Michael
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Posts posted by Michael
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Yesterday I drove my '78 280z for the first time. It has a near-stock 454 big block engine and Doug Nash 5-speed transmission. With the stock tires, wheel spin is unavoidable in any gear. In traffic, the car is best driven by starting in 5th gear and never shifting. Maneuvering around the parking lot is possible in 1st gear, provided that the gas pedal is never touched and the clutch is feathered while the engine just idles.
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Well, I just drove my rat-powered 280Z for the first time (see post under "Chevy V8" topic for more details). The car has a Doug Nash 5-speed. Even after reworking the shift linkages and oiling the shifter mechanicals, the thing is still incredibly notchy to shift. It's so bad that more time is spent on the 1-2 shift than under power in 1st or 2nd gear. There is essentially no feel for neutral, and telling 3rd and 5th apart is very difficult. Fortunately, the engine has so much torque that with street tires, 3rd and 5th gears are indestinguishable.
So, to anyone contemplating the Doug Nash or Richmond transmission, let me caution them to beware of the king of notch.
Perhaps with time this thing will smooth out.... I hope! But at least the clutch is light and smooth (3/4" Tilton master cylinder, McLeod hydraulic throwout bearing, Centerforce Dual-Friction clutch).
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I ended up going with a Simpson 5-point camlock harness, about $160 at Summit. It's a bulky setup, with the shoulder straps and waist straps 3" thick. Putting it on takes much, much longer than putting on a regular seat belt. But, with the camlock, it comes off very quickly - and this is certainly the most important consideration in a race-type situation.
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I'm the oddball here, but I thought I'd post anyway....
My "set back rat" Z has a 454 BB from a Suburban (1978). I installed a Comp Cams "Extreme Energy" hydraulic flat-tappet 218/224 (@0.050") .504/.510 lift, 110 degree lobe separation. It's relatively mild for an engine that big. But, with stock rockers, I'd run out of rocker slot gap with a larger lift cam. And the bone-stock heads are probably no good above 5000 rpm anyway.
Now here's a question for the experts: to get heads with relatively small-area ports and small valves to breathe better in the midrange (I got the low end covered, and don't have high aspirations for high-rpm performance), is an otherwise too big cam (high lift) a good idea?
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Pete,
Actually, I think we're talking about the same thing. In particular, I'm referring to page 16-14 of the JTR book (6th printing). I wanted to get the largest backspacing possible, being fully aware that the tires will still stick out from the rear fenders, and that the fenders will have to be cut. That was for structural reasons, to keep the wheel's mounting face not too far inboard of the wheel centerplane. JTR says that coilovers increase room for additional backspacing in the front, but are of no help in the rear. I wanted to confirm their comments.
The plan is to get Centerline 15x10 wheels for the rear, with 4", 4 1/2", or 5" backspacing (I need to decide which!), and 28.5x12.5-15 Mickey Thompson "Sportsman Pro" Tires. That's the drag racing setup. The "street" setup I haven't yet thought about.
Would you happen to know the thickness of a stock 280Z brake drum? If I understand your web page correctly, the maximum backspacing for a 17" wheel is 149mm minus the difference in thickness between the stock drum and your setup's "hat"?
I'll post something about my "set-back Rat" Z in the non-tech forum next week.
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My guess is that the BMW Z8 guy’s comments about no aero testing were just bravado. At the very least, they must have done some kind of wind-induced NVH testing, to make sure that the playboy in the driver’s seat isn’t subjected to too much wind buffeting, and that his escort’s hair doesn’t get messed up.
As for the headlight covers – all of the ones that I’ve seen follow the contour of the hood’s sharp front lip. Cosmetically, that makes sense, but I’m not impressed by the design. Jim Biondo’s fiberglass “front clip†looks like a very sensible route (does he have any data on his design?), albeit the Ford Taurus-looking front “face†is not very appealing, at least to me.
