Michael

280Z's have a reinforcement bar inside the doors. If you can figure out how to mate the door and latch, a 280--> 240 retrofit is one option (the latch design changed in 1975, I think). For my car, I went all-out and had an X-bar welded into both sides of the car. Looking at the car from the driver's side, the top left of the X-bar is welded to the windshield valence panel/top door hinge mounting area, the bottom right is welded to the "pocket" where the seat belt retractor used to be (and also joins the rocker panel), the top right is welded just behind the lower front corner of the "rear" window sill, and the bottom left is welded where the dead pedal (next to the clutch) used to be. At all but the bottom left, the X-bar also connects to some one of more other bars in the roll cage. Present use of the car does not justify such extravagance, but the "room for future growth" is nice to have. Getting into the car is moderately difficult, but I've learned to deal with it. Evidently I'm one of the few people on this list that is both under 6' and not overweight , and climbing over the X-bars keeps me that way! A bigger challenge is welding in the various bars butted against the existing sheet metal, to maximize what little interior space there is, and to improve structural strength. It requires all sorts of oblique cutting of the tubing.

Since Pete invited a response, I shall oblige. It is rather awkward to attempt to “instruct†anyone, but I will try to share some thoughts I had about the Z’s aerodynamics. A proper explanation really requires a book. One such recent book is “Race Car Aerodynamics: Designing for Speedâ€, by Joseph Katz (Robert Bentley Publishers, 1995). And that is not an especially good book – but it is a good intro. Sadly, the 240-60-80Z has one of the worse shapes in terms of aerodynamics of cars in recent memory. It has small cross sectional area, which greatly helps. But apples-to-apples, it had more drag and un-downforce (lift) than cars like the Chevy Chevelle. Basically, the reason is that for good aero performance, the car’s body should be smooth and swoopy in some places, but sharp and abrupt in others. Generally, the smooth part should be up front – the grill area, the headlights, the hood/windshield juncture. The sharp and abrupt part should be in back – the trunk, rear of the cabin, etc. The Z is swoopy and smooth in precisely the wrong places, and sharp and abrupt – again! – in precisely the wrong places. It’s almost as if the Z’s designers worked long and hard to deliberately do a bad job on the car’s aerodynamics. And to add to the injustice – cars like the VW Rabbit and Ford Pinto had far superior aerodynamics! Second, all spoilers, whether highly-cranked NASCAR wings or rice-boy trunk jobs or the flat panels behind NHRA pro-stockers – are all intended to do primarily one thing: increase downforce. Downforce – or negative lift – can be explained by several alternative and equivalent ways. One way is: higher pressure above a body than below it will cause downforce. Another: pushing air up will cause (by conservation of momentum) downforce on the body doing the pushing. The main difference between a NASCAR spoiler and a F-1 wing (which passenger cars sometimes try to emulate) is that the former is designed to act as an accessory to the car’s body, while the latter is designed to act like an upside-down wing in isolation. And that design choice makes sense: NASCARS are big and cause a lot of air disturbance, while F-1 cars are small and narrow. Also, all spoilers cause induced drag (drag due to lift). But some also cause additional drag, while others actually reduce drag! A downsized NASCAR-style spoiler will actually reduce drag for most street cars, especially when coupled with a nose airdam. The long, essentially horizontal “spoiler†of NHRA pro-stock cars is based on the idea that the fully-separated flow behind the car and underneath the spoiler is low pressure, while the partially-separated flow on top of the spoiler is of higher pressure. It probably has very little impact on the drag. Third, the exhaust smell plaguing the Z is indeed caused by a low pressure above the hatch lid, which leads to entrainment of the exhaust. Any gap in the hatch seal will allow a leak. Opening a window makes this worse. Fourth, and most important: because flow over a car is largely separated and unsteady, with strong ground effects thrown in, car aerodynamics are much, much more complex than airplane aerodynamics. The reason that there are so many competing designs, so much mystery and so much empiricism from the mom-and-pop race track to the