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

High Rpm question

Old 05-17-2005, 06:58 PM
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High Rpm question

I done some research and could not find the right answer. I have 71z with l24 block, e88 head, elec ignition, and type b tranny. I had mechanic that work on Z's do an inspection to the car and make minor adjustment like the timing and valves. The car idle and runs fine until i hit 4k rpm's. Car shakes and rides rough peakes out at 5k rpm's. I look at the tach and it indicates 6500rpms. Has anyone had this problem before and what they have done to fix the problem.

Last edited by 1971z; 05-17-2005 at 08:19 PM.
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Old 05-17-2005, 07:57 PM
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Originally Posted by 1971z
I done some research and could not find the right answer. I have 71z with l24 block, e88 head, elec ignition, and type b tranny. I had mechanic that work on Z's do an inspection to the car and make minor adjustment like the timming and valves. The car idle and runs fine until i hit 4k rpm's. Car shakes and rides rough peakes out at 5k rpm's. I look at the tach and it indicates 6500rpms. Has anyone had this problem before and what they have done to fix the problem.
when you say that the car runs fine till 4k and then peaks at 5k and your tach says 6500 rpms, are you saying that the motor is at 5k but your tach says 6500?

Besides that, the Z is rated for 150hp at 6000 rpms. That means that anything over 6300 or so is going to start some valve float, so you don't want to go too far over 6000. The Z will actually slow down after 6300 or so, because it can't accurately make power at that high of rpms. I just got done rebuilding my Z ( I have an L24 block with an E88 head, Pertronix Electronic Points condenser system, stock exhaust headers with glasspack, no cat) and it pulls hard up to 5k. I haven't gone too far over that, because the motor only has 20 miles or so on it. Try taking a timing light to your Z to make sure that your mechanic did the job right, and try checking your plug wires and make sure that your plugs are all firing.
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Old 05-17-2005, 08:00 PM
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Check your damper. It's on the front of your motor. The rubber might eb seperating and throwing your engine off balance at higher rpms.
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Old 05-17-2005, 08:11 PM
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Im sorry let me rephrase it. It runs fine until 4krpms. 4-5rpms the car shakes real bad and loses power. I can not push the car beyond 5krpms. I thought i could drive it to 6500 rpms because of the red line.
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Old 05-17-2005, 08:17 PM
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what kind of ignition do you have?
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Old 05-17-2005, 08:18 PM
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ok i will check on the timing, plugs and wires, as well as the damper. Im new to the Z so i just need to learn more about the car.

Thanks
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Old 05-17-2005, 08:23 PM
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what the hell's the damper?
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Old 05-17-2005, 08:56 PM
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i was not sure whats a damper is but i was taking the advise of other Z owners. Maybe there was something i did not know.