Forward of the radiator supports, there isn’t much structural metal in the Z – even in the 280’s. My impression is that the stock hood can be cut with a sawz-all just forward of where it bolts to the hinge mounts, and the resulting “hole†can be filled with fiberglass. For a template, a piece of pvc drainage pipe (say, 6†or 8†diameter) might work! By that I mean, wrap fiberglass cloth around the pipe, held laterally across where the hood lip used to be. The resulting “hump†will probably have to be reinforced somehow, but it’s a start. Then, the headlight sugarscoops would be cut to match, the remainder of the scoops filled in, and the headlights moved down and inboard. My guess (unscientific, of course!) is that this will get the total Cd down below 0.4.
By the way, apparently Nissan claimed a Cd of 0.385 for the 280 ZX! That's a huge drop from the Z, considering that the two cars are of similar shape.
I have pictures of the water tunnel tests, but until I figure out how to scan in slides, I won’t have anything to post. Ditto for the rest of my project.
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I would like to ask the complementary question: if the stock spring and strut assembly is retained, what does that do to the possible choices of wheels and tires? Or, phrased another way, is it true that in the rear, coilovers do not afford any greater tire clearance advantages? I would eventually like to run large diameter (28" or greater), large width slicks. The olny Z's that I've seen with such tires were back-halved.
Any info would be greatly appreciated.
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The technique of taping tufts or strings to the surface of a body to get a sense of the flow around it, is a tried and true method. It tells if the flow is smoothly following the surface, or if it’s “separatedâ€, which generally (but not always) means low pressure. It also can give clues about flow reversal, such as in a large separation eddy or local backflow. Unfortunately, tuft flow visualization says nothing about how much air is flowing, how fast it’s flowing, etc.
What makes engineering an effective cooling flow scheme difficult is that to do it right, other aspects of the flowfield about the front end of the car have to be considered, and that means taking into account front end lift (or downforce), contribution to the vehicle’s total drag, supply of dense, cool air to the carburetor, etc. For example, how to integrate the radiator ducting with the front air dam. On some late model cars, the radiator actually draws from behind the air dam. This reduces cooling flow (tapping the air in a low pressure zone) and reduces effectiveness of the air dam.
As Pete pointed out, Terry Oxandale’s setup is an excellent compromise of the above factors. But, besides requiring major sheet metal surgery, it may not be practical with even the JTR engine setup (engine needs to be VERY far back), plus it will have problems in the rain.
As for the 70-78 Z’s aerodynamics, well, they are not very good, to say the least. Taking a survey of information reported in several coffee table books on the Z, I get an average Cd of 0.45. So, the Z is no better (and occasionally worse) that sedans of the same vintage. Why – especially because it looks so “swoopy�
Well, I tested a model of a Z in a water tunnel. I did not have a wind tunnel, just a water tunnel. I made a 6†long model out of wood, bolted it to a “ground plate†and put the assembly on a supporting arm, inside a 18â€x24â€x72†test section of a low speed, low turbulence water tunnel (max flow rate: about 1 ft/s). With such a small model and such a low flow speed, scaling effects will invalidate any attempt at gathering quantitative data. But, injecting a carefully controlled stream of dye (food coloring) at various point in the vicinity of the model, I found three curious things:
1) that sharp hood front lip is a killer. A large swirling eddy (when scaled to full size about 1 ft long) sit on top of the hood lip. The front stagnation point is just below that region, and the accelerating flow can not go around the lip without separating.
2) Flow over the roof separates at the vicinity of hatch (deck lid) front lip. The Datsun engineers made a very poor choice of hatch slope. It’s not low enough for the flow to remain attached, and not steep enough to keep the separation controlled. The VW Rabbit, for example, has a steep hatch angle, and that design actually has a lower drag!
3) Flow from underneath the car will swirl up towards the rear of the deck lid. This accounts for the infamous Z exhaust smell inside the cabin, and also has a role in why the drag is so high.
Unfortunately I do not have information on longitudinal and especially the transverse pressure profile over the hood.
