johnc

> I wish I had places like Dave's near me! Pete, There's gotta be a 1/4 or 1/2 mile dirt track near your home. Go to one of the events, walk through the infield, and ask who the best fabricator is. Find that guy, talk with him, buy him a beer, and you've found your local shop. ------------------ John Coffey johnc@betamotorsports.com

The only exception I see to this are diesel engines. You can't rev most diesel engines to 5252 rpms, but I guess if you extrapolated the curves out they would cross. And what about two stroke engines? ------------------ John Coffey johnc@betamotorsports.com

Thanks for education guys. ------------------ John Coffey johnc@betamotorsports.com

The front diff is the same as the rear on the 4x4. The output shaft from the transfer case spins in the correct direction. ------------------ John Coffey johnc@betamotorsports.com

Huh? Where is it stated that the hp/torque intersection point is fixed? What if you're engine doesn't run higher than 5,000 rpm? What if your engine is redlined at 17,000 rpms? ------------------ John Coffey johnc@betamotorsports.com

Nash Metroplitain with a Rat motor. There was a white and teal two-tone one that used to run 10s at OCIR. Very squirelly car; took out the Christmas tree once. ------------------ John Coffey johnc@betamotorsports.com

Although I haven' done this mod myself, I've seen it on a couple cars... You will need to remove the cowl cover and add some bracing from the hood latch area back to the firewall. Or you might be able to add a 1/8" steel plate to spread the load out on the vertical section behind the hood latch. Once that's in place then you can build a triangulated front strut tower brace: 1 leg from tower to tower and the other two going back and inward to the hood latch area. Make each of these legs removable so you can work on the engine. ------------------ John Coffey johnc@betamotorsports.com

What I described was the cold startup procedure for $85,000+ motors in a racing Dodge Viper GTS-R (just ran at Sebring) and for a racing Porsche 996 GT3 RS. The steps involved primarily exist to keep from breaking the scavange and pump drives for the dry sump system itself. I assumed that someone retrofitting a dry sump system to an engine will use racing parts similar to what's installed on the two vehicles listed above. Dry sump systems fitted as factory OEM are designed differently than race-only parts. I've seen scavange and pump drives shear at cold startup when the oil was too cold and when the drainback into the engine sump wasn't cleared before the engine fired. If the engine has been run with the past few hours and the engine oil has retained some heat then you can probably just hop in and fire it up. I even prime the engine (with the starter) in my wet sump 240Z before firing it up on a cold start. It was built loose so it will rattle a lot if its started immediately. ------------------ John Coffey johnc@betamotorsports.com

In addition to the cost, you have a more involved vehicle startup procedure. You can't just hop in and turn the key. Here's a rough outline: 1. If the outside temp is below 60 degrees, preheat the oil tank (15 to 60 minutes). 2. Disconnect the scavange pump drive belt, attach a drill motor, and run the scavange pump for a minute to drain the engine sump. 3. Connect the drill motor to the pump side and run the pump for 30 seconds to prelube the engine. Alternatively you can turn the engine over with the starter while leaving the ignition switch off. 4. Turn the ignition on. 5. Hit the starter and fire the engine. Keep the RPMS idling under 1,500 until the engine oil reaches 80% of operating temperature. 6. Hop in and drive away. ------------------ John Coffey johnc@betamotorsports.com

I've kinda fogotten where I got my header coated orginally. Let me look through some old paperwork and make some calls. Watch this space... ------------------ John Coffey johnc@betamotorsports.com

Here's a header coating tip: find a place that coats outdoor furniture. I've got a .25 mm thick silver aluminized coating on my headers that really holds the heat in (egt temps @ 1300+ degrees at the collector exit) and keeps the engine bay cool. They orginal set lasted 5 years and still looked new. I ended up bending them on a stupid off-track excursion. ------------------ John Coffey johnc@betamotorsports.com

Back to basics... Check for spark. Check for fuel. One of them is missing. Probably need to get a Bosch L-Jetronic fuel injection book. ------------------ John Coffey johnc@betamotorsports.com

Clarification on the California smog exemption: 1973 and earlier vehicles are not exempt from California smog laws. They are only exempt from the bi-annual and ownership transfer inspection. You can still get "inspected" by a California Highway Patrol officer and, if your vehicle triggers a roadside sniffer, then you must still go to an inspection station and go through the full certification process. ------------------ John Coffey johnc@betamotorsports.com [This message has been edited by johnc (edited March 05, 2001).]

Go to Bryan Little's page and look at the pictures to figure out what's in the car: http://www.mindspring.com/~blittl/engine.html ------------------ John Coffey johnc@betamotorsports.com

Perfect link! From page 2 and 3: "If the effect of the propeller is neglected, it is apparent that the maximum pressure obtainable from the air stream is the dynamic pressure due to the forward velocity of the airplane. Not all of this dynamic pressure is available for increasing the carburator-intake pressure, however, since losses occur int he carburator intake ram. Friction losses are present in every ram and cannot be eliminated. Anothe rloss exists int he form of an entrance loss, part of which is due to entrance shape and location and part tot he fact that the velocity of the air entering the ram must be reduced from that of the air stream to the velocity required at the carburator." "As this reduction in velocity occurs without expansion in the case of the external constant-area type, it is reasonable to expect losses due to spillage and turbulence to exist. If it were possible to take the air into the ram at the velocity of the air stream and expand it until its velocity were reduced to that required at the carburator, it should be possible to eliminate the losses due to spillage and turbulance." The document goes on to discuss the construction of two type of constant-area rams with five different types of entrances. It looks like I understated the importance of the speed of the air entering the ram. Synchronizing the air entry speed with the needs of the carbutor appears to by importnat and the plenmum right behind the ram intake appears to achieve this sync to some degree. ------------------ John Coffey johnc@betamotorsports.com

