Michael

Transmission choices are to some extent constrained by the bellhousing: in many applications a blowproof bellhousing is imperative, especially with engine setback. When I started my swap (1999), there was no blowproof bellhousing for the T56. I ended up with a Doug Nash 5-speed (which fit the standard Lakewood bellhousing for Chevy), on the strength of the recommendation of a hot-rodding buddy, and because I stumbled into a good deal on a used one. In hindsight this was a poor choice: shift quality is horrible, there is no overdrive and the gears are too close together. Every application is different, but for a light car with a very torquey engine, the wider the gear spacing the better. My ideal gear ratio choice would strike some folks as outright ridiculous: 3.5:1, 2:1, 1:1 and 0.5:1, with a 3.54:1 rear. 3.5:1 would be used only for drag racing with 33â€-diameter slicks (or similar). With 25â€-diameter street tires the other three ratios would be used - but that’s with an engine that is happy cruising at 1300 rpm. When I drove Pete’s car with the Tremec 5-speed, I found myself yearning for a deeper first gear (numerically higher ratio) because I’m a dweeb and don’t know how to shift; I tend to upshift at 2500 rpm.

Contemplating a “quality†late-model used car purchase, I got interested in the 2002-2003 Mercedes C32 AMG, which is their souped-up C-class sedan, with the 3.2V6 topped by a positive-displacement blower. Depending on mileage and condition, these cars can be found for < $25K, which is about 50% depreciation over 4 years. Internet discussion on these cars is awash with nothing but glowing praise, but I’m concerned about reliability and cost of maintenance. Does anyone have any experience with these cars? My test-drive was very satisfying. Punch the gas pedal and seat-of-the-pants acceleration is exactly what I’ve been looking for in a daily driver. If reliability were not a problem, I would likely buy one.

Mention was made of getting adequate traction, and reinforcement of the unibody to support a particular level of spirited driving (which, the racers tell us, has more to do with a stiff suspension and sticky tires, than with a high-torque engine). But what about the cost of building up the engine and driveline? There is a "knee" in the curve of hp vs. $, and it depends more on the choice of engine and skill of the builder, than on the choice of car into which the engine will go. In other words (and this will be controversial!) the cost is roughly the same in a Chevelle as in a Z. I mean, a $7000 SBC Chevy (or whatever engine) doesn't know into what chassis it was bolted into. But then there's the assertion that the Z is lighter, so less power is required for the same performance feel, relative to a muscle car. True, but does a 350 hp engine cost that much more than a 250 hp engine? What about a 450 hp engine? Again, the point is: consider the potential and the cost of the powerplant first, and don't worry (at first) about Z-specific engines. In my case the swap itself was relatively straightforward, but care and feeding (and repair and re-repair!) of the engine is interminable!

I ended up with a cam from Cam Motion because Pete told me to do it. Actually, I wanted a mechanical roller cam with moderate duration and relatively aggressive profiles, with quite a bit more duration on exhaust than intake (to partially compensate for a small-diameter exhaust tract and poor e/i ratio for my heads). No such cam was available off-the-shelf from Comp, Crane, Crower or Isky. And if I were to go for a custom grind, I might as well pick a niche manufacturer. Carolyn Boone at Cam Motion says that they (Cam Motion, that is) do not have valvesprings suitable for my application. Instead, she recommended 933 springs from Comp. Meanwhile, my prefered supplier ("Wolfplace", in Northern California - he does not post here, but frequents the Chevelle Tech forum) gave the nod to Comp's 26094 springs, which have the right numbers but are quite pricey. So the quandary persists....

I was in a similar predicament recently - needed to revise my choice of valve springs, to match my "low lash" mechanical roller cam. Unfortunately Comp does not make a beehive spring for this application - and in fact their tech line counsels that a single-spring (no damper) is risky for mechanical rollers. On the other hand, low-lash roller take surprisingly low pressure (160 seat, 450 open) relative to what's common for usual mechanical rollers, which really confuses tech line guys at the major manufacturers (the manufacturer of my cam, Cam Motion, does not sell springs). I'm probably going to end up with Comp 26094 springs - which are advertised as being for flat-tappet cams. Thought coil bind should not be an issue per se, my machinist recommends extending the 0.060" rule to 0.100" for endurance applications - a standard that the 26094's fail. Crane makes a similar spring good for 0.700" lift, which might be a better fit. Anyway, I'm mumbling here. Bottom line is that some half dozen considerations of spring pressure and valvetrain geometry have to be taken into account, and for the relatively unusual applications there is no good off-the-shelf solution.