Why is the Z so screwed up? Part of the blame rests with Albrecht Goertz. It’s his “reverse swept†grill shape that motivates the sharp hood forward lip. But Nissan conducted wind tunnel tests on the Z (including tuft grid visualization!!). One photo that I found on the subject shows the Z in a wind tunnel test section, sitting on foot-high blocks underneath the wheels. These blocks evidently housed force balances. Possibly they did not want to set the car on the tunnel bottom, to avoid tunnel boundary layer effects. But what they did is an awful way to test cars! Not only does it miss ground effects, but their testing condition severely alters the flow about the front grill. They could easily have concluded that the sharp hood is “streamlinedâ€.
So, what to do about this? As a first cut, modify the hood front lip and grill. But, as for cooling, my reaction is to first run the car and then see if it actually overheats. Chances are, it will be fine as is. Shakedown tests of my big block ’78 Z show no overheating, and that’s with a 28â€x19†Griffin radiator (I cut out the stock radiator supporting structure to accommodate a larger radiator and leave room for later mods) and Flex-a-Lite “Black Magic†electric fan.
About NACA ducts…. I’ve been following the discussion on Carl Beck’s Z-car mailing list. Generally, NACA ducts are designed to draw ambient air inside a cavity, but some designs do the reverse (expel air). However, this works best when large pressure gradients are involved – for example, expelling the exhaust of an aircraft piston engine. I doubt that the pressure difference between the flow over the Z’s hood and inside the engine compartment is sufficient to make the NACA duct worthwhile. But if you can fabricate a duct system that fits over the housing of your radiator fan, and completely routes that air outside of the engine compartment, that should work much better.
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I have a Doug Nash 5-speed (same as the Richmond 5-speed) behind the 454 big block in my '78 Z. The car is oh so close to actually running, but right now it's sitting in a parking lot. The transmission fits in the 280z tunnel without too many problems. There was actually room for a dual 2 1/2" exhaust. However, the shifter is DEFINITELY a problem. I had to cut a 5" hole in the driver's side of the transmission tunnel, and then fabricated a cylindrically-shaped "box" to accommodate the shifter. These externally shifted transmissions evidently all have that flaw. Also, as pointed out by my hot rod buddy, some of the Richmonds have sloppily installed linkage rods. This is often misdiagnosed as hard shifting. We ended up having to cut, bend, and reweld several of them.
The Richmond 5 (and 6) speeds are hot rodding staples, reputed to be the only transmissions that can handle serious drag racing. The official 450 ft-lb torque rating is very conservative. But, in hindsight, I would not recommend the Richmond 5-speed. It has no overdrive (5th gear is 1:1), and the shifter, like I mention, requires some finesse. But, if you have a "serious" racing engine (I actually don't, unfortunately), and want a stick-shift transmission, this is probably the safest option.
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This is not entirely on-topic, but for those of us that have already committed to a transmission, and have a 3.7 or 3.54 R200, there aren't many options left to reduce cruising rpms, other than to get taller rear tires.
Wheels and tires come up for discussion all the time; normally the topic is how to get the widest tires possible, but still get them to fit with the stock Datsun sheet metal. My question is, what are the TALLEST tires that people have been running in the rear? For a first iteration, I'm considering pickup truck or full-size Detroit landyacht tires in something like 28"-29" diameter. Yes, that will introduce traction problems, but with gas hitting $2/gallon, well, you know...
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I bought a 20 gallon aluminum "fuel cell" from Triangle Engineering about six months ago (via Summit). The welding is beautiful, but keep in mind that it's NOT a true fuel cell, because it has no fuel bladder inside - just foam.
Also, the fuel filler cap is supposed to have what amounts to a check valve; it should vent air into the cell as fuel is depleted, but it should not vent fumes out of the cell. Well, I mounted the fuel cell inside the rear hatch area (no room under the floor due to center-mounted dual mufflers), and if I leave the windows rolled up overnight, in the morning the cabin is completely soaked with gas fumes. And when the fuel level drops to maybe 1/4 of the cell, fuel draw also drops, indicating that not enough air is let into the cell.
