Michael

NHRA won't approve a cage unless the main hoop is at least 0.120" thickness DOM mild steel. Chromoly is a different story, but if you're using 0.095 mild steel, the cage won't be legal. Unfortunately, most 0.120 mild steel DOM tubing is actually 0.118-0.119! Some NHRA tech inspectors will fail that! I can't claim first-hand knowledge, but I have heard of people spending $2000+ on custom cages with 0.120 tubing, only to get their cars failed. This is why it's something of an industry standard to use 0.134" tubing for the cage main members. My car has 0.134" for the main hoop and various other parts of the cage. Strut tower bars, main backbone, and the various diagonals range from 0.065" to 0.120", to save weight where possible. I agree that some folks are a bit too eager to install roll cages in street cars. Yes, even mediocre cages do offer some measure of safety, but a poorly designed cage is almost certainly more trouble than it's worth - and can lead to a false sense of security. In my opinion, there is no substitute for X-bars to side impact protection - yet few people would go to the extreme of welding in permanent X-bars, to hard points welded to the unibody. "Doing it right" rapidly spirals into the construction of a bumper-to-bumper tube frame. That's what happened to me. This is fine, I suppose - except that the result isn't what one might seriously call a daily driver.

As with most things, yes, it has been done before. There are two drag Z's on this site with 454-based engines, and then there's my "street" Z with a 454 from a 1978 Chevy Suburban. All three cars have heavily modified frames. For pics of mine, see Pete Paraska's web page - there's a link to some information about my car. Weight distribution is the main issue. My solution was firewall setback. That may or may not be necessary, depending on the car's intended use and the driver's preferences. But one lesson that I have learned is that this is a difficult swap. Not impossible, by any means - but certainly difficult.

It seems to me that the key to getting good weight distribution with a big block is chassis mods to set the engine further back – way, way back. Shameless self-promotion: see my car at http://members.home.net/pparaska1/MichaelOlsBBZ.htm. Of course, with that sort of approach, something like GN V6 would result in a combo with even more rear weight bias, even less loading on the front springs and even less need for upgrading the brakes. The “can I and/or should I use a big block” question comes up over and over again... I think that the reason for using a big block is low-end torque. Not peak hp or even peak torque, or actual 1/4 mile numbers. There are crate engine small blocks out there making 500 ft-lbs at 4000 rpm. Not to mention the various turbocharged combinations – V8 and V6. But how many of them make 500 ft-lbs, 400 ft-lbs or even 300 ft-lbs right off idle, at 650 rpm, with no lag and no hesitation, on pump gas, for thousands and thousands of miles of trouble-free operation? In racing, you get a chance to spool up the engine before you drop the hammer. Whether it’s a manual or an automatic transmission, the prudent driver anticipates when he will need the torque, and pre-revs accordingly. Lazy off-idle response is less important than on-design performance. But what about on the street? If you’re driving along at 25 mph, with the tranny in neutral and the engine idling, when that pesky minivan in front of you finally turns and you get the spontaneous desire to punch the throttle – that’s when you want a torrent of torque right at idle. Not at 2000 rpm, but at idle. By the time I get to 2000 rpm, I like to upshift. With that kind of driving style, the big block is the way to go. The 502 weighs the same as the 454 or the other stock big blocks. Tall deck and “bowtie” blocks weigh some 40 pounds more. “Superblocks” based on the Chevy BBC architecture, but displacing up to something like 800 cubic inches (!), weigh another 100 lbs or so. So the 502 will fit anywhere where a 396 fits. The issue is what to stick behind that 502 to handle the torque and to provide appropriate gearing. For example, it’s hard to find a sufficiently strong transmission that has overdrive. I was thinking about getting a ZZ502 crate engine from GM, but now my sentiment is towards building an engine with help from the local machine shop; that would be based on a 454. Now the question is, how to go about doing that without getting ripped off...

