John Coffey

Yes, I did it again... I must have pissed off the powers above earlier this year. Yesterday (last June) I was at a driving school at Buttonwillow race track near Bakersfield, CA. Got through a couple sessions and on my third, while coming down off Magic Mountain (a little hill on the west side of the track) I heard the now familiar BANG followed by a weird, wiggly feeling in the back of the car. It was a little scarier at 80+ mph, but the wheel stayed on and I found that I could apply power if I loaded the left side of the car. So, I made it back to the pits and spent the rest of the school bumming rides with the instructors. This time I broke the stub axle on the right side of the car and, luckily, it didn't trash the brake drum. Since the shot peened Nissan Comp stub axles aren't available anymore, I've been doing some research on Cryogenic treatment (in addition to shot peening) and found that there really isn't much REAL information specific to this application. Here's a note regarding the subject from a Professor of Metallurgical Engineering: ----- Dear Mr. Coffey, The relationship between cryotreatment and fatigue of steel parts has not been studied that much. While there are many who have tried cryotreament for one reason or another, only a little scientific work has been done on it. Many sales claims are out there with little proof. Having said that, there are also a lot of people who have tried it and are very happy with what it does for them. I have spoken to a number of them and they seem to know what they are doing, so I believe that it is doing something to some of the properties of certain materials, particularly certain kinds of steel. Only a few people talk about it improving fatigue however, instead, most of the claims are for improved wear resistance. I have not seen any literature that speaks to the effect of cryotreating on welds. That doesn't mean that it doesn't do anything for the weld, it just means that no one I know has looked at it. My recommendation to you is to bypass the speed shops and steel treaters and talk directly to some of the full time cryotreaters. They will often do a trial run for free and let you see if you like the results (some of the steel treaters might also if you push them a little). This lowers your financial risk (assuming of course that you don't damage your car due to an early failure of one of the treated parts) and lets you see for yourself if it is worth the cost. I won't recommend any specific companies to you, as I would rather stay neutral, but you can find a large number of them through an internet search. ---- So, I guess I'll have my next set shot peened and cryo treated to see if I can keep the wheels on my car! ------------------ ---------- John Coffey johncof@veriomail.com

The 2000 Autocross season is winding down and the 2001 season is fast approaching. Here are 30 things you can do now to get ready for it: 1. Put on clothes you would typically wear on a hot day. Run in place, in your shower, with cold water cascading down on you, and sporadically bend over and pick up something. Do this for 1 hour. 2. Throw $25 away right now (SCCA members throw away $20). 3. Fill a blender with ice, hit the pulse button and let the spray blast your face. Leave the ice on your face until it melts. Let it drip into your clothes. 4. Throw $25 away right now (SCCA members throw away $20). 5. Put on clothes you would typically wear on a cold day. Go to a steel plant and run in place next to the smelter and sporadically bend over and pick something up. Do this for 1 hour. 6. Throw $25 away right now (SCCA members throw away $20). 7. Got to a tanning salon and get a good sunburn on your face. Then, put your face in front of a fan, turn the fan on, and throw sand into the back of it. 8. Throw $25 away right now (SCCA members throw away $20). 9. Crawl under your car and sporadically drop nuts and bolts, hot oil, grease, and old rubber hoses on your face. Scrape a hose clamp across your knuckles. 10. Throw $25 away right now (SCCA members throw away $20). 11. Pour oil and anti-freeze all over your body, put sunscreen in your eyes, and stand in the sun for 1 hour. 12. Throw $25 away right now (SCCA members throw away $20). 13. Don't drink any liquid for 12 hours. Then quickly drink 4 cans of beer. 14. Throw $25 away right now (SCCA members throw away $20). 15. Drink 3 cups of coffee and wait 6 hours before going to the bathroom at the worst gas station you can find. 16. Throw $25 away right now (SCCA members throw away $20). 17. Push your car up and down the block 3 times wearing your helmet with the visor down. 18. Throw $25 away right now (SCCA members throw away $20). 19. Find a highway construction area and run over every orange cone you can see. Then get out, walk back, and put every cone back in its place while arguing with each construction worker you encounter. 20. Throw $25 away right now (SCCA members throw away $20). 21. Get up at 4:00am and drive in heavy traffic for five hours - anywhere - towing your race car. 22. Throw $25 away right now (SCCA members throw away $20). 23. Push a small bucket over your head before you go to bed each night. 24. Throw $25 away right now (SCCA members throw away $20). 25. If you wear glasses, begin wearing them with glue smeared on the lenses. Sporadically pop one of the lenses out and scrape it on the ground. 26. Throw $25 away right now (SCCA members throw away $20). 27. Buy a new pair of driving gloves or shoes and immediately throw one away. 28. Throw $25 away right now (SCCA members throw away $20). 29. Slam your thumb in a car door. Take a short length of 2" round pipe and bash yourself in the head with it. Run over your foot with your car. Periodically stumble and fall. 30. Repeat all of the above every Sunday until it's time for the real thing. ------------------ ---------- John Coffey johncof@veriomail.com [This message has been edited by John Coffey (edited 09-29-2000).]

