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.

I need BIG block advice

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by simply_signs, Aug 24, 2003.

  1. simply_signs

    simply_signs Registered Member

    Joined:
    May 30, 2003
    Posts:
    9
    Likes Received:
    0
    I am building a 78 Blazer and I want a BIG block with some tork. I have options to buy a 402, 454 or 502. All are long blocks and are mostly stock. Never been rebuilt. And all still run. I would like to no which has more tork?

    My 78 has 44's (boggers), 400/205, 5:13 gears (locked). This will NOT be a everyday driver. Just for play!!! /forums/images/graemlins/usaflag.gif
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,060
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    No substitute for CUBIC inches, when in doubt bore it out. The 502 stock will have more than the 402 or 454.
     
  3. boz42

    boz42 1/2 ton status GMOTM Winner

    Joined:
    Jun 3, 2003
    Posts:
    3,181
    Likes Received:
    0
    Location:
    Hopewell, Tn 38058
    i have to agree. 502, 454 at a minimum(splg).
     
  4. the professor

    the professor 1/2 ton status

    Joined:
    Feb 6, 2003
    Posts:
    130
    Likes Received:
    0
    THe 402 is an "emissions" motor, basicly a lo-compression slightly overbore 396
    --
    The 502 is a "new-design" motor, with some changes like the rear main and the way the valve covers mount..
    AND it has roller lifters..and "round-port-heads" (I think they are the same as the 'small-oval-port" but I could be wrong...
    --
    The easiest will be the 7.4L/454.. cheaper, usualy
    -
    BUUUT... if you want the best torque from a 454, you need the 1988 or later motor..

    That motor is a "small-oval-port" motor, it has "guide-plates" for the pushrods and some other small improvements to the heads..again, similar to the 502

    Most notibly it produces MORE torque and HP, than the earlier oval-port 454 engine...and does so on just about any cheap gas you can find without any pinging...

    It has to do with the combustion chamber and port design, which is similar to the 502
    +++++++

    Ultimately the 502 will produce the most, torque and hp...

    +++++++

    Forget the 402, use the SB 400.. the 402 doesn't make enough torque and HP to make up for the increase in weight and parts cost...

    "earlier" 454's would be "ok", but they I would say for sure go with the 502

    One thing.. be sure you driveline is up to a 7.4 or even more so a 502.. These puppies produce ALOT of torque and WILL break things..

    For general usage, you can run a TH700 or 350 / 208 behind a relatively "stock" 454,(I do, did)as long as its properly built and in good condition, but you might have problems with a 502..

    For your use you will probably need a modified TH400, I say "modified" because even a TH400 being used the way you are using it may have problems if not in the best of condition...

    Make sure you got a "big" Torque Converter, the "small" torque converter usualy used behind a SB will generate WAY too much heat.../forums/images/graemlins/cool.gif

    Oh yea, I have a 1989 454HO,4-bolt crate motor in my 1978-K20 -700r4/208 now, and have used TH350 and TH700/ NP205 in this truck..

    I also have a 1989 3/4t Suburban TBI 454 on a stand in my garage /forums/images/graemlins/truck.gif
     
  5. big pappa b

    big pappa b 3/4 ton status

    Joined:
    Jan 3, 2003
    Posts:
    6,328
    Likes Received:
    0
    Location:
    Falcon, Colorado
    Not sure if it's still a problem but I have heard that the 502's are notorious for using a LOT of oil. Like needing to add a few times before a scheduled oil change.
     
  6. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    [ QUOTE ]
    Most notibly it produces MORE torque and HP, than the earlier oval-port 454 engine...and does so on just about any cheap gas you can find without any pinging...

    It has to do with the combustion chamber and port design, which is similar to the 502


    [/ QUOTE ]
    I'm sure that the dismal compression ratio of somewhere around 8.3:1 /forums/images/graemlins/eek.gif really helps to prevent pinging as well. /forums/images/graemlins/frown.gif But that can be a good thing when you're dragging way too much weight up a long mountain pass, keeping the cooling system on the ragged edge of its capacity. /forums/images/graemlins/cool.gif
     
  7. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

    Joined:
    Mar 14, 2002
    Posts:
    7,324
    Likes Received:
    9
    Location:
    Grass Valley, CA
    [ QUOTE ]
    Forget the 402, use the SB 400.. the 402 doesn't make enough torque and HP to make up for the increase in weight and parts cost...

    [/ QUOTE ]

    Uhh, No. Have you driven anything with a 402 for an extended length of time? Comparing a SB to a BB is a retarded comparison. Even when the differenceis only 2 CI. My 402 runs close to 400hp with pretty much bolt on stuff. What does it take to get 400hp from a small block 400? Alot. /forums/images/graemlins/thinking.gif
     
  8. Bhintz

    Bhintz 1/2 ton status

    Joined:
    Mar 28, 2003
    Posts:
    1,341
    Likes Received:
    0
    Location:
    Roswell, Ga
    actually its very easy to make 400hp on a 400ci smallblock
     
  9. fad2blk99

    fad2blk99 1/2 ton status

    Joined:
    Feb 19, 2001
    Posts:
    860
    Likes Received:
    0
    Location:
    Charleston, SC
    A mild cam in a SB400 w/, say... vortech heads, good intake, you would easily get 400+ torque and HP... Checkout last months Chevy HP magazine....
     
