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anyone build a 383 stroker w/ 6 inch rods?

Discussion in 'The Garage' started by WantedaDodge, Jan 29, 2007.

  1. WantedaDodge

    WantedaDodge 1/2 ton status

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    So, I think my next project will be rebuilding the motor in my K5 next winter.

    I'm only wanting around 300-350 HP, but I am a fan of long rods. Small block chryslers all had 6.123 inch rods, why can't my Chevy? I was thinking some Eagle I beams.

    The only problem I have is I can't find a good low compression piston for this set up. I want 9:1 CR MAX! I want to be able to run 87 octane with out blowing it up(this is kind of an expedition truck, and lots of destinations only have the low octane stuff.

    I have some mid '70s heads laying around, I was thinking 1.94/1.60s, a good dual plane, a comp XE262 cam, a Holley Street Avenger 670(got one that is almost brand new and a set of headers.

    What do you all think?

    a 6 inch rod should rever better and wear better as well.
     
  2. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Out of the several motors I have built every single one of them had some type of custom piston in them. Its been a while but it didn't seem like that much more. Also a 6" rod doesn't leave alot of room for a dish. The piston is very short
     
  3. kontradictions

    kontradictions 1/2 ton status

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    do it.

    go Carrillo...but im alittle one sided about connecting rods, considering i work for Carrillo! :D
     
  4. sled_dog

    sled_dog 1 ton status

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    Well, the advantage to rod length is RPM(rod to stroke ratio). 6" rod in a 383 is completely doable, but the question has to be asked, why use factory SBC heads on that engine? Power is found in heads. You could EASILY build a 383 to make the power you want with 5.7" rods and save yourself some dough. My teacher in school noted that of the last say 20 engines he built, none of them had off the shelf pistons. Its not much more to have them custom made with the compression height, dish, etc you want. If you are running 76cc heads(which yours likely are) and 6" rods, a little dish may well get you low in the 9s of compression. But why have an engine that wants to rev with heads that don't? As for the wear thing, thats a non-issue I'd say. I mean tons of people run 5.7" rods in stroker motors for years/miles. You are right that it should wear and rev better, but is the extra cost worth it if you aren't going all the way? The money would be better spent on a good balance job I'd say. A good full rotating assembly balance will not only increase bearing life but allow the engine to rev much freer as well.
     
  5. WantedaDodge

    WantedaDodge 1/2 ton status

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    I realize that 6 inch rods are usually reserved for high rpm motors and I realize a 5.7 inch rod is easier/cheaper to do. But I like doing $H!T a little out of the ordinary. I wouldn't skimp on the balancing and stuff like that.

    Basically, I want a DD motor that live a happy long life and rev like stink to 5500 RPM. To tell you the truth, I don't know the deck heights of small block chevy's real well and I guess I'm not real sure how tall the pistons would be, cause short pistons don't like to run in street motors to much either, but that's something for consideration.

    If it's gonna be as tall as a 360 though, I'd have no worries.
     
  6. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I agree with sled dog here, there are tons of stroker motors out there that will never see their full potential becuase they are using stock style heads. Vortecs would be alright but mid 70s head are probably smog heads and will more than likely cost you 50 hp or more on your motor.
     
    79rustyk10 likes this.
  7. 1977k5

    1977k5 3/4 ton status Vendor

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    Agreed, and I decided to go with the 5.7" rods that came from my 350. I looked at 6" rods for a long time and decided that my money was better spent elsewhere, and trust me, I have plenty of money invested in my motor.

    6" rods will only gain you a couple percent in wear. I forget if you gain any power from it, but there is some more complex stuff about how long the piston dwells near TDC etc. based on rod length.

    Regardless, I didn't want to deal with more expensive rods and pistons. Are there problems with piston slap with those short (6" rod) pistons? How much will I really gain from having 6" rods in a 383 versus 5.7" rods?

    I felt that the money spent on the rods and pistons would be better spent elsewhere in the motor.




    This whole deal really comes down to rod ratio, which is pretty relevant to the overall performance (both power and durability of a motor). The rod ratio for a stock Chevy 400 is pretty bad with its short (5.665?") rods. Those motors are still considered pretty durable (with the same 3.75" stroke).
     
  8. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    I looked into doing exactly what you were gonna do using 6.00" Buick rods and the cost/annoyance of clearancing the block alone made it not worth while. I am very happy with stock rods and a set of Edelbrock E-TEC 170 heads (where most of my money went) when I decided to listen to everyone who told me 6.00" rods were not worth it.
     
