Announcement

Collapse

All new PerformanceForums is here

The long-awaited upgrade and server move is complete.

Whinge about shit HERE.

Looking for Tapatalk functionality? See this thread.
See more
See less

Modifying cam gears

Collapse
X
Collapse
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #16
    When I had mine there were a couple of ways we did the cam timing
    1) Use the offset dowel locating kit for an L series datsun - Just bore out the hole in the cam gear and use offset dowel inserts on the standard dowel. This works but is fiddly and the access is terrible, I did drop an insert down into the sump once which was a real pain. You can just slot the gears with a mill and rotary table, they are just case hardened and it's not thick.
    2) In the end I just modified the gears to have 4 holes which were slotted, no dowels and 4 8x1.5 cap screws into the end of the camshaft.

    Unless you have a high comp motor I wouldn't bother with aftermarket cams as these have shit dynamic comp and you just end up making the problem worse with larger cams. Also when changing cam timing you need to be very careful about valve to valve contact, the high valve angle means it doesn't take much for them to kiss and then they are fucked.

    Comment


      #17
      Originally posted by Morcs View Post
      Actually looking at the pic on pc there is a dowl alinging cam to sprocket fairly simple.
      Yep, however just realized that in standard form the cam only uses the centre hole of the gear to locate it - its held in position by 1 dowel and 2 bolts, meaning the centre hole would also need to be tapped.

      Originally posted by private9 View Post
      Not quite what you’re asking for, but I vaguely recall Rollmaster made a timing chain set for these. If they did, most of their models feature adjustable sprockets. But, from very limited memory here, I think they were pulled from the market.
      Might be worth searching to see if anything is available, or even if anything secondhand is available.

      Edit, also search JP brand.
      Rollmaster set with the offset dowel holes/fixed degrees of adjustment was for the Z series SOHC motors; wont work this is a completely different kettle of fish

      Originally posted by Komdotkom View Post
      When I had mine there were a couple of ways we did the cam timing
      1) Use the offset dowel locating kit for an L series datsun - Just bore out the hole in the cam gear and use offset dowel inserts on the standard dowel. This works but is fiddly and the access is terrible, I did drop an insert down into the sump once which was a real pain. You can just slot the gears with a mill and rotary table, they are just case hardened and it's not thick.
      2) In the end I just modified the gears to have 4 holes which were slotted, no dowels and 4 8x1.5 cap screws into the end of the camshaft.

      Unless you have a high comp motor I wouldn't bother with aftermarket cams as these have shit dynamic comp and you just end up making the problem worse with larger cams. Also when changing cam timing you need to be very careful about valve to valve contact, the high valve angle means it doesn't take much for them to kiss and then they are fucked.
      Engine is forged bottom end/12:1 comp, E85, big cams etc etc. Accessibility and or ease of adjustment isnt really a concern as once the timing is set im hoping to not have to adjust it ever again [yeah i know wishful thinking]. Valve to valve can be engine builders responsibility; he seems to think it will be ok but last time we spoke he wanted gears regardless to retard/advance as required. Cams are A-symetrical profile and on different lobe centres so hoping it doesnt cause issues because the lift is quite large. Kanaris can sort that out, i just need to get him the right bits.

      I remember you mentioned 4 hole/no dowel thing a while back; was the effective PCD of the bolts holding the cam down being small not a concern? Probably showing a lack of understanding but wouldnt the distance from cam centre to where the chain is effectively cause leverage on the bolts?
      1978 Gemini Sedan - Powered by i change my mind every week
      1980 Gemini Sedan
      1992 Land Rover Discovery 200TDI

      Comment


        #18
        We did geminis in the olden days by drilling a hole in every gap with about three or four degrees difference in each. It's only maximum effort engines that need single degree variability. Easy to do, even with a pistol drill as long as you can get through the surface.

        Comment


          #19
          Originally posted by F3ARED View Post
          Yep, however just realized that in standard form the cam only uses the centre hole of the gear to locate it - its held in position by 1 dowel and 2 bolts, meaning the centre hole would also need to be tapped.



          Rollmaster set with the offset dowel holes/fixed degrees of adjustment was for the Z series SOHC motors; wont work this is a completely different kettle of fish



          Engine is forged bottom end/12:1 comp, E85, big cams etc etc. Accessibility and or ease of adjustment isnt really a concern as once the timing is set im hoping to not have to adjust it ever again [yeah i know wishful thinking]. Valve to valve can be engine builders responsibility; he seems to think it will be ok but last time we spoke he wanted gears regardless to retard/advance as required. Cams are A-symetrical profile and on different lobe centres so hoping it doesnt cause issues because the lift is quite large. Kanaris can sort that out, i just need to get him the right bits.

