SR20DE/KA24DE Roadster Engine Swaps
as commented on the Roadster List by Michael Spreadbury

The Question

Michael,

I really appreciate you taking the time to respond to my question. I will ask a couple more if you don't mind. The reason I was considering the sr20det was the increased HP. With my admittedly limited knowledge of this engine, it seems to me that the ka24de would make more sense than the NA sr20. I know the ka's are more readily available and cheaper. I think also (correct me if I'm wrong) that a ka24de makes more HP than the sr20de and have heard several people on the list speak of how simple of a swap it is. I don't recall anyone saying that the crossmember had to be notched (although maybe it does since these 2 engines are a direct swap in the 240sx) to accept the ka. However, at the same time, I know there are many 240SX owners opting to remove the ka in favor of the sr, something I don't really understand. I guess I'm sort of rambling here, so I'll just list out a few questions for you.

What are your feelings SR vs. KA?
Are the transmissions interchangeable on these two engines?
Are you aware of body or frame mods necessary for the ka?
What do you consider a fair price for a 40,000 or less mile SR20de?
What kind of mods would be necessary to use a front drive engine in a rear
drive application?
How much of a notch was required in the crossmember for the SR?

Again, thanks for your time.

Alan Horton

P.S. That is a beautiful job on your 66.

The Answer

Hi Alan,

I have a few spare minutes this morning, so I thought I would catch up on a little e-mail. Your post brings up lots of good points, and really when you think about it, all engine swaps come down to personal preference for what is going to work best for a persons skills tenacity, mechanical ability, and their desire to do something different.

The KA24DE found in the Nissan 240SX makes for a great swap into a Datsun Roadster. I have seen several of them, and the owners that I talked with have all been very happy with their conversions. The KA-series has the advantage of easily sourced parts, and now that lots of 240SX owners are pulling them out of their cars to install the SR20DET engine, they are cheap and easy to find on the used market.

With it's 2.4-liters of displacement, the KA24DE makes lots of torque, and as we all know, torque is what makes our cars fun to drive. However, a lightweight car like the roadster still responds extremely well to the 2.0- liter SR20DE.

However, ask anyone who has buzzed both a KA24DE and an SR20DE to their respective redlines and I think you will find most will agree that the SR20DE is a much more refined engine package. The SR is so smooth all the way to the redline, it really is remarkable. Another advantage of the SR20DE is its all-aluminum construction unlike the KA24DEs aluminum head, iron block arrangement.

Both engines use nearly identical engine management systems (my SR20DE is running on a KA24DE harness and ECU), and the gearboxes are the same internally (though the SR20DE has a different bellhousing).

RWD SR20DE's can be purchased very cheaply from engine importers, I have seen them as cheap as $500, all the way up to $2000 depending on what you are getting. Of course you would want to buy as complete of a package as possible, be sure to get the engine/transmission, and most important, get the starter, it is unique to the SR- family. I like to estimate ~ $1200 for a super clean, low mileage power train.

Using a FWD SR20DE can (and apparently has) been done. I have never seen photos, so I really can't comment, but since RWD SR20DE's are not that difficult to source, I would not waste my time converting a FWD SR20DE engine into a roadster. Why invest your time reinventing the wheel?

The notch that is required to clear the front sump oil pan goes to the first set of welds on the inner structure of the crossmember (about 1.5' in from the outside edge). If you have ever cut one apart, you will see that there are a couple braces welded into the center of the crossmember. Basically, the notch we make butts up to the first reinforcement. The notch is mostly to ease installation of the engine and transmission, I have heard of people just smashing in the crossmember to clear the front pan, but I prefer to remove the material and weld in a new cap rather than using a hammer to gain the clearance. With this material removed, the engine and transmission install into the Roadster's engine compartment very easily.

Anyway, enough rambling. Both the KA and SR make a great swap into a roadster, my preference has, and always will be with the SR-series engines, and I think if you ever get an opportunity to drive a roadster with this engine, you would agree! I have yet to have someone take my car for a spin that was not sold.

Michael Spreadbury
1966 Datsun Roadster (with SR20DE power)
1969 Datsun 2000 Roadster (soon to be with SR20DE power)
1970 Datsun Bluebird SSS Coupe (SR20DET/6-speed project)