I own a '73 240z and want to swap out the original engine for more power.

I recently just bought a P90a F54 rebuilt engine and was wondering if this is a good set-up or not to run SU's on a '73 240z? I initially was going to by just an L28 N42 Long block but was told the P90A F54 was a better engine for the same price. I don't know if I got taken or not. Now that I have it, is it a better set-up than just rebuilding the original engine. I know the P90A F54 is off of an '83ZX and that the P90A had hydraulic lifters (I don't know what that means cause I don't know much about engines---how often do the lifters go bad and how hard are they to replace?) And I know the P90A is set up for a turbo----I don't want a turbo, I want SU's. Do I keep the P90A F54 or do I keep just the F54 Block and change the head---is this hard to do? If I do just need to change the head on the F54---how do you do that and where do you get one? Someone please help!

First - not all P90a heads were hydraulic lifters. But if this one is, finding a non-turbo cam for hydraulic lifters is virtually impossible. The hydraulic lifters can be converted to solid, and then you can use a normal performance cam.

P90a is a good head for flow, although it's not a really high compression head. If your F54 block has flat-top pistons (and it should, unless it was also from a turbo), the P90a/F54 combo should give around 8.5:1 compression. Not really very high, but eases your octane requirements for street use.

I know several people around this forum who have F54/P79 combos who are very happy with them. The P79 is said to not flow as well in the exhaust, so if you can get a decent cam in the P90a it should work well.

I'm told the P90A cam is stock and that it has over-sized flat top pistons with a compression of around 9.1/1. Is that good? Will the stock Cam not for for someone who just wants an SU Carb set-up? Am I better off getting an N42 or a P79 and selling the P90A for someone who wants a turbo?

Hard for me to say. The turbo cam is a rather mild grind. It will work with the SUs, but won't make as much power as other cams would. Depends on what you want out of it. The turbo cam requires boost to make power at higher RPM. On a NA (naturally aspirated, or non-turbo) motor, it's likely to feel pretty soft at higher RPMs.

First, why did you buy the engine and then ask if it is a good engine? In the future I would suggest researching before you make any purchases.

The P90a and P90 heads are great flowing heads. They also have the advantage of having heart shaped chambers which lends itself to developing excellent quench characteristics. However, in order to take advantage of the quench, you need to increase the compression (i.e., shave the head, lengthen the stroke, switch to a 1mm head gasket, etc.)

In you case, I would try to sell the P90a head and pick up an N42 or P79. However, the P90a head is not very desirable. Most everyone either wants the N42, P79 or P90 heads.

As Arne indicated, your F54 block may have flat top pistons if it came from an N/A car. This is exactly what you want.

I would be interested to know what they meant by oversize pistons. It seems strange that someone would put in different pistons but leave everything else alone.

Thanks Arne and KTM for the input. I truly appreciate it. I purchased an N42 but then showed up and was told the N42 didn't pass the compression test so he was giving me the P90A instead and that it was a better engine. As an idiot I took it without realizing it wasn't as good as the N42 for my purposes. Had already rented an engine hoist so I took it----dumb mistake. Anyway, I appreciate your input and expertise and am better informed for it. I contacted the seller and he agreed to sell me a P79 re-built head for $200 bucks and I install it myself or I can wait for an N42. How hard is it to install a new head on a block? Is it hard or should I wait for an N42?