Dane

I have a rust hole in my front wheel well that I want to try repairing myself. I don't have a welder, but I do have a torch that I can use for brazing. I haven't brazed before, but I've been doing some reading about it, and I know that to braze a joint the metal needs to be very clean, and the two pieces need to fit tightly together with decent overlap for the filler metal to bond properly. I was planning to grind the area around the hole to bare metal, take a sheet metal patch and use a hammer to get the patch to conform to the body of the car, probably put in a few screws to hold the patch in place, and then braze. One of my major concerns, and this is another thing I read about, is that on some cars you're not supposed to use brazing for sheetmetal repairs (if its a certain type of steel, if I remember correctly). So can brazing be used to install a sheetmetal patch in a '71 240Z wheelwell? By the way, I did a search under "brazing" and not much came up.

Hmm...this made me think. Does this mean that bringing the rotational inertias of the flywheel and damper closer together (by using a lightweight flywheel, closer to damper inertia), you will reduce torsional vibrations in the L6 crank? And since there will be less torsional vibration in the crank, less vibrations need to be dissipated through the damper? So a lightweight flywheel by itself could improve crankshaft durability? Is this the way it works?

Today I was driving down the road in my '71 Z. A guy in an S2000 pulls up next to me and looks my car over really quick. The guy gives me a thumbs up and drives off. Little things like that can really make your day. It's kinda funny, I'm an S2000 fan myself.

I was just reading this and wanted to make sure I understand the feeler gauge trick correctly: So the idea is that you stick a feeler gauge between the tip of the rocker arm and valve stem. Then you spin the cam and check the cam lobe wipe pattern on the rocker arm contact pad. If the wipe pattern is okay, then the thickness of the feeler gauge is the thickness of lashpad that needs to be used? Would you also need to subtract the valve lash (measured between cam base circle and rocker arm) * 1.5 (rocker ratio) from the feeler gauge thickness to get the true lashpad thickness, or could you just use the feeler gauge thickness as previously stated and then adjust the valve lash from there? Am I on the right track here?

Please excuse me for reviving such an old thread, but I was reading this in the archives and made a few quick physics calculations based on the weight reductions made to the pistons, and I came up with some numbers that are surprising enough that I thought it was worthy to post. The numbers were so surprising actually, that I think I could have made a mistake and wanted some second opinions. So here goes for the calculations: Lets assume you have an L28 crank spinning 6000 RPM. That correlates to a maximum piston speed of 24.8 m/s. I used the equation v=rw, with one rotation being 2pi radians, r is half the stroke so 39.5 mm (0.0395 m). (6000 Rot/min)*(2pi rad/rot)*(1 min/60 s) = 628 rad/sec = w v = rw = (0.0395 meters/rad)*(628 rad/sec) = 24.8 meters/sec By removing 150 grams (0.150 kg) from the pistons, and using the kinetic energy equation KE=1/2mv^2, the kinetic energy of a piston at 6000 RPM (24.8 m/s) is REDUCED by 46.13 Joules (J). (1/2)*(0.150 kg)*(24.8 m/s)^2 = 46.13 J The piston decellerates from full speed to a complete stop at TDC. This repeats for BDC. So for each engine rotation, the piston loses all of its kinetic energy two times. So in this case, the DIFFERENCE IN ENERGY CONSUMED by accelerating the pistons after weight reduction is 2*46.13 J = 92.26 J. At 6000 RPM, this happens 100 times per second, and with 6 pistons this leads to: (92.26 J/rotation)*(100 rotations/second)*(6) = 55,356 J/s = 55,356 Watts 1 HP = 746 Watts, so: (55,356 Watts)*(1 HP/746 Watts) = 74.20 HP ?!?! Basically this is saying that the power required to accelerate 150 grams from rest to 24.8 m/s...repeated 200 times per second...and multiplying this times 6 for each piston...is equal to 74.20 HP. Thats the DIFFERENCE in power required at 6000 RPM after removing 150 grams from each piston. Can this number be accurate? Judging by gut instinct, 74 HP just seems like A LOT of power saved by lightening the pistons by that much. Is reducing the reciprocating mass really that important for building high performance engines? If somebody can see a mistake I made...please point it out. But if this is actually true...all I can say is thats FRIGGIN SWEET!!! I could be making a mistake in my reasoning based on how the piston, crank and rods exchange kinetic energy as a system: When the piston is at maximum speed halfway up the stroke, both it and the rod are traveling straight up and down at exactly that instant. When the piston stops at either TDC or BDC, the rod is swinging over with its max rotational speed. But the energy of the rod at TDC or BDC can't be greater than its energy at max piston speed...so that can't be what makes up the difference. When the piston accelerates, its taking energy away from the crank. But when the piston decellerates...is it giving energy back to the crank? I think that could be the conceptual issue that this whole thing hinges on.

