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-   240Z, 260Z, 280Z Performance / Technical (https://www.zdriver.com/forums/240z-260z-280z-performance-technical-124/)
-   -   High Rpm question (https://www.zdriver.com/forums/240z-260z-280z-performance-technical-124/high-rpm-question-13079/)

1971z 05-20-2005 06:34 PM

I'm going to order the coil from summitracing this weekend. No water that i could see just a little oil. Wires are good condition bought them same time as the plugs few months ago. I will get the ngk plugs when the coil come in next week.

emo236 05-20-2005 09:20 PM

if the plugs were oily at all, one or more was prolly faulty. You must have oil consumption I'm guessing. if any of your plugs foul out, then you won't be running on all cylinders.

Fast240Z 05-25-2005 08:00 PM


Originally Posted by zbuild
Just as a bit of an explanation. . . the damper or harmonic balancer is the pulley at the front and bottom of the motor. . you'll see a belt that runs round you alternator, water pump and to a big pulley near the bottom of your block.
This pulley is attached to the end of the crank and is made of 2 pieces, an inner section and an outer section. The 2 sections have a rubber section in between, and can move independently of each other (only a very small amount) this helps "dampen" vibrations created in the engine. When you get your engine balanced, they normally balance the crank and the damper as one piece (or at least they did with mine).
When they get old, the outer section can sometimes move a little on the inner section which can give you inaccurate timing due to the fact that you use a notch on the outer ring to time your engine.
Cheers - Simon

hmmm, that's strange...neither one of my blocks had any rubber in between the two pullies (sp?), the only rubber pieces I have on the front of my motor is the timing cover rubber seal. I've rebuilt 2 blocks, and neither one of them were as you described. But, I would agree, they can become loose and cause vibration.

By the way, did you get that coil? I was wondering if it fixed your problem/gave you more power.

zbuild 05-25-2005 08:20 PM

Whoops! deleted this post thinking I'd put it on the wrong page . .

Just as a bit of an explanation. . . the damper or harmonic balancer is the pulley at the front and bottom of the motor. . you'll see a belt that runs round you alternator, water pump and to a big pulley near the bottom of your block.
This pulley is attached to the end of the crank and is made of 2 pieces, an inner section and an outer section. The 2 sections have a rubber section in between, and can move independently of each other (only a very small amount) this helps "dampen" vibrations created in the engine. When you get your engine balanced, they normally balance the crank and the damper as one piece (or at least they did with mine).
When they get old, the outer section can sometimes move a little on the inner section which can give you inaccurate timing due to the fact that you use a notch on the outer ring to time your engine.
Cheers - Simon

found a bit more about dampers: on "Inner Autoparts"

" The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm."


The rubber isn't in between the block and the pully, its actually part of the pulley.
cheers - Simonl

Fast240Z 05-25-2005 09:48 PM

oh! I know what you are talking about now. I just thought of it as I was typing. My pulleys had that rubber damper at one time, but due to age and heat, it became brittle and fell off, I believe. Now, here's another question, by taking off the outer piece of the pulley, I would lose a little bit of weight on the crank, so would that give me more power, per se, because the car doesn't have to work that much harder to spin the belts? I don't have an a/c, so I just need the innermost pulley. I know I'd have to put another couple of washers on the crankshaft bolt that holds the pulleys on, but would it be worth it to do that?

zbuild 05-25-2005 10:56 PM

I wouldn't mess with the harmonic balancer. . .. . what some people do is put the european single belt pulley on (lighter) but you would be far better off doing this at the time you build your engine and get the engine balanced with the lighter balancer on. An easier way to remove weight is to lighten your flywheel. You can take a lot more metal off a flywheel a lot more cheaply than by messing with the harmonic balancer.

Just as an aside, you can get racing or fluid filled harmonic balancers for very high rpm applications. . .but I haven't seen anyone making them for the L Series engine and they seem to cost an arm and a leg.

Cheers - Simon


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