What we want to achieve with an intake system is to provide a larger VOLUME of air than is needed by whatever device we are supplying the intake air to. By containing this larger volume in a plenum we achieve some small level of pressurization. Often there is a mis-understanding concering air intakes and the marketing term "Ram Air" that Pontiac trademarked. In no case are these intake systems ramming air into the carburator. What they are really trying to do is get a large volume of air into the plenum right above the carburator. The larger the volume in the confined plenum the greater the pressurization. The speed that the air enters that plenum is only relevant as it relates to the volume of air that gets into the plenum. For an intake system with relatively long ducts, placing a plenum right behind the intake opening, the amount of air that piles up in front gets reduced thus increasing the volume of air that actually gets into the intake and eventually to the plenum over the carb. Remember, the longer the intake tube, the greater the restriciton and volume reduction. This sounds counter intuitive, but I read some original research on this subject on the NASA report server. I tried to dig this up to post here but I'm getting a 603 timeout when I try to access one of the documents. Here's a list of possibly relelvant documents and a link to the server. I'll try tomorrow to see if I can get through. http://techreports.larc.nasa.gov/cgi-bin/NTRS 572 -1 An experimental investigation at large scale of several configurations of an NACA submerged air intake, NACA-RM-A8F21, Oct 19, 1948 498 -1 Internal-flow systems for aircraft, NACA-TR-713, Jan 01, 1941 484 -1 An experimental investigation of the air-flow of a scoop-type normal-shock inlet, NACA-RM-A55A13, Apr 28, 1955 479 -1 Investigation of air flow in right-angle elbows in a rectangular duct, NACA-WR-L-328, Oct 01, 1941 407 -1 The structure of turbulence in fully developed pipe flow, NACA-TR-1174, Jan 01, 1954 ------------------ John Coffey johnc@betamotorsports.com

What's important in any kind of ducting is to build a way to get the air in and not let it back up. What you need to build is a large area behind the initial opening and then duct air from that. Bad diagram: < front of car _|----|___________|-------| /-|____|-----------|_______| If you just build straight tubes or a decreasing funnel shape as you mention you'll get air packing up in front and the flow will reduce significantly. Look at ProStock, F1, and any number of other hood scoops. Also look at the brake cooling ducting systems on closed body sprots cars. They all have a large plenum area behind the opening. ------------------ John Coffey johnc@betamotorsports.com

http://www.scca.org Solo 2 - low speed (70 mph or less) events held in large parking lots, air strips, etc. where the course is marked with cones and you get three timed runs. They are very safe and are low stress on the car. Solo 1 - high speed time-trial events usually held on a race track or on a closed public road (hill climbs.) No wheel-to-wheel racing but there still a risk of injury/damage/death. Your V8 Z would be classed: Solo 1 and Solo 2 - at any National and Divisional level event - E Modified (you would be an "also ran".) At local events there's always a "run what ya brung" class where your car would fit in. Solos are pretty casual and the organizers will find a class for your car where you have some good competition and lots of fun. Road Racing - real wheel to wheel racing. You would run in a local ITE (Improved Touring) or SP (Super Production) class. Your will have to meet all the safety rules in the SCCA GCR and, at least here in SoCal, you'll bang fenders with highly modified Corvettes, Saleen Mustangs, Vipers, ex-NASCAR, and Porsche Turbos. Good luck... ------------------ John Coffey johnc@betamotorsports.com

Nothing. Positraction is General Motors brand name for a Salisbury type of clutch pack limited slip differential. ------------------ John Coffey johnc@betamotorsports.com

The best description of the process I've come across: http://www.gordon-glasgow.org/lsd1.asp Its not difficult (I can do it), just tedious. FYI... if you can feel the diff grab and release then its too loose. BTW... I don't run a clutch pack diff anymore. A Quaife is absolutely the way to go and its worth every penny. ------------------ John Coffey johnc@betamotorsports.com

Dan, You're correct. But autocross is a different animal than road race and is really hard on clutch-pack LSDs. Autocross has tighter corners, lower speeds, and you never get into 4th gear (and rarely into third). A higher preload is definately needed. If I was setting up a Z for track events only than I would go with the 70 ft. lbs. that Nissan Motorsports (Ron Johnson) recommends for an ITS car running 225/50-14 Hoosiers. I also think that 45 ft. lb. number is an old recommendation - tires have improved a lot since the mid-1970s. ------------------ John Coffey johnc@betamotorsports.com

The car sounds like an old GT2 project. Pull up the carpets and look for the cut-off remains of a roll cage. ------------------ John Coffey johnc@betamotorsports.com

http://www.stahlheaders.com/index.html Probably the best headers you can buy. You can also buy header kits from Jere and build your own. ------------------ John Coffey johnc@betamotorsports.com

OK, so you guys wouldn't go for my jerk factor theory. I think drag is the correct answer. If someone with a more mathematical bent can solve this equation, I think we can find out how much power Scottie needs to generate to experience the same level of jerk... Power required to overcome drag: P=Fd*v=1/2Cdpv3A P = Power Fd = drag force (Fd=1/2Cdpv2A) v = Velocity Cd = Drag Coefficient (Cd=Fd/1/2pU2L2) p = Fluid Density A = Cross Sectional Area I'm not a mechanical engineer and just barely a software engineer, so math just confuses the hell out of me. ------------------ John Coffey johnc@betamotorsports.com

Exactly! Scottie's Z has a lower jerk factor that the when he was running the L28T. I'm thinking he needs to increase his vehicular jerk factor. Maybe a big wing on the back? ------------------ John Coffey johnc@betamotorsports.com [This message has been edited by johnc (edited February 12, 2001).]