Michael

Folks, Somehow this whole high-performance in a big block thread left me with a jarring feeling of uncertainty. The reason that my post on big block heads may appear scatterbrained is that I have been pondering this issue for a very long time, and have long ago lost sight of the original “goals”. I’ve been through Staeffel’s book, and Currao’s, and various books by Vizard; and on the more technical side, C.F. Taylor’s engine “bible” and Lumley’s recent condensed version. But somehow that is of little help in choosing which brand of which component to buy. The trouble is theory vs. practice. Every time that I go to a machine shop, the first words out of the guy’s mouth are (besides the canonical “speed costs money”), “how much does the car weigh and how fast do you want to go?” So I end up making up a number to placate him, and to get the conversation started. In reality, however, I don’t particularly care how fast the car goes down the quarter mile, so long as it pulls hard enough to scare me. This is why I can only think of a tentative performance number. Then as soon as I mention a number, the machinist starts lecturing me on how “one number does not a race car make”, etc. Then the machinist proceeds to tell me that I don’t need a solid-tappet cam, that stock heads are going to be fine if they are sufficiently modified, that I do need forged rods, etc. Oh, and no one fails to mention that the rear end will grenade as soon as I cast a glance at it, that only stuffed-shirt poseurs run an independent rear suspension, etc. You get the picture. I do not believe that most machinists are obtuse technicians or callous crooks (though some certainly are), but I seem to be unable to avoid “a failure to communicate”. Talking about limiting values of Z-factors doesn’t exactly help. Maybe I should just glue my business card to my forehead? I can’t build the engine myself, because I will forget to pre-lube a rod journal or something like that, and a bearing will spin 20 minutes after I start up the engine. That is just a consequence of the way that I go about doing things. Not smart on a $6000 engine. I can’t even remove the valve springs off my stock heads (the C-clamp style of spring removal tool keeps getting bent, before the spring itself compresses!). I have never driven a car that, to my knowledge, was faster than high 13’s. A few years ago I test-drove a then-new Z28 Camaro, and it was far faster than anything else that I had ever driven. For a number of years I had a Mark III turbo Toyota Supra; I thought that it was fast – but it ran 15.9 at the Pomona track (back when I lived in Los Angeles)! I narrowly lost to a rusted-out ’66 Mustang. So to me, at least at this point, 9.9 or 10.9 or 11.9 or 12.9 or whatever – they are all a jumble of fantasy, pie-in-the-sky, castle-in-the-clouds numbers so divorced from reality that I need not even bother calculating the optimum shift points or figuring whether I should use 0.040” quench or 0.035” or if I would be better off with 3.36’s than 3.54’s in my R200, or for that matter, how many tenth’s of a second I would get from painting the block Chevy orange and gluing Moroso and Jegs stickers to the windshield. Doesn’t it then make sense to just put together the engine that I already have? Maybe, but after 4 years of construction, a frame that’s supposed to pass NHRA tech for a 7.50 car (no kidding), and many other endeavors, it seems only fitting to go the bucks-up route on building an engine. Yet where to stop? Where is the point of diminishing return? Sure, a roller cam will free up some hp. Sure, a knife-edges crank with scalloped rod journals will spool up faster. But is it worth the money? A “stock” rebuild on a 454 costs about $900. But wait, shouldn’t I also get the crank balanced? Yeah, of course. $300. And that 9.5 CR calls for forged pistons, right? Add another $400. Then add ARP rod bolts. And that 2-bolt main could benefit from going to studs in the mains, right? Isn’t a high-volume oil pump a good idea too? Sure, of course. Then add the roller cam and the forged rods, and we’re up to the $3K range on the short block – or more. So why not throw in another $1000 and just get the GMPP 502 short-block? Or for that matter the Merlin II block (more aftermarket support for the 2-piece crank seal, right?), maybe with roller needle bearings on the cam. And the Lunati $2000 crank – the one with the scalloped rod journals. Maybe one of those Keith Black aluminum blocks, or a ZL-1? Up and up the ladder we go, up and up the beanstalk. Or just go find some 70’s GM truck with a big block, pull the engine out of that and call it Version 1.0. Wait a minute – been there, done that. So this is why I want to make up a number, like 500 hp – it is a line in the sand. It is not the belief that one design point will turn my life around and turn me into a happy smiling dude, but that somehow a decision has to be made – and short of throwing darts at my Summit catalog, the “knee in the performance/price curve” strikes me as the most logical approach. Opinions? Thanks! -Michael

