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  1. #1

    gp800 w/ 1300 cylinders?

    How do you guys think a gp800 engine will work for bottom end with 60T non power valve 1300 cylinders and Riva cast heads. 1/2 of the stock head gasket so compression is at 160 psi per hole. stock porting for now


  2. #2

  3. #3
    powerstroke specialist mikegp's Avatar
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    if i'm not mistaken ,pv engines and non have different timing.this is new for me too.
    i have never seen anyone using non pv 1300 cylinders on a pv 1300.

  4. #4

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    The standard 800 cyls are much more aggressive in port timing, so you could expect to see a power loss with 1300cyl. Don't forget you will need 1300 pistons too, the 800 pistons are the size of the 1200 pistons, not the 1300 ones. Also you will have to bore the 800 head gasket to the larger piston size.

  5. #5
    Quote Originally Posted by LT1GMC View Post
    The standard 800 cyls are much more aggressive in port timing, so you could expect to see a power loss with 1300cyl. Don't forget you will need 1300 pistons too, the 800 pistons are the size of the 1200 pistons, not the 1300 ones. Also you will have to bore the 800 head gasket to the larger piston size.
    +1

  6. #6
    Does anyone actually know the port timing number differences? head gasket is bored to 87mm, new 84mm pistons are installed and I'm seeing 160 psi with Riva heads

  7. #7
    also have 46 novi's to go with this setup. anyone have a different aftermarket head? I think I am going to sell the Riva heads with the Tim Judge 1300 pv top end

  8. #8
    Not much info on this motor out there huh? not many aftermarket parts either?

  9. #9
    porschemaniac's Avatar
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    Ive built several big bore 66e motors and would recommend using the 66e cylinders over the 1300. The port timing is not only more aggresive but the transfers are also much larger. You can use 2/3 of a big bore 66v motor and make great numbers from one. a 90mm bore is just unfer 1000cc and 86 is 927 if i remember without going back and looking at my build sheets. All my big bore 66v motors i use the 66e cylinders as a starting point-weather im doing a mild port or going with radical port timing. I really dont see a increase going from a stock 66e to a 1300. Stock the 800 makes .17 hp per cc the 1200 makes .13 hp per cc and the 1300 makes .13 hp per cc. This isnt even taking into consideration that each cylinder you add going from a single-twin -triple ect adds more hp than the sum of the cylinders due to several factors such as rotating weight doesnt necc double or triple- inertia from one cylinder helping carry the next through the power cycle ect.

  10. #10
    Thanks! but I think I have decided to sell all my gp motor parts and go with a powerhouse performance motor

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