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cam timing

Discussion in 'Engine Building' started by racerroy, Aug 11, 2012.

  1. racerroy

    racerroy New Member

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    Hi just playing with a D16Y7 getting the head shaved .080 just wondering how many degrees I should retard the cam? is there any general spec as how many degrees adjustment for material removed
     
  2. Dual-500

    Dual-500 Well-Known Member VIP

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    Retard the cam timing? The machine work you are proposing will retard the cam timing. The cam will need to be advanced to compensate, not retarded.

    To compensate for removing metal on the head to raise compression (i.e. Milling the Head) will require the cam(s) to be advanced relative to the timing belt and/or pulley(s).

    How much? Do the math. Compute circumference of the timing pulley(s) and divide by the total amount the head is moved towards the crank/block. Take the circumference in thousands of an inch and divide by 360 to get thousands of an inch per degree. Divide that by the amount the camshaft(s) are closer to the crankshaft.

    Example: D16A6 SOHC the cam timing pulley is ~4.5" in diameter or 14.13" in circumference. Multiply by 1000 = 14,130 and divide by 360 to get distance of circumference in thousands of an inch per degree = 0.03925 tousands of an inch per degree.

    The change you are making, assuming the same thickness as OEM head gasket is used, is roughly 2 degrees of retard induced into the cam timing. So, advance it 2 degrees to compensate if the pulley on it is ~4.5" in diameter as the D16A6.
    An easy way I've done it in the past is to set the distributor mid point in it's adjustment and bring the timing in using an adjustable cam pulley. Then tweak it from there based upon test driving.

    Remember, 2 degrees of camshaft timing is 4 degrees of crankshaft timing.

    0.080 is a good amount of material removal. I had the head done on a DOHC ZC and it only took ~0.025 as I recall to raise it up to 10:1 and from there going from a 0.051" to a 0.031" head gasket it picked it up from 10:1 to 10.5:1. You're talking raising that thing up from ~9.5:1 to 11.5:1 or something on that order of magnitue. That will also require fuel delivery compensation - an increase or it will be lean.
     
    Last edited: Aug 12, 2012
  3. newb

    newb phresh VIP

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    0.08 is a ton of material. Are you sure the valves will still clear the pistons?
     
  4. racerroy

    racerroy New Member

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    so dual500 what model honda should i look for, for a set of injectors sorry miss print only ,040 to 050 comming off head thanks
     
  5. Dual-500

    Dual-500 Well-Known Member VIP

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    Figure out exactly what you have first. What I had in the D16A6 that were transferred to the DOHC ZC were Peak and Hold and if memory serves me correctly were OEM rated at 225cc flow. I went with a set of 240cc flow rate aftermarket injectors that are Saturated type and am removing the resistors and box.

    I haven't put it together yet. Changing the injector plugs too, the wiring harness to match the new injectors without adaptors. Also, adding a Blox adjustable fuel pressure regulator and have a high performance aftermarket fuel pump that's going in it.

    Do some research to see what injectors go in the D16Y7 and go from there.

    For what you're doing, I would recommend you get some assistance with it. Even if it's from the shop that's doing the head work. Find someone that can advise you.

    You could burn a motor down or hose it up being too rich with the compression ratio you're going to be playing with. My ZC is only 10.5:1. Going higher than that you may be best off changing the ECU and having it tuned. You will also want to have the exhaust system stepped up, header and at least a 2.5" catback would be my approach. I changed the ECU with the swap and socketed and chipped it with a custom P29 map. Then, as mentioned, in this incarnation increased injector flow from 225cc to 240cc and am adding the adjustable fuel pressure regulator.

    Make sure you have a success story. Trying to setup and tune something like that using an online forum isn't recommended. Cuz, if you hammer it and it's detonating it won't last long. Under worst case conditions, if it's severely detonating, you could burn it down going through the gears one hard pass.

    At this point I'll recommend, since your heading towards 11.5:1 compression ratio, you had best consult a tuner. :)
     
    Last edited: Aug 14, 2012
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