i found this write up ..

How to modify a Datsun/Nissan steel crank to fit a Crossflow

I'd like to stress that I do not claim to be an expert - having said that I have modified seventeen cranks to date. Fitting of Datsun cranks into Ford Kent pushrod type engines has been very popular here in New Zealand for a number of years. It has also been done in Australia ans South Africa. Bob Homewood told me about this alternative when the crank in my Escort Twin Cam was cracked and all susbequent Ford/Lotus cranks I found were cracked too !!. Since then I have modified a number of Datsun crank shafts to suit Lotus Twin Cams, Ford/Cosworth BDAs, and 1600 Ford Crossflows. All L16 and L18 Datsun engines are made from a factory steel forging. I haven't been able to find out what grade of steel it is but it is certainly tough as it gives the cutting tools a very hard time when being machined. These cranks are an inexpensive alternative to the steel cranks sourced from the UK, not as strong ultimately but certainly far stronger than the OE Ford cast iron cranks.

First step is to find a crank. For Ford 1500cc precrossflow blocked engines using standadrd 72.75mm stroke then a crank from a Datsun 1600 (L16) is required (73.3mm stroke). For Ford 1600 crossflow engines using a standard stroke of 77.62mm then a crank from a Datsun 180B (L18) is required (78.00mm stroke). A Datsun 200B 2lt (L20B) can be made to fit. into a Ford 1600 crossflow blocked DOHC engine such as the Twin Cam or BDA. The longer stroke crank (86mm) requires a lot more machining. Also the block requires a lot of machining to allow clearance for the crank and rods. I am lead to believe that to get the L20 crank to fit Isuzu Gemini rods are used. I am unsure of what pistons are used. Rod to stroke ratio is important so the longer the rod with the L20 the better..

Why do it? - Is it economical for you?, or worth the bother?. For me the Dasun crank provides an affordable steel crank compared to the more expensive purpose made UK cranks. Access to the neccesssary machinery to modify the crank keeps costs down. I only pay for grinding and balancing Datsun cranks do have different counterbalancing compared to the Ford and Lotus items. Miles Wilkin's quotes BRM as having modified standard cranks by adding more counter balance weight. This is a topic in itself. Personally I think the OE Ford and Lotus cast iron cranks are built to light with a flywheel that is far too heavy (standard Ford 1600 Xflow flywheel weighs 10kg). I believe the heavy flywheel on the light crank causes them to crack. Having said this it could be argued that the Datsun crank is overweighted. For this reason I feel happy to machine down the counter weights to reduce the Datsun cranks' mass.

What has to be done to make it fit? If you lay the Datsun crank next to the Ford it will be self evident. The front snout has to be machined down, and cut back. The overall web diameter has to be reduced to aid clearance in the block. The rear flywheel mounting flange is shortened and the spigot bearing hole bored out to suit the Ford bearing. The webs and counter-ballances will need to be slimmed down, and some chamfered. As the Main and Big Ends are larger these can be ground back to suit standard Ford bearing sizes and strokes. Don't forget to have the all important fillet radii preserved when the crank is ground. The keyway for the front pulley can be milled in. The Datsun crank is a 5 bolt not 6 like a Ford. You can make a flywheel to adapt the Ford clutch plate and starter ring gear to fit the Datsun crank. This isn't hard. A medium tensile steel (EN8) or a high tensile steel (EN25) can be used. Or try modifying the Datsun flywheel. I have always made a flywheel as I prefer this solution. Also I can safely make a light weight flywheel with a steel blank. Samples shown . A video of my Escort engine with Datsun crank running can be seen at Escort Dyno Page. If you would like any assistance with sourcing or getting a Datsun crank modified feel free to contact me. For more information go to:




The photo above shows five different types of crank shaft.
Far Left: Standard OE Lotus Twin Cam cast iron crank (72.7mm stroke)
Second from Left: Datsun L18 fully counterbalanced crank modified to suit 1600 Crossflow.
Centre: Datsun L18 fully counterballanced crank modified to Suit Ford/Cosworth BDA.
Second from Right: Datsun L18 fully counterbalanced crank prior to machining.
Far Left: Datsun L18 partly counterballanced crank prior to machining.


The photo above shows a more detailed view of the differences bewtween the partly and the fully counter ballanced Datsun L18 crankshafts.


The photo above shows roughly where the crank will need to be machined. The pens are pointing to areas that will need to be machined.


The photo above shows the modifying of a Datsun crankshaft - in this case a L16.


The photo above shows the modifying of a Datsun crankshaft - in this case a L16.


The photo above shows the modifying of a Datsun crankshaft - in this case a L16. The rear of the crank is machined as per the Ford crankshaft.


The photo above shows the modifying of a Datsun crankshaft - in this case a L16. The webs are machined to clear the webs in the Ford cylinder block.






The photo above shows a flywheel made to suit both the 5 bolt Datsun crank, and the Ford Lotus Twin Cam 8.5" clutch. In order to reduce weight five 20mm holes were drilled near the centre, and segments were milled at the periphery of the flywheel. Total weight is around 5.75Kg. EN8 medium tensile steel was used.


The photo above shows a L18 fully counter weighted crank set up for a Lotus Twin Cam. The flywheel has been made from EN25, and mates to a Tilton single plate competition clutch. The front of the crank has been machined to suit the Twin Cam sprocket and pulley.


The photo above shows a L18 fully counter weighted crank set up for a Lotus Twin Cam. The flywheel has been made from EN25, and mates to a Tilton single plate competition clutch.


The photo above shows two types of flywheel I have made to suit the Datsun crank. The flywheels with the six radial slots are for a 7.25" sintered racing clutch. The flywheel weighed in at 4.1Kg including ring gear and was machined from EN25 - a high tensile alloy steel. The other flywheel has been made for a 7.5" OE type Ford clutch (Formula Ford competition will be used). It was made from 4140 high tensile steel and weighed in at 4.3kg including ring gear.


The photo above shows the milling of the six radial slots for the 7.25" sintered racing clutch style flywheel. The flywheel weighed in at 4.1Kg including ring gear and was machined from EN25 - a high tensile alloy steel. I machined in the slots in order to reduce its weight as the slots saved 0.8Kg. Also the removal of mass on the outer diameter to reduce the flywheels Rotational Moment of Inertia.


The photo below shows the CNC milling of the six radial slots

A big "Thanks" goes out to Martin Lucas in New Zealand for this feature!


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The issue from a Lotus point of view!



Rebuild Using a Modified Datsun Crankshaft.
The engine rebuild from hell! The most likely reasons why a Datsun crankshaft would be used instead of the original Lotus cast iron crank are:

The original cast iron crankshaft is cracked, and a suitable replacement can not be found. The Datsun crank is steel, utilising this crank results in the obvious advantage of the increased strength of a steel crank versus cast iron. This conversion is alot cheaper than a