GS Big Block

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  • yoshisakan
    • Jan 2026

    #1

    GS Big Block

    I have a 1980 gs1100L 16 valve. My motor is in need of some attention though. It is burning oil and I can see slight smoke coming from my pod filters, this may be mostly due to old valve stem seals. Over the winter I am either going to replace the valve stem seals, or go with a big block setup.

    In keeping this a street bike, is running a big block feasible? I just bought some brand new sticky Pirelli Night Dragons, but I don't know that they are necessarily going to hold traction with the added ~50-75hp of a big block. People with experience, what are your thoughts? I would like the bike to be able to keep up with newer 1L sport bikes, but at the same time be practical to ride with a passenger. I'd like to keep the stock wheels, swingarm and fork. I will definitely stiffen the suspension though.

    Thanks for your thoughts.
  • rapidray
    Forum Guru
    GSResource Superstar
    • Oct 2006
    • 8195
    • So Cal

    #2
    If you are in the US, call me at 714--356-7845 & I will answer your questions & suggest your BEST way to go. I build GSs (& have been since 1977) & build everything from stock to over 600 HP. I know how to make big street engines make good, RELIABLE horsepower. Ray.

    Comment

    • blowerbike
      Forum Guru
      GSResource Superstar
      • Aug 2008
      • 7057
      • Ohio Closer to KY Than Cleveland

      #3
      you WILL NOT get 50-75 HP from just a big block.
      plus a big block will run hot in every day normal use.
      you need to have VERY DEEP pockets to continue....

      Comment

      • yoshisakan

        #4
        Originally posted by blowerbike
        you WILL NOT get 50-75 HP from just a big block.
        plus a big block will run hot in every day normal use.
        you need to have VERY DEEP pockets to continue....
        I would not just slap a big block on there with a stock head. I'd definitely build the head too. I don't think 50-75hp is unattainable from adding 400ccs of displacement and better flowing heads. I'm not about to water cool it though, how about an oil cooler?

        Comment

        • Big T
          Forum LongTimer
          Past Site Supporter
          Super Site Supporter
          • Mar 2005
          • 12387
          • West Slope, OR

          #5
          Call Ray, he builds big blocks

          It'll be cheaper to buy a used modern bike with more HP, tho
          1978 GS 1000 (since new)
          1979 GS 1000 (The Fridge, superbike replica project)
          1978 GS 1000 (parts)
          1981 GS 850 (anyone want a project?)
          1981 GPZ 550 (backroad screamer)
          1970 450 Mk IIID (THUMP!)
          2007 DRz 400S
          1999 ATK 490ES
          1994 DR 350SES

          Comment

          • rapidray
            Forum Guru
            GSResource Superstar
            • Oct 2006
            • 8195
            • So Cal

            #6
            180 RELIABLE HP is easy but DOES require some specifics to do so. Ray.

            Comment

            • blowerbike
              Forum Guru
              GSResource Superstar
              • Aug 2008
              • 7057
              • Ohio Closer to KY Than Cleveland

              #7
              big bore and big block are 2 different things folks............

              Comment

              • rapidray
                Forum Guru
                GSResource Superstar
                • Oct 2006
                • 8195
                • So Cal

                #8
                I have 13 big blocks in stock, from 1260-1570. I would recommend 1327-1400 for the street. Ray.

                Comment

                • blowerbike
                  Forum Guru
                  GSResource Superstar
                  • Aug 2008
                  • 7057
                  • Ohio Closer to KY Than Cleveland

                  #9
                  what about sneaking 1400 liners in an 1150 block.
                  there is a couple of those around here that john done.
                  he bought the used pistons from me and cut the domes to a street happy compression.

                  Comment

                  • Guest

                    #10
                    So then how would you cool it down ?????

                    Comment

                    • Guest

                      #11
                      Originally posted by blowerbike
                      what about sneaking 1400 liners in an 1150 block.
                      there is a couple of those around here that john done.
                      he bought the used pistons from me and cut the domes to a street happy compression.
                      Interesting....I didn't know that you could go that big in a stock block
                      Hmmmmmm...
                      Rethinking everything now....Dammit

                      Comment

                      • blowerbike
                        Forum Guru
                        GSResource Superstar
                        • Aug 2008
                        • 7057
                        • Ohio Closer to KY Than Cleveland

                        #12
                        Originally posted by mr wu
                        So then how would you cool it down ?????
                        with a water hose?????
                        WTF are you talking about

                        Comment

                        • Guest

                          #13
                          Originally posted by rapidray
                          I have 13 big blocks in stock, from 1260-1570. I would recommend 1327-1400 for the street. Ray.
                          Ray I was thinking of you today.....So you are saying 1500 is no good...1327-1400 is the max for the street ????

                          Just when I decided on which way I was going you guy's come here and throw me a few knuckle curv's.....

                          Comment

                          • Guest

                            #14
                            Originally posted by blowerbike
                            with a water hose?????
                            WTF are you talking about


                            I meant keep it from running hot on the street....

                            Comment

                            • rapidray
                              Forum Guru
                              GSResource Superstar
                              • Oct 2006
                              • 8195
                              • So Cal

                              #15
                              I use big GSXR, curved oil coolers, top end oilers, & 750 pump gears. I also do some internal work to the cases to improve flow. Improving the flow increases the cooling also. Ray.

                              Comment

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