JDX engine for a 300?

[75greenmachine]

I have had this idea for quite a while, but I haven't really looked into it that much. I was thinking that I could take the engine from a JDX and drop it into my '75 300, and make kind of a 300 "sleeper". I would keep the sled painted mean green and keep all of the 300 decals on. Would it be a direct bolt in? Or would I have to do a fair bit of modifying to make it work?

[Matt]

Any 00/JDX engine would be a bolt-in. You have lots of choices. If you were to put a 440/5 in, it would basically be a 500, or a 440/22 w/ CDI & tuned pipe would be an 800. Other then the engine they're basically the same.

[75greenmachine]

Awesome, thanks a lot. I'll be keeping my eyes open for one now.

[400brian]

I own a green machine that started out life as a '74 300.
It has since been re-powered with a 340/5 out of a '74 JDX4 Special.

I believe you will find that the motor mount with the pipe hoop for dash support will have to come from the donor sled.
My machine is green, but has the black steel engine mount and hoop out of the X4. I believe the hoop out of the 300 is narrower. Something to due with the Kohler? You will also need the driven sheave from the donor.
If your 300 doesn't have a speedo, you need a drive bushing installed into the driveshaft at the minimum.

I'd say a donor sled would really simplify things, but it's all a bolt together swap.

[Matt]

Good call Brian. I have a Kohler JDX4 in my garage right now, and next to the 600, it clearly has a different hoop. I don't think you could use the Kohler in the 600 either as that exhaust manifold would probably hit the hoop.

[75greenmachine]

I'm still new to vintage sleds so I have a pretty stupid question, what's the driven sheave? And why would I need a drive bushing installed on my driveshaft if I don't have a speedo?

[400brian]

You have two sheaves ( belt pulleys ) on your sled, the clutch on the engine is the primary or driving sheave, and the one on the jackshaft is the secondary, or driven. The clutch and secondary are a matched set for the most part.
So if you swap engines, you need to also swap the secondary as well. The chaincase gearing could also be different.

The drive bushing I referred to, is a small steel bushing with a square hole in the middle. It is pressed into the end of the driveshaft, and the speedo drive key mates it and the angle drive to the speedo via the speedo cable. Thus driving the speedo. My 300 apparently never had a speedo, as there was no drive bushing in the driveshaft.

The exploded views at <JDParts.com> can be very helpful.

[75greenmachine]

Alright, that makes a lot more sense now. Thanks a lot!