Daytona 500, is NOT that car guys are ignorant and airplane guys are knowledgeable, but that cars are so much harder to figure out. Most of the improvements in recent years have been through trial and error. Of course, some things really are obvious; these include things like reducing gaps between body panels. So, what to do about the Z? Well, precisely because the stock shape is so bad, this is a fortuitous case where just about any hack job will actually be an improvement. Cheezy bolt-on parts that you find on E-Bay for $20 actually can help – whereas the analogous parts for a Honda Civic only screw things up. Here is what happens in a boxy sedan: flow that streams over the windshield then goes over the roof, then “separates†(no longer follows the body’s contour) where the roof ends. That flow could go on behind the car. But it can be argued from the basic equations of fluid mechanics that a fast flow (over the roof) mixing with a slow flow (behind the rear glass) will cause the fast flow to bend toward the slow flow. So, the wake behind the roof bends down. In a well-designed sedan (best example ever: Lexus GS430), the truck lid probably (I say probably because I have NOT seen Lexus’s data, and I doubt that they would be eager to share it with me!) “catches†the wake as it bends down. That means that there’s separated flow behind the rear glass and over the trunk, but the wake behind the car is only as high off the ground as the rear of the trunk. Generally, the smaller this “effective area†of the separated flow behind the car, the lower the overall drag. So paradoxically, the blunt-rear sedan emulates a “teardrop†shape! But what about an actual teardrop shape? Well, for the flow to remain attached over the rear portion of the teardrop, the teardrop has to contract very gradually. A truly teardrop-shaped car would be something like 40 feet long! If you guys ever get the chance to look at a wind tunnel, note that wind tunnels are very long and gradually expanding pipes (from the test section to the fan). That’s in order to avoid flow separation from the diverging walls; this also follows the teardrop shape. The same idea is used in air conditioning ducts, jet engine nacelles, and all sorts of devices that depend on airfoil not separating from the walls. So, while the Z’s hatch looks gently sloping, from the aero point of view, it’s not. One idea is to make a 40-foot long teardrop-shaped car, and then cut off the back 20 feet. Then, maybe the flow will not separate until it reaches the very back of the car, which is fairly small in cross-sectional area. This is called the Kamm tail. The Z is NOT a Kamm-type design. NO PRODUCTION CAR HAS EVER SUCCESSFUL FOLLOWED THE KAMM DESIGN! The closest attempt that I’m aware of is the Saturn EV-1. Ugly looking thing, but it works. Unfortunately, a failed Kamm-type design can be worse than a brick-type design. That is what happened with the Z. Here’s a paradoxical (but verified!) trick: remove the hatch lid of the Z completely, turning your Z into a mini-El Camino. The exhaust smell will go away (for various reasons) ! Is a BRE-type spoiler superior to a whale-tail spoiler for the Z? Well, to be honest, I really don’t know. My GUESS is that the BRE spoiler will be better, because the whale-tail acts more like a wing, which is better in a smoother flow than that behind a Z hatch. But it’s very apples-to-oranges because the whale-tail has much larger area and sits further back than the BRE spoiler. Look at what the GT-2 Z’s ran – I think it was a NASCAR-style spoiler, an aluminum plate. That is probably best for high-speed stability (makes more downforce and stabilizes the wake). Finally, back to the original question – will a rear spoiler reduce exhaust fumes in the cabin…. My opinion is that the spoiler will help, but to a limited extent. The reason is that the spoiler – regardless of its shape – will mount to the hatch, and not to the body underneath the hatch lip. So, the low pressure underneath and behind the spoiler will still be sitting over the hatch gap. The exhaust will be entrained into the region underneath the spoiler, and will still try to get into the crevice between the hatch and the body. In that sense, the spoiler fails. But, with good spoiler, it is likely that the overall flowfield behind the car will be “massaged†such that the overall exhaust entrainment behind the car will be weaker. So if you are thinking about a spoiler to reduce drag or increase downforce, but are also concerned about the exhaust fumes, by all means buy the spoiler. But don’t buy it solely for purposes of controlling the exhaust smell.

