Michael

I think that for many of us, the main problem with switchng to a solid rear axle is cost and complexity of the operation - and not an aversion to the setup itself. Most of the engineering challanges encountered in our V8 conversion projects are a matter of how to construct something. The "design" aspect comes down to how to make things strong enough, to make everthing fit together and stay together. Changing suspensions, however, involves a conceptual design change, and that includes textbook calculations. In other words, you essentially have to know how to design cars from the ground up. And that, at least to me, is a little scary. Independent suspensions have their main advantage in road holding over poor surfaces, and not in getting power to the pavement. As a somewhat relevant comparison, many people consider that the Z28 Camaro (solid rear axle) handles as well as a Corvette (I.R.S.) - at least, up to its traction limit, launches considerably better, but has problems on rough pavement. Obviously, most of us have no intention of racing on bad pavement. I.R.S. of course also has less unsprung weight, though it seems to me that this too is more of a ride quality than a performance issue.

I second Mike KZ's comments. Regardless of the eventual details of your front suspension, you'll have to have something that spans wheel-to-wheel to accommodate the steering, and it would be great to get the crankshaft pulley behind that something. That makes working on the engine MUCH easier, not to mention the improvement in weight distribution. Will the windshield and A-pillars remain in the stock location? If so, you still have something like 10" of space to set back the firewall, before the distributor cap hits the front windshield lip. That's because of the awfully deep valence panel that Z's have behind the hood, where the windshield wiper assembly is housed. I set back the firewall on my Z by 6 1/4", and even though I run a big block, the crank pulley is just behind the steering rack, and the valve covers are almost completely behind the strut towers. Your setup will have even more room - not to mention advantages like better flow through the radiator, and the opportunity to lower the hood line and solve most of the Z's front-end aerodynamics problems. As for the oil pan, keep in mind that with a low-profile pan, the show stopper will actually be the bellhousing! I have a 9" deep sump, and even so, it's no deeper than the lower lip of the bellhousing, and that's with the lip ground flat. Granted, I'm using a Lakewood "blow-proof" bellhousing, designed for a 14" flywheel - and the OEM T56 bellhousing is probably smaller. But still, before you spend the $2000 for a dry sump or even $400 for a low-profile drag racing oil pan, consider what to do about the bellhousing. You might end up with a [NASCAR?] multi-disk clutch, small flywheel and custom or semi-custom bellhousing. Drag cars get the engine very close to the ground, but they get around the clearance problem by running automatic transmissions with small diameter torque converters (or just clutch packs).

I suppose that like most upgrades, this one comes down to a matter of personal preference. About a year ago I was also thinking about an aluminum block - aluminum big block, that is. GM performance parts had reissued the much-vaunted ZL1 "aluminum cylinder case", and Merlin (World Products?) has a whole line of aluminum big and small blocks. The cheapest aluminum BB is around $4-5k; SB may be around $3K. Costs aside, one issue is how to mount the bearing caps. The GM LS1 is cross-bolted, which I was told works very well, although another chorus claims that LS1's are notorious for spinning crank bearings. The earlier generation blocks are 4-bolt, which may or may not be a weak point. The other problem is cylinder sleeves. The Zl1, for example, has cast iron sleeves, essentially poured into the aluminum, as opposed to pressed in. That evidently solves the leakage issues that caused head gasket failures, as in the original Chevy Vega ( 4 cyl.). I tend to side with the folks that consider an aluminum block to be more trouble than it's worth. The economy of scale just isn't there yet. The blocks themselves are expensive, and machine shops don't feel comfortable handling them. At least, that's my impression. The only truly successful aluminum block is the severely modified Chrysler Hemi, run in pro drag racing. And those guys have essentially infinite parts and repair capacities. If weight - or rather, weight placement - is a significant concern, consider relocating the firewall further back, giving yet more room for engine setback. That's been my approach.

Stay away from Supras! I used to own a '87 Supra turbo. The engine reputedly weighs more than a Chevy small block, and though the bottom end is truly stout, head gaskets blow very easily. The turbo is tame in stock form, and Supra tinkerers claim huge performance increases due to higher boost (the stock electronics and plumbing will allow up to 13 psi before fuel cutoff issues appear). BUT, we're still stuck with the low end torque issue. Turbo lag on these things is tremendous, and very frustrating off the line. Years ago, I thought of yanking the inline-6 in my Supra, and swapping in a Chevy small block. This has actually been done with a "Mark II" (82-86) Supra, though the "purist" emotion is strong among Supra owners as well. But then I realized that 1) this would never pass smog check, 2) the electronics are bewilderingly complex, and 3) there's just not that much room under the hood. The Z engine bay will accept just about any engine. But my opinion is that V-type engines, regardless of the manufacturer, # of cylinders, or displacement, are a better swap than another inline engine, because of the weight and balance issues.

