Compression Ratio's Type 4

Discussion in 'Mech Tech' started by Deefer66, Nov 24, 2019.

  1. 77 Westy

    77 Westy Supporter

    Nor me; once bitten etc.
     
    nicktuft likes this.
  2. contact made with Thorsten, his first email went to spam folder duh duh :rolleyes:. 10mm swivel feet ordered.:chewie:
     
    77 Westy and Deefer66 like this.
  3. about 5 years ago when I decided to go DTM Type 4 conversion I visited Stateside to discuss. I was disappointed and was pleased to leave..............................
     
  4. 77westy did you use a particular grade of steel for your rocker arm spacers? I've ordered mild steel seamless without thinking.

    I tracked down uprated type 4 rockers arm studs, USA 10 and 8mm threads, too rich for my pockets around $150 to the door. I cant find anywhere in Europe, I did find T1 studs (Heritage) but I think they are different thread pitch???
     
  5. 77 Westy

    77 Westy Supporter

    Last edited: Aug 22, 2022
    Gnasha likes this.
  6. 77 Westy

    77 Westy Supporter

    Pedestal, thrust washer, rocker, washer, spacer, washer, rocker, washer, pedestal. Total axial clearance 0.004”.

    IMG_6439 (Medium).JPG
     
    Gnasha likes this.
  7. Home made .. steel shims each side in case oillite bronze was too soft
     

    Attached Files:

    Gnasha likes this.
  8. Thanks for the responses. So, first pass geometry set up.

    The Maths.

    max lift at the cam X rocker arm ratio.

    0.381" X 1.3 = 0.4953"

    Half the lift 0.4953/2 = 0.24765" I used 0.248"


    Intial set up with No1 TDC and the shortest push rod adjustment and v/v clearance adjuster wound right back the rocker shaft sat proud of the stud base. I tried a 1.5 mm washer, (not shim)

    With the valve compressed .248" (half compression height) these are the following photos. There was some considerable faff on adjusting the valve adjuster along with pushrod length.

    Fig 1

    IMG_4667.JPEG

    Fig2 note the gap between rocker arm and stud clamp. When spacers fitted and shimmed correctly this will be reduced and help with the position of the elephants foot relative to the valve stem.

    IMG_4664.JPEG


    Fig3,
    IMG_4665.JPEG

    Fig4
    IMG_4666.JPEG

    Fig5 This full compression position. There was some clearance between the first and second turns of the spring, is there an acceptable clearance in this position? I think there is still enough clearance for full movement of the foot in this position. not the best of photos.
    IMG_4670.JPEG as usual thank you for your help and assistance, comments and advice would be much appreciated.

    John
     
  9. 77 Westy

    77 Westy Supporter

    You might find the maths doesn’t correspond to reality for the valve lift (the cam might not have exactly the advertised lift and the rocker ratio isn’t exactly 1.3), I measure the valve lift and halve what it actually is.
    I don’t really understand what you mean there.
    The geometry looks good – I like those button levels – but the swivel foot seems a long way out of the rocker – did you modify the rocker to allow articulation of the foot? Don’t use those thick washers under to pedestal nut, although presumably they’re just for the mock-up.
    0.060” is usually the minimum recommended distance between coils.
     
    Gnasha and Zed like this.
  10. Zed

    Zed Gradually getting grumpier

    How did you set the datum for those funky level things?
     
    Gnasha and 77 Westy like this.

  11. I put one bubble on the valve retainer and one on the adjuster , got the retainer one level then used that as a datum for the lifter being in line with it.

