Michael

Folks, We've covered a lot of ground on the issues of roll cages, subframe connectors, floor pans, torque tubes, etc. But, I probably speak for many people when I say that the actual effect of these modifications is still shrouded in mystery. in other words, do we really know what increase in, say, torsional rigidity such modifications produce? So, here's my question: has anyone attempted a "test" of their chassis's torsional stiffness, e.g. by shoving a long beam in the vicinity of the steering crossmember, clamping the rear fixed, loading the far end of the beam, and measuring deflection? Alternatively, does anyone have ideas on quicker and simpler methods? The point is not to question people's structural designs, but to ascertain what's the maximum benefit for the minumum cost and effort.

Folks, I just wanted to interject a question about suspension design into the discussion. The 4-link has various advantages for drag racing purposes; specifically, the ability to tune for anti-squat, while managing wheel hop, etc. Yet, the 4-link is generally regarded as inferior for road-type applications - even inferior to the Satchell link arrangement (two longitudinal links, two links angled toward the center of the car) or the NASCAR-style trailing link arrangement, because of poor roll compliance. That's actually a plus for drag racing, but evidently a minus for road racing. My question is not about solid rear axle vs. IRS, but regarding the various ways to locating the solid rear axle. Does anyone who races both SCCA and NHRA have any comments on pros and cons of 4-links? Recognizing that specializing for one form of racing almost necessarily reduces performance in other forms, I was wondering what's the best compromise.

The old driveshaft will work. However, you will almost certainly want to replace the driveshaft for V8 purposes. I bought JTR's driveshaft flange for adapting Chevy-size U-joints to the R200/R180 input flange, and a yoke for the opposite end of the driveshaft to fit my transmission. Everything takes Spicer 1310 U-joints (maybe 1350 - I can't recall the specific number). The rest of the job is left to a driveshaft shop.

Matt, As far as a suitable candidate for a block, probably any junkyard refugee (350) will do, even a 2-bolt. In the build-up process, most likely you will have to replace absolutely everything except for the block itself. Shameless commercial plug - consider my stuff in the "for sale" section. However, if you farm out all of the work to a machine shop (that is, they build you a turnkey engine), they may be reluctant to work on a block that you supply to them, because that's less profit for them. Check ahead of time. Yet another option is to buy an assembled shortblock, for example from http://www.speedomotive.com/. That's the route I was planning on taking, before I went with "plan B" and got my big block.

Is this a Ford 428 (FE, or maybe a cammer?)? Assuming that it's about the same size and weight as a Chevy 396/427/454/etc., you're looking at about 150 lbs more than for a small block. It will be about 3" longer, with similar increases in width and height. If you plan on using a stock bellhousing and oil pan, ground clearance issues will force placement of the engine such that the air cleaner sticks out above the hood line (unless you get a really low rise intake manifold). I'm installing a 454 in my '78 280Z. But, the firewall was set over 6" back from stock, by cutting out the firewall, floor boards, and transmission tunnel as one integral piece. Room was cut in the floor area behind the seats, and after the whole thing was welded back in, the "gap" at the former firewall locating was filled in with sheet metal (double reinforced inside the the subframe members). With a full roll cage, it's a very tight fit in the interior. Apparently I'm the only one on this forum to attempt such a drastic solution, but as far as I can tell, the other two guys with big block Z's both have modified firewalls. So, the implied concensus is that sheet metal surgery is the only way to go, if you're concerned about weight distribution, and especially if you don't go with a solid rear axle. Bottom line - it's a HUGE amount more work than a small block. But it IS worth it if you want a steetable naturally aspirated engine that is nonetheless suitable for high-end amateur drag racing.

Folks, Thanks for all the advice! My original posting on this topic was quite some time ago, and since then, I have already bought the unit from Stealth Conversions. It looks very well made (much better than the TH400 yoke that I bought for the opposite end of the driveshaft). When we lost a bunch of postings on the forum, this particular topic floated up to the top of the heap, since it apparently was the latest posting that was not deleted. By the way, do we know whether the damage to the site was due to a technical malfunction, or hacking???

