head swap

[ianray]

I have a 1973 240z and I want to know if a 1978 280z head will fit. What I'm trying to do is get more horse power with the larger combustion chamber fron the 280z and not worry about using unleaded fuel in the 1973z which take leaded fuel, (the 280z doesn't). Also I want to get rid of the fuel injection system of the 280z and stay with carbs. Will the caburetored intake manifold from a 240z fit the 280z head? Has anyone done this swap?

[zguitar71]

The head will fit but the larger chamber will not give you more power. The compression will go down so will the power. The carbs will swap too. Do you have the flat top SU's or the round top SU's? If you have the flat top then think about switching to the round ones from the earlier models. The only advantage with the head switch would be larger valves than what your e-88 head has now. However; your head may be the later e-88 and alreeady have the larger valves, but I do not know how to tell the two apart. If you search you might be able to find the cut off date from small to large valves for the e-88. The larger valves in the larger chambered (n42,47; p-79,90,90a) heads should help with power some but I think the loss of compression would more than counter act it though. If you must change heads then go with the N-42, you will have the square exaust ports with that head and better compression than the P heads. The N-47 (found on the `78) has round ports and exaust liners, though some say they are not a bad thing. You are better off having the seats in the head changed (stainless) and putting larger valves in it (if it does not already have them) so you can run unleaded and keep the compression.

[jmortensen]

You would also have to notch or eyebrow the block, because the L28 valves will hit the cylinder walls. So it's not just a bolt on. Much better option would be to get a whole L28 engine and put that in your 240.

[beandip]

It is true that he 280 heads will yield lower compression , unless you mill the head. Do this when you change he heads and also do a valve grind . What is the condition and or how many miles on the L-24 your running now. If it original and in need of a rebuild . Consider installing a ZX engine , it's like a bored and stroked L-24 and stock it will liven up your '73 . I milled .030 off my P-79 head and that gives me 9.5 to 1 compression and have no trouble with fuel. If you are going to spend a bunch of money on a engine why not do it on a improved version of he L-6 . It runs great with SUs. Gary