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Project itch.. need advice


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i am new to this... 

i have been looking to starting a new project

73-74 Datsun 620

my idea is to shorten the bed 1-2 feet (on a shortbed) yes on a short bed.

changing suspension to an independent suspension ( also looking to add air ride system)

and an engine swap with high mpg.. ( Honda crx engine ) 

any advise willing to take in consideration

if you know a shop that can assist with the fabrication

near S. Cali in area of Los Angeles would be great..

any input

chopping bed....

swapping suspension....

engine swap..


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like i said in my question.. i need an high mpg engine.. if you think crx is ridiculous then what would you advice... not looking for racing looking for daily driver for work 100-150 miles per day 6 days a week.

Not worried about swap, since its a pre swap. i have had 60's cars and have done swap and no issues before.. i just have not done one on Datsun and don't know where to begin.. 

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Everyone needs to keep in mind that there is a lot of old American sheet metal down there with modern engines in them(big V8s), how are they getting away with it in California?

I would not ask the DMV anything, I would ask the ones that have done it and follow suit.

So he owns a Datsun and came to a Datsun site and asked, let us let the ones that know answer to the question answer the question.

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The answer is you don't talk to the DMV. After registering the vehicle in your name you never deal with them again aside from paying registration every year. Period. If Datsun owners in CA took Mike's advice there would be about 90% less Datsuns registered in CA.


CRX engine is mounted transverse, and, assuming you want the B16, there is no rwd longitudinal transmission option, not to mention it and most other Honda motors spin the wrong way for a typical rear end. Could it be done? Sure, but your post doesn't strike me as an unlimited budget build with a lot of high dollar one-off parts. You'd be better off just starting with an f20c if Honda is your end game.


IRS in these trucks has been done at least a handful of times so you can search those builds out.

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You want high mpg, run an L16, fuel injected, with a really good economy map. And a 5 speed. Match that with a properly selected rear end gear and a good tire size.


But running a crx motor won't work without fwd swapping the truck. By the time you spend the money to do that job, you could have driven a vehicle that only got 17 mpg for 15 years and spent the same amount of money.


Don't step over a dollar to pick up a dime.

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i do have a place to work on it.. No fab skills reason for asking for a shop.. i have a friend that is an expert welder and can do anything on cars but is too busy been waiting on him for weeks to give me a starting point and nothing yet... budget was 5 to 7 but that does not look possible, unless i start youtubing the fab work myself.. i have a master mechanic that will be assisting when it comes to swap... he is more of traditionalist, does not like swap, but is willing to assist with technical stuff (electrical and getting it running) he just does not fab any work

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ka24de been done many times 25 to 30 or so mpg good horsepower and torque 

if you must go with a non nissan motor  s2000 has a great power plant great horse power and i dont know about the fuel mileage 

if you have done many swaps then you know where to begin get a truck then find a suitable power plant that fits in the engine bay 

just my 2 cents 

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The L16 should give fairly good mileage. An engine that gives better in a car may not give the same in a truck. For one the 620 has a 4.375 differential and it's RWD. Probably cheaper to buy a Subaru or something with fold down seats cargo area in it.


RWD engine swap.


Need transmission also, is clutch hydraulic?

Should swap the differential for something more MPG friendly

Must convert to EFI, wiring, fuel pump

Convert to internally regulated alternator

Custom rad? electric fan?

One off engine and transmission mounts

Does oil pan fit?

Drive shaft length mods

What side is exhaust on?



Probably never been done before so everything will be first time and unknown.


This is not a good idea and with dubious outcome for mileage goals.

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The 620 is a brick.  It will NEVER get 35-40 mpg, unless you drive it like a Prius and stay under 40 mph.  It has 20 square feet of frontal area, most of which ranges from 45 degrees to flat vertical.  Its not aerodynamic.  And with the quantity of fabrication you want done, you realize you could buy a used Prius for 1/8 the money this project will cost, right?  Even then it will leave you disappointed.  How about just buying a rotary Mazda pickup?  

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Sounds like you don't even have a truck yet. Go to the DMV and see what the laws are concerning engine swaps on pre emission check vehicles. I suspect it will have to be smogged if a newer than '75? engine is used.

Or don't. Less information is better at CA DMV.


They aren't worried so much about engine swaps here in CA as they are about chassis swaps. If it's old enough, any engine can be swapped in.

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I'm curious. What are your actual goals?


Small truck, with great mpg?


Lots of cargo capacity and great mpg?


What goals led you to decide a 620 with a fwd 1.5L swap was the best solution?


When i read your plans for independent suspension, shortened bed, fwd, It draws a very different picture to me. One that is much more easily accomplished.


Subaru brat with FWD transmission swap.


Now you have a SHORT bed vintage Japanese truck, already has 4 wheel independent suspension, will get ok mileage with fwd trans and won't cost $5k to get on the road.


If you want better mileage then other Subie motors can offer that.

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I know that what follows is not what you wanted to hear...


I get that you really want to make this out of a classic Datsun so it fits your needs and your desire for looks, and although I do agree with Lockleaf about the Brat being a good fit, they are somewhat hard to find from what I've been told by Subaru friends, so the long and short of it, if you are dead set on a modified vehicle it would make way more sense to truck a Civic to fulfill your needs than to heavily modify a 620 to fit.


The plans you have for modifying a 620 require extensive fabrication skills and a lot, I mean a lot, of money.  Plus it sounds like you have a timeline where you want this sooner rather than later.  That said, I really think starting with a Civic and "trucking" it would in the end be a better choice to fits your needs.


It would already have the FWD platform, already get good MPG's, already be a short wheelbase, once "trucked" it would have the shortened bed you're after, and all that is required is the much shorter and easier to complete fabrication of the new rear wall.








There were even a few pics out there of clean looking conversions, but of course those pics are hosted on Photobucket so I can't link them here.  Google civic truck and you'll find them.


Feel free to completely ignore my post and do whatever you want, just thought I should throw in my 2 cents lol



Oh, and the obvious easy button, but higher buy in, is a VW Caddy with the diesel.



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