Is this the same for all 70-81 half shafts (i.e. 240's, 260's, 280's, and early 280zx's that still have U-joints)?

I can't say that the rear spoiler will entirely fix the exhaust fume problem, because there will still be some flow separation - just not as much. The front spoilers often come with "ducts" to accommodate plumbing for brake cooling, or just to install fog lamps. If you don't have either, just fill up the holes with, well, duct tape.

Hi Matt, The engine is a 350 with 4-bolt mains. The bores are 0.030" over, and in pretty good shape, though there may not be enough material for a further overbore. Casting on the block says 1970. Carb was a Rochester 4-barrel spreadbore on a cast iron intake manifold. Basically, that indicates that the engine was of mild high performance, but not top of the line. Heads have 1.94/1.50 valves. Everything is disassembled, and in boxes. Most likely, the engine was not run in quite a while. I pulled it from a Jaguar that some one converted to V8 (with JTR methods, in fact!). I'd like $100 for the whole thing.

The BRE stuff is hard to beat for being unobtrusive yet effective. The lower air dam is a mixed blessing for some cars, but it's very effective for the Z, because 1) the Z has severe front lift problems, and 2) these problems are caused by relatively minor but far-reaching design mistakes. After some digging (I don't want to elevate it to the status of "research", so let's just call it digging), I've come to the conclusion that the original wind tunnel testing done by the Nissan engineers had the car elevated on blocks underneath the wheels, possibly in a misguided effort to get around flow quality issues in their facility. Thus, they completely missed some critical ground effect issues. The stock Z's smooth under-bumper skirt is consistent with this notion. Anyway, just about any front spoiler is superior to no spoiler at all - whether it's Motosport, Arizona Z-car, BRE "spook", etc. The rear spoiler is more convoluted. Rice boy wings generally don't work, because they have a poorly chosen and incorrectly oriented "airfoil" cross section and because they are placed in a flow region generically called "turbulent", where their effectiveness is greatly reduced. Given the Z's rear hatch slope, the #1 problem is controlling large-scale flow stuctures over and the hatch and rear bumper area. They are responsible for a host of problems, like the exhaust smell seeping in through the hatch weatherstripping. A scaled down version of a NASCAR-type spoiler, of which I believe the BRE spoiler is an example, is the best bet. Properly designed, it even reduces drag, by calming down the big roller-type structures separating off the hatch.

JTR sells a Datsun-to-Chevy driveshaft adaptor, evidently to be used with Spicer #1310 U-joints. Has anyone ordered this piece from them, and if so, what do you think of it? has anyone made their own? The flange of a Chevy driveshaft can probably be machined for the appropriate Datsun "pilot diameter" (2.25"), but I wonder if there is enough room to drill the Datsun-compatible bolt pattern.

This probably belongs on the "for sale" message board, but it fits the thread so I'll list it here. I have a 4-bolt 350 block, from back when I wanted to install a small block. In fact, I have the whole engine (heads, crank, etc.), in unassembled form. Ironically, I pulled it out of a Jaguar for which some one did a JTR V8 conversion. Chevy small blocks have almost no value stock and unassembled, so if some one gave me $100 for the lot, I'd love to get rid of it. Unfortunately, I'm in Pasadena, CA, which is a long way from Washington. Shipping will cost far more than the engine is worth.