    To be honest eyeing it in line would prob do on a bus..you can tell its out but playing is fun


    .. edit.. and as above measure actual lift not calculated and half that
     
    Last edited: Aug 23, 2022
    Gnasha, 77 Westy and Zed like this.
  12. I put one on the valve stem, the jack the side of the engine stand to suit as well as rotating the engine. IMG_4613.JPEG

    IMG_4614.JPEG
     
    77 Westy and Zed like this.
  13. I got no where near 0.060" between the top turn and the next one down?

    Bubble levels: there are cheaper but this was quick delivery, https://www.ebay.co.uk/itm/233773886452?var=533459097680
     
  14. after all of that, I removed the adjustable pushrod with out tightening the locking nuts........................................:rolleyes:
     
    77 Westy, Deefer66 and Zed like this.
  15. 77 Westy

    77 Westy Supporter

    :oops:
     
  16. 77 Westy

    77 Westy Supporter

    But you have much more in the centre of the spring – it will be fine and won’t be coil bound at full lift.

    I’ve had another look at the pics and I don’t think you have modified the rockers, consequently you’ve had to screw the adjuster a long way through the rocker and compensate with a shim under the pedestal. Nothing particularly wrong with that but it’s better to countersink the rocker to allow the swivel foot to articulate with the adjuster at a more normal length through the rocker.

    If you need a shim under the pedestal, make it a full contact square one, not a round washer.

    The washer I meant not to use are the ones under the pedestal clamp nut, it looks like they may be normal spring washers and there is barely enough thread through the nut. They should be part number N0122345 – a thin wave washer.
     
    Gnasha likes this.
  17. I worried about that one for a bit then couldn't figure out a mechanism for it to overturn/rotate so just went round engineering shim instead of washer for a flatter contact
     
    Gnasha and 77 Westy like this.
  18. 77Westy deefer66, thank you for patience, and taking the time to share your knowledge and experience.....yet again

    As suggested by 77Westy I have measured the full stroke of the spring from the top of spring retainer as per photo. Spec cam lift (see photo) is 0.381" I measured an actual stroke of 0.473" 0.092"/ 2.34mm difference.

    What am I doing wrong?


    Why do you need to multiply the valve lift by the rocker ratio 1.3 when im measuring from the spring valve retainer?

    To allow more of the elephants foot to protrude from the valve side I fitted an additional 0.8mm washer (total now 2.4mm) underneath each rocker shaft clamp and a wavey washer under the nuts. I am now using the original aluminium pushrods, will they take the extra load from the HD springs and higher lift? Im surprised at this, did your mention you used the spec pushrods Deefer66?


    For those interested in using the bubbles at some point I glued each one to a Neodymium Magnet (ebay)



    IMG_4679.JPEG



    The 0.307 incorporates the rocker ratio of 1.3. I think when the valve clearance is set the bubble will match the reference bubble.

    IMG_4678.JPEG


    IMG_4677.JPEG

     

    Attached Files:

  19. Zed

    Zed Gradually getting grumpier

    The cam lift 0.381 moves the pushod end of the rocker that much.
    The valve end moves 1.3 x as far because it's 1.3 x further from the shaft than the pushrod end. i.e. the valve end is longer than the pushrod end.
    As you measured 0.473 valve lift for your 0.381 cam lift the actual ratio of your rockers is 0.473/0.381 = 1.24. That's assuming your cam does actually lift 0.381.
    Or
    If the ratio really is 1.3, then your actual cam lift is 0.473/1.3 = 0.363.
    Or somewhere in between. You could measure the lift at the pushrod end and find out the cam lift, then work out the rocker ratio if you cared.
    Me, I'd be pleased you haven't got the full 0.381 x 1.3 = 0.495 (12.5mm). Less might be more in this case.
    The C35 in my type 1 with 1.1:1 rockers I assume (never measured it) had 0.419 lift (10.6mm) and went like the clappers above 3,000 rpm. I trial fitted but never ran 1:3:1 rockers - I didn't like the look of the fully open and closed angles. Maybe it would have been better at lower revs with higher ratio rockers. :thinking:
     
    Last edited: Aug 24, 2022
    Gnasha and Deefer66 like this.
  20. Table is for lift at cam.. in case ypu change the ratio so 1.3 x .381 is .495 which is close to your measurement

    Yes im on stock aluminium rods with Scat hd springs

    Sent from my SM-G973F using Tapatalk
     
    Gnasha likes this.

Share This Page