I also think that the halfshafts would be the greatest problem. How wide is the 8.8" IRS pumpkin? Fabricating mounts for the differential is nontrivial but can be done with some basic machine tools. Custom-shortening and reflanging half shafts can not. It's the same problem with the Ford 9" rear. The Z's track is just too narrow for conventional applications. One suggestion to solve the halfshaft length problem was to alter the rear track width - for example, by sectioning and widening the transverse links. That of course alters the rear camber. The strut perches can also be moved outboard, I suppose. Sounds gruesome, but "it's only sheet metal work." For the adventurous, my hot rodding buddy suggested Oldsmobile Toronado halfshafts. I'm not sure about length, but they can easily take the torque.

My guess on the sidebar issue - specifically the bar that goes from the driver's left shoulder area down to the footwell (clutch dead-pedal area) - is that the ineffectiveness of the sidebar is due to the footwell being a non-structural area. That area is unsupported sheet metal, outboard of the frame rails. Without additional reinforcement, the sidebar has nothing rigid to anchor to. On my car, the clutch dead-pedal is cut out and the area is draped by a 1/4" sheet metal plate - actually two plates, one of which drapes over the rocker panel. And outside of the car, there is a bar from the end of the rocker panel/footwell area diagonally to the tension/compression strut perch on the framerail outboard side. That's on both the driver and passenger sides. In addition, the passenger side has a bar running diagonally from the passenger rocker panel area to the midpoint of the dash bar (that's where the heater core sits in the stock Z). Also, the second sidebar, running from just above the door hinge area down toward the "box" where the seat belt retracts, adds to the structure. Together the two door bars form an "X". That makes getting into the car difficult, but I have a relocated steering column and quick-release steering wheel. These are rather extreme modifications, but thought I'd throw them into the discussion. I have not driven the car aggressively, so I can't yet report whether "theory is supported by practice".

Big block V8 Z conversions take lots of extra effort. While the block mounts the same as the small block, the fit is much tighter. The frame rails won't clear even block hugger headers without notching or relocating the rails. I don't think the engine will fit in the JTR setup - not enough clearance for the starter, the steering shaft, etc. Mine is set back 6.25" from the JTR setup by relocating the firewall and reworking the frame rails, among other things. You CAN get the car balanced and everything to clear, but by the time you're done, you might as well have built a complete tube-frame car and draped the body skin over the frame. I can't say that it was worth the money or the effort. Big block parts are much more expensive than small block parts; I wish I took notice of that before I began my project. Typically double the price. Edelcrock aluminum heads are $1650. Better heads are $2000+. While decent small block heads can be found for $900 or less. Likewise for the bottom-end components. Much of the beauty of the V8 swap is in the bang-for-the-buck and ease of finding parts. But that's really only true for small blocks. But, once you get the conversion to work for the big block, downgrading to a small block is a breeze. I just might follow that route myself, if rebuilding my present engine proves to be too expensive.

Mine is a rather extreme example, done in a friend's shop. The front clip (forward of the firewall) was cut off, then the firewall and floor were cut out. A cage was build on a jig, welded together, then raised into the shell of the car, and welded to the body. Then the floor and firewall were welded back in. The frame rails rebuilt with the front clip welded back in, with new sheet metal bent to accommodate the new location of the firewall. Then the front strut towers and tension/compression strut mounting points were connected back to the cage. The headliner is the only piece of interior paneling left unmolested. X-bars in the door openings make entry difficult, but not impossible (a relocated steering column and removable steering wheel help). A bigger nuisance is the longitudinal bar connecting the front strut tower and rear strut tower superstructures - it runs the length of the cabin, bisecting the car. Pictures can be found on Pete Paraska's site, under "Michael OL's big block Z".