SpencZ, Well, first of all, this car is still under construction, so it will be a while before I actually kill myself. Second, it's a full tube car, with what amounts to a GT2 roll cage and extensive reinforcements beyond those required by the various race sanctioning bodies, and well beyond those described by JTR. The assembly is currently on a chassis jig, custom built just for this car. There is not much loading ahead of the strut towers. Funny cars, trans-am cars, and many others don't have any structure ahead of the strut towers (except for a lower bar to tie together the left and right side frame ends), other than some mounting mount for the nose clip. I'll have some photos next week - I keep promising, but slides are difficult to get scanned. Third, I've done a little bit of tooling around with air flow issues. In fact, I probably would not be making a bogus claim to say that I'm the only person on this list that has actually done laboratory testing on the flowfield over the Datsun Z. Granted, lab is not real life, especially with the so-called Reynolds number affects that govern things like flow separation and boundary layer stability. But, it's a start. Angling the radiator to accept oncoming flow upstream of the air dam is a usual practice, albeit not with Z's. Also, with the stock Z hood lip geometry, flow above the grill-area stagnation streamline will separate, causing a serious loss in stagnation (total) pressure. The part of the fan behind the hood lip area is getting nothing but some minor eddy flow from the local upstream shear layer instability ("Kelvin-Helmholz"). And with the angled fan, ejecting the flow exiting the radiator cores (you do have to conserve mass, after all) is more efficient, given the location of the engine. Two-core vs. 4-core is a moot comparison without actually considering the effective convective heat transfer coefficient. That is due to a number of factors, such as the tube shape and diameter, tube head losses, fin density, air flow losses across the fins, etc. The downstream cores of a 4-core radiator are much less efficient than the upstream cores. Thus, more is not always better. The reason for using electric fans is NOT to eek out the last big of hp, but to build a more mechanically practical assembly. My motor is 6" further aft of the JTR setup, and the ducting to use an engine-driven fan would just not be practical. My question regarding electric fan efficiency was asked to learn 1) whether folks that have switched from engine-driven to electric fans really did notice an increase in hp and torque, and 2) to find out how advertised fan CFM rating compare with what people have found to be sufficient to cool their engines.

Does anyone have any particular preferences for electric cooling fans? I'm using a Griffin aluminum 2-core radiator, 27 1/2" by 19" (it fits when angled forward, and when the stock Datsun sheet metal crossmember connecting the inner fender is cut out), and I'm trying to cool a 350 hp 454" big block. With the angled radiator, a pulley-driven fan is not practical. Also, I'm sure that people have noticed the claims that while pulley driven fans may absorb on the order of 10 hp, electric fans supposedly draw less than 1 hp max (1 hp at 12 volts = ~60 amps!). Granted, the blades of electric fans are more efficient, electric motors are about twice more efficient than internal combustion engines, and there are fewer parasitic losses (rotational inertia of fan clutch, friction of pulley belt, etc.). But we're talking orders of magnitude here! I just don't see how the numbers stack up. Any ideas???

I'm no welding expert, but I'm working with a guy that is. He definitely recommends mild steel instead of chromoly for anything short of a pro race car. The Chassis Shop guy might be a pompous twit, but basically, he has a point. Chromoly steel tends to brittle. The heating and (cooling down) inherent in the welding process tends to exacerbate the natural brittleness of the material, and may cause the formation of local microscale imperfections. These are the weak links in the chain. The result will still be strong in continuously applied loads, but if you whack the welded are with a hammer (or crash the car!), it might crack at a lower load intensity than the corresponding mild steel structure. Your estimate of 125 lbs for the roll cage weight sounds about right, if you're building a full cage. With chromoly, you will save about 50 lbs. So, we can invoke the usual statement that it's easier and cheaper to add a little more power to the engine than to try to shave off the last bit of weight off the car. If you have your heart set on chromoly, it might be worthwhile to first visit a local welding shop and talk to the pros. "Chassis Shop" has a good deal on chromoly, but NOT on mild steel DOM tubing. You will have better luck at a local supplier.

