Fully counterweighted crank?

[KiKiIchiBan]

I know there was an 8CW Datsun comp unit available 40 - 50 years ago that needed some extra plugging and drilling to live with the demands of racing but I'm not sure what's available now.

In my research for the parts needed for my engine, I've had my old crank scanned into a computer and with the eyes of an engineer from Cosworth redesigned it to make it better.

The computer estimates it to be 14.15kg cut from European supplied EN40B (My L18 4CW crank was 15.8kg) and it says it'll rev past 9000rpm while keeping the oil pressure consistent on the rod and main bearings. The oil passages are designed similar to that of the FIA BDA crank.

I might pull the trigger and get one cut as I have access to a 7-axis machine that is used to make cranks over here, it's not cheap but if anyone else is interested the price is reduced based on volume. Shipping might be an issue for those in the America's but we can discuss. He did mention the bronze pilot insert in the tail end could have a needle roller bearing in there instead.

DM me if this gets you excited and if you have any questions I should be asking the Cosworth engineer and the machine operator, please drop them below.

[BEO 510]

It sounds very interesting what you are doing, but i am not looking for a crank like that at the moment.
I am not sure what the differences are between the comp crank and those L-18 cranks with 8CW other than the comp have 6 flywheel bolts.
The later L-18 came with only 4CW and are not fully counter weighted, guess both your's are the later ones?

[KiKiIchiBan]

Every L18 crank in my possession is 5 bolt and 4cw. This one I've designed will use 5 bolts purely because that's what my flywheel is. I did think about 6 bolts and dowels like the Electramotive one but from what I was told, 5 bolt (arp type) will be enough.

[BEO 510]

I have one L-18 crank with 4CW, the other's are 8CW. All have five 12mm standard bolt's, i think the comp one's was 14mm.
My understanding is that the standard crank's are proven to be more than enough adequate for racing when prepped right.

[iceman510]

I'm going to have to check my L8 cranks for CW count.

Theoretically, couldn't the flywheel mount surface be a "blank" and you could drill it for 5 or 6 crank bolts as desired?

What's the proposed manufacturing method? A forged billet of your proposed material prior to machining? Or just a block of the material? Not an expert by any means, but I believe the Datsun cranks are a forged blank prior to machining.

The info on that EM40 indicates it takes well to nitriding. Is the intent to nitride the surface as well? It does mention it is often supplied as hardened and tempered, but that's not necessarily the same as forging.

What's the ballpark price being bandied about?

[gooned]

Wow, scratch built crank!!

[KiKiIchiBan]

Forged block prior to machining, and yes absolutely can do them as a blank and you drill your own if interested, this would make the most sense and give some flexibility. The shop said they can offer (ISO rated) gas nitriding, plasma nitriding, PVD coatings, DLC and other "experimental" surface finishes. They're used to custom one off for motorsport applications, this is just something on the side for me.

[KiKiIchiBan]

Forged block prior to machining, and yes absolutely can do them as a blank and you drill your own if interested, this would make the most sense and give some flexibility. The shop said they can offer (ISO rated) gas nitriding, plasma nitriding, PVD coatings, DLC and other "experimental" surface finishes. They're used to custom one off for motorsport applications, this is just something on the side for me.

[Byron510]

This is a very interesting discussion. A good friend spent the weekend with me as he was doing a work upgrade course here in the lower mainland this weekend, and it’s funny because we were discussing his one and only Comp crank I have ever put my hands on. This is a 1600 unit, 8CW’s as mentioned. It was a 6 bolt FW flange with dowels. It also has the comp flywheel (doweled as mentioned) and comp small dia stamped steel front pulley - all of these parts are as rare as hens teeth today.
But like my close ratio roadster gearbox, I can no longer trust these parts due to its age (I’ll retire the said gear box this winter, opting to use the ZX gear box for my vintage race car moving forward because I can still buy parts for it).
As a machinist, I am intrigued and will follow your project, however. I’m not sure I play at the level of using custom one of cranks. To be honest it seems exotic. But maybe todays production methods can bring such a unit down to a tolerable cost, given what we do at a club level. But as Iceman said, the Nissan cranks are not known to fail and I know that can last in constant use up to 8500 RPM.
But I’m still following, keep us posted.
Thanks, Byron.

[iceman510]

I was able to take a peek at one of my A87/L18 cranks this past weekend, still ensconced in the complete short block I have sitting here. It has 8CW. I forgot to look at the flywheel bolt count, but as it is from a stock engine (probably a 620 truck source, but not sure as I traded for it), I suspect it is the normal 5 bolt.

[KiKiIchiBan]

This is a very interesting discussion

I shall keep you all updated.

I was able to take a peek at one of my A87/L18 cranks this past weekend, still ensconced in the complete short block I have sitting here. It has 8CW. I forgot to look at the flywheel bolt count, but as it is from a stock engine (probably a 620 truck source, but not sure as I traded for it), I suspect it is the normal 5 bolt.

I'm not sure what you have, but the L18s I've seen here are all 4CW and when looking to buy a 8CW all I could see referenced was the old Datsun Comp one or the Refresh60 2.2l crank and they're NLA, hence why I warmed up the CAM software and put my new M2 Mac to use

[BEO 510]

53044254797_cad55e7577_k.jpg (532.32 KiB) Viewed 481 times

Forgive me if this not working. I try to learn how to post pictures. It is a picture of your engine from your build thread. As you can see it looks like a Z-20,22 or a block for Z-18 & L-18 in this case when it comes to the casting for the engine stamp. But the casting for the Z stamping is blank i guess. And usually when it's equipped with an L-head it have the L-18 xxxxxx stamping on the usual right side. Most of the Z-20 & Z-22 i have seen also have a blank L-motor stamp on the right side. So what i consider "late" L-18's with 4CW are those cast as both Z and L-series engines. What year came the Z-16 & Z-18, my guess is that's the year the 8CW L-18 crank's became 4CW. My L-18 cranks from the 610 and 810 here in Scandinavia are 8CW, the one with 4CW are from a 910.

[BEO 510]

30.JPG (145.5 KiB) Viewed 463 times

This is a brand new L-16 short block, but as you can see it is ready for Z-16 stamping too.

[BEO 510]

PB290025.JPG (294.2 KiB) Viewed 461 times

PB290028.JPG (251.41 KiB) Viewed 461 times

Here you can see a different version of the casting for the Z-18 stamping.
I think here in Europe you must look for L-18's not newer than late seventies/1980 or one without the casting for Z-engine stamping if you want a 8CW crank.

[iceman510]

PB290025.JPG
Here you can see a different version of the casting for the Z-18 stamping.
I think here in Europe you must look for L-18's not newer than late seventies/1980 or one without the casting for Z-engine stamping if you want a 8CW crank.

Interesting it also has the later style oil filter boss with the threaded holes around the perimeter. I have only seen this on Z engine blocks, not early L (but not a comprehensive survey by any means).