79 280 into 72 240

[Z dreams]

Hi all,

My 240 engine needs work, I found a low mileage 79, 280 engine with N-47 head and tranny. What am I looking at to do this transplant? I'll be using S.U.'s I want to be clear on what I may need for parts or change's I need to do.

Thanks, John

[Zed Head]

In principle, theory, on paper, in your mind, it's a pretty easy bolt-in swap. You might just need to retune the SU's for the bigger engine (I don't know SU's). The dimensions of the parts are the same.

In reality, you'll break a bunch of bolts and studs when removing various parts, like manifolds or exhaust pipes. So you just need to be prepared to fix some broken stuff. If you really want to be prepared you'll have some taps and tap drills waiting and just decide to replace parts that might or might not need it, like manifold bolts or studs.

I'm not sure, but I think that the 240Z exhaust manifold and exhaust system might be a little restrictive for a bigger motor. I think that they're restrictive for the stock L24 even before you start. The pipes look small compared to 280Z pipes (you'll see if you compare).

The 5 speed transmission will bolt right in. The shifter or shifter opening might need some work, or not, 1972 might be big enough. Early cars couldn't handle the throw of the 5th gear position.

Overall, it's easy. But the broken bolts will be aggravating. And, of course, there's the "what should I do while I have it out" project bloat. Clutch, flywheel resurface, rear main seal, transmission front seal...etc.

[tlorber]

This should be a pretty easy swap. Engine will go right in, as will the tranny (keep your old shifter though). As stated above you should plan on a header and new exhaust ( or use the one from the ZX if there is not too much smog crap on it). You will need the 240 intake manifold and the balance tube to drive the brake assist. You should also use the ZX alternator (get Dave Irwin's adaptor plug) and distributor. Keep in mind thought that your gear ratios may be a bit tall unless you swap out the diff for a shorter (numerically higher) one.

Edited September 3, 2014 by tlorber

[EuroDat]

Do you know when in 79? The transmission could be the same as the 280Z which had the same ratios as the 72 240Z , but with the 5th gear. They changed over around August 79 I think. Another point, if it came from a 280ZX 2+2 it will be the same as the 280Z, but with the heavy duty clutch.

[zKars]

The N47 head also has no provision to mount the mechanical fuel pump. Well you can, but it you have to machine out the port on the side of the head. The three bolt/stud holes are there but none of the N47 heads I've seen have the opening into the head. Perhaps this is the time to consider a low pressure electric pump.

[EuroDat]

Do you know when in 79? The transmission could be the same as the 280Z which had thewhene ratios as the 72 240Z , but with the 5th gear. They changed over around August 79 I think. Another point, if it came from a 280ZX 2+2 it will be the same as the 280Z, but with the heavy duty clutch.

A little clarity. Regarding the pre August 79 or 2+2 engine transmission combination. The ratios 1st through to 4th will be the same as what you now have, but then you will have an extra 5th gear for highway cruising.

Its after 79 when they changed to the close ratio 71B transmissions. Those have a high 1st gear specially when used with the 240Z difff ratio.

Chas

[Z dreams]

Thank You, for sharing your knowledge guy's. Looks like a road trip tomorrow!

[Zed Head]

If the diff is available you might consider getting it also. The 79 ZX had a variety of diffs but at least it will match the transmission.

Euro, I thought the same on the transmission but the FSM says that 72 still had the 3.592 first gear, not the later 3.321. It also says that it has a 3.9 diff ratio though, which would give a very low 14:1 overall first. I'm not sure the FSM numbers are right though, the 240Z guys would know for sure.

Anyway, it's definitely doable. Good luck.

[EuroDat]

I stand corrected. I didn't know the 3.9 came out in the US models. Thought it was only in the non US 5speeds. Learning something new all the time when it comes to these cars.

But I did quote the early 71B 4speed as the same as the 280Z 4speed, which it is not. The 240Z used a similar ratio setup as the 720 trucks in the 80's had in the 5 speeds.

Anyways if he has the other ratio (3.364) then he would end up with a 12.1 ratio compared to the 11.2 he would of had with the original 4speed.

Chas

[Z dreams]

Well I did the road trip and bought the 79,280 engine and tranny. Transmission appears to be early 79. O.K. for my stock 72, 180 rear end?

[Diseazd]

Z dreams.......I'd use your early 240Z intake and exhaust manifold (plug the air injection holes). Then.....all you need to do is figure out what goodies you want to add to the head if any. Either tranny will work fine, just make sure you match clutch parts to whichever pressure plate you decide on.

[EuroDat]

Hi Diseazd, Will the exhaust manifold line up ok one the N47 head? It has the round exhaust ports and the head he has now has square ports. On a stock engine it probably won't make a noticable difference in performance and he is going to L28 which will more than compensate.

Chas

Edited September 8, 2014 by EuroDat