It's great that we're addressing handling issues for a car that's supposed to be "all straight line"!!! I have a question for the cognoscenti: why are V8 Z cars reputed to understeer? Of course, this is a rather complex issue. But stripping it down to the essential details, nose heavy cars will tend to understeer, but tail heavy cars will oversteer. Things change if the rear tires are much stickier than the front, if the front suspension has different camber gain than the rear, if one end has a stiffer roll bar than the other, etc., etc. But in general, I'd intuitively expect a V8 Z with lots of engine "set back" to oversteer (and I don't mean torque-induced oversteer - that's a no brainer). My car, with all that sheet metal relocation, has the crank pulley just over the steering rack, and the harmonic damper behind the front crossmember - and this is with a big block. With a hardcore (heavy!)roll cage, I expect a weight distribution of 45/55 (tail heavy). The other issue that I wanted to discuss is that of lowering the car but keeping the engine fairly "high" under the hood, or lowering the engine with respect to the car, but keeping the car at essentially stock height. My oil pan is 9" deep, and I'm using a Lakewood bellhousing. It's a huge piece that really hampers ground clearance. Since I'm mounting the engine to the frame rails, and not to the crossmember, engine mount geometry is something to worry about. I wonder how low people have been setting their cars; for instance, what is the distance from the ground to the bottom of the frame rails under the floor pans, or from the ground to the steering crossmember?

Though I've annoyed some people by saying this, I really think that moderate performance cars don't really benefit from roll cages etc. My guess is that your stock 305 conservatively makes about 160 hp and 220 ft-lbs of torque, in real-world numbers. A more precise estimate would depend on the head casting (and valve size, and many other things). With a decent dual-plane intake manifold, four-barrel carb, 1 5/8" block hugger headers, mild cam and a little tuning, plan on about 220-250 hp and maybe 280 ft-lbs of torque. If that feels like too little, consider that my '78 454 big block, with 149 more cubic inches and a much better head design, only makes 215 hp stock, because in stock form it signs off at around 4000 rpm, if that much. My admittedly unexperienced opinion is that it's better to do the conversion with the stock engine, and then hop the engine up, once the car is running and you've comfortable with the setup.

As far as I know, NHRA indeed requires 0.120" thick DOM mild steel tubing. Chromoly, if you choose to use that, only has to be something like 0.83". Oddly enough, the industry standard for mild steel is 0.118" ! And that apparently won't pass tech. So what I did was reluctantly follow my hot rodding mentor's advice, and went for the 0.134" tubes - these are the next thickest size. In 1 5/8" diameter, these are kinda beefy. I figure the whole cage will weight at least 100 lbs, maybe 150. That's with diagonally crossed "door bars" (really more to connect the dash-area bars to the B-pillar bars, than to protect the driver in a crash) and a system that ties into all four strut towers. We just bent the big hoop that goes behind the drivers head (the "roll bar", I suppose). We got it to fit just ahead of the roof pillar supporting the hatch hinges, and right against the headliner.

Wow, this thread grew quickly.... Anyway, let's first mention an obvious but important thing about the stock rear end - make sure it's an R200, not an R180. If you have a 70-74 240/260 or automatic 280, you're saddled with an R180 - but it's a bolt-in swap for the R200. I had to do it with my car parked next to the curb on the street (no garage, sadly). Regarding costs of a 4-link and Ford 9" combo.... I was quoted $5000 for parts and labor, from a very competatively priced one-man shop. Basically, you have to "back half" the car. That means not only work on the body and subframe, but also on the rear axle (shortening the housing, custom axles, etc. - and maybe even custom brakes). On the other hand, getting parts for the Ford 9" vs. the Datsun unit is like getting parts for the Chevy SB vs. the L28; cheaper, stronger, far better selection. Alternatively, you could retain the independent rear suspension and install either a Ford 9" center section with custom halfshafts, or use shortened Oldsmobile Toronado halfshafts, or even an Olds Toronado center section. This is not a common swap, but some chassis gurus (such as Herb Adams) claim that the Olds swap is cleaner and stronger than the Jag or Corvette. But I've never heard of it done to a Z.

XtrmSpeedFrk, I saw a car like what you describe at a "Super Chevy " show a few years ago, except that he had a 406 (on nitrous) and a Powerglide. It seems that hard core drag racers prefer the powerglide automatics. The guy ran mid 9's, with all-steel body (except for fiberglass hood), subframe connectors, minimal roll cage, and Ford 9" rear hung off a 4-link. I'd venture to say that the hardest part of your project - by far - will be changing the rear suspension. That's a lot of custom work, and its not covered in the various V8 Z conversion literature. Nevertheless, NHRA rules apparently state that you can't run faster than 11.00 with an independent rear axle. Perhaps you'll write a tech article on the subject when you're done???

