Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

SBC 350 .040....with 6.00" rods opinions please

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by twenty_below0, Jan 11, 2002.

  1. twenty_below0

    twenty_below0 1/2 ton status

    Joined:
    May 16, 2001
    Posts:
    436
    Likes Received:
    0
    Location:
    Haines, Alaska ...u.s.
    SBC 350 .040....with 6.00\" rods opinions please

    I have just acquired a set of NICE 6.00" rods and want to build this set up,( 350, .040, with 6" rods and flat tops) but would like some opinions about the longer rods and has anyone used this type of set up before, I also have a 400 and am trying to decide which one to build, if I go with the 400 I will have to keep the botom end stock with some decent pistons and decent heads, all opinions are happily recieved! THX Mike
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,060
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    If it were me, i would use the 400 crank in the 350 block at 4.030 with the 6" rod and that makes for a nice stroker. I have done this with my blazer and it makes almost 400 HP and 500 ft. lbs. torque. HP is peaked at about 3600 RPM but the torque is peaked at 1500 RPM.
     
  3. twenty_below0

    twenty_below0 1/2 ton status

    Joined:
    May 16, 2001
    Posts:
    436
    Likes Received:
    0
    Location:
    Haines, Alaska ...u.s.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    HUM.....that is a good idea, I will look into that, still curious how the 350 would do with the long rod
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,060
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Let me start by saying i am an automotive machinist. A long rod engine is always better due to the fact that the longer rod has less cylinder wall side loading. A 6" rod in a 350 would be good, but until you have built a stroker you have no idea what the difference in power is if you build it with the right combination of parts. The stroker that replaced my 350 which only had 60,000 on it, was twice the motor of the 350.

    <P ID="edit"><FONT class="small">Edited by 4X4HIGH on 01/11/02 11:07 PM.</FONT></P>
     
  5. RedDwarf

    RedDwarf 1/2 ton status

    Joined:
    May 9, 2001
    Posts:
    816
    Likes Received:
    0
    Location:
    North Central Florida
    Re: SBC 350 .040....with 6.00\" rods opinions please

    The side loading bit is true.

    Also this: the longer rod causes the piston to dwell longer (in crank travel) at TDC. This is good because it causes more complete combustion. That means more power.
    The longer rod also makes the engine less sensitive to detonation.
    You are making a good choice.
    Stroking the engine will reduce the effects of the longer rods. Keep it a 350.
     
  6. Triaged

    Triaged 1/2 ton status

    Joined:
    Feb 21, 2001
    Posts:
    3,808
    Likes Received:
    0
    Location:
    CA (LA/OC area)
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Be carfull in choosing to do a stroker with 6.0" rods. If there is not enough clearance with the cam you will have to use a small base circle cam (read: $$$). It all depends on the type of rods...call the people that make them and ask them befor you fork over any $$$.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  7. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Good question.
    Long rod
    Addvantages
    - A long rod will help upper RPM power. Like the others have said. A long rod will keep the pison at, and closer to TDC longer. Increaseing cyl pressure after the spark (less space, same explosion). When the engine is in the upper RPM ranges, everything is happening so fast, so trying to keep the piston closer to TDC helps. (I think it would help lower RPM power too, but not as much)
    - A longer rod as more leverage on the crank, so it can be more efficiant than a short rod.
    - Less "side-loading" on the cyl walls
    Disadvantages
    - Higher cost to assemble, Higher cost in machine work and balanceing,
    - Custom pistons (w/rod pin higher) possibly requirring forged pistons unless there are hypereutectic pistons avalibe
    - With Stroker engines, the pistion rod wrist pin may be pushed into the oil rings. Also, less material above the pin, might make the piston "rock" and scuff the skirts/cyl-walls.


    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
     
  8. twenty_below0

    twenty_below0 1/2 ton status

    Joined:
    May 16, 2001
    Posts:
    436
    Likes Received:
    0
    Location:
    Haines, Alaska ...u.s.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Could you give me just a little more reason why the stroker idea is bad? with the 6.00" rod, the cam I'm going to use is a extreme 4x4 comp cam with 214,218 lift at .050" do you think this will work if I use the stroker option? THX everyone for the info appreciate it!
     
  9. m j

    m j 1/2 ton status

    Joined:
    Dec 28, 2001
    Posts:
    4,606
    Likes Received:
    0
    Re: SBC 350 .040....with 6.00\" rods opinions please

    just build the 400, it will make more power then a 350 or 383.
    long rods aint all the magasines have made them out to be. bigger bore = unshrouded valves + more cubes

    BBC chev is example of successful short rod motor.
    also chev had to cast custom 8.02" deck motors to try and be competitive in trans am racing, if the long rods were all that they should have had an enormous advantage over the little ford. NHRA prostock also uses cut down deck hieght motors

    formerly 77chev
    still a jerk though
     
  10. RedDwarf

    RedDwarf 1/2 ton status

    Joined:
    May 9, 2001
    Posts:
    816
    Likes Received:
    0
    Location:
    North Central Florida
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Long rods DO make the piston dwell longer at TDC. You can check this with a degree wheel.

    Bigger bore unshrouds the valves. True, so inches for inches, shorter stroke is better.

    The reason that the stroker will offset the rod advantage is because is it a function of rod length divided by stroke length. Higher dividend is better. You can see that the longer stroke will create a smaller dividend with the same length rod.

