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a couple of questions about raising compression and changing the cam

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  • a couple of questions about raising compression and changing the cam

    I am putting together a parts order and fixing to take a spare head to the shop.

    The goal is a fast road car 90% of driving is around town on the weekends racing from light to light and some high way cruising.

    Right now I am planning on cutting the head down to 45cc which would give me a 9.61 compression ration per Richard's chart. I already had hardened seats and new valves put in the head before I cc'd (59.2 cc's)

    I am also looking at the wbc518v2 cam, with their springs and tappets.

    I sent off my stock rockers to get rebuilt. Also planning on using the stock keepers. The block is pretty standard except for being .20 over. (No cam bearings)

    Stock manifold, falcon ss exhaust (the one that looks like the stock i.e. twin pipes to a single muffler, SUhs6 carbs)


    So the questions:
    is 9.6 a good compression ratio? 9.5 seems popular. can I go higher? should I go higher? should I go lower? Just looking for what I can safely run with stock rods and pump gas (not sure about the pistons)

    any thoughts on the wbc cam? it seems people love the cam but then everyone loves the GP cams as well.

    Can I run the wbc or GP2 /Gp3 cams without cam bearings?

    Is there anything under the outer spring to keep the springs from biting into the head? One of my heads had shims under the outer spring but one of them didn't. I see that richard sells some hardened spring cups but then I don't see any other . Are those needed? if they are is there cheaper alternatives that don't require cutting the head?

    the engine only has about 1500 miles on it from the rebuild. Can I reuse the timing chain and gears? They are stock ones from moss or BPNW.
    If I need to replace them, Are the vernier gears worth it? are the hardened ones worth it?

    I have a set of the shortened push rods, can I reuse those? or do those need to be replace?

  • #2
    I think you are doing the smart thing when you say you're looking at getting the cam, springs and tappets from the same source...be that Wishbone as you state ...or Goodparts.
    Whoever you decide, get those 3 interworking components from the same person.
    I'll have to reserve commenting on your choice of carbs, though.
    Driving a 1973 TR6
    Doing ZS carb repairs
    email kencorsaw"at"aol.com

    Comment


    • #3
      The carbs are what came on the car. There is a set of stromberg's in a box but no idea about their condition.

      Comment


      • #4
        The carbs are what came on the car. There is a set of stromberg's in a box but no idea about their condition.
        You can send the ZS's to Ken (PB) and he can rebuild them for you, assuming he still does that.
        And refitting the Strombergs will simplify the crankcase breathing and fuel tank evap. issues.
        I good buddy of mine and poster here, had a go fast motor with even higher comp. that you are contemplating and the original carbs were quite sufficient for the engine, which also had a hot cam.
        CF1634U+O Pimento/Chestnut
        2nd owner, since 1975
        Now in Fair Oaks, CA

        Comment


        • #5
          You should check with Wishbone WRT cam bearings. If you are going to his cam, you should follow his recommendations.

          Your pushrods may be reusable, the measurements will tell you if you can use them or not. You can ask about something to go under the valve springs at the same time.

          2 Strombergs or 2 SU HS6 carbs should be able to provide enough fuel and air for your engine. One of the main reasons that people
          go to the SU's is that there are many more needles available for the SU's. Another reason for the swap is that many don't understand the Strombergs, and can't make them work. Ken (Poolboy) understands them and can make them work great.

          9.5 or 9.6 is a pretty good and very streetable compression ratio for today's pump gas. You'll want to make sure that your dizzy is in good shape and advancing properly, you MUST prevent detonation.

          Comment


          • #6
            Already had the dizzy rebuilt by advanced.

            I was going to call wbc and richard before I order anything. I just wanted to get some insight from everyone here before I give them a call

            Comment


            • #7
              You can only get so much HP out of your motor. Are you planning on racing you car? Have you checked the price of racing fuel. I built a motor years ago it had most everything you could do to that motor. I was young then. Ask the machine shop your using how much you are going to gain in performance by higher compression . I would go with a light flywheel first.