Solidworks proficiency is a very worthwhile skill to acquire, especially now that Solidworks seems to be taking over from some of the higher-end drafting packages. However, take care not to pigeonhole yourself as a draftsman or "mechanical designer". They get paid less than engineers with equivalent experience, and tend to be hired as short-term contractors.

This would only be worth $1.5M to a effete billionaire trying to gain street cred with a more "real" crowd. Sold individually - if every part were cleaned and sold - the sum total might amount to $1.5M, but the labor involved would be high 6-figures. But those dogs are really awesome!

Did the scales really protrude 1-1.5" above the tunnel floor, thus elevating the car by that amount? If so, then this is a pretty significant flaw in the A2 tunnel. Scales should ALWAYS be flush with the floor! One solution is to make a plywood template with cutouts for the scales, and a ramp several feet in front of the car, thus elevating the flow back up to "curb height" relative to the car. How much more expensive - and how much busier - is the larger tunnel?

Looking at your data set, I think that the most important info is contained in three columns: CD, CL_front and CL_rear. The number of runs is very impressive for a one 8-hour shift, and compares favorably with what our engineers achieve for airplane-type testing in our tunnels. I would caution that every wind tunnel is a little bit different, so comparing numbers from your test with published numbers or measurements in other facilities is always a bit dicey. That said, the baseline numbers for lift and drag coefficients sound about right; drag is a bit high, but it would have been lower (I think) with a moving ground, or a least a boundary layer sucker upstream of the test section. There may also be some "blockage" effects that can not be entirely eliminated, despite what certainly appears to be commendable good sense on the part of the facility operators. I am however surprised that the various approaches at drag reduction did not yield more than they did. But not being part of the crew I can only speculate whether lift reduction, as opposed to drag reduction, was the primary objective. An anecdotal comparison - so, let's not get too worried about it - is that of the Hot Rod 2nd-generation Camaro - which evidently dropped something like 40% in Cd, with the various modifications tried during testing in A2. It still seems to me that the culprit is the Z's sharp hood lip. The G-nose doesn't help (I'm not surprised), but what "should" help is radical surgery to the hood, dropping the radiator upper crossmember by some 2" and sloping down the hood lip. This is unfortunately difficult to implement and is only practical for a V8 car with lots of engine setback (and probably firewall setback).

I bought a 454 out of a Chevy Suburban with something like 130K miles. I did a cam swap, and got maybe 20 miles out of the engine before wiping the cam. Years later I rebuilt the engine with some pretty high-quality parts, but the cam sprocket bolts (not the 3 that hold the cam timing gear to the camshaft, but the rosette of 6 which hold the 2-piece adjustable timing gear together) worked loose, dug into the aluminum timing cover and scattered aluminum shavings all over the engine’s oil path - after 43 miles of driving. Engines fail early because owners are incompetent, complacent or just plain unlucky. While there are the occasional bad apples, a blanket statement that “Brand X engines fail much more readily than Brand Y engines†is, in my opinion, pointless. That said, if I kept the original L6 in my Z it might still have been running…

Returning to the original question in this thread.... The choice comes down to this: doing your own engine swap belongs to a particular lifestyle. Does that sound like your sort of lifestyle? If so, then any alternative to doing it yourself will be unsatisfying and will leave the proverbial poor taste in your mouth. If not, then by doing it yourself, you’re setting yourself up for frustration - or worse. So the satisfaction of building your own car is not to be denied, but be wary of the flip side: many years of toil with no completion in sight --> dejection and self-doubt. And ask me how it feels when you’ve been working on an engine for 7 years, then drive the car for 40 miles, open it up for minor tuning and find significant internal damage… There are so many disparate yet related aspects to this hobby - the craftsmanship, the engineering, the sport, the camaraderie. Achievements in many of these is possible even if you never finish your car. Still, it’s hard to be proud of a project with recurring setbacks, like blown engines or broken suspension parts. And it’s hard to maintain motivation when seemingly even the simple things backfire (such as the carburetor ). But hanging out with knowledgeable people is a rewarding experience in its own right - whether in the car hobby or essentially anything else. In hindsight my own project has many regrettable aspects. Strictly in the practical terms of owning a fast car, I would have done far better by either buying an OEM sports car and leaving it stock, or performing minor bolt-ons on such a car, or buying some one else’s complete or nearly-complete project car. Going your own way as an engineer/hobbyist has an ineluctable romantic pull. I couldn’t resist, to my detriment in practical terms. But only in practical terms! The emotional and intellectual rewards defy quantification. They will remain even if the engine’s oil pan doesn’t get reinstalled for 20 years. Welding, cutting and measuring, fabbing parts etc. are often regarded as the tough part of a hybrid engine swap. This is not necessarily true, depending on one’s mix of skills and one’s experience. The tough part can be the “routine†auto mechanics - keeping a high-performance engine together.