  10. m j

    m j 1/2 ton status

    Joined:
    Dec 28, 2001
    Posts:
    4,606
    Likes Received:
    0
    the BB heads are a much better design the sb
    that is the big difference
    canted valves less shrouding
     
  11. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

    Joined:
    Mar 14, 2002
    Posts:
    7,324
    Likes Received:
    9
    Location:
    Grass Valley, CA
    Thank you mj.
     
  12. thor

    thor 1/2 ton status

    Joined:
    Aug 20, 2003
    Posts:
    512
    Likes Received:
    0
    Location:
    Wa
    Go with the 502, cost is same as 454/402 to rebuild, much torque....
     
  13. K30CJ

    K30CJ 1/2 ton status

    Joined:
    May 16, 2003
    Posts:
    429
    Likes Received:
    0
    Location:
    IN
    [ QUOTE ]
    BUUUT... if you want the best torque from a 454, you need the 1988 or later motor..

    That motor is a "small-oval-port" motor, it has "guide-plates" for the pushrods and some other small improvements to the heads..again, similar to the 502

    Most notibly it produces MORE torque and HP, than the earlier oval-port 454 engine...and does so on just about any cheap gas you can find without any pinging...

    It has to do with the combustion chamber and port design, which is similar to the 502


    [/ QUOTE ]

    I'm sure the proofessor is trying to be helpful, but....There's nothing wrong with the older big blocks. The only issue I'd take care of is the poor cam oiling. There are oval port heads (better for torque vs. the square port heads, which are better for higher rpm HP) that go back to the early big blocks, this is not an '88 and later-only thing. The old heads had guideplates too. /forums/images/graemlins/thumb.gif
     
  14. WARP1

    WARP1 Registered Member

    Joined:
    Apr 8, 2000
    Posts:
    63
    Likes Received:
    0
    Location:
    Omaha, Nebraska
    While were on the subject of big blocks. How much hp and torque could I expect from a '70's 454 long block. I see these motors for sale in the paper for around $750. With a rebuild, reconditioned heads, new alum. intake, and the proper cam what could I expect. This route wouldn't cost anymore than building a 383 out of my current 350.
     
  15. Sparky87k5

    Sparky87k5 1/2 ton status

    Joined:
    May 6, 2001
    Posts:
    726
    Likes Received:
    0
    Location:
    Lynden, Washington, 4 miles from Canada
    Just for the record, my '68 427 with '75 454 oval port heads and a Comp Cams hyd. roller cam, Doug Thorley headers, MSD, Edelbrock intake w/ 670cfm Holley, 9.1 compression, 8qt. Moroso pan and external oil cooler, runs with the best of them. I agree about the early 454's being somewhat a problem. But I've never had problems with either of the 427's I've owned over the years. I like the internal balance of the 396-402-427 series but shy away from the external balanced early 454's. Max torque comes only from max cubic inches, all else being equal. For that, go 502.
     
  16. fortcollinsram

    fortcollinsram 1/2 ton status

    Joined:
    Nov 8, 2001
    Posts:
    2,261
    Likes Received:
    0
    Location:
    Fort Collins, CO
    for torque, stroke wins every time....Personally I would go with a 496... The 502 is WAY over-square (too much bore, not enough stroke) but if you wanna run with the BIG boys go with a 540 or bigger...The 496 is just a 454 block bored .060" over (so 4.310") with a 4.25". But if you have the choice on the of the 3, I would get the one that has the GenVI block...I bet the 502 is in a Gen VI block...I would get that one, bore it over .030, throw a 4.25" Stroker crank in it, put on some "049" or "781" heads (or spend some green on the Edel 6045's. All this will put you well into the 500hp range...

    I say go with the Gen VI block b/c it is cheap and easy to use a roller can an you can use ANY BBC heads....The MKIV and GEN V block are expensive to use a roller cam ($800+) and you are stuck with the aftermarket roller lifters...

    But that is just me and I have a problem of not being able to leave well-enough alone..just ask everybody that wathced my COMPLETELY rebuilt a 454 the ran just fine when I bought it just b/c I could... lots of money after that, I have a strong TBI injected 460 (454 bored .030)

    chris
     
  17. sickquad

    sickquad 1/2 ton status

    Joined:
    Jul 23, 2003
    Posts:
    785
    Likes Received:
    0
    Location:
    Ma
    The 502 is a serious motor. A friend of mine has one in his truck, it's nasty.
     
  18. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

    Joined:
    Aug 28, 2002
    Posts:
    9,095
    Likes Received:
    144
    Location:
    california
    How about a 632. /forums/images/graemlins/laugh.gif

    85K5 3/4ton,14boltFF,10bolt,9"lift, 35"boggers, 16.5x14 welds, big horse 406SBC/700R4 /forums/images/graemlins/k5.gif /forums/images/graemlins/angryfire.gif
     
  19. fortcollinsram

    fortcollinsram 1/2 ton status

    Joined:
    Nov 8, 2001
    Posts:
    2,261
    Likes Received:
    0
    Location:
    Fort Collins, CO
    now your talking...
     
  20. fortcollinsram

    fortcollinsram 1/2 ton status

    Joined:
    Nov 8, 2001
    Posts:
    2,261
    Likes Received:
    0
    Location:
    Fort Collins, CO
    too bad he would have to get a $2000 Merlin Block to accomodate the 4.600" or so bore...
     

Share This Page