Do a compresion check. ------------------ ---------- John Coffey johncof@veriomail.com

Sorry for the late reply. Four possible problems: A. I suspect you've got the distributor off by 1 tooth or more so you have something like 50 degrees of initial advance and you're actually timing the car to the number 5 cylinder. B. The advance mechanism in the distributor isn't working. C. The exhaust system is plugged. D. Cam timing is off. But first, always remember, when your at your wits end, always go back to the basics. Get out your shop manual and do each of the steps below according to what the manual says: 1. Do a simple compression check to make sure the rebuild is OK. 2. Check the cam timing as you've said. Try the number 2 hole if everything checks out OK. 3. Adjust the valves (use the cold clearance settings). 4. Check the distributor and make sure its installed correctly. 5. Check all the vacume hoses for leaks. 6. Check the fuel pressure. 7. Adjust the carbs (again). 8. Adjust the timing (12 to 15 degrees initial and 28 to 32 degrees of total advance by 3000 rpms). Good luck! ------------------ ---------- John Coffey johncof@veriomail.com

Try Motorsport Auto at http://www.zcarparts.com. ------------------ ---------- John Coffey johncof@veriomail.com

Any good electric fuel pump (Carter, Holley, BG, etc.) will work. I would run one regulator (down to 4 to 5 psi) on the right fenderwell. You can also buy fuel pumps that have a built in regulator. I run a Carter - part # 180-P4600HP which is priced at $69.99 at Jegs: http://www.jegs.com. What's nice about this pump is that its internally regualted 6 to 8 psi so I don't need a regulator. - John

I would guess low to mid 20s on the highway. ------------------ ---------- John Coffey johncof@veriomail.com

I was hoping to have time to cruise the junkyards, but work is getting in the way again. So, I'm looking for 2 280Z stub axles and companion flanges (these are the 27 spline variety). I will also consider a set from a 240Z, but I prefer the 280Z axles. Wheel studs can be trashed, I'm going to replace them anyway. Thanks. ------------------ ---------- John Coffey johncof@veriomail.com

E31 heads are probably the most valuable, particularly for racers. $375 is a reasonable price to get a valve job, new seals, etc. Try to avoid having the head shaved if at all possible. ------------------ ---------- John Coffey johncof@veriomail.com

I'm assuming you haven't started the car for 6 months... That little hicup is probably a temporary lean condition. I think its time to do a complet tuneup - its spring time and the car will love you for it! 1. Adjust the valves. 2. Go through the iginition system and make sure everything is in good shape and adjusted to spec. 3. Go through the full carb adjustment/sync ritual. 4. Change all the fuilds and filters. 5. Check all the belts and hoses. 6. Adjsut the clutch. 7. Crawl under the car and check the suspension, chassic, fuel tank and lines. 8. Pull the wheels off and check/bleed/adjust the brakes. You've got a 3 day weekend ahead of you. Can you think of a better way to spend it? OK, maybe you can... ------------------ ---------- John Coffey johncof@veriomail.com