              Comment


              • #8
                Hi Jackag91,

                Unless you don't mind getting back into it in fairly short order ( that's a year or two in my book ) you might solicit testimonials from users of this cam:

                wbc518v2

                It's lift / duration ratio seems to dwarf the P.I. cam's, for example, and doesn't bode well for longevity from that standpoint. The GOODPARTS offerings look OK that way and enjoy a sterling reputation , though no cam has the factory's track record of which the CP " 150 " P.I. cam gives the highest performance.

                Tom

                Comment


                • #9
                  wow. are they really that short lived?


                  is the 150 cam usable as a street cam?

                  Comment


                  • #10
                    wow. are they really that short lived?


                    is the 150 cam usable as a street cam?
                    I have no idea how long they ( wb cams ) last - I suggest you inquire of other users before planting one in your engine! The 150 cams certainly do, and are good for ~ 150 BHP when the head and fuel system are brought up to TR5 spec. I have 87,000 miles on mine so far with no signs of deterioration. That's not a lot of power these days but the cars are light and it will move them pretty fast.

                    If you're using twin single barrel carbs you will have to use more cam, more c/r and other head work to get that much.

                    Tom

                    Comment


                    • #11
                      The carbs are what came on the car. There is a set of stromberg's in a box but no idea about their condition.
                      You can send the ZS's to Ken (PB) and he can rebuild them for you, assuming he still does that.
                      He does and you should. Cannot say enough good things about Ken's work....Poolboy, you can send the check directly to me.... :evil:

                      Comment


                      • #12
                        Since it is a spare head, I'd make sure it is one from the later run of cars. Right out of the box, they flow over 15% better due to a change in the casting on the intake track. The flow through the head on the 2.5L becomes more and more important as things like compression, exhaust flow (header), cam and carbs are modified. Its also the most "mysterious" and most expensive to improve - with many "improvements" actually working the other way. When its done right, the additional flow livens up the engine all thru the range and since Triumph provides it on the later casting, I'd take the Triumph engineered 15% when I could.

                        See Chris Witor's site for the casting difference between early and late heads and well as how to identify what you got. His article on inlet flow will give you some insight on the various carb option (SU, ZS, Weber & PI) as well.

                        https://www.chriswitor.com/technical.php

                        Comment


                        • #13
                          You talk about spring to head cups/shims.. Puhleeze do a bit of research, with competition machine shops that do heads, then you will DEFINITELY install some.

                          They serve several purposes. First preventing damage to the head from aggressive springs, Secondly, and very importantly, they provide valve turning. Making sure the valve turns slightly each stroke of the valve, so that the valve face and seat do NOT hit the same spot and burn the valve. Thirdly they can make sure that the valve height is set equally on all the valve, by utilizing different thickness shims.

                          Comment


                          • #14
                            You asked about compression but I did not seean answer. Might have missed it.

                            As compression goes up the possibility of predetonation goes up. To prevent this the easiest thing to do is to use a fuel with a higher octane rating. 9.5:1 is not a magic number but you can still use service station fuel. 9.5:1 was also the compression spec for the original CP series PI engine. As you go to higher in compression your HP will go up but at some point you will need to run racing or aviation grade fuel with the high octane ratings. This will be expensive and limiting as you won?t be able to pull over and fill?er up.

                            Our engines are very simple and don?t have the anti-knock devices that the modern muscle cars have to allow high performance operation with lower octane fuels.

                            Comment


                            • #15
                              Hello Jackag91,

                              many things been said already. Did you look at Kent and Newman cams? Cam bearings are not required. Nice, but not required. If you keep stock rollers/rockers, with modified head you can use the PI push rods. I drive with CR10. With casted pistons this is not a problem, incl. 30 degrees advance timing. The Stromberg carbs are not complicated and are superior to the SUs.
                              Timing chain and wheel must be checked! Aftermarket parts are not hardened and the chain should be a double-chain. The little sheetmetal tensioner need to be from the correctmaterial, or it will be nothing but dust after a few miles.
                              Good luck!
                              Jochem
                              Flying Dutchman drives: TR6 - 1973 - 56/11 - CF1xxxxUO - J-OD - Kent 280° - EFI EMU Black - Phoenix - 205/60 on 7x16

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                              a couple of questions about raising compression and changing the cam

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