I second the observation that "front flexing" is a problem on the Z. When my roll cage was installed, before the front strut tower diagonals were in place, the car would still flex, as observed when it's abruptly lowered from a hydraulic lift. After the diagonals were installed, the flexing was significantly attenuated. The diagonals pierce the firewall and connect to a dash bar and "backbone" running down the middle of the passenger compartment. For pictures, see http://mywebpages.comcast.net/pparaska/MichaelOlsBBZ.htm

This is sort-of off topic, but from reading this thread I suddenly get the impression that there are actually HybridZ people in Ohio!?! Especially in southwest Ohio? That’s it, we gotta have an Ohio HybridZ gathering! I live about 20 miles southeast of Dayton, almost straight down I-71 from Columbus. My car is currently engineless but I’d be glad to have people sit in it, and I’ll push the car around. You can make vroom-vroom noises.

After doing the bumpsteer crossmember mod, I discovered a weird wheel alignment problem with my V8 Z: in the front, the driver’s-side wheel appears to stick further outboard than the passenger’s-side wheel. But in the back, the situation is reversed. The car has 14x7 wheels with 225-60 tires, and stock suspension components, with the possible exception of the springs (courtesy of the previous owner). Making reasonably accurate measurements in the rear, I found that the left vs. right control arms do not measurably differ in length, and the distance from the control arm outer pivot (that ~8" shaft that's so hard to hammer out) to the wheel rim lip has a left vs. right difference of at most maybe 1/16". In other words, at the bottom, the left and right wheels are pretty much symmetric about the car's centerline. Not so at the top! The rear right wheel has significantly more camber than the left rear. With the rear jacked up, a broom stick leaning vertically against the tire also touches the left wheel fender lip, but is 3/4" outboard of the right fender lip! In other words, standing in back of the car and looking at the rear wheels, the left wheel is at the 11 o'clock position, and the right wheel is at the 2 o'clock position (1 o'clock would have been symmetrical). With the car on jackstands, the wheels are of course hanging down, so both have high camber, but the right-side rear wheel is ridiculous. Evidently the right-side McPherson strut has a different angle between the strut and the stub axle axis! Weird. At the front, the situation is similar, but reversed; using the lowest point at the wheel rims as reference, and measuring to things like control arm pivot points, reference points on the steering crossmember, and so forth, I get pretty much the same numbers. So the "bottoms" of the wheels in the front are also nearly symmetric about the car's centerline. However, the minimum gap between the coil spring perch and the inboard surface of the tire on the driver's side is about 0.5", maybe even 0.75". On the passenger side, it is almost ZERO - so that tire almost rubs! That explains the visual effect of left-right asymmetry, but it does not explain the mechanical cause. I did, by the way, switch the left and right wheels, just to make sure that there was no funny asymmetry in the wheels themselves - and there isn't any. What's going on????! Looking at old photos of the car, with its original wheels and before the V8 swap, I can discern tell-tale signs of the same stuff going on. So this is not something that happened in the history of the car since I bought it - either due to the steering crossmember mod, or the V8 swap. And for what little time I drove the car after the V8 conversion, I did not notice any bias in the car's tracking. In other words, it FELT correctly aligned. Opinions? This can’t be a feature of the stock Datsun design, right? Nor is it the result of any obvious accidents or mechanical damage (none that I can tell, at least). Could the spindles be bent? That might account for the problem in the front, but in the rear??? By the way, a NEW photo description of my car is hosted on Pete Paraska’s site (thanks again, Pete!) at http://mywebpages.comcast.net/pparaska/MichaelOlsBBZ.htm. It contains construction photos and details of the roll cage, engine mounts, etc.

I have a big-block Z. Well, sort-of. Some old but reasonably illustrative pictures can be found on Pete Paraska's site; look under "Michael OL's big block Z". I said that I sort-of have a big block Z. That is because my engine is apart and won't come back together until a long, long session of soul-searching, book learning and hands-on trial and error. Why? Because, as the guys have already mentioned, big blocks are big potential but also big bucks and big effort. Yup, it's all big. I have a 454. 454 is the natural big block. A 632 all-aluminum jewel box is nice, but let's face it - for most folks, that's ridiculous. A 454, however, is ROUGHLY analogous to a 350. They're out there. They can be pulled from old cars bought cheaply. But they are much, much rarer than small blocks. My car was set up for a big block from the very start. Radical frame mods, firewall setback, and a tube frame connecting all four strut towers. It balances 51/49 with an all cast-iron BBC. Stock suspension. And even now, after over two years and extensive semi-professional assistance, I often wonder whether it wouldn't be easier to just get a 350 for the time being, and start driving the car rather than staring at it.