Anywhere from $10 to $2,000 depending on type and condition. What type of head are you looking for (E31, E88, N42, P79, P90, P90a,...)? ------------------ ---------- John Coffey johncof@veriomail.com

Take the $800. Complete, used, running Nissan L6s are very common at $600. ------------------ ---------- John Coffey johncof@veriomail.com

FYI... this little adventure happened exactly a week before my recent excursion into the PIR turn 2 tire wall. Third autocross run (the money run) at the Cal Club autocross at Hollywood Park in Inglewood, CA. I KNOW this will be the fast time of the day (FTD) run! Funny how you get that feeling just before... Second gear, right hand turn onto the only real straight in the course. I'm pretty much foot-to-the-floor exiting the turn at 2500 rpm when I hear a BANG and the engine instantly hits the rev limiter. The car gets a little squirrley as I let off the gas and coast off the course. As I roll into the paddock I'm revving the engine a bit and trying all the gears in the transmission. They seem to engage fine but I get no forward propulsion. I can also hear a grinding from the rear. As I come to a stop and shutoff I'm thinking, "Blew up the $1,000 Quaife diff... Son-of-a-bitch!" I crawl under the back of the car and look around. No oil, no debris, nothing appears broken, but the car won't got forward under power. Great... Bryan Lampe drives up after finishing his third run (and kicking my arse). He seems to be around whenever I break something. I need to look into this some more, but first, let me see if I can kill him. I ask Bryan to look at the halfshafts while I start the car and put it in gear. He says OK and crawls under the back of the car. I fired the car up, put it in first, and applied a little power. After a few seconds Bryan's head pops up and says, "Stub axle's busted." I shut the car off and get out. He points to the left rear brake drum and, sure enough, the center is pushed out and cracked, looking all the world like a crater on the Moon. FYI... Quaife's need some resistance on each wheel for them to move the power around correctly, otherwise they send all the power to the axle with no resistance - my broken stub axle. So, we push my car onto the trailer and I'm feeling a lot better 'cuz a stub axle is a LOT cheaper than a new diff. On the way home I call Hiten Patel to see if I can use one of the stub axles he left at Erik's shop (EMI Racing) as part of the struts I'm having built (a whole 'nuther story). He says OK, so I stop by Erik's and grab both stub axles (never know which will work). Luckily I have a set of spare drums at home. On Monday I go to MSA and Sam sells me bearings and lock nuts. Monday night I jack the car up and start stripping the left rear. Well... the stub axle broke in a weird way. The flange separated from the axle so I had to figure out a way to use the halfshaft mounting bolts to keep the stub axle from turning while removing the lock nut (180 ft lbs of torque holding that thing on). Normally, a broken stub axle can be pulled/pounded out from each end. After bending two screwdrivers and breaking a Craftsman box wrench I had to find something better. Searching through my collection of old tools I found a thick open end wrench that said, "Forged in USA." It fit perfectly over a halfshaft bolt and the other end anchored to the lower control arm like it was made for the job. This is now my "Stub Axle Anti-Torque Wrench" and resides in an important place in my tool box. So... now I've got the rear of the car on 6 jackstands and 2 floor jacks, the crimped sections of the lock nut ground off, the SAATW wrench hooked up, a breaker bar on the lock nut, 4' of pipe on the breaker bar, and all 200 lbs (my wife says 210) of me standing on the pipe. Nothing. I wiggle a little bit while balancing on the pipe. Nothing. I jump up and land on the pipe. CRACK! CLANG! THUD-OOOF! Me and the pipe hit garage floor. My wife sticks her head in the garage, "Are you dead yet?" She's such a loving woman (I'm worth a 1/4 million dollars dead and she gets it all). Anyway, the CRACK was the lock nut breaking loose so I was in business! The disassembly, reassembly went easy enough and the next night (after a trip to the machine shop) the car was back together. I did learn that there are different sized stub axles. The splined end that goes to the halfshaft has a larger OD for 280Zs. There are basically interchangeable as long and the halfshaft piece matches the stub axle you are using and you use the correct spacer between the stub axle bearings (almost always the "B" spacer for a 240Z). FYI... I was VERY lucky that the wheel and drum stayed attached to my car when the stub axle broke. Stub axle failure is not unusual for a 30 year old 240Z that's raced/autocrossed. Next time you are working on the rear brakes, clean and check the parts of the stub axle and flange that you can get to. Look for hairline cracks. Also, pull the halfshaft and check the locknut for proper torque. ------------------ ---------- John Coffey johncof@veriomail.com