In hot pursuit of the no start/no spark problem of my big-block (454 Chevy) 280Z, I've decided to do an overhaul of my distributor. That leads to the following questions: 1) since I won't be revving the engine above 5500 rpm, do I need to worry about the stock or stock-replacement HEI unit losing voltage at high rpm? 2) is it worth to buy a complete distributor package, or to just replace the "guts"? Mechanically, the distributor shaft looks good. 3) what's a good aftermarket brand? 4) I'd like both vaccuum and mechanical advance. But lots of otherwise good aftermarket units (e.g. Mallory Unilite) are apparently only vaccuum or mechanical - NOT both. Comments? 5) What's a good general reference (book) on working on Chevy V8's, especially big blocks? I am not looking for books like "how to build your Chevy race engine" that talk about setting up dry sump systems or selecting forged vs. cast cranks. I'm looking for a book on stock maintainance of a Caprice or Suburban engine, that covers issues such as setting timing and specs on head bolt torque. It's amazing how much "basic maintainance" remains to be done after the "building" phase is apparently over!!!

Once the 280 and 240 are stripped down to the shell, the difference in weight is very small - maybe 100-150 lbs. 280's weigh more mostly because of the added peripheral components, of which the bumpers are the most obvious (but probably not the most significant). My 280-based big block car weighs 2725 lbs, and that's with an engine that's 250 lbs heavier than the L6, 100+ lbs of roll cage material, 100lb transmission and 40 lb bellhousing. But it also has a lot of sheet metal removed. Stock weight for 280's is ~2850, not 3075.

If the oil pressure problem occurs even while cruising at a steady rpm (and so, evidently at a steady speed), it might be a bearing problem, rather than an oil pickup problem. Does the oil pressure fluctuate when you rev the engine in neutral, with the car parked? Also, are there any deep rumbling noises that vary linearly with rpm?

Yesterday morning I walk out to the parking lot, and see a sight that breaks my heart: a puddle of antifreeze on the asphalt under my V8 Z. The temperature was maybe 15 degrees, and the cooling system was filled ~50/50 with antifreeze. When I removed the cap from the filler unit, which sits on a section of hose, inside I found crunks of green ice, as if the antifreeze had itself frozen! There were two dripping streams of coolant: one from a clamped hose end (no biggy), and one from somewhere under the block (biggy). It's too cold to check closely, but I suspect that at best, a freeze plug popped, and at worst, the block is cracked. Is is possible that I used too dilute a mixture of antifreeze? I can't imagine that such a simple mistake can have such devastating consequences!

Just some brief comments.... When taking pressure data, it is critical that we make note of dynamic vs. static pressure. If the mouth of the tube which acts as the pressure probe is flush with the surface of the hood (i.e the hood has a hole drilled in it, and the tube is inside that hole), it measures static pressure. If the tube opening faces the exact direction of the oncoming flow, and the other end of the manometer is connected to a static port near the same location, the measurement is the dynamic pressure. Any in-between orientation of the tube opening will give some mixed reading. In Morgan's experiment, the difference between what the tube end senses, and the cabin static pressure, would of course also depend on how the tube end was oriented. But regardless of the technicalities, there are some important issues raised by Morgan's data. Here's my attempt to reason things through.... If there were no flow separations anywhere on the car, the total pressure (static + dynamic) would be everywhere constant. Where the flow was faster, the dynamic pressure would be higher, and the static pressure lower. But, whenever there is flow separation, there is loss of energy, and thus a loss of total pressure (pressure is mechanical energy per unit volume, in a manner of speaking). I would expect the total pressure in the front of the hood to be slightly lower than at its trailing edge, because of the separation "bubble" near the hood lip. More important for purposes of venting and intake is the static pressure. Static pressure over the front of the hood should also be lower than towards its trailing edge, because the flow accelerates in going over the hood lip. Separation reduces total pressure, but the generally accelerating flow increases dynamic pressure, so static pressure falls yet further. Static pressure at the hood trailing edge/windshield junction is higher, because here the flow slows down, also with a possible separated roller along the windshield lower edge.

