turbeau Posted January 5, 2009 Share Posted January 5, 2009 i have a 71z with an L28, duel SUs, headers, straight piping, air filters, lightened flywheel, ngk wires, universal coil, 280 dizzy, all else is stock. i just got the car running after the motor swap but am having a hard time with the fine tuning. the motor gets really rough at 4,500k then can barely rev over 5k due to no power and a lot of vibration. also, acceleration does not sound smooth, like a fast thud thud thud instead of vroooooom. the torque is there, but no top end. vacuum leak? timing? fuel pressure is good. thanks for any suggestions. Quote Link to comment Share on other sites More sharing options...
ReefsRocket Posted January 5, 2009 Share Posted January 5, 2009 Did you mean fine tuning with the ecu,or mechanically? Quote Link to comment Share on other sites More sharing options...
saxfiend1967 Posted January 5, 2009 Share Posted January 5, 2009 START WITH COIL,the vibration would concern me since you had flywheel lightened .it may have the engine out of balance.rev engine gently to about 3000 rpm in neutral if you still have vibration you should pull flywheel and have it balanced (or at least checked) loss of power could also be valve adjustment or header may be causing too little backpressure in exhaust.. if it is the flywheel you will rip the bottom half out if not corrected,B Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 5, 2009 Share Posted January 5, 2009 Don't forget to check valve adjustment. Quote Link to comment Share on other sites More sharing options...
turbeau Posted January 6, 2009 Author Share Posted January 6, 2009 it is a fidenza flywheel and i ran it on the other motor with no problems, runs fine at 3k in nuetral. in nuetral i cant rev above 5100. no ECU so all mechanical tuning. i dont think its the header cause its the same exhaust as before. what is valve adjustment? im am very unfamiliar with the internals of an engine. could it be vacuum advance? ill check in the Haynes and see if i can check that. Quote Link to comment Share on other sites More sharing options...
spawpoet Posted January 6, 2009 Share Posted January 6, 2009 How do your sparkplugs look?? Are the SU's in a good state of tune and at the proper mixture? Quote Link to comment Share on other sites More sharing options...
turbeau Posted January 7, 2009 Author Share Posted January 7, 2009 I just replaced the plugs and fuel filter yesterday, i dont know how to check the level in the carbs. any how to's for doing that? Quote Link to comment Share on other sites More sharing options...
Noddle Posted January 9, 2009 Share Posted January 9, 2009 it is a fidenza flywheel and i ran it on the other motor with no problems, runs fine at 3k in nuetral. in nuetral i cant rev above 5100. When you revving it up 5K, what's the exhaust gases look like ?, is it black, smelling of unburnt fuel ? what condition is the air filter(s) ? I know years ago, my YZ wouldn't rev properly, and it was caused by a dirty air filter. Nigel Quote Link to comment Share on other sites More sharing options...
turbeau Posted January 10, 2009 Author Share Posted January 10, 2009 i have just airhorns on the carbs right now. white smoke when cold, then turns clear. i still havent solved this. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted January 10, 2009 Share Posted January 10, 2009 If you haven't already, replace your fuel filter. It's a cheap thing to do and should be done often. These cars have a tenancy to rust the gas tank. However, given that it never sounds smooth, it really sounds like a timing issue to me. Check your timing, check that you have all wires to the correct cylinders, and that your wires are in good condition. Quote Link to comment Share on other sites More sharing options...
spawpoet Posted January 10, 2009 Share Posted January 10, 2009 I'd do a full, proper tune up on the car including tuning the SU's. Set the timing, valve lash, make sure the plugs and wires are good and in the right order, and make sure you are getting proper delivery of fuel to the carbs. Once all that is done then properly tune the SU's. Most likely the car just needs a good tune-up. Is the compression good on the motor?? Quote Link to comment Share on other sites More sharing options...
turbeau Posted January 11, 2009 Author Share Posted January 11, 2009 i just did the fuel filter and will do a full tune next. i hope tat solves it and i will become a happy Z driver again. Quote Link to comment Share on other sites More sharing options...
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