Bryan gets grumpy sometimes...;-) Your '73 should be smog exempt in California. If not, move over to Stateline, behind the Casinos. Although I have no experience with the Weber downdrafts, I have heard they are not the best choice. I suggest you get a set of 1970 through early 1972 round top SUs. They really do perform the best on the L6. Check with Scott Bruning at Z Therapy (http://www.ztherapy.com) for tune-up videos and as a source for the best rebuilt SUs you can find. Good luck. ------------------ ---------- John Coffey johncof@veriomail.com

Why do you think you need to replace/repair the diff? ------------------ ---------- John Coffey johncof@veriomail.com

Well... it started out simple enough. Ya see, at the first few autocrosses of 2000 I was having a problem where the car would load up (run really rich) in grid and I would get a miss during the first 100 yards of the run. Then the car would clear out and run great. Some sleuthing by me and Bryan Lampe determined that my stock heat shield was not enough to keep fuel from boiling in the float bowls on the rear carb. So... I decided to build myself a new heat shield. Sounded like a simple enough project. Little did I know. I called Erik at EMI Racing to see if he might have one lying around. He said, "No, but I bet you can build one out of a titanium/aluminum/ceramic honeycomb that would be great." I said, "Huh?" He said, "Call Cherry Metals in Long Beach, talk to Mark and see if they have any titanium scrap lying around." I did and they did. $75 later I had a 4' x 4' sheet of 30 year old titanium/aluminum/ceramic honeycomb. Actually, Bryan Lampe had it 'cuz he works in Long Beach and I couldn't get to Cherry Metals before they closed. Bryan was kind enough to drop it off at Erik's shop. I called Erik the next day and said, "I'll come by tonight, get the sheet, and build it at home this weekend." Erik replied, "How are you going to cut it and bend it?" I replied, "With a hacksaw, vice, and body hammers." After Erik stopped laughing he said, "You can't saw it since its a honeycomb sandwich and you can't bend it with a vice and hammers 'cuz its titanium. Just come by the shop and we can use the table saw with a grinding wheel and my big sheet metal break." Great... It took two weeks until our schedules worked out. I drove the Z down to Erik's shop on a Saturday afternoon (we were supposed to meet Saturday morning but he worked until 6am that morning). Erik has the Grand Am GTO Viper on the lift. He's pulling body molds off it for a carbon fiber roof and he's moving the engine back 6" and down 4" in the chassis. Little stuff. I proceed to pull the stock heat shield off the Z and make a cardboard template for the new one, all the while trying to stay out of the way of Erik and "Stan the Carbon Fiber Man." After I have the template done I ask Erik where the table saw is. He points to a 10' pile in the corner of his shop. Great... I spend the next 1/2 hour digging it out. I ask Erik where the grinding wheels are for it. He says, "Home Depot. And buy yourself a class A breather when you're there." I ask why. Erik replied, "Because titanium dust is toxic, worse than asbestos." Great... After I get back from Home Deport (the first of 3 trips) I setup the table saw outside, behind the shop. Once everything is ready Erik comes out to supervise. He mentions, "Be careful not to get the metal too hot when you're cutting it. If the titanium ignites there's no way to put it out. Just look for bright white spots. If you see that, stop cutting and get ready to throw it to the ground." Great... So, I spend the next hour very carefully cutting the titanium/aluminum/ceramic honeycomb. I only saw one white spot and I was ready to toss it, but the spot turned orange, then red, and then back to gray. Now I get to drill some holes. I was ready for some very involved procedure and asked Erik what I needed to do. He replied, in a somewhat condescending manner, "Get the drill and use one of those carbide bits on the tool box." Drilling holes was pretty easy. After the holes were drilled, Erik's wife called and gave him the basic "get home and pay attention to me or you're a dead man" ultimatum so I had to stop work and get going. Unfortunately, to the detriment of my speedometer cable, I forgot to put the stock heat shield back on when I drove home from Erik's shop. Pretty amazing how quickly a set of headers burns through the rubber cable covering. It was another two weeks before Erik and I could get our schedules together. Sunday, I've got the aerospace heat shield cut out and ready to bend. Erik drags out this 6' sheet metal break and it takes both of us pulling hard to get the first bend in. We go to check it on the car and realize that we have to pull the carbs. So, I spend 1/2 hour getting the carbs off, and destroy the carb gaskets in the process. A call to Pep Boys, AutoZone, Chief, etc. yields nothing. So I go to Pep Boys and buy some gasket material and spend the next hour making 4 carb gaskets. Erik and I checked the heat shield on the car and, over the next 1/2 hour, make the necessary bends/adjustments to get it to fit. The heat shield is ready to install but its looking pretty old and aerospacy (don't want to draw too much attention to it, even though its a legal modification). So I run to Pep Boys and get some flat black header paint and make it "invisible." We get it and the carbs all installed, but the car is running funny. So, we tuned and rebalanced the carbs and everything runs great. The best part, with the engine at 200+ degrees you can use your bare hands to adjust the carbs! All this for about $100 in materials, a speedometer cable ($80), 4 grinding wheels ($20), a class A breather ($40), 1 drill bit ($5), and 6 hours of highly toxic and flammable work over a month! FYI... Early on I had the seemingly brilliant idea of making a bunch of these and selling them. NFW! But I've now got the best damn heat shield on any Z in the world! Of course you can adjust the carbs bare handed on Bryan Lampe's Z with his $10 aluminum heat shield... Great... ------------------ ---------- John Coffey johncof@veriomail.com

