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The Silver Buick's 1969 Firebird OHC six project.

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  • Big winter upgrade time. I pulled the Firebird into the shop today and removed the intake and exhaust manifold. Started cutting on the exhaust manifold to remove the exhaust crossover so now I'm committed to either making it work or will end up building a set of headers. I'll also make a push to get the intake manifold completed as well.
    Escaped on a technicality.

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    • I finally bolted the new intake to the engine in the car for a test fit. There was a slight interference with some brake lines by the master cylinder, but putting a slight taper on the tube, reducing the diameter by about 1/2" in the rear, gave ample clearance. I had contemplated tapering the tube some to begin with, but this just gave a physical need to. The throttle body lands right about where I wanted it to so I'm happy with that. I'll put a 90º fitting on it downwards so I can put an air filter on it until I get an intercooler installed (with a turbo).





      Then I made the big leap of cutting up the exhaust manifold and blocking the exhaust cross over. If I get a twin-scroll turbo I will try and plumb it in front and back.

      Marked out where I wanted to cut. Turned out to be a larger pain in the rear than I thought it would be as I wanted to keep the two halves connected still so they'd line up on the ports from the two end bolts. The metal is also quite thick in parts of these areas.


      I ground down the top of the remaining part of the heat cross over so if I go back to the stock intake manifold it would not be touching the intake at all. As I said, turned out to be a tougher cutting process than I anticipated.


      I cut, heated, hammered and trimmed the patches.


      Then because my welding is horrible my final shot is after I painted it =P I heated the manifold up in an oven to ~450ºF, while also leaving the metal patches on my wood stove, so every thing was quite toasty while welding. Even the welding gloves were at their thermal limits. I hammer peened the welds after welding short sections. After the welding was done I put the manifold back in the oven and incrementally lowered the temperature over a couple hours and then let the manifold cool in the oven. Crossing my fingers it all holds together! If I have a little exhaust leak here or there I'll put some "exhaust weld" epoxy on it.
      Escaped on a technicality.

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      • That actually looks really good. I believe you nailed it.
        Of all the paths you take in life - make sure a few of them are dirt.

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        • Awesome Randall!!
          Patrick & Tammy
          - Long Haulin' 2008, 2009, 2010, 2011, 2012, 2014...Addicting isn't it...??

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          • Very cool!
            Chris - HRPT Long Haul 03, 04, 05, 13, 14, 15,16 & 18
            74 Nova Project
            66 Mustang GT Project

            92 Camaro RS Convertible Project
            79 Chevy Truck Project
            1956 Cadillac Project

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            • Looks stockish if nobody knows what stock is supposedta look like...

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              • The manifold modifications will be hidden under the center two intake runners anyways. And I'm likely going to paint the intake manifold Pontiac Blue when its done to make it blend in a bit better, and hide more of my welding sins, lol. After I do the last bit of welding to the intake manifold, and before paint, I plan on giving all the welds a coat of fuel resistant epoxy.
                Escaped on a technicality.

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                • Nice job, Randal. Cast iron is not easy to weld without problems.
                  BS'er formally known as Rebeldryver

                  Resident Instigator

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                  • Thanks. Won't know for a while if I'll have problems or not with it.
                    Escaped on a technicality.

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                    • Did some more work on the intake manifold yesterday and today. Getting closer. I welded on a plate to the back side and the throttle body mounting flange made of 3/16" steel on the front. Not seen in the pictures are three 3/8th NPT threaded pipe/bungs welded to the bottom side of the outer shell that I can thread different sized nipples on to use as vacuum ports as needed. Tomorrow I hope to cut and drill out the fuel rail so I can make the fuel rail hold downs. After that a coating of epoxy over the welds and then paint

                      One thing now with the laid over fuel injectors is the fuel rail won't interfere with the OE water outlet if I decide to go back to the stock water pump system it'll work.


                      Cut and drilled the flange for a nice fit with the throttle body I have.


                      I would of liked more plenum volume, but this is what I have to work with on this version. I welded and formed a small piece of tin on the left behind the throttle body to try and keep the air flow from hitting the flat side of the first runner.




                      Escaped on a technicality.

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                      • Looks good.. It's progress!

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                        • Nice!

                          did you set the exhaust manifold on there to see if it fits right, after welding?
                          My fabulous web page

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

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                          • Thanks and thanks

                            No I haven't bolted the exhaust to the head yet.
                            Escaped on a technicality.

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                            • Made the fuel rail and hold downs today. Same method as last time, ran a 3/8" pilot hole into the fuel passage, followed up with the 17/32" bit but stopping a bit short of the fuel passage. Then used a dremel to bevel the opening followed by some fine grit (400?) sand paper, red scotch brite then green scotch brite. Tapped threads into the ends for the fuel fittings and then cleaned it and cleaned it.



                              Escaped on a technicality.

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                              • I had to cut a bunch more material out of the exhaust manifold's heat cross over. I'm glad I had already started to do so because it turns out it would have been required. But I bolted it all together on the head and cleared up any interference's, so now the only place the exhaust manifold is connected with the intake manifold is at the head and hold down bolts. Now the next step is giving the welds a coat of epoxy, then a nice coating of Pontiac Blue engine paint.

                                Escaped on a technicality.

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