    Regardless of what others say, longer rods WORK! High buck racing engines frequently use long rods. The pros know it's the real deal.
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,060
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    Re: SBC 350 .040....with 6.00

    You have 3 options here for you to choose from.
    (1) Build the 350
    (2) Build the 400
    (3) Build a 383 stroker
    --------------------------------------------------
    Advantages of building the 350

    All original internal parts
    Parts are plentiful
    Easy to build
    --------------------------------------------------
    Disadvantages of building the 350

    not as many cubic inches as 383 or 400
    --------------------------------------------------

    Advantages of building the 400

    All original parts
    easy to build
    --------------------------------------------------
    Disadvantages of building the 400

    block more prone to cracking
    simeased cylinder walls leaves hot spots
    short rod
    hard parts not as easy to find anymore
    --------------------------------------------------

    Avantages of building the 383 stroker

    more torque than 350 or 400
    you can still use 6" rod
    350 block easy to find
    hard parts easy to find
    no simeased cylinder walls
    no steam holes in heads
    not prone to block cracking like 400
    can be built with internal balancing without mallory weight
    --------------------------------------------------

    Disadvantages to building 383 stroker

    cost more to build
    more machining involved
    must balance engine (can be done internally or externally)
    some special internal parts needed
     
  12. twenty_below0

    twenty_below0 1/2 ton status

    Joined:
    May 16, 2001
    Posts:
    436
    Likes Received:
    0
    Location:
    Haines, Alaska ...u.s.
    Re: SBC 350 .040....with 6.00\" rods opinions please

    OK, still undecided except I wonder will I get 400hp with the 350 6.00" rods Flat tops 76cc heads and the usual carb, dual plane, headers, decent ignition etc.
    ?? The cost effectiveness of the long rod 350 is appealing but the stroker has some appealing properties....still undecided THX for all the opinions KEPP IT GOING
     
  13. 502Burban

    502Burban 1/2 ton status

    Joined:
    Jun 8, 2001
    Posts:
    379
    Likes Received:
    0
    Location:
    Southern California
    Re: SBC 350 .040....with 6.00\" rods opinions please

    FWIW, I have to go with m j on this one. Just for giggles, I entered the info for all three engine combos into Desktop Dyno. The 400 definitely comes out on top, all other things being equal. From 2000 to 5000 rpm, the 400 makes more torque and more hp than either the 383 or 350 combos, and has the flattest torque curve, overall.

    Robb
    <a target="_blank" href=http://community.webshots.com/user/robbrj>'73 GMC Suburban - 502DFI</a>
     
  14. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Re: SBC 350 .040....with 6.00

    Nothing beats displacement.
    But, if something was to happen to the engine, like spining a bearing or something like that. It would take-out the block. If it was a 350 block, you could still reuse most of the engine, just find another block (plentiful). But if it was a 400, than you would have to find another rare and hard to find 400 block, inorder to reuse the parts. (also a good rule for choseing cyl over bore)

    Rod to stroke ratio:
    I've heard that 1.70 to 1.80 R/S ratio is "ideal". Mostly circle track racers, or drag racers run the longer rods, for the advantage they have in the upper RPM ranges. Probably wouldn't matter much for "wheeler". But you have 'em, so why not run 'em. They are better than short rods.

    350 w/5.7 rod = 1.63 R/S ratio
    350 w/6.0 rod = 1.72 R/S ratio
    383 w/5.7 rod = 1.52 R/S ratio
    383 w/6.0 rod = 1.6 R/S ratio
    400 w/5.565 rod = 1.48 R/S ratio
    400 w/5.7 rod = 1.52 R/S ratio
    400 w6.0 rod = 1.6 R/S ratio

    A short deck height's only purpose in life is to keep the hood low.

    Cast my vote in on a 383 combo w/the 6.0 rods (because you allready have 'em)


    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
     
  15. twenty_below0

    twenty_below0 1/2 ton status

    Joined:
    May 16, 2001
    Posts:
    436
    Likes Received:
    0
    Location:
    Haines, Alaska ...u.s.
    Re: SBC 350 .040....with 6.00

    THX I have heard of the r/s factor but never really had an I- dea what it was and now I have a little better of an Idea but still a little curious thx for the input and I will probly end up going with the long rod 350 because of the price unless I get some extra cash, and that is not likely but all the info is GREATLY appreciated,can some one give me an idea as to what the HP and torque will be,specs as follows: 350, .040, 6" rods, flat tops,76cc heads,dual plane manifold, accel ignition, headers,comp xtreme cam and roller rockers.....maybe a desk top dyno could tell me .....wish I had one.... lol, anyone wanna run the figures for me thx Mike
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,978
    Likes Received:
    189
    Location:
    Roy WA
    Re: SBC 350 .040....with 6.00\" rods opinions please

    Hmm, picture perfect article for what this post has become : )

    www.dorianyeager.com/index2.html
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  17. Ruthiford

    Ruthiford Registered Member

    Joined:
    Jun 25, 2001
    Posts:
    37
    Likes Received:
    0
    Location:
    Denver Co
    Re: SBC 350 .040....with 6.00\" rods opinions please

    I have a issue of hot rod mag. where they did a 400 block 327 crank 6.125 rods flat tops and air flow research heads 11 to 1 56cc chambers 1.990 intake/1.550 exhaust and 215deg duration 435ft/lbs@3800 412hp@5700 ON 87 OCTANE Cost arround 3500$ 1.91r/s ratio
     
  18. RedDwarf

    RedDwarf 1/2 ton status

    Joined:
    May 9, 2001
    Posts:
    816
    Likes Received:
    0
    Location:
    North Central Florida
    Re: SBC 350 .040....with 6.00\" rods opinions please

    The rods were 6.209"
     

Share This Page