L28 and ATI Damper

[Jitenshakun]

I'm trying to install my ATI  damper on the LD28 crank and it seems i jeed a major ch longer crank bolt. 

 

Has anyone installed an ATi? What did you have to do? 

 

I think i need a 50mm-55mm crank bolt, assuming a 10mm washer. 

[datzenmike]

This is an after market crankshaft damper??????? Why would someone making such, either supply the needed bolt or make it so it's not needed??? Also why a damper? a six cylinder is the best engine for smoothness and lack of harmonic vibrations. Is this a stock engine?

[Jitenshakun]

No, it is not at all a stock engine. 

[fiveoneO]

Crankshaft dampers are used to reduce something called Torsional Whip/Torsional Vibration. Even with a perfectly balanced crankshaft you will get torsional whip. Every time your sparkplug fires, that force applied onto the piston travels down the rod onto the crankshaft and twists that crank journal a little, then the journal untwists. If you think about how many combustion cycles happen at 6000 rpm and how much of a load is being put on each crank journal, that crankshaft is in a constant state of twisting and untwisting. Crankshaft dampers greatly reduce that harmonic.  

[Stoffregen Motorsports]

[Jitenshakun]

7 minutes ago, Stoffregen Motorsports said:

Thank you! I beleive a KA crank pulley bolt may be perfect. The McMaster-Carr is now my plan B. 

[Stoffregen Motorsports]

There is an ARP listing for an RB26 crank pulley bolt - https://www.summitracing.com/parts/arp-102-2501?srsltid=AfmBOor9m3psGpFWsncuka88b58Clx5f3s_HBLzF_ocGJ1bYxDO3VmUH

 

It shows 18mm, but I believe that's a misprint. I'm pretty confident that the RB crank pulley bolt is the same thread as the L series. Ironically, ARPs own website does not list the thread size...

 

For $35, it might be worth ordering to find out.

 

 

Edited December 23, 2024 by Stoffregen Motorsports

[Jitenshakun]

Thank you. With current freight challenges and the exhange rate the ARP is closer to a $100 bolt for me. 

 

I will keep it in mind though. 

[Jitenshakun]

2 hours ago, Stoffregen Motorsports said:

There is an ARP listing for an RB26 crank pulley bolt - https://www.summitracing.com/parts/arp-102-2501?srsltid=AfmBOor9m3psGpFWsncuka88b58Clx5f3s_HBLzF_ocGJ1bYxDO3VmUH

 

It shows 18mm, but I believe that's a misprint. I'm pretty confident that the RB crank pulley bolt is the same thread as the L series. Ironically, ARPs own website does not list the thread size...

 

For $35, it might be worth ordering to find out.

 

 

RB26 is a M30x1.5 and approximately 85mm long. Wee bit too long. 

[datzenmike]

6 hours ago, fiveoneO said:

Crankshaft dampers are used to reduce something called Torsional Whip/Torsional Vibration. Even with a perfectly balanced crankshaft you will get torsional whip. Every time your sparkplug fires, that force applied onto the piston travels down the rod onto the crankshaft and twists that crank journal a little, then the journal untwists. If you think about how many combustion cycles happen at 6000 rpm and how much of a load is being put on each crank journal, that crankshaft is in a constant state of twisting and untwisting. Crankshaft dampers greatly reduce that harmonic.  

 

That's understood. I don't think the LD28 had one as it wasn't revved very high. I was curious what's been done that it would need one.

 

That said, the diesel stroke would red line at 7,250 where the much shorter stroke L28 is almost exactly 1,000 RPMs higher. (on stock rods)

[Jitenshakun]

Forged rods, balanced crank, and intention to let 'er spin up if the rockers stay put. 

[Stoffregen Motorsports]

On 12/23/2024 at 1:39 PM, Jitenshakun said:

RB26 is a M30x1.5 and approximately 85mm long. Wee bit too long. 

30mm thread? That would be over an inch in diameter.

[Jitenshakun]

It's a giant head, a thicker untreaded part, then an M16x1.5 for the business. It's a bolt with a lot on the go. 

[datzenmike]

I thought my Crankshaft bolt was 27mm.

[Stoffregen Motorsports]

Kameari makes one that has a stock appearing hex head - https://www.thezstore.com/product/5271/price-drop-kameari-reinforced-crank-pulley-bolt-70-83-240z-260z-280z-280zx

 

...but it looks only marginally longer than stock.

[Jitenshakun]

On 12/26/2024 at 1:40 PM, datzenmike said:

I thought my Crankshaft bolt was 27mm.

27mm-30mm depending. 

[Jitenshakun]

58 minutes ago, Stoffregen Motorsports said:

Kameari makes one that has a stock appearing hex head - https://www.thezstore.com/product/5271/price-drop-kameari-reinforced-crank-pulley-bolt-70-83-240z-260z-280z-280zx

 

...but it looks only marginally longer than stock.

The Kameari resellers can be awful at specific details - like bolt length. 

 

These guys say 50mm, but I'd order direct from Kameari to be sure. 

 

https://www.z-services.eu/en/engine-block-crankshaft/980-kameari-crankshaft-pulley-reinforced-bolt-240z-260z-280z-280zx.html