Guys, Many thanks for the replies. When I got through writing my follow-up post, I realized that it ended up as more of a rant than a technical point, so I put it in a more appropriate place in the forum (the “I’m tellin’ ya” section). Please look at it if you get a chance, as it hopefully applies to a broader context than just big blocks. One quicky tech question though – has anyone tried "porting" an Edelbrock Performer RPM oval-port manifold to fit rectangle-port heads? This might not be as foolish as it sounds, because the Edelbrock oval manifold’s runner shape tends to be "square shouldered" (I’ve heard it referred to as “roval”) and there ought to be plenty of meat in the port walls. The reason for doing this, besides using what I already have if I go with the AFR heads, is the flow-quality issues for oval-shaped ports that I mentioned earlier, especially with a carburetor. Grumpy – would it be possible to continue this discussion off-line? My e-mail address is ol_70@hotmail.com.

This one is long and loquacious…. For some time now I’ve been tossing around the idea of getting good aluminum cylinder heads for my 454 big block. Currently I have 346236 GM heads – standard equipment on 1970’s trucks. I have been following the various discussions about heads for small blocks, power vs. torque, the significance of cfm ratings, piston speed, etc. – and while the basics of course apply here as well, the particular choices are very different. Granted, it’s the full combo that matters, not the individual parts. But decent aluminum BBC heads are $2000 ($3000 with serious porting), so I first want to get a feeling for the cylinder head selection. I AM in principle willing to spend $3K on heads – or more – but only if the expense is justified. The price vs. performance curve is not a straight line – there is a knee in the curve, which for big blocks evidently occurs at around 500 hp. A cursory summary of my situation: 2700 lbs car (with cast iron heads), to be driven regularly (in good weather) and suitable for occasional drag racing and maybe autocross-type stuff. The transmission is a Doug Nash 5-speed with 3.27 first gear, and the rear is a stock 3.54 R200. I want ferocious off-idle torque with a usable torque band up to maybe 5500 rpm. Anything beyond that is nice, but not important. It must be compatible with 92-octane gas and pull decent vacuum at idle. The goal is, tentatively, the aforementioned 500 hp. The very highest-flowing heads may be overkill, since the rest of the intake-combustion-exhaust flowpath may not be able to make full use of the high flow volumes at this relatively tame hp level. However, when I say 500 hp, I mean a LAZY 500 hp – the engine is not straining, stock cast crank and 2-bolt mains are doing just fine, pistons speeds are comfy low and I don’t have to constantly keep staring at the oil pressure gauge, and maybe even the carb and ignition tuning isn’t 100% there. The point is, there’s plenty of extra power available with the eventually combo – but 500hp is the notional benchmark for the first iteration. There is no particular goal in the quarter mile. This car is so weird that it would not be competitive in any class for which it would qualify (refuses to join any club that would take it as a member ), and I’m not interested in bracket racing. Information on big blocks is MUCH harder to find than on small blocks. Chevy High performance ran a series of cylinder head flowbench articles (available on their web site), also covering big block heads. This is my starting point. I plotted the various flow numbers vs. lift. Of the heads that they considered, I included: GM 049, 156, 236, 290 and 702 oval port heads; Brodix OEFI, Edelbrock Performer RPM, Dart and GM Performance Parts aluminum oval port heads; Merlin iron oval ports heads (they don’t make an aluminum oval head!); and Canfield and Merlin VR rectangular port heads. These were apparently all unported. I excluded the larger rectangular port heads based on the sentiment that their port volume is probably too large for my application (though port cross sectional area, or rather hydraulic diameter is a more significant parameter, I assume comparable port geometries and runner lengths). Of course, this is just a flow rate comparison. Combustion chamber design, spark plug location, etc., are not considered. Bore diameter was 4.250”. Some heads, like the new AFR heads (see below) flow much better with the larger 4.500” bore, for