1962 intake heat riser block off - NCRS Discussion Boards

1962 intake heat riser block off

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  • Jeff C.
    Expired
    • September 30, 1997
    • 233

    1962 intake heat riser block off

    I am putting a new raditator in my 340 HP this coming week end and would like to take the opportunity to pull the intake and block off the heat riser passage. The gaskets came with 2 different metal block off plates. One set would not completly block the passage and the second set looks like it will cause sealing problems with the intake. Is there a third set that are correct that I do not have?
    Thanks for your help.
    Jeff
    039.jpg
  • Dan H.
    Extremely Frequent Poster
    • July 31, 1977
    • 1369

    #2
    Re: 1962 intake heat riser block off

    Jeff, I use Paragon FI intake gasket sets on my 64 FI. They come with the block off installed and work great.
    Dan
    1964 Red FI Coupe, DUNTOV '09
    Drove the 64 over 5000 miles to three Regionals and the San Jose National, one dust storm and 40 lbs of bugs!

    Comment

    • Clem Z.
      Expired
      • January 1, 2006
      • 9427

      #3
      Re: 1962 intake heat riser block off

      Originally posted by Jeff Cheney (29688)
      I am putting a new raditator in my 340 HP this coming week end and would like to take the opportunity to pull the intake and block off the heat riser passage. The gaskets came with 2 different metal block off plates. One set would not completly block the passage and the second set looks like it will cause sealing problems with the intake. Is there a third set that are correct that I do not have?
      Thanks for your help.
      Jeff
      [ATTACH=CONFIG]42654[/ATTACH]
      what ever you use make sure the material is stainless steel or it will burn thru.

      Comment

      • Joe L.
        Beyond Control Poster
        • February 1, 1988
        • 43219

        #4
        Re: 1962 intake heat riser block off

        Originally posted by Jeff Cheney (29688)
        I am putting a new raditator in my 340 HP this coming week end and would like to take the opportunity to pull the intake and block off the heat riser passage. The gaskets came with 2 different metal block off plates. One set would not completly block the passage and the second set looks like it will cause sealing problems with the intake. Is there a third set that are correct that I do not have?
        Thanks for your help.
        Jeff
        [ATTACH=CONFIG]42654[/ATTACH]
        Jeff-----


        I believe this type of block-off plates are used in combination for complete block off. In other words, you install the plates with the holes into the side gasket cross-over holes. Then, the raised centers of the other plates "snap into" the holes off the first plates. These look like stainless steel. Every one of these that I've ever seen supplied with a gasket package were stainless, although not necessarily non-magnetic stainless.

        Keep in mind that if you block the cross-over passage you MUST eliminate the heat riser valve and replace with a spacer. With a completely blocked cross-over, I don't like the idea of just wiring open the heat riser because if the wire fails you've got problems. Either gut the valve or install a spacer.
        In Appreciation of John Hinckley

        Comment

        • Larry C.
          Very Frequent User
          • April 1, 1980
          • 279

          #5
          Re: 1962 intake heat riser block off

          For what reasons would someone want to block off the heat riser passage? It does serve a purpose, doesn't it? Someone please educate me.

          Larry

          Comment

          • Joe L.
            Beyond Control Poster
            • February 1, 1988
            • 43219

            #6
            Re: 1962 intake heat riser block off

            Originally posted by Larry Chilton (3506)
            For what reasons would someone want to block off the heat riser passage? It does serve a purpose, doesn't it? Someone please educate me.

            Larry
            Larry------


            Yes, it does serve a purpose. In the case of a 1962, the purpose is primarily related to heating the carburetor for better fuel atomization and improved cold start and warm-up performance but if one doesn't drive the car in cold conditions, this doesn't represent much of a benefit. In the case of most 66-74 applications it's also necessary for operation of the divorced-type choke. However, there are downsides, too. The heat can also cause carburetor problems and may increase the tendency to vapor lock. Also, having a cooler intake charge can increase power.
            In Appreciation of John Hinckley

            Comment

            • Stuart F.
              Expired
              • August 31, 1996
              • 4676

              #7
              Re: 1962 intake heat riser block off

              Back in the day, we used to make block off plates using tin cans cut to slip under the gaskets w/o taking the intake off. We would bend the rolled lip up to make sort of a handle to insert and remove them. We only used them in the summer up in Wisconsin and realized some performance increase due to a cooler mid-summer mixture, but also you get some more snarl in your exhaust sound - specially when running glass-packs. My engines then were SHP 283's w/o heat riser valves. We never had any tin plates burn through, but then we didn't keep them in for very long. I recall we also used fuelie or perhaps truck intake manifold gaskets that had metal plates with small oval holes in them.