Sunday, Phoenix International Raceway - the third of a three day NASA Advanced Performance Driving School (called that for insurance reasons). I'm in a four car pack consisting of a RT/10 Viper on Hoosiers (first in the pack), a Baby Grand (Yamaha powered 1,200 lb mini-stock car on racing slicks), a E30 M3 (chipped and on Kumhos), and me in a Solo2 BSP 1970 240Z. At the start of the session I spent a couple laps getting past the BMW and three more getting past the Baby Grand. Both are really quick in the infield. I was able to stay with them in turns 2 thru 9 and then power past them on the oval. But the Viper is a different story. I was able to go deeper into turns 1 and 2 than the Viper and I could really push him hard through the rest of the infield. He could out accelerate me so I had to get my speed coming out of the corners and out brake him at the end of the oval and the short straight between 7 and 9. So that was my strategy for 6 laps. I never could quite get by him but I got my nose inside of him in a number of turns. I was definitely worrying him and he did almost spin coming out of 3. That was my chance but I hesitated 'cuz I didn't know where he would end up. He caught it and continued on. I got pinched behind a Pro7 Rx7 and the Baby Grand got by me. The Viper pulled out a couple car lengths. Onto the oval I passed the Baby Grand. At the end of the front straight I was about 110 - 115 mph. (BTW1... The entry to Turn 1 is tricky because you are coming down off the banking into the infield part of the road course. There's a pavement transition that unsettles the car so you have to go through there straight and on the throttle. After that transition you brake hard, downshift, and set up for Turn 2, which is a decreasing radius.) So... I brake checked at the end of the front straight and went through Turn 1 at about 105 - 110. Squeezed on the brakes hard after the car settled and... Uh Oh! (you Z racers know the feeling) (BTW2... my car is setup for autocross so I'm not allowed, per the Street Prepared rules, to run brake cooling ducts. I do bleed and adjust the brakes after each session but they only last so long when the outside temp is 104 degrees and you're chasing a 400hp Viper.) The car is pushing out (my tires were pretty hot at this point too) and I downshifted and braked with all I had. I was able to turn in a bit for Turn 2 but I was way wide and the back end was starting to come around. I eased up on the brakes and added some throttle to settle the car but by then I was in the marbles. The car slid off the track and went through about 20' of dirt before bumping, completely sideways, into the tire wall at about 10 mph. Go into the accident routine: Shut the car off, look around inside and out for smoke/fire. Nothing. Give the corner worker a thumbs up. Start the car and check the gauges. Everything's OK. Point at the corner worker and he signals when its safe to go. Pull out and head back into the paddock. Well... the car is covered in dirt and every body panel on the right side is dented and scraped. It was a really nice, straight, and clean 1970 240Z. But, no real structural damage: door opens and closes fine, hood, door, and hatch gaps are the same, crossmembers are square, check camber and toe and they are OK, not a mark on the wheels or the bumpers, and the side marker lights are intact. I got off lucky. Maybe $1,000 worth of body and paint repair. So, I clean the car up, bleed and adjust the brakes, and run the next session without a problem. I did stay away from the Viper though... ------------------ ---------- John Coffey johncof@veriomail.com

Another post on this topic from Marc Sayer (I think he sent this out a couple years ago): From: Marc Sayer Subject: Triple S.U. Setup - not so good. Well I see I really opened up a can of worms with this. Before people start going out to buy up triple SU bits, let me run this down for you so you understand what's up. With the dual SU manifold the air / fule distribution is poor because the runner lengths are different. Datsun worked their butts off to try and compensate for this and really did a pretty good job (you should see how bad some of the British stuff is). The advantage of the dual manifold is that the pulsations come in even periods. Let me try to put this visually; 1--- 2------- 103020103020 / 3---/ A "0" represents a "dead" time slice, a time when none of the cylinders fed by this manifold are in the intake phase. Any other number indicates the cylinder which is in the intake phase. 