So I've read from multiple sources that MSA headers aren't that great and that the OEM exhaust manifold is actually fairly well designed as far as exhaust scavenging is concerned. I've also read that adding a 2.5" exhaust to the stock manifold is a worthwhile upgrade. So with this in mind, is it worthwhile to extrude hone an OEM exhaust manifold, as well as port matching and all the usual stuff of course? I know that extrude hone doesn't really remove a lot of material, just smooths out the surfaces inside the manifold...but I would consider this beneficial to flow, without changing the basic design of the manifold. At $500 for this kind of work, I know thats getting into the spending territory for a custom header. However...with a custom header, wouldn't a custom exhaust be needed? With an extrude honed OEM manifold, a 2.5" exhaust (which is readily available and cheap from what I understand...ie MSA) could just be bolted on, making things easier in that respect. Just for background...I'm considering building up an L28 in the summer of '08 (one of many options, still in the planning stage), if so it would have mild porting and a cam upgrade probably running SU's...just so you have an idea of the application. Not a serious race car, but a decent increase in power for a street car. Any thoughts?

I find this interesting so thought I'd ask a quick question (that I think is relevant)... When you refer to "inherent intercooling", is this just the latent heat of vaporization of the gasoline (energy absorbed by gasoline to convert it from liquid to vapor)? I have heard this effect is greater with carbs than EFI since with EFI the fuel is already highly atomized when it leaves the injector. I remember seeing some pics of one of those Holley draw-through carb set-ups. Seems like it wouldn't be too difficult to tune for driveability and power since you could independently tune the primaries and secondaries on the carb...

I've been thinking about this for a while and have searched the archives, but haven't been able to find much info regarding a high flow cold air intake for the SU's. Ive seen the K@N filter assemblies that are sold by Black Dragon and MSA, but those suck in hot engine compartment air. (BTW, do those K@N intakes include airhorns the way the stock air cleaner does? How about connections for float bowl vents?) Right now I have kind of a poor man's CAI, where the tube for the hot air intake instead goes through a hole in the front of the engine compartment, but that doesn't take the normal air intake into account. I was thinking of cutting an opening in the side of the fresh air intake (black plastic elbow piece) on the front driver's side of the engine compartment, and connecting a big hose from there to the air cleaner. I also had the idea of ducting air from the cowl area, but don't want to cut a big hole in the firewall for this. I saw Bryan Little's vented hood intake idea over at http://www.geocities.com/zgarage2001/z.html, but don't have a vented hood to use for this. (It also appears he took that article off his website). There should also be some sort of heat shielding between the exhaust and the intake, this is an obvious source of excess heat. So does anybody have any cool ideas for CAI for the SU's? Also, has anybody actually seen any dyno proven horsepower increases using the twin K@N filter assemblies, despite the fact that they aren't a CAI?

What if you also test removing sidemarker lights (maybe cover holes with tape), emblems, and the antenna? Or how about different styles of hubcaps? There are also several different styles of door mirror that could affect aerodynamics. These are all little things, but they could add up... Another interesting thing I read in a hot rod/muscle car magazine recently was that by taping a piece of cardboard to the front grill, some guys took about a tenth of a second off their quarter mile times...I'm assuming due to decreased air resistance at higher speeds near the end of the track (obviously not practical for driving long distances because of decreased radiator airflow). I know you guys will be pressed for time in the wind tunnel, but every little tweak that could be tested would help. Also, if we can't hit the $7000 mark for 2 full days, would it be possible to schedule 1.5 days of testing for say...$5250? Every extra hour of testing would help.

Just sent a little money...has anybody mentioned testing headlight covers and engine compartment-to-wheel well vents? (Sorry didn't feel like looking through this huge thread to see if someone mentioned it) These are both easy mods that can be done to just about any S30, so they should probably be tested.