I'm the BBC dilettante that Pete was referring to. Things are a bit hectic now, but I'll post with pictures of my setup in a couple of weeks. That's a promise - sort-of. Here's the summary of the project: The car was basically built by a buddy of mine, though I can take blame for most of the design. The front end was cut off, the firewall and floor cut out, a roll cage welded into the car, then the floor was shortened by 6.25", floor and firewall welded back in, front reattached with frame-rail doublers and lots of sheet metal in compound curves. The transmission is a Doug Nash 5-speed, with external shift linkage. The transmission tunnel was cut up in multiple places to accommodate the shifter, the driver's seat, and the roll cage tubes that support it. The shifter boot exits though a another piece of sheet metal with compound curves, made evidently on an English wheel. The engine mounts to steel pads welded to the frame rails over the joints where the tension/compression rods pick up. E-mail me at ol_70@hotmail.com if you have specific questions.

Well, I'm one of the bigblockers, though currently my Z is in a state of suspended animation while I work up the courage to spend $$$ on getting the engine rebuilt. It's a 1978 280Z with a 454 BBC, originally from a Chevy Suburban. 90% of the metal work on my car was done by a buddy of mine - not by me. The BBC vs. SBC thing has been kicked around a number of times; a search under "big block" will hit most of those threads. Basically, by going with a BBC you are committing yourself to a project well beyond the framework of the so-called JTR type of swap. It CAN be done, and it can be made to handle, but it can get rather complex fairly quickly. If you do go the BBC route, consider building as large a displacement engine as you can. Once you pay the weight, cost and fitting penalty of a big block, get at least 4.25" bore and 4.00" stroke (a 454). Your machinist friend might have more creative ideas. Small blocks are so common that there is a huge difference in price in main-line vs. unusual small block stuff. For big blocks, weird combos like aggressive stroker cranks aren't much more expensive than stuff in OEM sizes. Best of luck!!

These discussions invariably come down to some trite but true saying, like "Speed costs money; how fast do you want to go"? Some experience with Chevy big blocks suggests that the Mopar Hemi (426-based) will indeed fit - but not with the stock sheet metal. With the right exhaust headers you can probably clear the stock frame rails. Plan on setting the engine so far back that the motor mounts anchor on the frame rails right about over the area where the tension/compression strut mounts currently sit. And you will probably need to relocate the brake vacuum booster to clear the driver's side valve cover. This basically means a custom firewall and a "pedal box" for the driver's feet. I have seen 240Z-based cars where the engine was so far back that the windshield was notched for the distributor. That was a lexan windshield. As I recall, Hemis have front-mounted distributors, so at least your windshield could remain stock.

I have a Richmond 5-speed behind the Chevy big block in my '78 280Z. pros: incredibly strong (reputed to be the strongest shaft-gear manual transmissions, bar none); deep first gear; external shifter can be moved around for customized relocation; fit standard GM stuff, like Lakewood bellhousings and the GM 26-spline tranny shaft. cons: very notchy and heavy shifter, if the shifting linkages are professionally assembled - and impossible to shift otherwise, due to (among other things) manufacturing defects; no overdrive in the 5-speed, relatively deep overdrive in the 6-speed; expensive; shifter linkage will involve transmission tunnel mods, even in a 280Z. Richmonds are the natural replacement for a muscle car originally equiped with the Muncie series of transmissions. I do NOT recommend them for V8 Datsuns, unless you plan on running much, much greater than 500 hp.

Just out of curiosity, does the one-piece front clip include the "valence panel" and inspection lids? I've found that most fiberglass hoods terminate at the same aft location as the stock hood. For my car, the valence panel and inspection lids are riveted to the stock hood, and the whole thing lifts up. Also, how do the "fenders" of the one-piece clip wrap around the rocker panels, behind the wheel wells? Are the fenders somehow split, like on a C4 Corvette?

