teretonga

Sorry, I have checked those stuff before.
Universal joints are still brand new.
Driveshaft has been balanced.I can drive even 140km/h on the freeway and there is no vibration in the gearlever or the back of the car.And I have also replaced a couple of months ago the gearbox mounting as it started to get brittle due to age.
First gear the Datsuns don't have much speed, that is why in first gear you can clearly notice the vibration on the engine.That tells me it cannot be drivetrain as it is not even at a decent speed.
Thanks anyway for the reply.

Hi 1200GXman - I remember your vibration post from a while back. I am still convinced your problem with higher revs is in your drivetrain e.g. driveshaft out of balance, a bad uni joint, gearbox mount etc etc. Guarantee it is not coming from the motor.

Yeah in all seriousness do your best to find a 1400 block. Im not saying anything is wrong with the 1200 but by the sounds of it you want a quick car for as cheap as possible. The bigger engine is the way to go. It is a much better starting point.

Wrap up the 1200gx and keep her stock. She will be worth more that way plus you will feel better knowing you didn't ruin one. Maybe use the head on the a14 but definately use the manifold and hitachi su's.

Quote:
Good one.

Freak I will check for how much I can get a A14 block.
They are quite high in demand here in South Africa and that causes them to be a bit expensive.
I will see what my budget can do for me.
Thanks also for clearing the square engine issue.

The squarer the engine the better it revs. More horsepower. Some race engines are over square bore is much bigger than stroke resulting in a high horsepower reving engine. Less torque than a engine of same capacity with a longer stroke but much better revability.

1200gxman take the a12gx out rap it up in a big plastic sheet and let it sit there as a exhibit and you can always put it back in down the track. Fit an a14. No cutting or anything just to steel plates used as spacers. A14 with higher comp, twin su's, extractors, cam and some porting = a pretty quick car. Thats what I have now and it loves eating 6cyl commodores and falcons in the 0-100km/h.

Anyway if you alter the GX its no longer a GX is it. Just go the easy option for horsepower. More cubes.

Freak.
Yes, you are right about our A14 engines.
The thing is.I do not want to put in a A14 because then it will lose it's 1200GX naming.
I want to keep the A12 engine and just make it a bit better.

pro240c
I have read before about a "square" engine.
Something about boring the A14 a size out and then the bore and stroke is equal.
What are the benefits about this?

it's not just 200cc that makes the difference, it's the longer stroke which improves torque and moves to "square up" the engine a bit more and provide more useable "power".

i've seen a turbo'd A12 and an A14 make the same outright power, yet the A14 car was WAY quicker. why? MORE TORQUE!!!

You beat the bakkie because it has a single downdraught, plain exhaust manifold, lower compression, torquey cam for low revs(no power) etc. Put your good stuff onto a A14 and you'll kick yourself wondering what you've been doing in an a12 for so many years. Plus the torque increase in the a14 makes for a better daily driver. Much less work/dollars for equal horsepower with potential for more.

Freak

Yea, that is why I want to open up the engine again.I also suspect something is not 100% right.
Strangely enough, I took it a couple of weeks ago in second gear slowly up the rev range.It is smooth all the way up to 5000rpm and then it starts to gradually vibrate more and more.
My flywheel was skimmed two times in the past due to first being a clutch replacement and second time due to bad clutch replacement first time and also bad skim on flywheel with first clutch replacement. I wonder if it is not the flywheel that is out of balance due to all the skimming?

I plan on putting in a mild cam that will give good torque and good power all through the rev range.

About the A12 beating a A14?
Sorry, been there and done that.
I did it three times in a row with a new Nissan 1400 bakkie as we currently still get them in South Africa. Hooking 3rd gear, bye bye bakkie by about one car length.That time I pulled only 6000rpm and it was the first time I noticed the vibrations.
Ok, I must admit. The bakkies are build here for carrying large weight (500kg) and fuel economy and not for speed.

There is obviously a propblem with yours. My a14 with cam etc revs to 7000rpm unbalanced without any vibration. Even my old/worn stock a14 would rev to over 6000rpm without vibration. If you think an a12 will beat a a14 you must be kidding. The difference the extra 200cc makes is incredible. Bolt your gx head onto a a14 (modify oil galleries as required) you will notice a huge difference and it will save you from having to put a big cam in with the lumpy idle that you say do not wish to have.