  9. mtnman

    mtnman Scrap metal fabricator Premium Member

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    6" rods

    I went with the 6" rods on my 385 (.040 over) for the previously mentioned rod/stroke ratio - the tdc/bdc dwell time makes more cyl pressure and fills the cylinders better. If you are planning on buying rods and pistons anyway there is really no cost difference if you shop around ( I have Scat rods/crank and Probe pistons) The longer than 6"rods would make for scary short pistons w/ a stock block deck height, my pistons have a 1.025" compression height and from what I researched that is a MINIMUM # for a street engine, the pistons will rock and eliminate the long rod wear benefits. BTW I have 50,000+ HARD miles on mine and it still cranks out big power and definitely spend the as much as possible on your cyl. heads, my AFR 195's were worth every penny of the $1425 I paid, they made a bigger power diff. than going from 350ci. to 385ci. Sorry to run on so much but I love talking about my engine!!:D
     
  10. mtnman

    mtnman Scrap metal fabricator Premium Member

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    Hook me up!!! I wanna build a 434 small block!!
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Using a 6" rod when building a 383 puts the wrist pin into the oil ring and special measures need to be taken care of or disaster happens.
     
  12. ntsqd

    ntsqd 1/2 ton status

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    A point my former racing engine building employer made about long rods is to consider one of the side effects of a long rod in a low RPM - heavy working engine. That long rod increases TDC dwell time, something most of us know, but think about when you're working that engine hard & hot (pulling a grade ect.) and detonation. That longer rod will increase the engine's sensitivity to octane in those conditions. Whereas a shorter rod will be less prone to detonate in those same conditions.
    I went with the shorter rod.
     
  13. sled_dog

    sled_dog 1 ton status

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    an extremely good point I didn't think about before.

    Bare with me here, won't a camshaft have more oppurtunity to bleed compression due to the extended dwell time? Just a thought I am trying to work out in my head...
     
  14. WantedaDodge

    WantedaDodge 1/2 ton status

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    Well, I may end up sticking w/ a 350 anyways so it won't matter to much.
    I think you guys have a good point in that Sb deck height is just to damn short to get a tall enough piston in there. I'm used to small block chryslers, and they got room to run the longer rods.

    I did plan on buying new rods and forged pistons any way though, so the cost is really negligible since 5.7 and 6 inchers are basically the same money. I've always believed put your money in the short block, cause swapping heads and cams and intakes is easy. I want something that's buildable on. Not a cast piston, OLD resized rod, loose tolerance motor that is fine at 350 HP, but just be careful about pushing it any more.

    I talked to the previous owner of the truck a couple nights ago. He swears there is no more then 25,000 miles on that motor. I might just pull it, throw new gaskets, gear drive, decent cam and lifters, and I was looking at those Summit Heads that are $650 for the pair! I think that would get the job done.
     
  15. ntsqd

    ntsqd 1/2 ton status

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    It was a new to me point too. Caught me by surprise, but made some sense once I thot about it a bit.

    I think that the right camshaft could bleed off that excessive low speed cylinder pressure, but that is not the type of cam you're likely to put in an optimized low speed engine.
     
  16. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The cam rotates at the same speed no matter what the rod is doing.
     
  17. sled_dog

    sled_dog 1 ton status

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    correct, but if the rod is spending more time at TDC, time in this case meaning "degrees of crankshaft rotation", the camshaft is still moving and actuating the valves during that time, exactly the same as it would if the piston were spending less time at TDC.

    Ntsqd is right though, for a low RPM engine that this problem would present itself, the camshaft specs to bleed off the compression would make it a non-low RPM engine.
     
  18. misterfnygy

    misterfnygy 1/2 ton status

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    another option...

    What about a LS based stroker- 6"+ rods are stock- throw in 4.25 crank and run the hell out of it
     
  19. mtnman

    mtnman Scrap metal fabricator Premium Member

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    I believe that the "bleed off" comes as the piston is actually coming up in the compression stroke, as the intake valve doesnt actually close at bdc but rather a few degrees after. 4X4HIGH - I used Probe Racing sportsman race series pistons, with 3mm, 3mm, 3/16" rings and the wrist pin ends up below the oil control ring. I run 10.75 to 1 compression and 87 octane (@7000 ft elev.) with no pinging problems - even towing a 6500lb trailer and climbing long hills. I guess what I'm saying is - I love my long rod 383!!!!!!!!!!!!
     
  20. ntsqd

    ntsqd 1/2 ton status

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    Usually that's the result of a cam with lots of overlap. Which is not a usual feature of any cam intended for low speed operation.
     

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