              Stu Fox

              Comment

              • John N.
                Very Frequent User
                • February 1, 1975
                • 451

                #8
                Re: 1962 intake heat riser block off

                Originally posted by Larry Chilton (3506)
                For what reasons would someone want to block off the heat riser passage? It does serve a purpose, doesn't it? Someone please educate me.

                Larry


                Here is blocked heat riser test results by Frank Burrell in 1956 with 1956 Sebring Team Car #7 (Engineering Number 6911) which Sally and I own. I believe (by memory) that the heat riser blockers were in place on the 1956 SR-1's produced at St. Louis in June 1956. They may have been included in an envelope with other C-1s from the factory. I kept the heat risers blocked and the chokes inoperable on my 57 270HP and my 62 409HP that I own. The cars were used for extensive legal and illegal drag races in the late 50's and early 60's.

                Regards

                Comment

                • Clem Z.
                  Expired
                  • January 1, 2006
                  • 9427

                  #9
                  Re: 1962 intake heat riser block off

                  Originally posted by Stuart Fox (28060)
                  Back in the day, we used to make block off plates using tin cans cut to slip under the gaskets w/o taking the intake off. We would bend the rolled lip up to make sort of a handle to insert and remove them. We only used them in the summer up in Wisconsin and realized some performance increase due to a cooler mid-summer mixture, but also you get some more snarl in your exhaust sound - specially when running glass-packs. My engines then were SHP 283's w/o heat riser valves. We never had any tin plates burn through, but then we didn't keep them in for very long. I recall we also used fuelie or perhaps truck intake manifold gaskets that had metal plates with small oval holes in them.

                  Stu Fox
                  the problem of burning thru happened when you made full throttle runs like drag racing because of the exhaust pressure built up if you did not use stainless steel. back in the day people used beer can metal before aluminum cans

                  Comment

                  • Clem Z.
                    Expired
                    • January 1, 2006
                    • 9427

                    #10
                    Re: 1962 intake heat riser block off

                    Originally posted by John Neas (171)


                    Here is blocked heat riser test results by Frank Burrell in 1956 with 1956 Sebring Team Car #7 (Engineering Number 6911) which Sally and I own. I believe (by memory) that the heat riser blockers were in place on the 1956 SR-1's produced at St. Louis in June 1956. They may have been included in an envelope with other C-1s from the factory. I kept the heat risers blocked and the chokes inoperable on my 57 270HP and my 62 409HP that I own. The cars were used for extensive legal and illegal drag races in the late 50's and early 60's.

                    Regards
                    some of the dual carb corvettes came with a envelope with the block offs included.

                    Comment

                    • Duke W.
                      Beyond Control Poster
                      • January 1, 1993
                      • 15668

                      #11
                      Re: 1962 intake heat riser block off

                      Originally posted by Larry Chilton (3506)
                      For what reasons would someone want to block off the heat riser passage? It does serve a purpose, doesn't it? Someone please educate me.

                      Larry
                      Liquid gasoline does not burn. It must evaporate and mix with air. At idle the fuel is introduced into the inlet manifold as a fuel-air emulsion, and the fuel must evaporate before it reaches the cylinder for combustion to occur.

                      At low load fuel dribbles into the carburtor venturi in blobs. You can actually see this if you rev up the engine to about 2000 revs and look down the venturis.

                      For this reason the heat riser was invented to create a "hot spot" under the carburetor. As the liquid fuel hits this it evaporates. It's similar to the design of a hot surface steam boiler.

                      The heat riser allows good cold and warm up driveability, especially in cold winter weather.

                      But modern E10 gasoline has a lower mid-range boiling point, so it creates percolation problems, and blocking off the heat riser is one "solution".

                      I blocked off the heat riser on my '63 340 HP many years ago, but even in mild Southern California weather, it created a start-off stumble until the engine had been operating for at least 15-20 minutes, so I removed the block-off shims.

                      One solution might be to block off just one side. This will provide a dead-end passage and allow some exhaust heat to get to the manifold under the carb, but a lot less than if the path is completely open to allow exhaust flow between the banks.

                      In any event, blocking one or both sides of the heat riser requires that the heat riser valve be securely wired open or replaced with the FI spacer. If not, there will be no exit for the right bank exhaust.

                      For racing the heat riser is unneccesary since warm-up driveability is not an issue, and it has been well documented over the years that blocking the heat riser results in a meaningful increase in WOT power, but it may also require a different jetting scheme.

                      Port fuel injection engines don't need heat risers because injection pressure through a small orifice creates a finely atomized spray of the proper amount of fuel for each cylinder that completely evaporates in the port or the cylinder during the compressin process, which creates a completely vaporized proper proportion of fuel and air to combust in the cylinder under all operating conditions, including drive off after a cold start in cold weather.

                      Duke

                      Comment

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