Is there a clever trick to successful connection of the stock 280Z tachometer to an HEI distributer? The ubiquitous JTR book mentions the connection of two wires from the ignition module in the passenger's footwell: (1) the blue wire going to the "tach" terminal (with a resistor in series) and the black-white wire going to the "bat" terminal. But that's with the ignition module removed! It seems to me that the blue wire would then be connected to nothing. I've starting the rewiring of my electrical system from scratch. The ignition works, as do most of the lights. Now I have a bare ’78 280Z tachometer that I’m trying to connect. Evidently, only two wires are necessary for the tachometer to work: ground, and the connection between the tachometer receiver (green wire) and "tach" on the distributer. Done that way, the needle might bounce around, or be otherwise inaccurate, but at least there should be SOME signal. But I get no signal! Am I missing something, or does my tachometer have an internal problem?

I've found that if you have significant hot rodding and mechanical experience, you develop a "nose" for low-tech, low-cost, yet perfectly sound solutions. But lacking that experience, one tends to saddle himself with unnecessarily "high tech" methods. Part of the learning curve, I suppose. For a 300hp V8 Z, my opinion is that the only unavoidable "high tech" part is the manual transmission. Detriot products rarely came with stick shifts - especially the high-powered ones. The typical stick shift transmission (T5) is generally regarded as being too weak for 300 hp. The Muncie 4-speed is OEM, but those are rare, expensive, have an awful selection of gear ratios, and are probably notchy as well. Aftermarket choices - T56, Tremec, and Richmond gear - all involve some custom work, especially with clutch and bellhousing. Perhaps 300 hp is a "borderline case"; it might be better to go with, say, 250 hp (use a T5, don't worry about roll cages or subframe connectors, etc.), or go "all the way" for a 400+ hp street/strip car. Sometimes I really envy the muscle car guys. Their projects seem to be so off-the-shelf, so simple to assemble. The aftermarket industry offers trememdous support for these vehicles. But a V8 Datsun has a way of snowballing into an exotic custom creation, even with the most sober and "basic" intentions. It's a great engineering adventure, and surely gives the owner/builded more satisfaction than hopping up his Camaro or Chevelle, but sometimes "low tech" ends up feeling like a too-good-to-be-true fantasy.

The solid vs. independent rear comes up form time to time, but I've yet to see a rigorous explanation for the situations in which one is superior to another, except of course the superiority of IRS for rough pavement. Herb Adams' book is interesting reading, but too is vague about the issue. In the solid rear axle setup, the orientation of the rear tires relative to one another does not change, apart from minor motions caused by deflections of the axle under load. In the IRS, the camber of the left and right wheels changes relative to one another, depending on the vertical deflection of the suspension. That part is, of course, obvious. But what's far from obvious is whether this relative camber change necessarily reduces traction on launch (for example). There is little doubt that a Ford 9" solid rear axle is stronger than a Datsun IRS with R200. What I'm wondering about is whether in a hypothetical apples-to-apples comparison, the solid axle setup has better traction. IF the two systems, when "properly set up", have comparable performance - that is, if the difference is only a matter of strength and durability - I would prefer to stick with the IRS. But if I find that I just can't put the power to the pavement, even with huge slicks, then I would persuade myself to spend the >$5000 on a custom solid rear end and 4-link.

Very clever! where does one get ahold of liquid nitrogen - or for that matter, just dry ice???? I just completed my car's de-tarring. Took about a week with a chisel and hammer to do the whole floor and hatch area, and there's still a "residue" left. Lots of cursing and dozens of cuts on my hands. Pete's right - there is rust hiding underneath that tar, even if the top surface looks dry and pristine. The worst places are where the sheet metal panels join, and are covered by rubbery white glue. Rust wants to form at those joints. Of course, the metal is unpainted in those areas!

