Optimum Crank weight?

[ZD44TT]

Hi guys.........does anyone know if theres an optimum crank weight for a standard L26 crank?

 

e.g if I take it to a balancing place and want the crank lightened -  is there a weight I should tell them to shave it down to?

 

Cheers.

[620Z]

You could be dicing with death messing around with the crank weight to gain minimal power. I would be focussing more on the flywheel and balancer (But make sure you know what you are doing). Even if you are racing your car and trying for that extra half a second on the track I would be looking in different areas to make your car faster. There is no way you could go .5 of a second faster around a track by lightening the crank. I guess it all depends what you want to use your car for as well.

[gav240z]

Craig is right, lightening the crank is not an ideal thing to do. I don't know if a machine shop would actually do that for you?

 

Balancing it yes, but the standard crank is pretty well balanced from the factory. In fact you won't gain much as Craig stated. You could shot peen it for extra durability but I honestly don't think you need to in a street car.

 

You can buy a crankshaft from http://www.kameariusa.com/L6_3_1_Crankshaft.php if you got deep pockets . Even those are 22kg. I can't recall the weight of a standard crank but they are fairly heavy from memory.

[ZD44TT]

thanks guys.

 

another quick one...........can i use an L28 crank instead of my L26 to bump up cc?

 

L24:

83mm X 73.3mm

2393cc

Head = 42.4cc

 

L26:

83mm X 79mm

2565cc

Head = 44.7cc

 

L28:

86mm X 79mm

2753cc

Head = 44.6cc

 

Cheers.

[ZD44TT]

ok for the noobs like me who have no friggin clue..........

 

the 79mm is stroke on the L26 and L28............without going to the bigger pistons cc is the same.

 

 

[gav240z]

Yeah I've always been under the impression that the L26 and L28 are the same crank, its the L24 that is shorter. The L28 block is a bigger bore and therefore the reason Nissan went with the new design block.

 

The L24 / L26 blocks were P30 stamped from memory. You could overbore your L26 and get it to 2.8 fairly safely (at least I believe so).

 

So the answer your query, yes CC won't change unless you overbore.

 

What are you trying to achieve, perhaps we can help suggest some mods?

 

I know that Alan "260coupe" recently built a "budget" l26 with some modest results.

 

 

[gav240z]

http://www.viczcar.com/forum/index.php/topic,2415.0.html

[gav240z]

When it comes to crankshafts, or bottom end work. I believe that blue printing (balancing the rotating assembly) is a good idea for reliability, if you don't plan on racing your Z its probably not that necessary (depending on power you want to achieve).

[260Coupe]

I lightened my flywheel by a couple of Kg and balanced the entire assembly from harmonic balancer to clutch, the lightened flywheel allows the engine to spin up quickly making it more responsive and the balancing allows for smooth revving. Lightening of the rank is unnessary unless you are building a full blown race motor 

 

I utilised the skills of Chris Wood for the lightening and Motor Improvements for the balancing work .

 

End result was almost 50% HP gain at the wheels from a stock L26 (76 rwkw to 112 rwkw at 6200 rpm) and a very smooth tractable engine  .......next job is to fit the Triple Mikunis

 

http://www.viczcar.com/forum/index.php/topic,2415.0.html

 

cheers

 

Alan