Filling is also a problem. There is no filler neck - you have to remove the 3" diameter cap, again releasing fumes into the cabin. Avoiding fuel spillage from the filler nozzle is almost impossible.
Bottom line: having checked the market somewhat thoroughly, I've concluded that there are no REAL fuel cells for cheaper than $500. If I had to do it all over again, or if I could sell my Triangle unit, I'd buy the "pro-street" plastic fuel cell from Summit.
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Well Pete, since you threw down the gauntlet...
Gearing constrains how fast the car can go in principle, without exceeding the engine's power band. So let's assume that we have tall enough gears in the differential, and sufficiently many gears in the transmission, that any speed from 0 to 300 mph is allowable by a gearing/rpm calculator, like that web site that people have been referring to.
So, what limits the top speed of the car? The balance between power available and power required. That's true for any vehicle, be it your bicycle or a jet airplane. Power = force*speed. On level ground and in calm air (none of this talk about going downhill in a hurricane!), the "force" in that equation is aerodynamic drag and rolling resistance. Mechanical friction of the drivetrain's internal parts is also important, but we'll budget that as a tax on power available (rear wheel hp vs. crank hp, etc.)
So, we have:
rear wheel hp = (aero drag + rolling resistance)*speed
with a proportionality constant thrown in to make the units work out.
Experience shows that for passenger cars, rolling friction is definitely of secondary importance compared to aero drag, when the speed exceeds 80 or so mph - again, on level ground, on smooth asphalt or concrete. The formula for aerodynamic drag is:
Drag = 0.5*(air density)*(speed^2)*area*coefficient,
where air density is about 0.00238 slugs/ft^3 at sea level. Density DOES NOT vary as the car speed varies. As far as this formula is concerned, it's only a function of atmospheric conditions. The area is the car's cross sectional area. For Z's, it's about 20 ft^2, roughly. And the "coefficient" is the all-mighty drag coefficient that everyone talks about. For Z's, it's about 0.45.
So, to a good approximation, we have:
power required = 0.00006*speed^3, in horsepower, for a Z, with speed expressed in mph.
Thus, to go 100 mph, you'll need a whopping 60 hp. Maybe around 70 hp when you factor in rolling resistance. My stock 1978 Z would top out at around 120 mph, at which point it needs 103 hp at the rear wheels. That's somewhat of a low estimate, but not unreasonable, considering driveline losses, unaccounted rolling resistance, etc.
Now, according to this formula, to go 150 mph, you need about 200 hp. And to make it all the way to 200, you'd need 480 hp. But again, that's 480 hp - by this LOW estimate - at the rear wheels. So it's maybe 600+ hp at the crank. Probably 650 hp to be safe.
My mildly built big block is expected to make around 350 hp. If that's around 280 hp at the rear wheels, the car has enough power to reach 167 mph. But, the way my car is geared, I'll run out of rpm at around 125 mph. It's just that I'll reach it very quickly
Horsepower by itself says nothing about how quickly the car reaches top speed; that's more a matter of the entire torque band, and of course, the weight of the car. And weight, by the way, has almost no effect on top speed over a smooth level road. -
It will depend on the powerband of your engine, on the hi and torque levels, car weight, etc. (in other words, on the expected quarter mile time). Most likely, the 3.9 rear end will make hooking up off the line a problem, unless you run slicks. A lot of time is burned up in that first 60'. So, based on this reasoning alone, the 3.54 is probably the better choice.
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Pete,
I'm going to say something that you probably don't want to hear: STICK WITH THE TREMEC!!!
You've been working on your Z for how many years now? Probably your kids have no recollection of what life was like before that car went up on jackstands. I've never driven a Tremec either, but is the hearsay and bad reputation enough to justify scrapping a perfectly good setup, dumping $1500, and losing what may be several months time?
I've also installed a transmission with a 3.27 1st gear, but mine doesn't even have overdrive - and I have a 3.7 R200, and - gasp - stock wheels and tires! Is this stupid? Well, maybe, but I know that the combination will not break, that the car will slip and slide long before any gear teeth are sheared off or U-joints get ripped apart. The point is, get it on the road, get that smile on your face that it's finally running, and then worry about remedies for thing that you don't like.
