Direct "Dear Dave" tech letters to dave@eyesoreracing.com. Coleman will share mind-numbing details, earth-shattering revelations, and technical nerdisms in this space each month.
The Hard Way Or The Harder WayI own a naturally aspirated 1987 Nissan 300ZX (Z31), which has a VG30E in it (but you probably already knew that). The popular thing to do with the Z31 is to convert it to a turbo, but, being an NA lover myself, I've decided to be different.
Now, before you say anything about how unwise it is to be different, I figure that, since owning a Z31 is already pretty different, I might as well go all the way. I know the VG can handle up to 500hp on stock internals, and I know that even then, the engine can hold more with better piston rings.
I want to make 300 wheel-hp without a turbo. This is a large jump from the stock 160 crank-hp, so I already know it will be a difficult thing to do. I plan to bore out the engine and drop in higher-compression pistons, maybe 10:1. My question is: what else should I do to get the most power out of my engine, without making it unstreetable?Joshua FelderHardway, Idaho
Here's a brief outline of what you're in for, trying to double the output of any stock NA engine: first bore it out like you planned, stroke it with some VG33 rotating bits, do lots of arithmetic to figure out what piston dish you need to get the right compression ratio with the new bore and stroke and the existing cylinder head, then drop a wad of cash and wait for your custom pistons to arrive. Six months later, assuming they were made correctly, you can assemble your bottom end, then spend another bucketload of cash paying someone to extensively re-work your heads in a painful, expensive attempt to make an outdated two-valve design flow as well as the stock heads in your mom's Altima. Next, you'll need some big cams, stronger valve springs, lightweight retainers, adjustable cam gears... oh, don't forget manifolds. Your 160hp intake manifold probably won't serve up the flow for your 300hp engine. Time for port matching, extrude honing, junkyard engineering, or extreme fabrication. Don't forget headers too.
After all that, and the legion of overpriced little details I left out, you'll have to figure out how to tune this beast. Preferably without damaging it in the process.
Next, you'll need to blow it up two or three times. Doesn't matter if you do it through oil starvation, that wrench you left in the oil pan, lean spots in your incomplete fuel map, or any of the countless other ways you have a chance to screw up, just plan to rebuild it a few times. When it's finally dialed, you'll have a finicky, rough-running beast that bucks and bogs in traffic, but makes a spine-quivering wail at wide-open throttle-a wail heard at every doughnut shop in a five-mile radius.
And when you finally dyno test, it will probably be about 100hp weaker than you ever guessed.
Now, you know I (probably) wouldn't piss in your coffee like this if I didn't have an alternate idea. I do, and it's also expensive.
Shop long and hard-and with uncommon patience-until you find a good deal on a 350Z drivetrain. Get the engine, trans, ECU and wiring harness. Fabricate four parts: two engine mounts, a transmission mount, and a driveshaft. Get a wiring diagram and figure out what every single wire in the harness does and remove the ones you don't want. This sounds hard, but it just takes patience. Fire it up, do a burnout, and be confident in the knowledge that you have the second-fastest Z31 in the world behind Steve Mitchell.
Fundamentally, this seems like it should work. The only big unknown is the oil pan and whether you'll need to modify it to make the engine fit. Other than that, the VQ35DE is narrower and lighter than your VG30, and has a powerband you could only dream of from a VG.