I also think it is maybe harmonics as the console that is arround the gearlever also starts to make a harmonic type of vibration sound when I hit these revs.
When you hold onto the gearlever while it is making these vibrations it is a very similar feeling like I explained above of the hammer drill that I feel on the gearlever. A more rrrrrrrr type of vibration on the gearlever.
(The description sounds stupid but that is the only way I can describe it).
My tailshaft was once out of balance and it made a totally different vibration in the back.
The vibration does not feel like when your wheels are at the front out of balance and the whole front starts to shake. It is more like a harmonic type of vibration. That is why I wanted to know if you other guys have similar vibrations who's engines are not balanced but totally stock.
Maybe I must take it to my mechanic and show him and ask his advice.

gino
My exhaust is a straight 2,5 inch exhaust all the way to the back with one mufler at the back. No mufler in the centre.

It could be something touching the body. I installed a 5 speed in a 1200 once and the breather tube on the top of the gearbox was just touching the tunnel and it made a real racket. I almost took the box back as it sounded like it had a major internal problem.

Quote:
Yes it could well have made the flywheel go out of balance. It may also have skimmed to much of the surface so the springs in the clutch plate are touching the flywheel bolts.

Quote:

How will I know if the springs are touching?
The flywheel was skimmed quite alot.
It was previously skimmed by a mechanic but not done right.I needed to replace clutch as it shattered.These guys skimmed it again to remove the previous 2mm step.They tried to cut a new step and this was a mess as the cutter was not sharp enough.I told them to skim the messed up step out (it was about 2mm) and do not put a step in.So basically it was skimmed 2 times with about 4mm metal removed in total from the flywheel.It is currently driving for almost 10 000km with this new clutch.No problems.
I was present with everything and we bolted the flywheel/clutch assembled as one to the crank and then installed the gearbox.
Everything seemed fine.

It seems I will have to balance the whole engine sometime in the future.
I was actually looking for answers like "It's ok you can drive the car like that, the vibrations will not do anything".
It is that lesson again of "if you want to do something, do it right the first time."

Quote:

Sorry guys.
It was in total 2mm that was removed.
The step was only 1mm everytime and not 2mm.

stock engines are not balanced... i have the same problems at 4500... most of the people here have street tuned engine mostly are tuned to run above 5000rpms

stock engines like yours and mine are not meant to run that high.. the max hp is at just 5200rpm on stock A12 (compared to current 6400rpms on modern cars)

i'm going to do balancing on my engine. i'll tell you how it goes.

i heard A15 doesn't comes with harmonic balancers... can someone enlightened me?

Quote:

ocphangaz

I will be very very happy if you would inform me when yours is done. I am very interested in before and after comment.
This will tell if I will do mine also or not.
The reason why I do not really want to do it is the money involved. I will have to remove the engine again and might aswell bore it one oversize then. It was already reconditioned about 50 000km ago.
My fianc

hey 1200GXman,

my engine behave just like what u describe~!!
(both A12 and A15)

from idle to 3k rpm.. very smooth
3.5k and above start vibrate..

dono if all A series behave like that....

sam1741

Thanks for your reply.
I am happy that I am not the only one having this problem. I think it is that in the 70's technology was not so good as today.
Most of the people on this site have mixed new technology with old (Balancing all rotating parts of their A series engines).

I will take it to my mechanic to hear what he has to say. He was a Datsun mechanic for a private Datsun racing team in the 70's.
They raced a 1200GX and I think he will know what it is.
But as mentioned, if I want to rev it hard in the future, I wil have to consider a full balance on the engine.
I just hope it will not cause damage if I continue like this. An example is driving it on the freeway at 120 to 140km/h.
This is where the revs are at 4000 to 4500rpm.
At 120 to 140km/h you cannot notice the vibrations.Just hear the exhaust.
But in 1st and second gear where the speed of the car is still low it can be noticed.

hi
welcome~

seems like most A series engine have same behavior.. :)

well, good luck for your balancing, hope can see a smooth high-revving engine come out soon. :)
plz share with us what your mech do to balance up the engine. really appreciate that

ya.. travle at near 140kph really vibrate a lot...
well i do that maybe once or twice a month when i goes back to my parents place. (medium long journey). but i belive dats are very reliable.. :)