I'm using a Doug Nash 5-speed, which is a modest evolution of a 25 year old design. 5th gear is actually 1:1, so in terms of mileage and top end, it's a four speed. This and some of the older Detroit transmissions are "externally shifted", which means that the linkages are outside of the transmission case. In my '78 280z, that required substantial modification to the transmission tunnel (cutting sheet metal around the shifter, and welding in a new cver patch). However, the external shifting does have one advantage - you can move the shifter around, to get it physically where it's the most comfortable for you. Another issue is torque ratings. The word is that the T56 is very stout, and is even used on Vipers. I don't know for sure, but really hard core hot rodders told me that the Muncie "rock crusher" (and the Doug Nash) are stronger. If you are running around 400 ft-lbs of torque, my assumption is that you have lots of choices, including any old muscle car 4-speed, or the T56, the Tremec, etc. If you have ambitions for mountain-moving torque, the choices narrow down. But I've heard of Doug Nash transmissions behind blown injected-alcohol big blocks. If you really have $$$, look into the Richmond (ex-Doug Nash) 6-speed.

Regarding the California stuff - What Gene writes is very true. But, fortunately there's a break for pre-'74 cars. They are not required to submit to semi-annual smog inspections, and presumably, there is no "shake down" process at the smog referee station the first time that the vehicle is registered. The word on the street is that a "gross polluter" can still be pulled over on the street. But I have never actually heard of this happen. Besides, a properly tuned engine with reasonable cam should not be a gross polluter anyway, even with no smog equipment at all. As for how to purchase engines.... I had (still have!) a huge project, so the attraction of buying something like a complete donor car was not that great. But, I did want to get a running engine, so that I could first worry about getting my car together, and then spend the $$$ on hopping up the engine. So I bought an engine out of a 1978 Chevy Suburban (454 big block). I found the transmission for sale on a race car classified site on the web. Later, I made some minor mods to the engine, but definitely no machining or "rebuilding". When I get my car running and all the details sorted out, I'll probably spend the money on a serious crate engine, either the "GM performance parts" ZZ502/502 or a "Merlin" 509 (again, this is big block jargon, but the same applies to small blocks or Fords). This is definitely a better way (than building the whole thing yourself) to get reliable high hp at still reasonable cost, but for a first iteration, where the whole project is still unproven and cost cutting is critical, a used engine is probably a better choice. If you already have a source for a Ford 302, or better yet, a cheap late 80's/early 90's Mustang GT with 5-speed and fuel injection, that might actually be a pretty good combo. The main problem with Ford swaps, apart from the lack of precedent, is the awkward forward location of the sump (interferes with steering crossmember, evidently). But I was told that even that problem is moot with a Mustang swap, because of their revised sump location.

Owen, I won't be in Pasadena for too long - in fact, I'll be relocating to Dayton, Ohio, in two weeks. My Z will probably not be finished yet , which presents some logistics problems. Make sure to take good pictures at the MSA show!

I'm chiming in kinda late, but for what it's worth, I was probably the guy that started this mess with my posting on Camaro front rotors (this post evidently got lost in our recent crash). At a pick-a-part junk yard, I removed the rotor and hub assembly, complete with bearings and all the guts, from a Gen II Camaro (70 1/2 - 81; this looked like a '75), and slapped them onto the spindle of a 280Z. With the possible exception of the inner oil sealing ring, everything fit perfectly. I could not rigorously check the oil seal thing, because evidently that would require torquing down the retaining nut (I don't know the exact term for this nut), and then checking for binding and/or leaks. Also, the Camaro brake caliper has a very different mounting bolt pattern than the Z, while the Z caliper will not accept the Camaro rotor, which is much thicker than the Z's rotor. I have heard of people making steel adapter plates that mount the Camaro caliper to the Z spindle. Gen III Camaros (82-92) might also work, though I don't know for sure. Also, 70's Novas are essentially identical to Camaros mechanically, so they too probably work. Also, and perhaps of greater interest for high performance purposes, Wildwood (and many others) make relatively inexpensive bolt-in brake stuff for Camaros, like a gorgeous aluminum-bodied 4-piston caliper and lightened vented rotor. If the stock Camaro stuff can be made to fit, so can the aftermarket parts.

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.