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Dear Dave - Your Questions

Dave Coleman
Jan 17, 2007
0702_sccp_01_z+dear_dave+dave_coleman Photo 1/2   |   Dear Dave - Your Questions

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another bucketload of cash paying someone to extensively re-work your heads in a painful, expensive attempt to make an outdated two-valve design flow as well as the stock heads in your mom's Altima.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.

0702_sccp_02_z+dear_dave+1987_nissan_300ZX Photo 2/2   |   Dear Dave - Your Questions

Driftwagen EinI have a plan to fabricate a drift car using a Porsche 944 chassis with a custom rear subframe to house Nissan suspension. I am pretty sure this would work beautifully as it would allow me to put the instant center wherever I want. I am confident this would make an excellent drift car given the weight distribution and overall characteristics of the vehicle.I understand the subframe is going to require some R&D but would like your advice as to how much anti-squat to include (in accordance with 'Making it stick', SCC, December 2005)Wesley SkeltonCincinnati, Ohio

Your solution seems overly complex. Swapping complete suspension systems between cars is much easier when you can move the whole suspension and subframe as a unit. Since the 944 has a rear transaxle and the Nissan subframe is just designed to hold a differential, there's no way to just bolt the Nissan bits in. Obviously you know this, since you're proposing making a new subframe, but precisely locating all 10 inboard control arm mounting points is a daunting task I wouldn't wish upon anyone.

Instead, I would see how far you can get with the stock suspension geometry. Since the rear springs are torsion bars, it would be easiest to leave the stock torsion bars in place and add extra rear spring rate with a coil spring mounted over the rear shock.

The semi-trailing arm geometry can be a little tricky for two reasons. First, rear toe can change a lot as the suspension moves, making rear grip a little inconsistent. The simplest solution here is simply to make the rear really stiff so it doesn't move much, keeping toe consistent. Big anti-roll bars and some stiff springs will help a lot

The second problem is, as you guessed, the instant center. When lowered, the control arm will be flat, or even pointing down (looking from the wheel, forward) leading to quite a bit of rear squat. The simplest solution is to run near the stock ride height where the geometry probably works pretty well. If the drift judges poo-poo that solution, though, you can try raising the subframe up in the car by the same amount that you lower the car. This is a lot of work, but less than the Nissan idea.

Driftwagen ZweiI am the proud owner of a 1987 BMW 325is. I know there are a great deal of clubs devoted to BMWs, and that you guys give little press to their machinery, but I have a question most BMW guys can't answer. I would love to set the car up to drift. From what I can guess, I have the basic ingredients right: rear-wheel drive, limited-slip diff and torque in the mid-range. The suspension now is stock (as in 222,000 miles stock). What else do I need, and what settings do I need to make? I know it will cost a lot because of the emblems on the car, but I want a German drift machine.Kyle WalkerMunich, Idaho

On the surface, you need the same thing as the 944. A suspension stiff enough to negate the semi-trailing arm vices, and a little moderation when it comes to lowering. With 220,000 miles, though, add in stiffer bushings everywhere and a trunk full of kitty litter to clean the track when you blow your motor.

And after you blow that old motor up, drop a 302 in and glue a blue and white propeller to the top of your Holly double-pumper, so the club guys don't make fun of you.

By Dave Coleman
94 Articles

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