For the folks that have experience with broken half shafts.... What exactly happens? Do you hear a crack and a thud, and that's it, or does the loose half shaft rip apart sheet metal and hydraulic lines as it spins? The point is, I'd rather see for myself if the stock R200 half shafts are strong enough, rather than complicating my already huge project by an upgrade to pre-empt a possibly minor failure - if indeed the failure is "minor".

At the risk of ruffling some feathers, I'd have to say that a bolt-in pre-fab cage is not a good idea. That's especially true for Z's since NO MAINSTREAM HOT-ROD MANUFACTURER makes an NHRA-approved "kit" for the Z. If you call Morrison, S&W, Magnum Force, Steve Alston, whatever, they will sell you a generic package of tubes designed for a Vega or Pinto. They don't fit well, and they are plagued with unbraced bends in the tubes (prone to buckling). A real cage is A LOT of work. You end up stripping out the entire interior, the carpets, plastic body panels, everything. You clamp the unibody to a rigid chassis jig, so that the thermal stresses from welding don't cause displacements in the metal. Then you have to worry about where to anchor the tube ends. Sheetmetal? Forget it. You need reinforcing sub-structure underneath the cage. For maximum benefit, you need to weld a network of gussets to secure the cage to the room, B-pillars, etc. And you will end up with diagonal members barring the door openings and criss-crossing the car. IMHO, if this is not what you want, don't build a cage. (My appologies if I'm starting to sound like Mark Sayer )A hoop behind the driver's head might save your life if a tractor trailer rolls over the rear hatch, but it won't do much for the structural integrity of the car - especially for torsional stiffness. BUT - I've seen 11-second V8 Z's run at national drag racing events with simple roll bars and subframe connectors. We're not building 1200 hp pro mod dragsters here (and frankly, I think that these pro-mod dragsters are not very well braced either). If this is a budget V8 conversion, if you spent $500 of a Z shell and most of your money is going into the engine and drivetrain anyway, it makes more sense in the long term to just let that unibody twist and then discard it and to buy a new one. Building a cage becomes like paying more for insurance premiums than the cost of what you're trying to insure.

I'd be inclined to comment that a car with enough power and torque to appreciably cause structural problems with its unibody is already enough of a "race car" that we can no longer apply pure street-only concepts to it - regardless of whether you actually race it. Conversely, a car that is only driven in "street-type" situations probably would not benefit from a huge amount of torque, with the possible exception of rare and brief smile-inducing bursts that in themselves do not justify going to the effort of installing extensive structural mods. Probably your best bet would be simple strut tower braces. These can be home made with a drill, hammer, vice, and saw. Beyond that, consider subframe connectors, especially if you have a 240Z. I decided from the very start that I wanted a maximum effort drag car, and that drove my decisions on structural reinforcements as well. But perhaps people are too concerned with the example of those individuals who really do have full-effort race cars, and who really do need roll cages etc. Most V8 Z conversions would probably be fine with no cage and no braces of any kind. If I were doing the conversion alone and on a tight budget, I would not worry about structural mods, because the car that I could realisticly build would not need them.

Folks, Regarding the balancer issue for stroker motors.... Back when I was interested in a small block, and when I was about to use the JTR setup, I wanted to get a 383 or 406 with 8" Balancer. Concerned about the steering rack clearance issue, I e-mailed Mike Knell of JTR. He said to either 1) get the crank internally balanced, or 2) get the smaller 6" balancer (just make sure it has the 400-crank counterweight). For those of you in the Los Angeles area, last year I ran into a guy at the Orange County Z club with a '73 240 Z with a 383 stroker. He had his crank balanced internally (with 5.7 350-type rods and stroker pistons). Also, have we entirely ruled out the possibility to move the motor yet further back, clearing the steering rack entirely? If you're willing to ditch the stock hood latch location entirely, and relocate the brake and clutch hydraulic lines, there's got to be another inch of setback room lurking back there....