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Hi Tek Stainless exhaust manifold

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  • Hi Tek Stainless exhaust manifold

    I found some Hi Tek Stainless manifolds off Craigslist for a good price. The guy here in Fl shipped a pair to Cal. for a shamrock also. Anyone on here have them and any concerns? Also would a regular Fel pro gasket be a problem with the stainless to cast mating surface?

    It looks like the Hi Teks are not gonna exit all the way to the existing hose. Maybe 6-8" shorter than the cast manifold. Also I just redid my complete exhaust to hose so the idea was to add a short stainless pipe splice. Any problems other than the extra hose clamps and failure point?.

  • #2
    I've been running them for about 5 years. Had to raise the battery bridge so that it would clear the hoses. Get the best sparkplugs you can because once the manifolds are on you won't be seeing them again. After all I went through ordering and fitting I don't think I'd bother again.

    Click image for larger version

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    • #3
      Looks very nice.My batteries are in the motor front. It is a center console so it is a stretch armstrong move to get to anything. I took the old manifolds and risers off today and seems the second to last bolt on the front and back are too long at 1 1/4" because of clearance. Did you have this problem? a shorter bolt will hopefully work!

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      • #4
        They actually came with SS bolts that to me looked like header bolts. And that was part of the problem fitting. Had I known how ill fitting they were I would have bolted them up to a spare head in my workshop up north. Instead I climbed in and out of the boat so many times I lost count. I had to grind the welds where the tube to plate weld was because the built in washer on the bolt would bind up on the sloppy welds. I just didn't have access to the tools at my Florida house like up north. The limited spark plug access has me disappointed in them.

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        • #5
          Yes I just ordered some of the Header bolts in stainless. I see what you are saying about the plugs when dry fitting them yesterday. Looks to be a difficult to remove them with the hi teks. I am not sure they are gonna work with my exhaust though. Still figuring that out. I paid less on them than a set of cast runs. That and I do like that they are light and easier to work with. I agree with you 100%, great concept poor execution.

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          • #6
            The good news is once they're on, you're done for a long time.
            Atlantic City, NJ
            1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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            • #7
              I have not tried it yet but I bought one of these sockets. It looks like the only thing that will fit- you need something short that the plug will pass through and have a hex head to apply a regular wrench to. I have it cable tied to a wrench and always keep it in the boat
              Find many great new & used options and get the best deals for SLP Shorty Spark Plug Socket Part Number 30102 at the best online prices at eBay! Free shipping for many products!
              gary s
              Shamrock Addict
              Last edited by gary s; 03-17-2021, 08:53 PM.

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              • #8
                As far as the "splice" is concerned do you see any issues with cutting the exhaust hose about mid way aft and installing the splice/extension there...between the two equal length hose sections? You'd have less vibration at that area i would think.

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                • #9
                  I have a few of those "shorty" sockets. I just cut down some cheap sockets to different lengths.
                  1988 26' cuddy
                  1975 20' open
                  16' Sandpiper
                  14' Certified Fiberglass

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                  • #10
                    Jerry I thought it would be that easy. I tried and tried but could not find a socket that had a 1/2'" drive which is needed to let the porcelain portion of the plug pass all the way through and was broached with the hex all the way through to the base so that it could be cut off short. Today's cheap china sockets hex only goes down into the socket so far. And then you still need a hex on the end to be able to use a standard open or box wrench. Finally gave up and bought the above.
                    gary s
                    Shamrock Addict
                    Last edited by gary s; 03-18-2021, 02:39 PM.

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                    • #11
                      Click image for larger version

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                      1988 26' cuddy
                      1975 20' open
                      16' Sandpiper
                      14' Certified Fiberglass

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                      • #12
                        Gary, So with them on you can get the plugs out? When I dry fitted them it looked very close to them not having the clearing to come out.

                        I have the 220 center console. The motor is almost completely under the console. It is already a cross between a yoga instructor/Gumby/ Stretch armstrong act to get them out now. I should have all my bolts gonna head up to my shop and put them on today. Ill take some pictures.

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                        • #13
                          Finally got them installed. Had to use a 45% (not desireble to make them fit). Test run at idle. The port side was hotter at idle. Port was 110 to starboard 90deg with laser temp gun. Make a quick run up to plane about 1 min. Bring back to idle port hoses 300+deg and starboard 110deg. All new hoses. engine temp never rose past 160.

                          All new hoses. The port hose is a bout 1 ft longer. Would that cause such a wide swing in water flow?

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                          • #14
                            Fighting a similar issue on my PCM 351 with new exhaust manifolds/risers and pump. With boat on trailer can see the difference in water flow between port and starboard exhaust. On mine there is near-zero back pressure on the RWC side just before the risers. I'm using a non PCM Hx and beginning to wonder if there is a "flow orifice" designed in the PCM system that is not on the non-PCM Hx allowing one riser to pass more water, possibly creating a siphon, on one side versos the other. (Haven't looked at the manual yet.) It is interesting that mine will start with heavy water flow on port side then it soon goes to starboard side. As best I can tell currently on the trailer there is a 2 degree list to port. Still scratching my head and was getting ready to work on it when seeing your post.

                            Your new risers/manifolds may be passing water too freely for your pump to make-up sufficient water for both without some throttling prior to the riser to equal the flows (which would be the function of "orifices").

                            Will let you know what I find and would appreciate your doing the same. Thanks and good luck.
                            C Rhodes
                            26' Mackinaw - 1990
                            351 Indmar (1990-2006: Great Engine)
                            351 PCM (2006 - Current)
                            Southport, NC

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                            • #15
                              Had several delays and not finished but here is an update on my unbalanced exhaust troubleshooting. Recall in the above post the discussion about flow orifices to ensure more-equal flow to each riser versus starving one. Using plumbing fittings on each hose going to the exhaust manifold/riser, I reduced the hole size to 1/2 inch for proof of concept. This helped and reduced the maximum temp difference to 25 degrees (at idle when pump flow is minimized, little difference above 1000 rpm). Water flow was better balanced when looking at the stern exhaust. I could run the boat with this setup but still at idle, even with good pump performance, there is essentially zero back pressure on the water side and exhaust hoses get hotter than desired. I'm going to step in down to 3/8 and see if that is viable.

                              I saw a post of a PCM thermostat housing for sale and the discharge diameters appeared to be in the 1/2 to 3/8 inch range but that is a guess. I'm running the standard PCM pulley-mounted raw water pump (which I have never liked due to low capacity). Wish I could put a F-6 (higher capacity) crank mounted pump on but have the 4-bolt crank in my 351 PCM and they don't make a crank mounted pump for it (tmk).

                              In the below picture the the white fittings (both port and starboard) reduce the 1" hose to 1/2 inch and are joined by a galvanized 1/2" coupling. In the center is a gray plastic tee with a clear hose vented to atmosphere. Note at idle water level is at the top of the tee and does not reach the clear hose. (That much water is gravity-flowing through the rmanifolds /risers. Hardly any back pressure!) At 3000 rpm water level in the hose rose to about 6-7 feet, or about 3 psi.

                              More later but questioning if you have a similar issue with the Hi-Tek manifolds passing more water than your pump can make up.

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                              C Rhodes
                              26' Mackinaw - 1990
                              351 Indmar (1990-2006: Great Engine)
                              351 PCM (2006 - Current)
                              Southport, NC

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