4--- 5------- 050604050604 / 6---/ As you can see the pulse pattern is very even, being one time slice on, then one time slice off. This means that each cylinder is pulling on a column of air/fuel (what is contained in the manifold) with about the same velocity, because each cylinder is preceded by the same length of "dead" time in the manifold. This promotes all sorts of positive effects, and keeps air speed in the manifolds fairly constant. It limits the amount of "flow reversal" that can take place by limiting the length of "dead time" in each manifold. These effects are mitigated to some degree by the differences in individual runner lengths and by the distances from the main plenum of each manifold to each intake valve. But all in all this manifold and firing order do work fairly well together. Now here is the pattern for a triple SU set up; 1-- --- 100020100020 2--/ 3-- --- 003004003004 4--/ 5-- --- 050600050600 6--/ You can see from this that the front and rear manifolds have uneven pulsations. 3 time slices off, 1 on, 1 off, 1 on. This means that the cylinder that opens after the 3-time-slices-off "dead" period, will be pulling on a much slower column of air/fuel than the other cylinder will. This will cause those cylinders (#'s 2 & 5) to run a little leaner and their counterparts (#'s 1 & 6) to run a little richer. The reason for this is that air reacts to changes in velocity more quickly than the fuel does. Since the air/fuel mix in the manifold has 3 time slices to slow down before cylinders 2 & 5 draw on it, it will be slower for them and as it tries to speed up again, the air will respond more quickly and get to the cylinder slightly sooner that the fuel. By then the intake stroke for these cylinders will be ending, the extra fuel meant for these cylinders will stack up in the manifold and then cylinders 1 & 6 will open. They will be opening to a fast moving, extra rich, mixture. (On some 4 cyl motors this phenomenon is so bad that the engine idles on only two of the cylinders if the mixture is not within range). The center manifold is different, however, its pulsation pattern is even, with 2 off time slices followed by 1 on time slice. each cylinder will be pulling on a column of air/fuel with about the same velocity, but thatvelocity will be fairly low due to the fact that twice as much time is spent "off" as is spent "on". So the triple SU manifolding has three basic problems; First, the pulsing patterns are not the same for all manifolds and, Second, the outer manifolds will have distribution problems caused by uneven pulse patterns and, Third, the center manifold will suffer from reduced velocity. The third problem is the least important of the three and is true for triple Mikuni's as well (in fact they suffer from a 5:1, off to on, ratio). I would not be concerned about this except as it relates to the behavior of the outer manifolds. The solution for the outer manifold's distribution problems is probably going to be similar to what was done for the British 4 cyl, siamesed engines. The runners of the manifold were "aimed" at the lean running cylinders slightly. This helped to overcome the distribution bias that was created by the uneven pulsing. I am not sure how well this would work on the Z motor, but on MGB's it helped quite a bit. It didn't eliminate the problem, but it did significantly reduce it. The last problem, that of the manifolds not all having the samepulse patterns is not soluble except by altering the firing order. But by ameliorating the negative effects of this, we can to some degree cancel the problem out. If the manifolding is done well it will be equal to, or slightly better than the stock manifold for distribution, but will increase flow. If runner and plenum size is kept small enough to keep air velocities up, the drivability and throttle response should be better than a dual set up. Anyway, there's something for all you triple SU freaks to chew on for a while. You could solve all these problems by going to 6 of the 1.25" (32mm) SU's you know. :-) Marc Sayer