The smoothest shifting transmission that I ever drove was in my 1976 Toyota Corona. The T56 - at least the ones in Z28 Camaros - is awful in comparison. But there's a reason for that, not the least of which is that it's rated for about 5 times more torque. Shifting my Doug Nash 5-speed (with the car parked, and clutch inoperable) feels like trying to cut frozen meat with a plastic knife. But for now, I'm willing to call that setup good enough - and I've spent maybe 1/10th the time on my project that you have on yours.
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I think that for many of us, the main problem with switchng to a solid rear axle is cost and complexity of the operation - and not an aversion to the setup itself. Most of the engineering challanges encountered in our V8 conversion projects are a matter of how to construct something. The "design" aspect comes down to how to make things strong enough, to make everthing fit together and stay together. Changing suspensions, however, involves a conceptual design change, and that includes textbook calculations. In other words, you essentially have to know how to design cars from the ground up. And that, at least to me, is a little scary.
Independent suspensions have their main advantage in road holding over poor surfaces, and not in getting power to the pavement. As a somewhat relevant comparison, many people consider that the Z28 Camaro (solid rear axle) handles as well as a Corvette (I.R.S.) - at least, up to its traction limit, launches considerably better, but has problems on rough pavement. Obviously, most of us have no intention of racing on bad pavement.
I.R.S. of course also has less unsprung weight, though it seems to me that this too is more of a ride quality than a performance issue.
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I second Mike KZ's comments. Regardless of the eventual details of your front suspension, you'll have to have something that spans wheel-to-wheel to accommodate the steering, and it would be great to get the crankshaft pulley behind that something. That makes working on the engine MUCH easier, not to mention the improvement in weight distribution.
Will the windshield and A-pillars remain in the stock location? If so, you still have something like 10" of space to set back the firewall, before the distributor cap hits the front windshield lip. That's because of the awfully deep valence panel that Z's have behind the hood, where the windshield wiper assembly is housed. I set back the firewall on my Z by 6 1/4", and even though I run a big block, the crank pulley is just behind the steering rack, and the valve covers are almost completely behind the strut towers. Your setup will have even more room - not to mention advantages like better flow through the radiator, and the opportunity to lower the hood line and solve most of the Z's front-end aerodynamics problems.
As for the oil pan, keep in mind that with a low-profile pan, the show stopper will actually be the bellhousing! I have a 9" deep sump, and even so, it's no deeper than the lower lip of the bellhousing, and that's with the lip ground flat. Granted, I'm using a Lakewood "blow-proof" bellhousing, designed for a 14" flywheel - and the OEM T56 bellhousing is probably smaller. But still, before you spend the $2000 for a dry sump or even $400 for a low-profile drag racing oil pan, consider what to do about the bellhousing. You might end up with a [NASCAR?] multi-disk clutch, small flywheel and custom or semi-custom bellhousing. Drag cars get the engine very close to the ground, but they get around the clearance problem by running automatic transmissions with small diameter torque converters (or just clutch packs).
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I suppose that like most upgrades, this one comes down to a matter of personal preference. About a year ago I was also thinking about an aluminum block - aluminum big block, that is. GM performance parts had reissued the much-vaunted ZL1 "aluminum cylinder case", and Merlin (World Products?) has a whole line of aluminum big and small blocks. The cheapest aluminum BB is around $4-5k; SB may be around $3K. Costs aside, one issue is how to mount the bearing caps. The GM LS1 is cross-bolted, which I was told works very well, although another chorus claims that LS1's are notorious for spinning crank bearings. The earlier generation blocks are 4-bolt, which may or may not be a weak point. The other problem is cylinder sleeves. The Zl1, for example, has cast iron sleeves, essentially poured into the aluminum, as opposed to pressed in. That evidently solves the leakage issues that caused head gasket failures, as in the original Chevy Vega ( 4 cyl.).