Anyways I have pertronix ignition carb e.o. d-57 2

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Old 05-17-2005, 09:09 PM
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I also have the pertronix ignition, and it works wonders. My Z used to hesitate over 5k rpm's, but after switching to pertronix, it screams like a beast now.
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Old 05-17-2005, 09:10 PM
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The damper pulley. Sometimes it begins to seperate, if you let it seperate all the way, it can damage your crank.
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Old 05-17-2005, 09:13 PM
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Another idea may be to check out your plugs,may need a change. Also how are the carbs condition wise. Are they in tune? You may be running rich (black smoke out of the exhaust, black sooty plugs). The carbs may need to be adjusted for air/fuel and synched.
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Old 05-17-2005, 09:32 PM
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I replace the spark plugs and wires. I have no clue how to adjust the carburetor. If i mess up the car will run worst then before. Is it really that hard to adjust or should i take it to a shop?
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Old 05-17-2005, 09:40 PM
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unless you know what you're doing, I wouldn't adjust them. Most shops will tuns your carbs, set your timing regap your plugs and everything else for only an hour of work. As long as your air fuel mixture is right, then all you have to do is get a carb sync tool, called a synchrotester. All you do is put it over the air horn on the front carburetor, and get the float ball to stay at about middle at idle, and then check your rear carburetor to make sure it stays at middle. To adjust, use the screws on the side of the carburetor. You can get a sychrotester from motorsportauto.com, but they tend to rip you off with prices, I've seen them for as cheap as $12.00 at harbor freight.
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Old 05-18-2005, 09:41 AM
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Check the color of your spark, should be blue not red or yellow=bad coil. Check your vacuum advance. You may have a weak ground and connections on the distributor. This will cause the tach to bounce around too.
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Old 05-18-2005, 10:03 AM
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oh, and make sure your plugs are gapped correctly.
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Old 05-18-2005, 10:18 AM
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2nd on what fast240z said, don't mess with the A/F too much if you don't really know what you're doing. A lot of that either requires a colortune or just some experience. If there's someone who's been around Zs for a while in your area, they could prolly walk it through with you.
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Old 05-18-2005, 10:36 AM
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anyone know of a good Z mechanic in the sacramento area? I want to get my carbs retuned, and I wanted to take it to someone who knows their stuff.
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Old 05-18-2005, 02:30 PM
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I think specialty Z is in San Jose. There might be others.
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Old 05-18-2005, 07:58 PM
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Originally Posted by theramz
Check the color of your spark, should be blue not red or yellow=bad coil. Check your vacuum advance. You may have a weak ground and connections on the distributor. This will cause the tach to bounce around too.
I was not able to check on the car today, i will check it out tomorrow. WOW once in awhile the tech does bounce around like a pinball. i thought that the tech was going out. Theres something new i need to check out.

I believed i gapped the spark plugs at .034 or .035

Last edited by 1971z; 05-18-2005 at 08:12 PM.
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Old 05-19-2005, 08:48 PM
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I checked the spark plugs and they're black with some brown on it. I did not see any of those colors you had mentioned. By some chance did they ever match the yr and the month of the car to the black coil. If they did it says 12 -93182 being that another person put a used part not matching the car. Also its old and might need to be replace. The part is not expensive and i will not feel bad if thats not the case. I have the autolite 7.5mm ignition wires, bosch platinum +2, and gapped at .035. Any other suggestion or should i go ahead and buy a new coil.

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Old 05-19-2005, 08:53 PM
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Originally Posted by 1971z
I checked the spark plugs and they're black with some brown on it. I did not see any of those colors you had mentioned. By some chance did they ever match the yr and the month of the car to the black coil. If they did it says 12 -93182 being that another person put a used part not matching the car. Also its old and might need to be replace. The part is not expensive and i will not feel bad if thats not the case. I have the autolite 7.5mm ignition wires, bosch platinum +2, and gapped at .035. Any other suggestion or should i go ahead and buy a new coil.

Thanks
You may want to consider getting a new coil because it will give you a hotter spark, depending on the coil. I'd look into the Pertronix FlameThrower coil, they are about $30, and it makes your plugs fire hotter, at 44,000 volts.
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Old 05-19-2005, 09:13 PM
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I'm not sure but I think the Pertronic still needs a condenser on the distributor for the tach to work right. If the distributor shaft is worn out, it will push away from the pick-up. Check the side play. Good idea on the hotter coil.
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Old 05-19-2005, 09:17 PM
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Originally Posted by theramz
I'm not sure but I think the Pertronic still needs a condenser on the distributor for the tach to work right. If the distributor shaft is worn out, it will push away from the pick-up. Check the side play. Good idea on the hotter coil.
nope, the pertronix does not need a condenser (I have one). The first thing is says to take off is the condenser, as a matter of fact.
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Old 05-20-2005, 12:22 PM
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Also, many people have experienced bad performance with bosche plugs. I would pick up a aset of NGKs. As long as your wires are in good shape, they'll prolly be fine.
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Old 05-20-2005, 12:24 PM
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also, were your plugs a little wet at all?
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