240Z, 260Z, 280Z Performance / Technical Discussions related to performance motor enhancements, upgrades.

running rough, misfiring, and tapping

Old 09-26-2005, 08:04 PM
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running rough, misfiring, and tapping

well, I put the 260z e88 head that Tom gave me on the block, and I don't see any water leakage yet, but I'll have to verify that tomorrow for sure. I know that the valves need adjustment, so they are tapping, but the motor is running rough and misfiring, and is not idling very smoothly. When throttle is applied, it still runs rough, and doesn't sound like it's running very well. I rebuilt the carburetors before I bolted everything down, and when I had the original 240z e88 head on there, it didn't run so poorly, but it still seemed to have a little bit of a backfire, out of the exhaust and the carburetors as well. Where should I go from here to try to figure out how to get it to run smoothly and run well?
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Old 09-26-2005, 08:30 PM
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Don't make me come over there! You got to many things going on that were not resolved before continuing. You need to determine if the water leak is fixed first so just run it as best you can until you can check for the leaks. Then adjust the valves, timing, carbs, etc.
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Old 09-26-2005, 08:35 PM
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Originally Posted by theramz
Don't make me come over there! You got to many things going on that were not resolved before continuing. You need to determine if the water leak is fixed first so just run it as best you can until you can check for the leaks. Then adjust the valves, timing, carbs, etc.

sorry about being an *** and not wanting to use the head you gave me first. I bolted it on, and I don't notice any leaking yet, but I'll find out tomorrow. How hard is it to adjust the valves? I've read up on it, and I'm still confused. I'll mess with the timing tomorrow, to see if I can get it to idle and run right. Would incorect valve adjustment cause it to run rough and misfire?
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Old 09-27-2005, 09:16 PM
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Let it run as slow as you can untill it warms up for at least 20 minutes. Shut it down and after it cools check that #4 hole. If it's okay then proceed with setting the valves. With the timing mark on zero tdc and #1 cyclinder on the compression stroke (rotor will on #1 wire) you can check 1/2 of the valves. They will be obvious. Then turn the engine one rev to the timing mark again and check the rest. Don't try to take up all the lash on the ones that seem to be looser than the others. The head has been sitting a while. Re torque the head. Make sure you are using the tightening sequence in the book. Check the valves again. Get some Lucas oil additive, it will help loosen things up and soften the seals. Run the engine again and resist reving it over 1500 rpm untill you have it running perfect.
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Old 09-28-2005, 12:07 AM
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hey tom its zack, i came up there with jeremy when we picked up that E88 i finially goy my 280zx and i love it, im joining the military and ill be replaciing my L28 with a F54 TT with my sighning bonus.
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Old 09-28-2005, 10:04 AM
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You guys can come to NV again and we can test out the new four lane road to my house. Then we can straif the area with that potatoe gun!
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Old 09-30-2005, 06:39 AM
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Tom, I have everything bolted down, valves adjusted to the best of my ability, and the Z is running. The only problem so far is that one of the intake valves for either the 3rd or 4th cylinder has a pounded in/recessed seat, so that it will not allow me to adjust it (locknut and adjusting nut are right on top of each other), and the car is running poorly, idling rough, and sounds like a boat. Good news is that it's not leaking water and oil! I let it run for 20 mins or more, got it to a little over half on the temp gauge, let it cool down overnight, took the plugs out the next day, tapped my external hand starter, watched the spark plug holes, and no water splurted out.

So, the question is, do you think that the valve seats on that head (specifically the intake valve for the 4th cylinder and the exhaust valve for the 3rd cylinder, I believe) are pushed up, or pounded in? I called around to machine shops, and they said that as long as they don't have to weld the head back up to make up for any gaps or such that the head might have incurred due to the seats being recessed. I'm looking somewhere around the $100 range for 2 new seats, to have the valves and seat reground, and everything fit to match.
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Old 09-30-2005, 08:47 PM
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The seats are pressed into a counterbored hole so it can't go in any further. It could be that the seats were reground or replaced before with the wrong part, unlikely but possible. If you do pull it off make sure you reverse the tightening sequence. It is possible that warp in the head matches the warp in the block so if it isn't leaking, just have those valves fixed not milled. We need to find a new engine for you. In the mean time just get yours running.
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Old 10-01-2005, 12:25 AM
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Yeah, thanks for the advice and the head Tom. I'm going to be pulling the head off tomorrow (and it's not leaking...yes!) and take the valves out, and take it down to a machine shop. I've heard the early Z's used soft valve seats, and is a common cause of problems. I noticed that MSA and Victoria British sells hardened valve seats, and the mechanic at the machine shop said that they carry the hardened valve seats. I'll get it looked at, and hopefully end all of my engine woes!

I'll make sure to reverse the tightening sequence before I pull the head off. Is that from the middle out, or starting from the far left and following the reverse of the tightening sequence? I'd imagine it'd be from the left and following the reverse of the tightening sequence.
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Old 10-01-2005, 09:17 PM
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It's very important to follow the tigtening sequence. If you need a copy I can email one to you. Basically you tighten from the middle -out. And you do each bolt part way, like snug and then half torque then full torque then repeat. Critical on a long head.
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Old 10-02-2005, 12:18 AM
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yeah, I've been doing it right then. I took the valves out of the head and took it down to the machine shop to get the valves and seats checked out. The intake valve for the 4th cylinder was rounded out, instead of it being at a 45 degree angle. Would I be able to pull the valves out of another head and replace them with the valves in the head currently? Would they seal? How would I know? I know, lots of questions!
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Old 10-03-2005, 02:17 PM
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Now you got the valves mixed up? Take it down to that yayhoo machine shop and ask them to make one good head out of the parts you have.
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