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78-89 block differences???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by muddysub, Oct 2, 2003.

  1. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    ok im think im gonna buy an engine for my sub finally but i need to kno if itll work. i have an 89 suburban with a TBI 350 and the engine im gonna buy is a 78 350. can i put my TBI heads on this block?? id like to keep all my TBI stuff together for cost reasons. (im in college right now) and it needs to stay TBI to pass emissions. so are the blocks the same?? will the heads bolt up? i know the bell housing is the same but what about motor mounts?? i dont have any casting #s srry. please help me here!!
     
  2. Muddytazz

    Muddytazz 1 ton status

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  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    All Chevy V8 motor mounts are the same after the mid '60s when they started using the normal clamshell motor mounts.

    Yes your heads can swap over, any SBC head will bolt to any other SBC. The only restriction is trying to put big valve heads on a small bore motor, which doesn't apply to your setup.

    Although you can swap the heads, I would drill the intake and use the heads that are on it first.

    If you do choose to swap heads, put a set of valve seals in them while you're at it.
     
  4. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    well yea when i swap the heads over theyre getting completely rebuilt, new seals valves springs porting & polishing, valve seat grinding all of it.
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I would not waste your money rebuilding those heads. You would be better off to buy some aftermarket heads.

    For now, throw some seals in them.

    955-042770-1 76cc, 1987-Up Straight Plug-Assembled (Each) | More Details $379.99

    By the time you spend $400 on rebuild your heads, you could save that $400, wait, and drop $800 on these iron beauties that are cheap and will majorly outflow that stock TBI trash you have now and have all of these benefits:

    Powerful 170cc Intake Runners. 30 HP Over most OE castings
    2.020'' x 1.600'' Valves (S/R Torquer 305: 1.940''x 1.500'')

    If you really want to save money, buy them bare, get your valves ground and pop them in, but I personally wouldn't.
    67cc or 76cc Chambers (S/R Torquer 305: 58cc)
    Dual Pattern Raised Valve Cover Rails.
    Accepts All Early and Late Model Accessories.
    Unleaded Fuel Compatible Hardened Exhaust Seats.
    Manley 7° Chrome Moly Retainers
    Valve Springs Are 1.250'' o.d. x 1.800'' Installed Height (100lbs Seat Pressure).
    3/8'' Screw-In Hex Shoulder Rocker Arm Studs.
    TRUE Bolt-On Installation.
    Accepts Stock Pushrods.
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Your flexplate will not bolt to the "78" engine. You can however buy a flexplate that will work for attaching it to the engine and also allowing your torque converter to bolt up. GM changed the bolt circle from 3.58" to 3" when they went with the one piece rear main seal starting in 1986. Just another reminder, GM externally balanced the rear of all SBC engines starting in 1986.
     
  7. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    [ QUOTE ]
    By the time you spend $400 on rebuild your heads, you could save that $400, wait, and drop $800 on these iron beauties that are cheap and will majorly outflow that stock TBI trash you have now and have all of these benefits:


    [/ QUOTE ] my friend is doing the heads at his grandpa's shop, all im payin for is the valves springs and seals , just parts basically.
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    That's right. 2 piece RMS stuff is a dime a dozen though. It's when you go to 2 piece TO 1 piece you get screwed like I did recently. /forums/images/graemlins/angryfire.gif I had turned my 2 piece RMS flywheel then had to buy a new one when I blew the motor up and put the '86 motor in it.
     
  9. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    [ QUOTE ]
    Your flexplate will not bolt to the "78" engine. You can however buy a flexplate that will work for attaching it to the engine and also allowing your torque converter to bolt up. GM changed the bolt circle from 3.58" to 3" when they went with the one piece rear main seal starting in 1986. Just another reminder, GM externally balanced the rear of all SBC engines starting in 1986.

    [/ QUOTE ] so i would need a pre '86 internally balanced flexplate?
     
  10. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Thats correct, the GM part number is
    471598 for the 14" diameter or
    471529 for the 12 3/4" diameter
     
  11. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    wow thanks /forums/images/graemlins/thumb.gif
     
  12. R72K5

    R72K5 Banned

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    [ QUOTE ]
    All Chevy V8 motor mounts are the same after the mid '60s when they started using the normal clamshell motor mounts.

    Yes your heads can swap over, any SBC head will bolt to any other SBC. The only restriction is trying to put big valve heads on a small bore motor, which doesn't apply to your setup.

    Although you can swap the heads, I would drill the intake and use the heads that are on it first.

    If you do choose to swap heads, put a set of valve seals in them while you're at it.

    [/ QUOTE ]

    1973 was first year for clamshell in trucks, and it doesnt matter anyways cuz the engine mounting bolt holes pattern is same since at least late 55 or early 56 and up, but blocks same 55-79 and then 80-86 and then 87-up

    55-79 oil pans are diferent from 80-86 pans and 86-up crank snout is different from 85-down so fexplates and flywheels wont swap, the snouts look way different in 86-up for one piece rear seal, the are small and round instead of larger and flared and such like they always were

    ut none of this matters, just use whatever flextplate or flywheel fits the engine and use correct starter and youll have it
     

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