Folks, Regarding the very start of this discussion – I would opine that going 200 mph in ANY car is risking your life – that is not a risk specific to the Z. The main problem with car aerodynamics is that the car’s shape is not “smooth”, so it’s very hard to predict what the air flow will do. Most of our methods, from the hardcore theory down to handbook-style approximations, assume that whatever the vehicles does to the air, those changes actually differ at most modestly from the undisturbed flow. Airplanes are, as a rule, “smooth” – and so, much easier to analyze. A good example is the air dam vs. smooth floor pan dilemma. The air dam is supposed to block flow, while the underbelly enhances fast, low turbulence flow. Contradictory engineering objectives, but both are ultimately after the same thing: low drag, good downforce. In most cases, an air dam can be slapped onto a generic car without any analysis, and things will improve. Not so for the underbelly – that can only work if the whole car is taken into account. The underbody venturi effect, for example, won’t work if the entrance conditions at the tunnel are bad (flow angularity, pressure loss, etc.), or if the pressure recovery at the aft end is unfavorable (flow separation). To improve stability at 130 mph at the end of the 1/4 mile, the air dam is a much more practical choice. But at 200 mph – that almost automatically requires redesigning the whole car. No advice on that one….. As Pete Paraska mentioned, there are universities that might be interested in a student project on Z aerodynamics. Keep in mind that as the aerospace industry declines and facilities are idled, stuff like car aero is a great way to keep the facilities going. For example, NASA Langley essentially “gave” their famous 30’x60’ wind tunnel to Old Dominion U, who makes good money selling wind tunnel time to NASCAR and the like. If you are in the mid-atlantic area, also check with Virginia Tech, U of Maryland (who has an excellent wind tunnel – see their web site), and Penn State. All of these places have a “public relations”-type guy associated with their aero facilities, who would be glad to chat about car aerodynamics and retail customers – or even in-house cooperation with the students. Unfortunately, a bad wind tunnel is worse than a half-assed road test. It gives bad data, but makes you think that it’s good data because it’s “scientific”. Water tunnel flow visualization of a 6” wood model of a Z will give a simple picture that sort-of matches reality when gross flow features like massive separation over the rear hatch are concerned, but it is NOT a design tool. Neither is a cardboard wind tunnel driven by cooling fans.

I have "X" bars in my car (one goes from where the "dead" pedal used to be in the footwell to where the B-pillar should have been; the other goes from where the seat belt retract used to be, to the upper door hinge area). Getting in the car is NOT that difficult. But I'm way way smaller than the 6+ footers that seem to dominate this club . The Z is a pretty big car if you're short. I think of the X-bars as a means of making the car more rigid, rather than side impact protection. Those bars are so close to my left shoulder, that even if they deflect just slightly, they will smash my side, unless my seat also deflects. The bars help in bending and torsion by triangulating welded-in hard points with one another - points that would otherwise be "floating". But I agree that if "all" you expect is 300-400 hp, and safety takes priority over making the car rigid, there is probably a better solution than diagonal or X-bars.

An important point implied in the previous post is that most Detroit 4-speeds tend to be externally shifted (the linkage rods are literally rods bolted to tabs on the outside of the transmission case), while 5 and 6 speeds tend to be internally shifted. This is one reason that the latter are physically longer. My Doug Nash 5-speed (fifth gear is 1:1 - this is basically an Muncie "rock crusher" with an extra deep first gear) is externally shifted. Installation required radical modification of the transmission tunnel. I would guess that if you install an Muncie, a Saginaw, etc., you would have similar troubles. Now I'd like to switch to a T56, but I would have to undo many hours of custom sheet metal work. But one advantage of the old 4-speeds is that they all bolt up to the aftermarket blow-proof bellhousings - an important point if you go racing. The T56, as far as I know, requires its own (non race-legal) bellhousing and clutch setup.

In my case, the dashboard no longer fits, since a part of the roll cage currently sits where the dash used to be. With the mounts for the stock gauges gone, reusing the stock gauges was a lot less attractive. My brief experience taught me that mechanical gauges are generally preferrable to electrical ones; I bought a mechanical oil pressure/water temperature unit from Pep Boys for $30, and it works great. I could have used the stock tach, but that never worked right - the tach needle kept getting stuck. So I bought a $45 unit (with shift light) from Summit. I still use the stock speedometer unit. Another problem with the stock gauges is that if you install a small-than-stock steering wheel, the rim of the wheel can block the line of sight to the speedo or the tach. That is a very annoying problem on my stock '78 280Z. When the speed is in the 50-80 mph range, I can't see how fast I'm going, without leaning down and to the right. In my V8 Z, I bolted the gauges in a cluster around the steering column. This improves visibility and simplifies the wiring harness.

