jet intake is a real cost consideration..you'd pay $150 or so for a Performer Q-jet, and maybe $180 for the same, but Vortec. You'd still end up buying a manifold one way or the other, right? : )

    Don't forget full roller rockers, thats another "free" (ok, the comp steel full roller rail rockers run about $250) shot of power, to the tune of 15HP.
     
  17. Swanson52

    Swanson52 1/2 ton status

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    Good heads that I have personally used on a 383 are the World Products SR/Torquer heads. They flow well, are available with 67cc (I think) and 76cc combustion chamber sizes, and are relatively cheap at (agian, I think) around 800 bucks a pair complete. Good heads and a good value.
     
  18. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Yeah, they were so good that I can't seem to find a good enough 400 block to build. I haven't found a decent-priced standard bore block yet.

    5000 RPM is not a high HP peak. A 383 is going to make an insane amount of low-end torque compared to a 350 anyway--the added top end HP is just a bonus. For your information, that is building for torque. If you were building for HP, the peak would be more like 6000-6500. 5000 is not high RPM by any means.

    A stock Vortec 350 peaks HP @ 4500 and torque @ 3000. How much lower do you want it?

    Stall has nothing to do with HP peak. It has a lot to do with torque peak, but absolutely nothing to do with HP peak.
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

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    He's running a roller cam, keep that in mind.

    Add an RPM intake, a 210-220* @ .050" hydraulic roller cam, and try...let's say Dart 180cc heads and see what you come up with. You can't use "small tube" (I consider 1 1/2" small) headers on a 383, this is not a 350. Use 1 5/8" primary headers and see what that brings you to. Your combo is good, but I'm sure you can squeeze even more power out of it on the top end without sacrificing your torque at 2000 RPM.
     
  20. CaptCrunch

    CaptCrunch 1/2 ton status

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    I have to agree with dyeager here on most of the issues. I mean for 400 bucks there isn't head that will flow as well at low rpms. I also think that dorian is right when he talks about the other benefits of the compression chamber design. You seem to be able to get an extra 1/2 point of compression compared to the old camel humps, but alot has to do with cam selection. Tim is right that the costs of vortechs can add up, but they are an awsome head to say the least and only real down sides for a torque application is the egr hassles, and an extra hundred or so for the intake.

    Do take a gander at what tim said. The SR torquers are a great torque head!!! Personally for torque I wouldn't bother with big buck heads. They aren't worth the money unless you want HP up high whcih 75% of the population thinks they need, but never use. I personally had a 355 with these heads (10.5 compression with hyper. pistons, a roller cam, tweaked 650 Holley, and a Holley intake, heads had a 3 angle valve job and a pretty nice pocket job done) and pulled over 440 ft-lbs of torque THROUGH 4,000 rpm. HP was about 350 at 4,500 or 5,000 rpm. Dropped it in my street cruiser firebird and suddenly saw BF Drag radials disappear! I was really shocked as this motor was a cheap buildup (I actually got the SR's for 100 bucks from a local guy in Philly who upgraded and whole motor cost less then a grand if you take away the roller conversion) and I never expected that kinda torque down low. I want to say this was a 250 or 252 comp cams cam for this setup, but can't remember for sure. Then I switched the cam to a wilder Crower model and a 750 Holley which dropped my torque to a much better street tire range... went pretty aggressive 270-ish range... nasty idle and had a lot of go up to 6grand but the heads kinda died after that, but of course I never really did take it over that with just an arp studed bottom end. But take a look at the the first set of numbers... that is offical at the flywheel numbers on the dyno.
     

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