240z with 280zx non-turbo exhaust question.

[Duff]

I am building,rebuilding, really a 71 240z with a na 83 zx engine and 5 speed with SUs. I am building this as a semi-daily driver. As I will be 70 in a couple of months my need for speed has diminished and see no need to build anything but a dependable mostly stock vehicle. Therefore I decided to use the stock zx exhaust manifold versus going the header route. My question is will a stock zx down pipe fit with a minimum amount of modifications,or is a custom pipe needed?

[BluDestiny]

Actually headers will probably be easier to service (it's much lighter and you can easily see all the bolts on it). As for the stock manifold, I believe it will depend on if you have the EGR port or not, but every 2 port "midpipe" will bolt to any other header. They don't change much is design. 

[beermanpete]

The ZX downpipe will likely need a bit of modification to work. We have a 280Z engine with the cast iron manifold and downpipe (from a 75 280Z) in our 73 240Z. To make the downpipe fit we had to heat and bend it a bit. If I recall correctly, we did this in the car with the car on a service rack at the muffler shop. Not a big deal if you don't get fussy and worry about flow rates and such. Just be sure not to collapse the bend.

 

Also, there are at least two variants for the connection between the cast iron manifold and the downpipe. The early type has a different bolt pattern and I think the two pipes are slightly smaller as well.

[Montana13]

I have a 72 240z and I put in an 82 280zx naturally aspirated engine in it with the 5 speed and everything. I also put my su carbs back on. I am using the stock manifold for now and I went to the junkyard and had someone cut the downpipe off a 80 280zx then I welded my 2.5 in exhaust piping on it. It worked just fine and has lots of room. Also like Bludestiny said it would be much easier to service a header. My manifold is enormous and a pain to work on.

[Montana13]

Double post

Edited September 15, 2015 by Montana13

[Duff]

Montana,

How far down the down pipe did you cut it off?

[Montana13]

Let me try and get a picture up

[Montana13]

[Duff]

Thanks to all for the reply. I figured I should let those interested what I finally came up with.

I bought on eBay a 240Z head pipe(part number 20010-e4100 which is superseded by 20010-n3000).

Then I bought both a gasket for the 280Zx and the 240Z. Using the 280ZX gasket  I was able to mark the flange 

as to where the bolts had to be. The ZX's are larger and in different locations. I filled the 240Z

holes with three pieces of a bolt that just fit the holes then welded them in and smoothed both surfaces of the flange.

then, using a few drill bits and a rat tailed file I notched the flange.

 

 

I had a little trouble installing, as one of the pipes that went up into the manifold was out of round and would not allow me to

tighten the bolts. After fixing that it fit right in.

 

 

I like the length of the two runners on the 240Z pipe over the shorter ones on the 280ZX. 

 

I hope this helps any one trying the same swap.

Edited September 27, 2015 by Duff

[Montana13]

Great idea wish I would have thought of that! I hope it works well!