Another post on this topic from Kyle: John- Excellent post, very hard to <snip> down, so here's my attempt at distilling the data: Cyl Deg | f(2x) r(2x) | f(3x) m(3x) r(3x) 1 0 | 0 - | 0 - - 5 120 | - 120 | - - 120 3 240 | 240 - | - 240 - 6 360 | - 360 | - - 360 2 480 | 480 - | 480 - - 4 600 | - 600 | - 600 - John's point becomes very obvious when you look at the "-" in the chart; on a double carb (2x) setup, there's a pulse to each carb every other cylinder in the firing order. In a triple carb setup (3x) the pulses are not even, except for the middle (m) carb. A very interesting point, to be sure. Seems that there was someone around that ran triple SUs, was it Preston? I'd be interested in hearing what was done to work around this issue. A balance tube might do it, but I'd guess that the stock type tube would be too small. And if you have to run a common manifold (plenum), you'll get into the same problem as with four bbl manifolds - long intake path, fuel puddling. The rear carb in a triple setup would effectively feed the other cylinders in the "dead" space between #6 and #5, for example. With a dry-flow MPEFI setup, this might not be as big a deal..... but then again, why not just run a larger, single throttle body? Hey! All you have to do to make this work is change the firing order! A new cam and crank, and you're set! <> Looks like 1,5,3,6,2,4 might do it. 'Course, then the famous L6 smoothness would go bye-bye;-) Hmm... let's dig my grave a little deeper here... at 1000RPM, you have 3000 intake pulses per minute, right? If that's right, then you have an intake pulse every .02 seconds, on a 2x setup. That means that each "-" in the chart above is equivalent to a .02 second dead spot in the intake flow. (jeeze I hope this is right;-) Going further, that means that the biggest dead spot in a 3x setup would be .06 seconds. And that's AT IDLE. At 3000RPM, there'd be 9000 pulses, one every .0067 seconds, the worst dead spot would be .02 seconds. Does this mean that a 3x SU setup would be as smooth as an idling 2x setup? And mightn't velocity stacks or longer intake runners take care of this? Bench engineering is almost as much fun as bench racing! Kyle

