johnc

Steve's looking for a new motor after the MSA event. With a V8 he'll have to run EM which he can probably win locally but he'll get his butt handed to him at the nationals from any number of 13B rotary powered, 1,200lb creations. But then agin, 500hp in 1,900 lbs vs. 300 hp in 1,200 lbs might be an even match. He'll need huge brakes and tires - 12" wide rims all around at least.

As I say to my A Sedan Camaro racing buddies, "You guys sure know how to drive those Chevy pickups!"

Given equal drivers (how would that ever happen) I think a Porsche GT3R would easily beat my 240Z. I think my car (again with equal drivers) would beat a Porsche Cup car. The performance of my car on a road race track (with slicks) would be comparable to a SCCA GT2 class car. In your neck of the woods it would probably be 2 to 4 seconds per lap slower then a Holden or Monaro V8 Supercar (that's assuming their performance is equal to our Trans Am cars). That's a wild guess on my part based on the races I've watched late at night on Speed.

I never said it couldn't be done, I just said I had not seen or heard of one before. I have no doubt that a V8 Z can be built as light as an L6 Z and can be made to handle as well. I just have not seen anyone do it yet. Remember, I'm a racer. Prove it to me on a racetrack. Someone, somewhere build a road racing V8 Z. I know it can be built fast and I know it can be built to handle great. But, right now, its a mythical creature that most any 200 hp, 175 ft lb, 2,430 lb (with driver) ITS 240Z can beat. How many times do I have to pickup and throw down this gauntlet...? 8)

Not at all. I'm just skeptical of most weight claims. Having corner weighed a lot of vehicles I find most owners are surprised how much their car actually weighs. Many have come in saying, "Oh, my car wieghs x,xxx because that's the manufacturer's curb weight plus I've added lighter pulleys, light flywheel, etc." Then we scale the car and see it actually weights about 250 lbs heavier then the manufacturer's listed "curb weight". So let's look at a comparison between Ron's V8 conversion and my 240Z back when it was a BSP car: My 240, back when it was an autocross BSP car, weighed from 2,230 to 2,275 lbs with full tank of fuel depending on the scales it was weighed on. There were some weight savings effort done on the car but SP rules require a full interior, HVAC, etc. and my car has a roll bar. From Ron's web site: "Dry weight 2420 lbs." He paid attention to weight when building the car as evidenced by the fuel cell and the 15" Panasports. I'm also assuming his weight is from scaling the since he also lists a weight distribution of 49/51. Ron's car (without fluids) weighs from 145 to 190 lbs more then my car used to weigh. We can probably add an additional 77 lbs to Ron's weights for a full (9 gallon) tank of fuel, coolant, and oil. So now, his V8 conversion (the lightest I've ever heard of) is from 222 to 267 lbs heavier "wet" then my L6 240Z. So far then, the lightest V8 Z conversion I've heard of is still about 250 lbs heavier then a comparable L6 240Z. 'Course, if the BSP rules allowed a change to a 9 gallon fuel cell, aluminum radiator, and aluminum driveshaft then the weight difference would be greater still - close to 300 lbs.

I think there are very few (if any) V8 Z conversions under 2,700 lbs. Most folks forget about the additional weight of the modified driveline, bigger radiator, bigger brakes, etc. when figuring out how much their conversion will weigh. It can be done but a builder will have to focus on weight while putting the car together. There are also very few (if any) V8 conversion 240Zs that can handle as well as most any of the ITS 240Zs racing across the country each weekend. A lot of development has been put into the 2,430 lb (with driver) platform that an additional 500 lbs tends to screw up. I'm not saying it can't be done but I haven't heard of anyone who's done it yet. Most builders fall into the "horsepower/torque" trap and lose focus (and money and time) on the handling and braking side. BTW... if anyone does build a good handling V8 240Z conversion, I can get an ITS 240Z and my 3.0L 240 to run as comparisons on most any West Coast track. Just let me know.

Didn't you already post this request somewhere on HybridZ? If not, there's a very similar thread on here that has links to specific information about your subject.

80/20 chance that they will rub. What is the backspace of your 17 x 7 wheels?

Start over and re-index everything from TDC.

You're fine.

I haven't flown in jets, but my wife bought me a dogfight at Air Combat USA http://www.aircombatusa.com/. All I can say is you guys should save your pennies 'cuz its the most you'll have with you pants on! Plus, you get video of yourself when you're done. The funniest part of my video is when I'm in this continuous loop 45 degrees off vertical trying to get on the tail of my adversary. I'm pulling between 5 and 6 Gs for about 60 seconds and you can hear me grunting, squishing farther down into the seat, my head pinned to the seatback, and my cheeks sunken down to jowels. My friends say I looked and sounded like Jabba the Hut. Meanwhile, my instructor in the next seat is sitting bolt upright, looking around, talking, breathing easy, and generally on top of everything. And he was a retired Navy and retired airline pilot who was celebrating his 68th birthday that week!

