Xnke

That's actually NOT a Hemholtz resonator, but is instead a quarter-wave resonator. Hemholtz resonators are sized on volume, not length. The 1/4 wave resonator has a much higher Q, and thus cancels out a narrower band of frequencies and their harmonics. The Hemholtz resonator has a lower Q and would cancel a wider frequency range, probably would cover the second harmonic, but doubtful that it could achieve third harmonic or higher resonances due to the low Q. (In this case, the wider bandwidth is more valuable than the harmonic resonance damping.)

They are new injectors, with flow sheets. The manifold is the usual L28ET piece, that has ports 1 and 6 bowed down too low on the head, plus there is a little crown across the port face. It is not terribly out, but it's enough.

Got the manifold back from the machine shop today, but the plenum assembly was not ready yet. I'll have to run studs in the plenum, which I haven't made yet, since they are about 70mm long M8x1.25. No big deal. I will probably fit studs in every location, just because I feel like doing it that way. And I have a whole box (100) of M8x1.25 nuts.

He's saying the top of the head is now flat...and the bottom of the head is now flat...but the head is bent as if someone has put the front end of the head on one table, the back end of the head on the other table, and used a press to push against the center of the intake/exhaust manifold mating face. I have never seen an L head warped that way, but I guess it could happen. (I just went out and measured all of mine, all are straight along the manifold face, two are warped 0.004" and 0.009", five of them are fine.)

Think about the belt velocity, too. on a 6.25" diameter drive pulley, at 5000RPM, the belt is moving at a speed of 8180 linear feet per minute! This is with no belt slip at all...11452 feet per minute is the speed at 7000RPM. That's ridiculously fast...2.1 miles per minute...129 miles per hour! At 129 miles per hour, I think you'd be stretched pretty good too. (to calculate belt speed, 6.25"*pi=19.634" circumference...19.634/12=1.636 feet per rotation...1.636*7000=11452 feet per minute...11452/5280 feet per mile=2.1 miles per minute...2.1*60 minutes= 129 miles per hour)

Or just machine a spacer 6mm thick...

The reason *I* am not using a wider belt is that I don't need one, all the pulleys I can find for this supercharger are 6-rib, and in my setup, the belt would interfere with the fan if I went wider. It already interferes with the fan, but it's a fixable amount.

Belt orbiting is the effect that ALL belts have, it's kinda like how pizza dough gets flung up in the air spinning and stretches out into a circle. The belt is "flung" outwards, away from the belt path, which lessens the belt wrap around all the pulleys.

The problem is that the supercharger usually gets a small diameter pulley installed on it, and people don't think about belt wrap and tensioning. That's why superchargers eat belts. Look at the SII GM3800. That's an M90 supercharger, driven from the same belt as the entire accessory drive. The crank pulley size was upped to a little over 7" diameter, specifically to allow the supercharger pulley to be sized to 3.8". This allows as much belt contact area as possible while still retaining the six-rib belt and the required supercharger drive ratio. (I think it was the series II, could be the series I. One of the two uses the same drive belt, the other series uses a belt specific to the supercharger.) You have to figure the load on the belt, too...at full-song the M62 draws 36HP, plus another 3% or so in belt loss. Call it 40HP and be safe. How much contact area do you need to transfer 40HP? Now, since you know the amount of belt contact area you need, figure the amount of belt wrap you need on your chosen pulley diameter...figure out the area of belt contact based on the amount of belt wrap. Is it enough to transfer your 40HP? No? Then either increase belt width, belt wrap, or driven pulley size. Is it enough now? Yes. Now look at the belt orbit. When operating a roots-type blower produces a pulsating load. This pulsing is what causes the belt to slip, eventually...but the path to slippage makes a stop at belt orbiting. Right now, I'm looking at a potential belt orbit problem in my setup, the long unsupported span on the tension side of the belt (the high-side, coming down to wrap around the crank on the driver's side of the car) would tend to push outward, away from the idler and toward the driver's side of the car. This would be a good location for a second idler assembly, to shorten the unsupported span. Otherwise, this long span will be the major cause of belt wear; even if it isn't enough to justify engineering a new idler.

I've sent you a PM, Meph

Won't run long, since your alternator is also out of the loop...the battery can't hold a running vehicle plus an electric fan plus an electric water pump too...Look at the current requirements. You do NOT want to exceed the capabilities of your alternator!.

