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'51 GMC,4200 Vortec DOHC - Turbocharged

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  • #61
    Re: '51 GMC,4200 Vortec DOHC - Turbocharged

    try doing a thermostat on a 4.2 on warranty time
    or heads/mains with out snapping the torque to yield bolts

    good motor though

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    • #62
      Re: '51 GMC,4200 Vortec DOHC - Turbocharged

      I hear you ..

      I'd like have a discussion about the torque to yield bolts with the guy that made that decision and really understand why they went that way... to me taking a fastener past yield is really odd. The threads stretch and tend to lock in place which makes them a bear to remove - I busted 4 head bolts and 2 main bolts when I stripped the block.

      If you ever need replacement main cap locating sleeves (not serviced separate from the block) I had a bunch made up.

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      • #63
        Re: '51 GMC,4200 Vortec DOHC - Turbocharged

        90% complete... remaining

        - lower alt bracket ( rev 3)
        - serpentine belt
        - a bunch of vacuum plumbing and small items


        the colorado alt. fits the hole much better - why the @#$!@# idiots changed the alt. mounting pattern from the 4200 to the 2700/3500 is beyond me. Its same frickin' motor design....

        For 30+ years GM had the best part interchange in the biz.. now its crap- so one ought to tell Fritz...

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        • #64
          Re: '51 GMC,4200 Vortec DOHC - Turbocharged

          Chassis dyno day..

          ;D

          Maxed the injectors at 11 psi.... picked up 30 HP with the tune... had to do the runs in 2nd gear not to chunk the rear tires..... it red lines at 7000 rpm... 2500 rpm in 1:1 (4l60) is 63 mph....

          Track day Friday if it hooks I think I'm going to get tossed out for lack of a bar.

          More later...





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          • #65
            Re: '51 GMC,4200 Vortec DOHC - Turbocharged

            sounds good! how many hp worth of injectors do you have anyways?

            My fabulous web page

            "If it don't go, chrome it!" --Stroker McGurk

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            • #66
              Re: '51 GMC,4200 Vortec DOHC - Turbocharged

              My methanol fuel cell is on its way - once its here I'll install the methanol fuel supply system and 2nd megasquirt - the 12 72# injectors are waiting... Then back to the dyno... I'll start at 16 PSI and see if the transmission holds ... if so we'll go up to 18#. Currently at 11.

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              • #67
                Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                Originally posted by efi-diy
                the 12 72# injectors are waiting...
                :o Why a second MegaSquirt? Can't one MegaSquirt sink 12 injectors? (I honestly don't know....)
                Escaped on a technicality.

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                • #68
                  Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                  Staged injection... the methanol injection and boost control run out of the 2nd box... when enabled the gas injectors tapers off as the boost builds and the engine transfer to 100% . The 2nd MS fuel map will start at say 180 KPa and go up.

                  This will provide really fine fuel control under boost. I'm wiring the +12 for the boost control solenoid in series with a Hobbs switch - so if the methanol fuel rail pressure ever drops below a preset value the boost will drop back to where the gas injectors run. Try and keep a lean out from happening.


                  Oh here's a link to the gas only dyno session....

                  Quick video of the engine dyno'ed earlier this year on the engine dyno now installed with 99% of the final components ... After this video was taken - a seco...

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                  • #69
                    Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                    Been a long while...

                    Last year the rad leaked, engine got hot and started blowing coolant out of the overflow. Parked the truck for the winter while I was 100% tied up on a business venture.

                    Fast forward to July this year - pulled the engine and removed the head. Warped. So reinforced the head under the exhaust runners with aluminum 3/8 ready rod to add deck support and then re-surfaced the head.

                    Good - so I thought - WRONG

                    #1&2 leaked > 15% so looking at the walls found witness marks indicating the bores out of round. Pull the short apart.

                    Now the real crap starts - #3 rod bearing is already into the copper CL-77 bearing (3000 KM + dyno trime).

                    Look at the crank and its having oiling issues.

                    Send the crank for polish - the shop takes it below minimum limits - end up we > 0.003 clearance - not good. I'm mad as @#$%. Now the crank has to go - 020 and its the last stop as no one makes - 030 bearings for this engine yet.

                    Ge the the new - 020 mains and intsall them - bearing ID's are all over the map. Measure the main line - its all over the map. Now I have to find some competent to align hone a AL block with steel caps. Not easy to find. Ship the engine 300 miles away and pray it comes back OK.

                    Finally get the engine block back and start assembly - now Aug. 16.

                    Measure the bearing clearances and while Ok a bit tighter than what I wanted - but nuts I'll run it with 0W30 if I have to.

                    Engine finally went back in last Sunday, and not fired yet until I get the new rad mounted in the bed of the truck - also going to reverse flow coolant into the engine. Cool the head first. Harder on fuel economy.

                    While the engine was away - decided to change the crappy seats - thats 50% done.

                    Goal is to drive the truck to the world of speed in mid sept. B-Ville or Bust...

                    Comment


                    • #70
                      Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                      wow that's a lot of work.

                      Leave it to me to ask the dumb questions..... easier to find another engine that's all stock to start from?

                      Line boring mains on any straight six would be tough, AL block Steel caps? No fun at all. Glad you found someone who could do it.

                      How do you measure the main bore alignment?

                      There's always something new to learn.

                      Comment


                      • #71
                        Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                        I just found this build ... how the heck did I miss it?

                        Very cool my friend!
                        Whiskey for my men ... and beer for their horses!

                        Comment


                        • #72
                          Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                          Originally posted by milner351
                          wow that's a lot of work.

                          Leave it to me to ask the dumb questions..... easier to find another engine that's all stock to start from?

                          Line boring mains on any straight six would be tough, AL block Steel caps? No fun at all. Glad you found someone who could do it.

                          How do you measure the main bore alignment?

                          Starting over was not an option - its lots of work to prep the block and install the Darton sleeves. This all has to be done on a mill - this ws the root cause of my grief the #$%@!#$ A hole that did it pulled the alignment caps out of the block thus requiring an align hone which was not up to snuff.

                          How do you measure the main bore alignment? Master Bar.... not easy I hope never to have to do it again.

                          Comment


                          • #73
                            Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                            I figured it had to include some kind of killer straight reference like that.

                            Sorry you've had so much time in machine work hell - this sure is a great project.

                            A friend of mine designed and machined a line boring machine for locomotive engines - very neat piece, I begged him to make a small version for car stuff - but it would have been way way way too expensive for anything but a super high end machine shop - and therefore not worth his time. The thing is sweet -
                            There's always something new to learn.

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                            • #74
                              Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                              After 16 weeks the truck is finally moving under its own power.

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                              • #75
                                Re: '51 GMC,4200 Vortec DOHC - Turbocharged

                                cool!!!! was there any good news in the refurb?
                                Doing it all wrong since 1966

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