datsky Posted March 15, 2011 Share Posted March 15, 2011 HI guys I just got my EFI 260Z runing few days ago. Everything was fine. Then i started to perform a valve adjustment. Before the valve adjustment, I checked the clearance of the intake and exhaust. The intake was excess .010" and exhaust was more than .012". Refer to the Factory Service Manual, the intake is .010" and exhaust is .012". ok, then i warm the car up to normal temperature for about 15 mins and adjustment is done. after the adjustment is done, the engine started to knock. I wonder if I have adjusted the valve pushing too far so the piston is touching the valve, but it is the clearance the factory want. however, i think the cam is stock after test drove it a bit. I didnt feel lots of power change by comparing to other Z. at this point, Can anyone give me a hind what is going on? thanks Quote Link to comment Share on other sites More sharing options...
burninator Posted March 15, 2011 Share Posted March 15, 2011 Did you adjust the valves cold? The cold adjustment is 0.008" intake and 0.010" exhaust. I don't know if that difference would make the valves contact the pistons. I wouldn't guess so, but I don't know for sure and I don't know what else it could affect. Quote Link to comment Share on other sites More sharing options...
datsky Posted March 15, 2011 Author Share Posted March 15, 2011 Did you adjust the valves cold? The cold adjustment is 0.008" intake and 0.010" exhaust. I don't know if that difference would make the valves contact the pistons. I wouldn't guess so, but I don't know for sure and I don't know what else it could affect. I adjust them when the temperature is at normal operation. the intake is adjusted to .010" and exhaust is .012". I have only narrowed the clearance by .001" for all the valves. Even I have a thin head gasket installed would not lead to the piston-valve contact. The cam shaft is OE. I dont see any excessive wear on the cam lube. However, Im not sure the condition of the rockers. The funny thing is: the knock will go away at higher RPM such like after 2.5K RPM. I suggest it would be unbalance air-fuel mixture or hot-spot in cylinder.. Quote Link to comment Share on other sites More sharing options...
twofouroh Posted March 15, 2011 Share Posted March 15, 2011 Forget the hot-spot, just start adjusting fuel toward rich and retard spark until it quits. Here's where a wideband O2 comes in handy. Quote Link to comment Share on other sites More sharing options...
datsky Posted March 16, 2011 Author Share Posted March 16, 2011 Forget the hot-spot, just start adjusting fuel toward rich and retard spark until it quits. Here's where a wideband O2 comes in handy. Thank you for your advise. I dont have the wideband O2. All i have now is the adjustable meter fuel regulator. I adjust it to regulate fuel at about 52 PSI and retard the spark timing. It idle at 1K RPM and now idle at 500RPM. Some what i still hear a very little of the knock. It knock when I let go the throttle from about 3K RPM or more. I read the Datsun Z EFI system, and noticed that the fuel injector will complete shut off at deceleration from 3k RPM or above. That is when the knock start to be heard. Since the throttle is shut, the injectors will operate at idle speed. However. the engine RPM is not at idle yet (lets say it is coming down from 3K RPM). I wonder if enriching the idle fuel mixture will cure the knock? and how? Some people suggest it would be a rod knock due to lose bearing. thanks Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted March 16, 2011 Share Posted March 16, 2011 Thank you for your advise. I dont have the wideband O2. All i have now is the adjustable meter fuel regulator. I adjust it to regulate fuel at about 52 PSI and retard the spark timing. It idle at 1K RPM and now idle at 500RPM. Some what i still hear a very little of the knock. It knock when I let go the throttle from about 3K RPM or more. I read the Datsun Z EFI system, and noticed that the fuel injector will complete shut off at deceleration from 3k RPM or above. That is when the knock start to be heard. Since the throttle is shut, the injectors will operate at idle speed. However. the engine RPM is not at idle yet (lets say it is coming down from 3K RPM). I wonder if enriching the idle fuel mixture will cure the knock? and how? Some people suggest it would be a rod knock due to lose bearing. thanks If your running a stock EFI system instead of Megasquirt or something else your Fuel pressure should be around 32-36 PSI IIRC but you should check a FSM for the year EFI system you have on the car. Quote Link to comment Share on other sites More sharing options...
datsky Posted March 16, 2011 Author Share Posted March 16, 2011 If your running a stock EFI system instead of Megasquirt or something else your Fuel pressure should be around 32-36 PSI IIRC but you should check a FSM for the year EFI system you have on the car. The car is running stock EFI. May it be the bad injector? The injectors are spread as jet instead of mist? Injectors are not cheap. Arh... Quote Link to comment Share on other sites More sharing options...
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