If you want to generate downforce from the underside of your car you need to get the air under the car moving faster then the air moving over the top. This will create a low pressure condition under the car and the entire upper surface will be pressed upon by the higher pressure air above. Ultimately what you are trying to do is create a venturi under the car. Look at the side view line drawing at the top of this page and note the shape of the belly pan: http://www.mulsannescorner.com The reason a rear diffuser typically has a 7 degree kickup is that's about as sharp a turn as the air can make and still remain attached to a simple, flat surface. You can run a shallower angle but downforce will be reduced unless you make changes in other areas. You can also run shallower angles if you're an aerodynamacist and have access to CFD software. Look at what's being done on the Bentley: http://www.mulsannescorner.com/bentleylmgtp3.htm And look at what you can do up front: http://www.mulsannescorner.com/bentleylmgtp4.html

Compression Pressure is commonly referred to as Cylinder Pressure. Cylinder Pressure is what folks should be focusing on, not static or dynamic compression (something I don't think exists in the real world) ratio. You should be concerned about absolute pressures in the combustion chamber, not ratios. Check out this article at SDS: http://www.sdsefi.com/meltdown.htm

Thread engagement should be flush with the end of the nut. Anything more is just extra weight. For closed end nuts thread engagement should equal the diameter of the bolt/stud.

Now for the more serious answer: it depends. Drag Racing Gear the transmission so the rpm drop to the next higher gear is right at the torque peak. Gear the rear so that the engine hits redline in top gear at the lights. Get ready to make lots of gearing changes based on actual ETs. Road Racing Gear the rear so that the engine hits redline in top gear at the end of the longest straight (or fastest part of the track). Gear the transmission so that the car will accelerate quickest from the corner that exits onto the longest straight or fastest part of the track. Get ready to make lots of gearing changes based on practice lap times.

Qualifying on the pole and leading every lap...

An argument from the other side... You folks are forgetting about weight. A daily driver 1970 240Z with an L6 can weigh 2,340 lbs including AC, radio, etc. I have yet to see anyone post the weight for a V8 conversion (including AC, etc.) that weighs less then 2,600 lbs (most folks forget about the weight of the different transmission, R200, bigger radiator, etc.). A simple BSP L6 motor (stock pistons, cam, headers, ignition) making about 200hp and running SU carbs will turn mid-13s in the 1/4 mile at a 2,496 lb weight (including driver), get 24 mpg on the highway driving at 75 mph, and will normally out corner and out brake a heavier V8 conversion. The $1,200 for the Chevy crate engine can be put it into the L6 engine and you can get at least the above level of horsepower and 1/4 mile performance. I'm assuming money spent on suspension, brakes, etc. will be equal in both build ups. A low cost good running L6 is not as slow as some would have you think.

Amazingly similar to the link posted above...

Well... comparing a track car's first gear is really irrelevant. Most track cars use third, fourth and fifth only on a race track. First and second gears are for getting out of the pits and are generally geared to get the car going without hurting the clutch too much. You'll want to look at the last three gears to identify anything meaningful.

The NASA AZ region specified 1/4" Lexan and the weight of that sheet and the required supports (single) equaled the weight of a stock glass windshield on the C5 Corvette I was helping build. That is an unusual specified thickness but I keep hearing rumors that SCCA is going to increase its minimum thickness for windshield Lexan. Whether these rumors ever come true is anyone's guess.

Borla XR-1 Raceline.

Check with whatever sanctioning body(s) you intend to race that Lexan windshielded Z. In many cases the specified thickness of the Lexan makes it weigh very close to the stock windshield. Regarding the rear hatch and glass - Hiten Patel (little.simba@cox.net)

Yes they do. I can put my hands on at least a dozen broken Viper rears done with stock motors making less horsepower and torque then you list above. Heat is their big problem. When you got the rear suspension did you note the angles of the upper and lower control arm inner mounts? Those angles (in both planes) are critical to getting the correct caster and anti-dive and you'll have to duplicate that or you'll end up with some really weird geometry. Good luck and call Erik Messley at (714) 713-9096. He knows the Viper and the Z better then most anyone out there.

While I don't agree that there is something called "Dynamic Compression Ratio" here's a short article describing what some folks think it is. I feel Cylinder Pressure is what people should be thinking about. http://cochise.uia.net/pkelley2/DynamicCR.html

A stock engine works best with the stock cam. A mildly modified L6 works best with the stock cam.