Why more is not always better when it comes to the L6: A triple SU carburator setup might work if they are attached to a plenum. If you try to feed individual runners from triple SU (two runners per carb) you'll have trouble making as much power as dual SUs. Why? The firing order of the L6 is: 1 5 3 6 2 4. Keep this in mind while we assume that front SU feeds cylinders 1 & 2, middle SU feeds cylinders 3 & 4, and rear SU feeds cylinders 5 & 6. On a dual SU installation you get an intake pulse to each carb every 240 degrees of crankshaft rotation, and this is evenly spaced. You end up with a pretty even mixture balance between all the cylinders. On a triple SU installation you get an intake pulse on each carb as follows: Front SU: There are 3 cylinders (intake pulses) with 360 degrees of rotation between 1 & 2 and 1 cylinder (intake pulse) between cylinders 2 & 1 with 120 degrees of rotation. This causes an imbalance in the mixture (rich to lean) between cylinders 1 & 2. Middle SU: There are 2 cylinders (intake pulses) with 240 degrees of rotation between cylinders 3 & 4 and 2 cylinders (intake pulses) with 240 degrees of rotation between cylinders 4 & 3. This creates a balanced mixture between these two cylinders. Rear SU: There is 1 cylinder (intake pulse) with 120 degrees of rotation between 5 & 6 and three cylinders (intake pulses) between cylinders 6 & 5 with 360 degrees of rotation. This causes an imbalance in the mixture (rich to lean) between cylinders 6 & 5. I may have my number of degrees off, but I think I've illustrated how it would be difficult to achieve a balanced mixture across all cylinders during one full power cycle (720 degrees of crankshaft rotation) with a triple SU carburator setup using individual runners. Again, if you ran these triples to a plenum and then out to the runner, you could work up some power. ------------------ ---------- John Coffey johncof@veriomail.com [This message has been edited by John Coffey (edited 05-04-2000).]

Bryan Lampe and I are going to PIR for three days of track time May 12, 13, and 14. NASA Arizona region puts on a great event and their web site is http://www.nasa-az.com. Cost for all three days breaks down to: Friday or Saturday intro school (for those who have never driven at PIR): $175.00 Lapping in the Red (Novice) or Green (Advanced) classes: $125.00 per day Saturday or Sunday. Saturday night BBQ dinner: $15.00 You'll get four 1/2 hour sessions on Friday and four 20 minute sessions each day on Saturday and Sunday. You can do one, two, or all three days. ------------------ ---------- John Coffey johncof@veriomail.com

It you can get away with that much on the MTBE infested gas we have here in California, go for it. Remember, you want a total advance (mechanical and vacume) of 28 to 32 by 3,000 RPMs. Most of the folks I know run about 15 degress initial advance. ------------------ ---------- John Coffey johncof@veriomail.com

I'm not sure ('cuz I haven't done it myself) but I don't think you have to remove the crank. I think the flywheel has to come off and you might have to remove the last bearing cap, but I think the seal fits over the end of the crank. When all else fails, RTFM! ------------------ ---------- John Coffey johncof@veriomail.com [This message has been edited by John Coffey (edited 04-20-2000).]

Sorry, diff's not for sale anymore. ------------------ ---------- John Coffey johncof@veriomail.com

As the subject says, I'm selling the differential I took out of my 1970 Solo 2 BSP Z when I put in the Quaife. Its all setup and ready to bolt in. Lots of preload so it acts as a locked differential under power but freewheels while coasting. $500.00 and you get to pay shipping. I can deliver it pretty much anywhere in Southern California. ------------------ ---------- John Coffey johncof@veriomail.com