Also, the big blocks and small blocks are two completely different families of castings. For example, in the Chevy line, the SBC as 4.4" cylinder bore spacing (centerline to centerline), while the BBC is 4.9" (I may have the exact numbers incorrect, but they're close). This is why there can not be a 4.5" bore small block - you just run out of block! There may, however, be aftermarket redesigns that allow nonstandard overbores. Companies like Merlin make "superblocks" - loosely based on the stock big block - that allow 700+ cubic inches. That's "two" 350's! Parts from one family do not interchange with those of the other. The ONLY exception is the distributer. If you somehow use rods from a BBC in a SBC, you will at the very least have to do something about the main journal diameter, which is much larger for the BBC. I do agree that for most Datsun conversions, big blocks are overkill. In my case, the fellow that did the welding was a BBC lover, and convinced me to follow that route. Otherwise, I would have bought a 383. Mike Kelly - thanks for your compliments! - but the metalwork of my car was done by a hired gun - I would not have been able to get this project done alone. It's one thing to design, and quite another to actually build.... Now I'm learning that I can't even tune that engine properly. Ah, theory vs. practice.

As a big block Datsun adherent, here’s my brain dump on the issue.... Each of the “big three” Detroit manufacturers had basically two series of V8 engines – the small and the big blocks (specifically referring to pushrod V8s). Around 1954, the pushrod V8s started coming out (the first was from Cadillac (?) ), displacing around 300 cubic inches, and replacing their flathead precessors. Some 5 years later, new families of larger, beefier V8s came out; Ford had the FE series, Chevy had the W-motors (348 and 409). Ford kept changing their big block species, while Chevy settled on one block design around 1963, with a much-improved combustion chamber and head design over that of the W-series. That became their canonical big block, which was installed in passenger cars until 1976, and soldiers on even today, albeit only in 3/4 ton and larger trucks. The distinction between BBC and SBC is a little weird, since often the largest small block displaces more than the smallest big block. From what I heard from “serious” hot rodders, the attraction of the big block, besides bragging rights, is considerably higher mechanical strength, better flowing cylinder heads, and greater potential for increasing displacement beyond stock. Typically, OEMs introduced their big block family only after the comparable small block was around for some time; so, the BBC design is often incrementally better. An example (Chevy) is the small block’s close-together middle exhaust ports, which evidently cause local overheating and blown head gaskets, vs. the big block’s evenly spaced exhaust ports. Hot-rods equipped with big block conversions have a reputation for being unruly race-only machines, too extravagant for the street. This is unfair, as a stock big block can actually be smoother and more drivable than a small block. But, once you go BBC, the temptation to modify way beyond stock is just too great. After all that work just to make it fit, why keep it stock? Unfortunately, the OEM big block is rapidly dying. Small blocks will soldier on in one form or another, even if GM does terminate the Camaro/Firebird line, and Chrysler never builds a [non-exotic] rear wheel drive car again. Undoubtedly they have the strength in numbers. About big blocks and Datsuns…. Well, as I see it, basic hot-rod V8 Datsun = SBC; all-out race car V8 Datsun = BBC. An entry level small block is MUCH cheaper to build than an analogous big block, which is where I choked in my own project. But, as the power level climbs, the costs begin to even out. At around 600 hp, I’d say that the big block is actually cheaper – and will have a smoother, flatter torque curve as well.

The Chevy big blocks are probably the best choice for maximum cubic inches. The largest displacement possible with a "stock" block is on the order of 540 cubic inches, though the most common production size was 454. Beyond that, you can get a truck block (0.40" taller deck height) or one of the aftermarket blocks. The latter can be bored and stroked out to 800 cubic inches and beyond. I have a 454 in my '78 Z. Be advised that the big blocks take substantial extra work to fit into a Z. They do fit - but it takes things like notching of the frame to accommodate the exhaust. In my case, the firewall was set back 6.25". I don't know of any big block Z's that have completely stock frame rails and firewall, but there are about a half dozen with those mods.