          I remember you mentioned 4 hole/no dowel thing a while back; was the effective PCD of the bolts holding the cam down being small not a concern? Probably showing a lack of understanding but wouldnt the distance from cam centre to where the chain is effectively cause leverage on the bolts?
          You still need to be able to adjust the gears once the engine has been built, I've never had an engine yet that makes the best power/curve on the recommended timing. There's too many other factors at play, you need to fuck around with it on the dyno to get it perfect.
          The 4 bolts are just generating the compression of the gear against the nose of the cam, they don't drive it. It's the friction caused by the two mating faces being forced together. They need to be lock wired and become part of the maintenance schedule.

          Comment


            #20
            I recall a post from TK i think it was, about building a marlin engine for some guy for tractor drags or something like that, any way if memory serves me correct that guy was a gear builder, riverina screamer was/is the name of the tractor from memory, guess it depends on the budget if its worth chasing up with them
            you cant spell advertisements without semen between the tits

            Comment


              #21
              Originally posted by Morcs View Post
              Actually looking at the pic on pc there is a dowl alinging cam to sprocket fairly simple.
              Ah, light and dark shadow.

              Maybe telling you how to suck eggs, picked this fairly simple trick up on holding the wheel and avoiding tooth damage. https://imgur.com/3O347sn

              Comment


                #22
                Originally posted by Tripper View Post
                I recall a post from TK i think it was, about building a marlin engine for some guy for tractor drags or something like that, any way if memory serves me correct that guy was a gear builder, riverina screamer was/is the name of the tractor from memory, guess it depends on the budget if its worth chasing up with them
                Riverina Screamer has been sold to Gonz from Gonzlab, the Merlin is going in a ZC Fairlane.
                "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

                Comment


                  #23
                  Originally posted by gxxr View Post
                  Ah, light and dark shadow.

                  Maybe telling you how to suck eggs, picked this fairly simple trick up on holding the wheel and avoiding tooth damage. https://imgur.com/3O347sn
                  Cheers thanks for that, was just planning on using copper pads in the 4 jaw...that way looks a lot more of a positive engagement.

                  TK's Merlin thread
                  http://www.performanceforums.com/for...rged-insanity!

                  Comment


                    #24
                    Originally posted by Morcs View Post
                    Cheers thanks for that, was just planning on using copper pads in the 4 jaw...that way looks a lot more of a positive engagement.

                    TK's Merlin thread
                    http://www.performanceforums.com/for...rged-insanity!
                    Small chunks of aluminium rod dropped into the valleys of the teeth is another good way to clamp.
                    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

                    Comment


                      #25
                      Doing shit on this found suitable chunk of steel to make some bits and turned it into hot chips mainly...
                      Actually got the inserts roughed out pretty quick being that the cams were not needed have used the register in the gear on the outer of the cam a feature along with the dowel position for alignment. Have convinced Feared that we will be dropping out the 2 bolts instead for the single larger one for attachment purposes as per the pics in thread previous.



                      Made a jig so i could mark/time the gear it was not hard at all even in the induction hardened looking stuff the premium chinesium sacrificial centre drill survived.



                      And marking some lines. I have done the marks 180 degrees out from pics as my busted endmill was in the road doing the sprocket and make no difference all said and done.

                      Comment


                        #26
                        I really need to measure that cam for you! Mate was meant to drop the micro over last night but the slackarse never showed, might just have to buy one. Also need to look into the bolt for through the middle
                        1978 Gemini Sedan - Powered by i change my mind every week
                        1980 Gemini Sedan
                        1992 Land Rover Discovery 200TDI

                        Comment


                          #27
                          Good job.

                          Often wonder how useful the degree markings on this stuff truly is...other than appealing to end users, who seem to think it's de rigueur. :)

                          Comment


                            #28
                            Been a little while...
                            After stuff ups with local supplier some blank sprockets have finally arrived. Was not happy with how the cam locating would of turned out plus having to undercut the sprocket further then i felt comfortable with. There is simply just not enough real estate ld have to make a press on ring to locate to the cam.
                            Feared sent another pic in which the other method was machining a register on the cam.



                            I made the bore of the sprocket the same as to what the register in the oem sprocket.
                            Centering up and clocking sprocket so that bolt holes line up to tooth for a reference to oem sprocket.

                            (yes it is surface rust on the rotary table joys living on the southern coast will clean up and put it away with a different oil on it...)

                            Setting the timing marks in with a 2mm carbide endmill.



                            The inserts are pretty much the same as previous incarnation only being offset has changed a little
                            Timing marks done and stamped for reference.


                            Need to grab some needle files to finish deburring then will put them in the post for feared.

                            Comment


                              #29
                              Fuckyeah. Check my PM when you get a chance and ill fix that up for you as soon as you're ready. Reckon i should get the insert coated, or no point given that its floating in oil?
                              1978 Gemini Sedan - Powered by i change my mind every week
                              1980 Gemini Sedan
                              1992 Land Rover Discovery 200TDI

                              Comment

                              Working...
                              X