reasons attributed to valve unshrouding. The main results were: * all the stock GM heads, except for the 049, all almost dead equal on both intake and exhaust (especially up to 0.500 lift) and dead last. The 049’s are considerably better, especially on the exhaust side, with numbers half way between the stock GM heads and the aftermarket heads. * Among the oval port heads, the Brodix (and Merlin) heads have good low-lift intake numbers, but become mediocre by 0.400 lift (intake) and are in the back-of-the-aftermarket-pack on the exhaust side. * Among oval heads, Dart heads are middle-of-the-pack for intake at lift below 0.3, but after 0.4 they are clearly in the lead, and have the best E/I ratio because they’re really good on the exhaust side. The Dart heads reach 300 cfm intake flow at 28” of water at 0.550 lift – that is, at about the max lift that plan to run. * Among the oval heads, the GMPP heads are probably all-around second to the Darts (surprising!). * The Canfield and Merlin VR heads have similar intake flow at 0.4 and lower; then the Canfields pull ahead. Both are superior on intake to all the oval port heads. Canfield is also the hands-down winner on exhaust, where the Merlin VRs are mediocre. Not included in the original CHP series were the new AFR BBC heads (available only with rectangular ports). But a recent article in Hot Rod and AFR’s web site give some data for the 305cc (or rather 315cc) head. Unfortunately it’s apples-to-oranges, because these heads were CNC ported. With that in mind, the AFR heads were amazing, reaching 300 cfm intake flow at 0.370” lift, with the best E/I ratio (for 4.5” bore). At this point, if I choose aftermarket oval, the choice is Dart. If I go rectangular, it’s Canfield or 305cc AFR. The sentimental favorite is AFR. First question: what is the potential of my 346236 heads? If I spend some time porting them, and have 2.25/1.88 valves fitted with a good valve job, what hope do they have of supporting 500 hp with the above-mentioned conditions and, say, a .550” lift flat-tappet hydraulic cam? By gut feeling is that money spent on getting these slugs to “perform” is money wasted. Second question: should I limit my choice to oval heads, as the local engine builders recommend? This is a relatively low-rpm engine, and I do want the low-end torque. But in the big block world, mine is a very light car, and it is deeply geared. Third question: why are Canfield heads so rare? Do they have some hidden flaw that racers know about, but don’t divulge? Fourth question: the Dart heads really wake up at large valve curtain areas, despite having among the smallest port volumes (and hence port cross-sectional areas). My guess is that there’s a big loss due to separation at the “pocket” just upstream of the intake valve seat, so that even at moderate valve lift the flow past the seat is not attached (low discharge coefficient, so to speak). Does this imply that pocket porting would really improve these particular heads – more so than their near competitors? Fifth question: I think that there are reasons (consequences of secondary flow) why oval-shaped ports should flow more “cleanly” than rectangular-shaped ports, when normalized to the same flow rate – especially for “wet” flow (carburetor). So then why is it that maximum-effort race big blocks are based on rectangular-port heads, instead of very large oval-port heads? And by the way, how can I post the Excel plots with the port flow data?

I’ve made some front-end modifications to my ’78 280Z that preclude the reinstallation of the stock headlights in the stock location. The likely new location will be in the grill area, where 280Z’s normally have the front amber parking lights. Assuming, for the sake of argument, that such an installation is legal and all that, I still have to make the choice of whether to attempt to install the stock headlight assemblies, or to switch to a set of those compact headlights, such as the high intensity discharge units that have recently become popular (unfortunately, with rice boys). Does anyone have experience with such lights? They’re the ones that are around 2” in diameter. Are they strictly for auxiliary lighting, such as fog lamps and the like, or can they serve as the primary headlights in a “streetable” car? I am referring to a pair that costs maybe $50, not the $600 stuff that was briefly discussed on the forum last year.

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.