I'm with motomanmike. My '72 had suffered a similar hit, but instead of a direct hit in the front, mine was pinched from front driver to rear passenger, between a semi-trailer and a wall. It had been previously repaired, and I finished the job, by building a wooden frame cradle with the hard points layed out and pinned, and using hydraulic tools, cutting of damaged sheetmetal, replacing some panels, removing and replacing the roof, making a new front headlight extension, ect. The core support up front had been wrinked in a second accident, but it was able to be straightened sufficiently to restore the proper dimensions. When I started, my car would teeter on the passenger front and driver's rear tire, using a single finger on the rear decklid. It can be fixed, it's all in how you want to fix it, and how much time you're willing to put into it.

Overhead cam heads get the shaft in most machine shops that don't deal with them often...long L6 heads, especially. The proper way to recondition one is measure for flatness, and then STRAIGHTEN it, not just mill it flat. Once it's been straightened, then the deck can be milled to clean it up, and the cam bores need to be line-honed, unless like the L head, they are removable. If they are, they would then be removed, the valvetrain completely dissassembled, and the top of the head milled flat. The head can then be reassembled, and the towers WILL realign...it's pretty hard to disassemble a mated assembly that was produced with a flat surface, and then reassemble it on a flat surface, and have it come out less than flat. I don't understand the big deal about not removing the cam towers...they're doweled into place, as long as they are carefully reassembled and aligned onto the cam such that it spins freely when they are torqued to the required value, then there is no reason to remove them.

That means the head was NOT straightened before being shaved. You will need to have the top of the head skim cut to correct this issue.

No....You have completely missed the message here. Headwork. Not a valve job, Headwork. That means getting it ported, flow tested, ports touched up, flow tested, match the intake manifold to the cylinder head, pick a cam appropriate for the port flow, intake manifold flow, and desired torque peak, and then tuning it all to play nice together. In addition to all the above, you would install new valves, have the seats recut, install springs suited to your cam lift and seat pressures, install the correct spring shims, measure for and install the correct thickness lash pads, and ensuring that you are using new or reground rocker arms with your new cam. Some folks say you don't need them...others, including myself, wouldn't install a new cam without reground rockers. A flat-top L28, with a P90 head, will net you 8.8:1 compression, approximately. Shave the head until your chamber size is reduced enough to produce the compression you want...but you'll need to have the valves unshrouded BEFORE shaving, because the chamber size will increase 1-2cc with this operation. If you're not ready to spend either a LOT of garage time with the correct tools and patience to finish the job, or spend the equivalent in cash money to someone who is, just put together a flat top bottom end with quality parts, and install the P90 head. A set of nice headers, a properly sized cam (talk to you cam grinder about that) and make sure you set up your cam geometry, and call it a day. Skip the dual webers, if you're talking about the DGV downdrafts. They're *ususally* more trouble than they are worth, and don't have any real advantages over a set of SU's. If you are talking about the Weber MCHH sidedrafts, then they *MAY* have some advantages, but you will need to construct a custom linkage. I don't know the answer on that one.

I am familiar with it; and as long as you recognize that when your supercharger eats a belt, you'll loose your waterpump at the same time, and you're OK with that, then there is no reason to not run the single serpentine belt. As far as the water pump pulley goes, look at the KA24DE pulley in the pickup truck, or the VG30E. Might find something to fit there.

You shouldn't weld on something like that unless you know exactly what it's made out of. Call Powerforce and ask, would be my thought. I had the tape on the car last night, getting an idea of what has to move where to get the drive belt on. The radiator needs to move 1/2" forward, or I need a thinner fan than the Hayden Trans-Kool that's on the car now. If the core support was flat, instead of having those 1/2" raised panels that the radiator mounts to, then I'd have just enough clearance, I think. The radiator is a 240Z 3 row copper unit. I am pondering moving to a 280Z (taller) aluminum 2-row (thinner) radiator.

No. If the bottom surface of the head is flat, then they don't need to torque it to anything when they mill the top.

