Original '70 454 high horsepower?

Discussion in 'VIN, Trim Tag & Drivetrain Decoding' started by Olympia77camaro, Nov 17, 2016.

  1. Olympia77camaro

    Olympia77camaro New Member

    19
    0
    May 31, 2014
    Murfreesboro, Tennessee
    I have a 454 I got for a trade recently and am going to drop this into my 77 camaro, but I'm still trying to figure out what it is.?
    -Block number is 3963512
    -Vin number is T1008CGU
    -Partial Vin is 10R1153
    Here is where I'm very confused, drive head is a 336781 head dated "D 7 76" but the passenger head is a 353049 head dated "F 21 78". Both heads stamped "pass" for passenger car.
    This block is all kinds of Frankenstein to me and I haven't taken heads off yet to see pistons. Ideally I'd like to drop this into my car with maybe just a cam swap and possible springs and rockers but now that this thing has different heads i don't know what to do.? Someone please chime in thank you and God bless!!
     
  2. Z28PILOT

    Z28PILOT Veteran Member Lifetime Gold Member

    2,022
    15
    Oct 8, 2009
    Emerald Isle , NC
    I think the port sizes are different . I would find another 33681 if your going to reuse one. I doubt they are expensive . Have a machine shop rebuild the heads , start from new so you know what you have. This is .... if you can 't afford some modern heads .
     
  3. Gary S

    Gary S Administrator Lifetime Gold Member

    21,375
    387
    Apr 14, 1999
    Bismarck, North Dakota
    CGU is Passenger car 454/390hp engine for 1970. It should be a 2 bolt main block.
    That engine should have originally had 3964290 heads with 101cc chamber.
    A 336781 head has a 113cc chamber.
    A 353049 head also has a 113cc chamber.

    Those two heads should work OK together, but will obviously give lower compression than the original 1970 heads.
     
  4. Olympia77camaro

    Olympia77camaro New Member

    19
    0
    May 31, 2014
    Murfreesboro, Tennessee
    If I were to use those heads what would my compression be at if I used original thickness head gasket? This is more of a budget build right now but will be fully built come next winter
     
  5. Gary S

    Gary S Administrator Lifetime Gold Member

    21,375
    387
    Apr 14, 1999
    Bismarck, North Dakota
    You would need to do calculations using your piston design and the head chamber design to know the final compression.
     
  6. davepl

    davepl New Member

    4
    0
    Oct 19, 2012
    Redmond, WA
    I find it interesting, but not surprising, that it's the same casting code as the 1969 427/390 motors. I guess the bore stays the same and it's just the stroke that changes...
     

Share This Page