Fascinating drawing! Yet more evidence that this is by far the most useful automotive forum on the internet! One thing to notice is how the 280's frame rails continue for a long distance underneath the floor pan, but terminate ~6" ahead of where the rear subframe begins. A lot of unibody cars are apparently designed that way - almost full length frame rails, but not quite. I heard that the reason for this seemingly idiotic design flaw was NVH; splitting the frame like that is a deliberate compromise of rigidity to reduce vibration and harshness. On my '78 280, the "stock" subframes were retained, but were extended to the rear clip, and now terminate at the hard points where the rear sway bar used to mount. It's also interesting how the rocker boxes - probably the strongest beams in the whole car - just appear to float in space, supporting neither the engine nor the suspension loads directly. The roll cage design that I was talking about in an earlier thread was an attempt to tie into these rocker boxes.

Well, there's more than one way to skin a cat, of course. But, I just wanted to make a couple more comments about the method that I attempted to describe.... With the roll bar "opened up", it ends up outboard of the seat. In fact, the seat backs up all the way to the wheel well. I'm only 5'9", but the firewall (and pedals, and steering wheel, and everything else) in my car is 6.25" set back from stock. With the way I have the seat mounted now, my legs are too short to even reach the pedals. The top of the roll bar sits underneath the stock roof "bridge". It's right under where the dome light used to be. But, I have to admit that I'm not using a stock seat. I have a Kirkey aluminum "drag race" seat, which is thinner and narrower than the stock seat.

Owen, I don't have the S&W cage, but the main hoop of my cage is anchored the way I'm describing in the following paragraphs.... My advice is to weld a 6"x6"x3/16" (or similar size) steel plate right over the "box" where the seat belt retractor thingy used to sit, and where the end of your roll bar hoop currently sits. That distributes the roll cage loads over a broad surface, instead of introducing a stress concentration, as would happen if the roll bar ends were welded into the seat belt retractor box. Tie that piece of steel over to another piece of similar thickness, welded along the side of the rocker box. Then cut the roll bar ends, and butt weld them to the plate. If you have access to a means of bending tubing, I suggest that you "open up" the roll bar (that is, reduce the angles of the bends in the corners at the roof and the side windows), to get the bottom ends of the roll bar to sit further outboard - that is, closer to the rocker boxes. Then you can weld the ends of the roll bar into the "corner" of your 6"x6" plate and the rocker box, and leave more room to pull back the driver's seat. That also makes a natural hard point for welding in X-bars in the door openings, and for a bracket for the lap belt portion of the safety harness.

The "NMCA drag racing series" has recently been featuring turbocharged Chevy small blocks in its semi-pro classes. These are making well in excess of 1000 hp. The hot setup is twin-turbo, with a huge intercooler sitting in front of the radiator. These are $50,000+ engines. One guy is even running a turbo destroked big block. On first impression, there is something mutually exclusive about turbo and V8. The combo can work, but I don't think that there is enough of a customer base to justify significant involvement from the retail aftermarket. Evidently that's why the V8-type car magazines only talk about the super high-end when they mention turbo V8's. At how many psi does a stock Buick GN boost? I wonder what tinkering would be required with the SBC bottom end to survive with the same boost level....

Folks, This might not be entirely related, but I was just wondering what people considered to be a "tube frame". My idea of a tube framed car was one where every body panel just bolts to the tube superstructure. So, the floor boards, the firewall, the roof - everything - is just along for the ride, while the "tubes" take care of all the loads. So funny cars are "tube framed", but something like the GT-1 Porsches and Corvettes are not.... ....which probably means that a roll cage bolted to a ladder frame, with the stock body welded on top, is not a tube frame. Any opinions? As to the original posting in this thread, I would have thought that the strongest part of the stock Datsun body is the structure forward of the firewall. So this would be the last portion of the car that one would remove and replace with a custom piece. The spacing between the frame rails is wide enough to fit even a big block, though accommodating the exhaust does require some modification. The area where the tension/compression struts mount underneath the frame rails is a natural hard point, and a good place to weld supports for engine mounts. With some fabrication, it is fairly "simple" to splice the front end of one Datsun into the rest of the body of another. The front clip of my car was completely cut off (and then welded back together), to accommodate my firewall setback project.