For you guys currently in ME undergrad programs - this stuff should all gel by the time that you're halfway through your junior year. That is when you get the coursework with some real-world examples. To get a head start, consult the books.... An easy but useful book - intended for airplanes, but just as applicable for cars - is "Introduction to Flight", by John Anderson. Ignore the stuff on compressible flow, but concentrate on the first 4-5 chapters. Once you have read that, have a look at "Low-speed Wind Tunnel Testing", by Barlow, Rae and Pope; http://www.amazon.com/Low-Speed-Tunnel-Testing-Jewel-Barlow/dp/0471557749

Why don't you guys contact the Mechanical or Aerospace Engineering department at your local university? They probably already have the facilties that you would like to use, and can answer your questions in detail.

Some more philosophy to add to the pile.... Engine swaps are big projects. They might appear to be comparatively small to folks already well-versed in automotive craftsmanship, but especially for the fellow just starting out with tinkering in the garage, it's a big undertaking. As some testaments above have already noted, you CAN be successful with the V8 Z swap with little or no prior experience, but the key is having the right mindset - the combination of self-confidence that gets you through the rough spots, with the humilty of knowing when to ask for help and to admit making mistakes. The creativity of finding your own answers, and the studiousness of researching answers already out there. It certainly helps to have a mentor, to be part of a club or other support organization where the proverbial greybeards look out for the proverbial cubs; it helps to have a shop full of high-end tools, and the experience to use them. But mostly it's a matter of personality, of mindset. From personal experience I can attest that even if you have most of the tools and some hot-rodding experience, you will be frustrated with the engine swap if you're not the do-it-yourselfer type. Me - I'm more of the armchair theoretician. I kept getting stymied by "simple" problems that a more even hand would have detected early. Why not buy an older V8 car - not necessarily high-performance - and just spend a few months wrenching on that? Play with the timing, the fuel delivery, etc. Swap intake manifolds, and later swap cams. Get to know the engine. And then, once the "basic" mechanical stuff is under your belt, start on the swap itself. To a large extent what's hard about the V8 Z engine swap is not making the mounts or fitting the driveshaft or splicing wiring harnesses; it's the care and feeding of a high-performance engine.

In any actual wind tunnel test there will be variations from run to run; repeatability is never perfect, especially if the schedule is tight and the fan rpm control system is ... well, not the best that money can buy. So in every run, the wind speed in the test section will be slightly different, despite the desire for the same nominal conditions. Sometimes it will be 80.7 mph, other times 78.9 mph, and so forth. But each time, the value is recorded, converted to dynamic pressure, and saved for future reference. Then, the physical forces for each run are normalized by the corresponding dynamic pressure for that run, to be reduced into coefficient form. If you want the actual lift and drag at 120 mph instead of at 80 mph, multiply the numbers for 80 mph by (12/8)^2. At 120 mph Q = 36.7 lbf/ft^2. In the end, variations during the tunnel runs are pretty small. We're trying to improve CD from 0.45 to 0.35 (for example); a 2% error here or there isn't going to make that much of a difference. Do we have any means of doing a group teleconference, where we could all go over the highlights of the data? I'm not trying to imply that somehow magically I have all of the answers, but it would be easier to explain some of the lingo verbally, so that we're all on the same page.

Q is the dynamic pressure, 0.5*density*V^2. If the testing were at 80 mph (=117.3 ft/s), at "standard" conditions Q comes out to 16.3 Lbf/ft^2, in the usual engineering units. Cross-sectional area times Q times the drag (or lift, etc.) coefficient gives the drag (or lift, etc.) force. I really regret that I didn't participate in your wind tunnel test....

