Expert: Dan Liddy - 12/30/2004

Question
Dear Dan,

I have a 1982 280zx. I am rebuilding the engine in it, and I was wondering what kind of modifications i can do make more horsepower. I want to keep it naturally aspirated.

I also have a turbo engine with no turbo. Would the block and head in the turbo engine make better horsepower on a NA engine?

Any help would be greatly appreciated. Thank You.

Answer
Hi David:

Boy you're bringing back some cool memories. My favorite all-time car was my '76 280 Z  (no X ) and I could take it out on Saturdays and go looking for Camaros without fear of embarrasment.

Get on E-Bay, do a search for 'Datsun Z cars" and get the book "How To Hotrod and Race Your Datsun"  I have forgotten who wrote it but it's absolutely the best advice and information anywhere.  Those of us that race use it as a bible. There's another about building Datsun-Nissan race engines, also a good buy.
Let me manswer your second question first.

The Turbo head will have fairly low compression, and without a turbo will not produce many grins.  The block assembly should be the same as others, but it might have a deeper dish piston, also limiting compression.

Here's how you can make it really howl, without sacraficing reliability.

Bore the block oversize by 020" ('twenty thousandths') and buy from NISSAN a set of the flat top pistons for the '81 ZX get the rings with them (unless you are actually going to race, then write back ) Have your engine machinest fit them with about .003" clearance.

Have the flywheel 'turned' to lighten it as much as possible.  The stock one weighs about 28 Lbs. and with the turning you can remove about 9 Lb.  It makes a whale of a difference in acceleration. Also have the shop put a 'step' in the clutch mounting surface so that the pressure plate sits closer by about .025"

Have your engine shop balance all the crankshaft components beore assembly, this costs a bit, but will be worth it both in performance, and reliability later on.

Get a cam grinder to grind you a 'street' cam for high performance. Stock cams have a lift of about .450" at the valve, you want about .470 to 490" and more duration.  I use Cam Techniques in Bradenton Florida, and he's great, used to do all of Bob Sharpe's work (Scott Sharpe's dad).
You'll need to get thicker lash pads to take up the difference, and correct the valve geometry, but you'll feel the difference in the seat !

And have the machine shop do a "competition", or "three angle" valve job for you.

Of course , there are a dozen other things that are done to 'real' race motors.  Some of them are for reliability, some are for a little performance. On a street motor they would make very little difference. Once you get the 'How To" book you'll see what I mean.

Now. Once the block assembly is done, you need to concentrate on the cylinder head, I mentioned a cam above, and a valve job.  But what really helps it to have the head ported, and flowed by a professional race engine shop (that's where you should take all this anyway)  it's expensive, but it's where the horsepower is really at.
You need to try and find an early injection head. I think the good one is called an "N-47" .  Small combustion chambers, large ports, and no pollution stuff.

Finally, an exhaust header, and Weber throttle body should do the trick. about the only thing that you won't really challenge will be Corvettes, and turbocharged super cars.

I hope this has been a help, feel free to write for more info or clarification.

Good luck

Dan Liddy
Sarasota, Florida