I tend to side with the folks that consider an aluminum block to be more trouble than it's worth. The economy of scale just isn't there yet. The blocks themselves are expensive, and machine shops don't feel comfortable handling them. At least, that's my impression. The only truly successful aluminum block is the severely modified Chrysler Hemi, run in pro drag racing. And those guys have essentially infinite parts and repair capacities.
If weight - or rather, weight placement - is a significant concern, consider relocating the firewall further back, giving yet more room for engine setback. That's been my approach.
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Stay away from Supras! I used to own a '87 Supra turbo. The engine reputedly weighs more than a Chevy small block, and though the bottom end is truly stout, head gaskets blow very easily. The turbo is tame in stock form, and Supra tinkerers claim huge performance increases due to higher boost (the stock electronics and plumbing will allow up to 13 psi before fuel cutoff issues appear). BUT, we're still stuck with the low end torque issue. Turbo lag on these things is tremendous, and very frustrating off the line.
Years ago, I thought of yanking the inline-6 in my Supra, and swapping in a Chevy small block. This has actually been done with a "Mark II" (82-86) Supra, though the "purist" emotion is strong among Supra owners as well. But then I realized that 1) this would never pass smog check, 2) the electronics are bewilderingly complex, and 3) there's just not that much room under the hood.
The Z engine bay will accept just about any engine. But my opinion is that V-type engines, regardless of the manufacturer, # of cylinders, or displacement, are a better swap than another inline engine, because of the weight and balance issues.
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I'm using a Doug Nash 5-speed, which is a modest evolution of a 25 year old design. 5th gear is actually 1:1, so in terms of mileage and top end, it's a four speed. This and some of the older Detroit transmissions are "externally shifted", which means that the linkages are outside of the transmission case. In my '78 280z, that required substantial modification to the transmission tunnel (cutting sheet metal around the shifter, and welding in a new cver patch). However, the external shifting does have one advantage - you can move the shifter around, to get it physically where it's the most comfortable for you.
Another issue is torque ratings. The word is that the T56 is very stout, and is even used on Vipers. I don't know for sure, but really hard core hot rodders told me that the Muncie "rock crusher" (and the Doug Nash) are stronger.
If you are running around 400 ft-lbs of torque, my assumption is that you have lots of choices, including any old muscle car 4-speed, or the T56, the Tremec, etc. If you have ambitions for mountain-moving torque, the choices narrow down. But I've heard of Doug Nash transmissions behind blown injected-alcohol big blocks. If you really have $$$, look into the Richmond (ex-Doug Nash) 6-speed.
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Regarding the California stuff -
What Gene writes is very true. But, fortunately there's a break for pre-'74 cars. They are not required to submit to semi-annual smog inspections, and presumably, there is no "shake down" process at the smog referee station the first time that the vehicle is registered. The word on the street is that a "gross polluter" can still be pulled over on the street. But I have never actually heard of this happen. Besides, a properly tuned engine with reasonable cam should not be a gross polluter anyway, even with no smog equipment at all.
As for how to purchase engines.... I had (still have!) a huge project, so the attraction of buying something like a complete donor car was not that great. But, I did want to get a running engine, so that I could first worry about getting my car together, and then spend the $$$ on hopping up the engine. So I bought an engine out of a 1978 Chevy Suburban (454 big block). I found the transmission for sale on a race car classified site on the web. Later, I made some minor mods to the engine, but definitely no machining or "rebuilding". When I get my car running and all the details sorted out, I'll probably spend the money on a serious crate engine, either the "GM performance parts" ZZ502/502 or a "Merlin" 509 (again, this is big block jargon, but the same applies to small blocks or Fords). This is definitely a better way (than building the whole thing yourself) to get reliable high hp at still reasonable cost, but for a first iteration, where the whole project is still unproven and cost cutting is critical, a used engine is probably a better choice.