Pete, by way of comparison, I e-mailed the Barry Grant tech-line for advice for my application. I told them that mine was no daily driver, seeing maybe 200 miles/year on the street, that it weighs 2600 lbs (about right) and should have its torque peak at 4000 rpm (probably about right, too). The rest you already know. Well, the recommendation came back today: "750 Mighty Demon P/N 5402010GC". The recommendation is reasonable, but probably errs on the side of conservatism. The fellow said that "this carb is capable of 900 cfm..." Well, he's right - but at what pressure drop? Even a 390 CFM Holley 2-barrel can flow 900 CFM, given enough pressure drop - and consequent VE losses. What are your thoughts on downleg vs. annular boosters?

The idea is intriguing, but the business case is difficult. Most of the people amenable to "checkbook hotrodding" would prefer a high-dollar restorod. Whereas the average guy would feel silly paying anyone for a custom job; he would rather do it himself, even if he is incompetent - because he thinks that paying some one else somehow cheapens the whole experience. And he might not trust anyone else to "do it right". And most people would rather spend pennies on the dollar by buying some one else's nearly-complete project, and then finishing it themselves. It's a much better business case to sell/install rims, spoilers and exhaust-tips.

You moved to Dayton? WHY? WHY? WHY? My life’s obsession has become moving out of Dayton! Anyway, welcome! - and perhaps now we’ll have a critical mass for a Dayton-area Z meet? I’m out in the “countrysideâ€, about halfway between Xenia and Wilmington.

I drove an automatic 6-cylinder 1991 190E for about a week (300 miles mixed city-highway) last fall. Competent car, but nothing particularly special. 1st gear would not engage unless the gas pedal were really mashed; otherwise it would leave the line in 2nd. Top gear felt unusually short for a German car; highway rpms were quite busy. Looking under the hood, its swap candidacy did not impress me; the L6 fits snugly, and distance between the strut towers looked considerably less than a Z. But the seats were comfy and the interior felt more solid than in my similar-vintage BMW 325is.

All of us are incompetent in our own little ways; if we had laws banning stupidity, most of us would be incarcerated for life. The scary part is how modern technology can both magnify the effects of our incompetence, while simltaneously shielding us from its immediate obviousness. I too get annoyed when drivers swerve, brake at the last minute, devote more attention to their phone conversations or to disciplining their children or fondling their pets than to the task of operating their vehicles. But it seems to me that being on the road is, fundamentally, a risk. By getting into my car I implicitly agree to subject myself to the flaws and failures of my fellow drivers - as they agree reciprocally to mine. It is however worthy of mention that our society is tremendously dependent on automobiles for routine transportation; no civic reengineering plan could possibly alter that. It's the fact that we live in our cars that raises the odds of horrific rarities to the point where we each know some one who has suffered catastropchically in a motor vehicle. But - callous as it may sound - perhaps this is the "disease" of our times. Centuries ago it was plague or tuberculosis; for us its car accidents.

Why not just a hydraulic throwout bearing? No clearance problems, easy installation, relatively inexpensive.

Grumpy, what were the build specs on that 496? And if you were to drop the compression ratio by one point, but keep everything else absolutely unchanged (so, think of it as shaving the piston dome but magically not affecting the flame propagation or quench, what would be the estimated drop in the torque curve? BTW I bought my heads (Brodix Race-Rite), lifters and a bunch of other parts for my 454 from Mike Lewis.

For me the purpose of the Z is to have something with which to tinker and to get creative. Bang-for-the-buck it would make more sense to buy a late-model used G35, Corvette, M3, or even Z28 Camaro. Where the Z excels is (1) much easier to modify on a fundamental level (as opposed to bolt-ons), and (2) does not depreciate just sitting in my garage. But in hindsight it would have been better to have several Z's: one "stock enough" to be a nearly daily driver, one with minor mods suitable for recreational racing at the local track, and one that's truly wild (and therefore completely unreliable, tempermental and expensive). I have been justifying my Z hobby by sticking to bottom-dollar daily drivers, such as 20 year old Accords and Sentras. Perhaps the best compromise is a $10K-$20K daily driver that's in the category of being inexpensive enough to justify driving it hard, but still new enough to be reliable and nice enough for relaxed normal driving.

The best reason to do these kinds of upgrades is if you're doing a rebuild anyway. That is, if replacing the bearings, rings, etc. - and especially if upgrading to an aftermarket rotating assembly, or if pondering a rod resizing/crank grinding job - then that's a good opportunity to upgrade to a stroker crank. The justification is quite a bit more tenuous if the 350 is already running strong as-is, and you're just contemplating a stroker upgrade.