Folks, OK, here it is - pictures of my car: http://members.home.net/pparaska/MichaelOlsZ.htm A big huge thanks to Pete Paraska for hosting my "web page"! I apologize for the sloppy photography - hopefully I'll have better images soon. The last photo sort-of shows how the engine is installed, but the rear 1/3rd of the engine sits under the windshield valence panel, obscuring the view. If you look closely, you can see the Griffin radiator angled forward. With the hood closed, the air cleaner just barely sticks out. Big blocks are tall. I had to either put up with the air cleaner sticking out, or the oil sump hanging too far below the frame rails. Contrary to what the label beneath my user name says, I now live in Dayton, Ohio. Which means that racing season is drawing to a close. It won't be until next spring that I'll get a chance to run the numbers on the car at the track. But, it will take at least that long to fix the rod knock, figure out how to upgrade the stock half shafts, sort out the wiring (I threw away the 280Z electrical system and started from scratch), sand out the rust and get the car painted, etc., etc. Currently there is no room for the windshield wiper assembly, the dash won't fit because of lateral roll cage bar that's in the way, the window cranks and arm don't clear the X-bars in the door, and the fuel cell sits right behind the rear strut towers. But these are "minor problems", compared to what had to be taken care of us to get this far

The best estimate that I have heard for fully dressed L28 (no transmission) is 425 lbs.

Some more details... The battery is in the rear, next to where the fuel tank vapor canister normally sits. The radiator is a Griffin 28"x19" (frame rails notched to fit the wide radiator). Suspension is completely stock. The motor is all cast iron, except for block hugger headers and aluminum intake. For big blocks, aluminum heads are claimed to save 70 lbs. I looked at the GMPP aluminum heads - they are one of the options, along with Edelbrock and Brodix, among the oval port choices. Do any of the big block drivers have a particular recommendation?

The transmission that I was talking about (Doug Nash 5-speed) was purchased used, with a claimed 20,000 miles on it. The application was in a V-12 Jaguar, and the seller claimed that he was selling it only because he upgraded to a six-speed Richmond (no overdrive in a Jaguar is even sillier than no overdrive in a Datsun). Anyway, what I bought almost certainly inferior to a brand new unit. But I only paid $750, with the shifter. The transmission also makes a dull "whirring" noise when going in reverse - and only in reverse.

My understanding of the flow measurement techniques is that cylinder head flow numbers are always obtained from tests on a flow bench, never on a running engine. On the flow bench, the head is subjected to a fixed pressure drop. Generally that number is 28†of water, which corresponds to approximately 1.0 psi. Each port is tested individually. The valve is held open at a set opening height, and flow volume measurements are taken for a sequence of opening heights. Generally, the intake manifold and engine block are missing; they are “modeled†by plastic pieces which attempt to approximate inlet and exit conditions at the cylinder head ports. And this is all done at steady state conditions and room temperature. So there is no combustion going on, no valve motion, no port-to-port crosstalk, etc. It seems to me that flow rate numbers are only useful as a relative comparison between different heads in the same catalog, and not as an accurate guide of what a particular head will flow in a particular engine. For instance, for my streetable big block, I can choose an “oval port†head that is rated to flow 140 cfm (intake) at 0.200†valve lift, 270 cfm at 0.500†lift, and 290 cfm at 0.800†lift, or rectangular port heads that flow 120 cfm at 0.200â€, 280 at 0.500â€, and 400 at 0.800â€. My cam tops out at 0.504†intake lift, so the rectangular port head’s high flow numbers at 0.800†are useless. But the oval port head’s better flow at low-lift will hopefully – hopefully! – increase low-end torque and throttle response. On the other hand, recent experience has shown that 450+ ft-lbs in a 2700 lb car and 3.27 first gear does not call for a lot of low-end torque. Probably the OEMs have the capability to measure flow in the ports while the engine is running; for example, by laser-doppler velocimetry. Otherwise they’d have a tough time designing such things as intakes with variable length runners. But I would be greatly surprised if any of the aftermarket manufacturers had comparable imformation. Making guesses is a big part of the hot rod hobby!