In 1984, the FS5W71C was born out of the earlier 71B box. It came with the 62mm countershaft bearing then. In 1986, the second gear syncro went to a double cone type. In 1987, the S12 200SX came with the 71G, which is a 71B box with the C shifter, upgraded 2nd gear synchro, nonsynchro reverse, and the large countershaft bearing...but the box is exactly the same length as a 71B box! No driveshaft mods needed. In 1989, the 71H received thicker gears, the large countershaft bearing, upgraded 2nd gear synchro, C shifter, nonsynchro reverse, and the case is two inches longer. A one-piece VSS sensor is used, as opposed to the two-piece sensor on the 300ZX. In 1995, the S14 got a further strengthened version, with some gears thicker still, big countershaft bearing, upgraded 2nd gear synchro, fully synchronized, including reverse, VSS sensor, different overdrive synchronizer (I have both a brass ring syncro and a black fiber crush sleeve type...not sure which is which, but both came from S14's) and the long case. This transmission also came in some of the 4wd trucks, and can be found with both married and divorced transfer cases. If you don't need a passenger seat, then it can be fitted up in a Z by removing a good bit of the passenger side transmission tunnel and reworking the floor...this allows you to enjoy the fun of fitting up a front diff and using the uprights from one of the Nissan FWD cars...I will leave the actual fitment up to the user to figure out. I don't remember the details and the car was never finished, or even driven at all.

My tank, including the bottom two inches of an L24 oil pan sump welded to the bottom, will hold 15 gallons if I drain the tank out and then put the plug back in. If I fill up when the gauge reads just to the bottom of the empty mark, then the pump will show 12.5 or 13 gallons; the very first time I put a full tank of gas in, the car was coming back to the house from paint on a rollback and the tank was completely dry. I had my buddy unload the car at the gas station, and he helped me roll it to the pump, we put the tank drain plug back in and the tank took 15.1 gallons. Best part is that even getting not great milage, it STILL lasts two weeks of driving to work, as opposed to my old van that I filled up the 24 gallon tank every week!

Yes, you can use Hybrid Alpha-N with MS1extra, and MSII extra actually has a naturally-aspirated ITB mode. The ITB mode, however, does not support boosted applications. I'll be running Hybrid Alpha-N, assuming that I don't make enough vacuum to run straight Alpha-N. Here's the assembled plenum, from the top: And Mistake #4. The fire-extinguisher-turned-plenum pulled enormously during the welding of the secondary plenum, and I didn't catch it in time. A little filler rod and some sheet cut to fit the gap fixed it, but it'll always be ugly. Good thing it's on the bottom side and won't be seen! The manifold is still at the machine shop, and I dropped off the plenum assembly today to get flattened. Hopefully I'll get them back next week.

Keep in mind the actual locations of the parts...your alternator is drawn quite high on the block. You need to ensure you have at least 50% belt wrap around the crank pulley, and shoot for no less than 30% on your accessories. Also, serpentine belts are designed to be run at a VERY specific belt tension, or they WILL slip. The only reason I'm using a manual tensioner assembly is that I already check my belt tensions every week, and it was quicker to package. I would seriously consider a spring-loaded tensioner assembly. If you are using an serpentine belt, then the tension should be at a minimum 25lbs*8ribs=200lbs. Consider this when you build your tensioner and idler setups. And yes, actually...that is two fire extinguishers that got welded together for the main plenum.

So do the work to bolt down the RB20e head onto the L block, run an L dizzy and triple mikunies, and custom cast an upper front timing cover and valve cover...call it an LY28 tribute... (Yes, I know who makes those castings and I wish I could afford to buy them!)

I did flare the ends of them a little more, they got mushed between the bores some. A little work with some cartridge rolls (these air horns are SERIOUSLY thin) blended the radius in better. These horns are 52mm at the base, OD, and 54mm OD at the top, and the internal bore is 48mm, tapering to 50.5mm, then the 1" radius starts. Like I said, this is the best *I* can fit ito the plenum. More photos of the assembled plenum this evening, including Mistake #4. This time, things are getting ugly.

Spend the money on the head. I'd budget 2000-3000 dollars in headwork, or 60-80hrs, depending on if you're paying with cash or with your personal time and tools. With a P90/flat-top piston configuration, shoot for 9.0-9.5 :1 compression unless you want to run a very late intake valve closing, or you are willing to work around detonation with either race gas or conservitive timing. You can get away with a little more, but it becomes much harder to work with very quickly above 9.5:1, although some folks run 10:1 and higher on pump 93. Cam accordingly.