If you already have a source for a Ford 302, or better yet, a cheap late 80's/early 90's Mustang GT with 5-speed and fuel injection, that might actually be a pretty good combo. The main problem with Ford swaps, apart from the lack of precedent, is the awkward forward location of the sump (interferes with steering crossmember, evidently). But I was told that even that problem is moot with a Mustang swap, because of their revised sump location.
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Owen,
I won't be in Pasadena for too long - in fact, I'll be relocating to Dayton, Ohio, in two weeks. My Z will probably not be finished yet
, which presents some logistics problems. Make sure to take good pictures at the MSA show! -
I'm chiming in kinda late, but for what it's worth, I was probably the guy that started this mess with my posting on Camaro front rotors (this post evidently got lost in our recent crash).
At a pick-a-part junk yard, I removed the rotor and hub assembly, complete with bearings and all the guts, from a Gen II Camaro (70 1/2 - 81; this looked like a '75), and slapped them onto the spindle of a 280Z. With the possible exception of the inner oil sealing ring, everything fit perfectly. I could not rigorously check the oil seal thing, because evidently that would require torquing down the retaining nut (I don't know the exact term for this nut), and then checking for binding and/or leaks. Also, the Camaro brake caliper has a very different mounting bolt pattern than the Z, while the Z caliper will not accept the Camaro rotor, which is much thicker than the Z's rotor. I have heard of people making steel adapter plates that mount the Camaro caliper to the Z spindle.
Gen III Camaros (82-92) might also work, though I don't know for sure. Also, 70's Novas are essentially identical to Camaros mechanically, so they too probably work.
Also, and perhaps of greater interest for high performance purposes, Wildwood (and many others) make relatively inexpensive bolt-in brake stuff for Camaros, like a gorgeous aluminum-bodied 4-piston caliper and lightened vented rotor. If the stock Camaro stuff can be made to fit, so can the aftermarket parts.
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Folks,
We've covered a lot of ground on the issues of roll cages, subframe connectors, floor pans, torque tubes, etc. But, I probably speak for many people when I say that the actual effect of these modifications is still shrouded in mystery. in other words, do we really know what increase in, say, torsional rigidity such modifications produce?
So, here's my question: has anyone attempted a "test" of their chassis's torsional stiffness, e.g. by shoving a long beam in the vicinity of the steering crossmember, clamping the rear fixed, loading the far end of the beam, and measuring deflection? Alternatively, does anyone have ideas on quicker and simpler methods?
The point is not to question people's structural designs, but to ascertain what's the maximum benefit for the minumum cost and effort.
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Folks,
I just wanted to interject a question about suspension design into the discussion.
The 4-link has various advantages for drag racing purposes; specifically, the ability to tune for anti-squat, while managing wheel hop, etc. Yet, the 4-link is generally regarded as inferior for road-type applications - even inferior to the Satchell link arrangement (two longitudinal links, two links angled toward the center of the car) or the NASCAR-style trailing link arrangement, because of poor roll compliance. That's actually a plus for drag racing, but evidently a minus for road racing.
My question is not about solid rear axle vs. IRS, but regarding the various ways to locating the solid rear axle. Does anyone who races both SCCA and NHRA have any comments on pros and cons of 4-links? Recognizing that specializing for one form of racing almost necessarily reduces performance in other forms, I was wondering what's the best compromise.
, which presents some logistics problems. Make sure to take good pictures at the MSA show!
a first drive - and spun rod bearings
in Gen I & II Chevy V8 Tech Board
Posted
whoops - the previous post got cut off.
Anyway, after a few laps around the block, I noticed a loud and annoying knocking sound coming from the engine. It is proportionate to the rpm, but it is not constant. Rather, when the sound is loudest (at any given rpm), oil pressure appears to drop. Then the sound intensity ebbs, and oil pressure returns. While I have no tachometer (yet), I doubt that the engine ever saw above 3000 rpm. Trivial errors such as crossed plug wires and vibration of under-hood components were elliminated.
Is this the tell-tale sound of a spun rod bearing? I'd hate to have to rebuild the engine before the car even makes its first pass down the drag strip.