Now that my engine runs again, I noticed that it makes a fairly regular sharp popping sound once every revolution. The sound tends to go away when the engine is under load, and is especially apparent at moderate rpm with the engine unloaded. Unplugging the #4 spark plug wire makes the sound completely disappear. Witht the engine running and the passenger valve cover removed, it appears that the #4 exhaust lifter is not pumping up - despite very healthy oil pressure. These are hydraulic lifters for a flat-tappet hydraulic cam (Comp Cams, X-treme energy 262 series). Lifters, springs, cam and timing chain were replaced as a set last summer - which is about 20 miles ago. So, how does a good lifter go bad? Is the only recourse to pull the intake manifold, fish out the bad lifter, and replace it? Or is there a good chance that some other, more ominous engine problem caused the lifter to go bad?

Well, my transmission tunnel was heavily reworked - with large swathes cut out and replaced with a sheet metal skirt, all in order to fit around that linkage assembly. It was interesting, to say the least, fitting the Kirkey aluminum seat into its cradle (anchored to the roll cage) alongside of the tranny tunnel. The shift rods were also reworked on my car, with various lengths and arrangements tried. Yet it's still notchy. Once the car is in motion, shifting is somewhat easier (that is, easier than it is sitting in the car with the engine off, just rowing through the gears with the clutch pushed in). But it still takes considerable effort, especially with a short-throw shifter handle. I bought my Doug Nash 5-speed (same as a Richmond) "slightly" used, for $750 with the shifter. So in my case, economics played a significant role in the decision.

Stay away from Richmond transmissions. I have a Richmond 5-speed, so I speak from experience. It has a 3.27 1st gear, and 1:1 5th. As some one already mentioned, these transmission are externally shifted. That's a plus if you are interested in custom shifter relocation, but a big minus in terms of (1) fitting the linkages inside the Z transmission tunnel, and (2) shifter feel. These things are NOTCHY! Downshifting is very difficult. But, according to rumor, they are obscenely strong - as in, the strongest clutch-engaged transmission available, period. The official input torque rating is 450 ft-lbs, but unofficial is >>1000 ft-lbs. Just don't put it behind a top fueler.

While pondering the next step in my efforts to make my car "streetable", I've had to make a painful admission: the simple things -like setting the correct timing, tuning the Holley carb, adjusting hydraulic lifters and telling apart noises made from spun rod bearings vs. malfunctioning mechanical fuel pumps - are not at all obvious! So, here is the question: what are folks using by way of a good, basic reference on working with Chevy engines? I don't mean "How to Hot Rod Your Small/Big Block", but something that tells you things like the cylinder head bolt torque settings. The ubiquitous Haynes has a book on rebuilding Chevy V8's, but even that one skips details like this one.

I second that. The Ford 4.6 is unbelievably wide - and width, not length, is the #1 enemy for Z V8 swaps. I have a Chevy big block in my Z. It does indeed take considerable work to get it right (example: even block hugger headers will not clear the frame rail on the passenger's side). It takes yet more work to get as good a weight distribution as you get with the JTR-type small block swap. But, if you do go big block, I suggest that you avoid the 396 in favor of at least a 454. With the weight and cost penalty of the BB, you might as well get as many cubic inches as possible. Curiously, apparently no one has done a Ford big block conversion. Of course, that has many of the same issues as the Chevy BB.

Talking about fuel lines, loss of pressure and pressure fluctuations, pumps cavitating, etc. ... I was wondering if folks' experiences are different for mechanical fuel pumps. My engine is mounted to the frame rails, rather than the steering crossmember. One advantage in doing this is that there is no interference with the stock mechanical fuel pump. Since the engine is presently not much different from stock, I left the stock mechanical fuel pump alone. I have a "Triangle Engineering" 20 gallon aluminum fuel cell with foam (not a wise decision, to say the least!), vented with an auxiliary tube through the filler lid. There's a 3/8" steel line from the fuel cell to just behind the fuel pump (that is, 6" from the engine block), then a 3/8" rubber line to the pump, and a 3/8" hard line to a cheapo T-bar feeding a 750 cfm Holley 4160 carb. No fuel pressure gauge yet, but I doubt that static pressure at the carb inlet is above 5psi. There is no return line. Things are OK if the fuel cell is at least 1/4 full (intermittent fuel draw otherwise, and it's nearly impossible to start the engine). But, my engine has never been north of 3000 rpm! I wonder what amusements await.