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About distributorguy

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    Senior Member
  • Birthday 09/11/1970

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    Metropolis, MN
  • Cars
    77 Datsun 620, 73 Datsun 620
  • Interests
    Rebuilding classic vehicle distributors
    Racing Bonneville
  • Occupation
    Irish terrier wrangler

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  1. Carbureted vehicles don't like stoich. They like 13-14:1 at cruise, 12.5-13 at WOT. Keep in mind the gauge may be skewed as well, and you need to figure out that skew by tuning until it runs well and use those numbers as your baseline. I'd add some fuel. Starting hard when cold is indicative of being too lean.
  2. If your timing is set higher, the throttle blades can be closed more to reduce idle speed which in turn reduces run-on. The real fix for run-on is to fix all your vacuum leaks and richen the mixture. Its caused by hot spots, and fuel is a coolant. Your high speed stutter is caused by a lean condition, so I suspect you have vacuum leaks. Replace every rubber hose under the hood, check the throttle shaft for movement/wear, and disconnect and bypass the brake booster to make sure that's not leaking as well. Cap every port on the carb until it runs better, then work back in the pieces you need like the brake booster.
  3. Do you have a degree wheel? Shoot for an INtake lobe centerline of 106-109. Works well for most 4 cylinders.
  4. I do a lot of manufacturing for my business, and what I've found is that overseas contracts are only honored for 2 years. After that, the manufacturer will produce your parts, although with slight variations, and sell them to other companies so they can make more profit from your tooling. The real solution here is to only have components made overseas and assemble the parts locally so counterfeiting can't happen. Devices like th MSD 6A box became difficult to source for a while because the counterfeits were more plentiful than the real thing due to a decrease in sales, therefor inventory - all over a $30 price cut on the fakes which failed all the time and depleted MSD's service department. Aeromotive actually has a service bulletin on their logo so you can spot a fake easily.
  5. The biggest obstacle I see coming is the space for the transmission. A smaller trans like a T5 would be a better fit, but eliminating the clutch pedal will give you more room for your feet. I just got started running 3" exhaust on my 620, so I'm positive there is room for it if you get rid of the torsion bars. You will want to ceramic coat any pipe under the driver and passenger feet, to where the pipe starts its horizontal run or heat will become an issue. If you go witha front clip replacement, try to set it up so you can use 12" coil springs instead of 10". This opens up shock options to something soft enough to give a decent ride. We run soft adjustable shocks with a 10" spring to limit travel (severely lowered) and its "kidney belt rough."
  6. Yep, but you'd be stressing the coil. Test your wires. NGK used to make them with over 7000 Ohms on the shortest wire. If you got some that have been sitting on the shelf a while, you found the culprit.
  7. Because you want to measure ALL of your exhaust, I'd put it in the collector just above the horizontal plane, after the last 2 pipes join together. In that 4" or so piece of larger pipe. If you run the sensor too close to the engine, it'll fail prematurely. That's an Innovate issue. They sell an adapter to extend it out of the pipe if you're too close to the manifold. This is the same gauge we use in the race truck. I use an LM-1 (now LM-2) for portable tuning, along with their tailpipe clamp.
  8. When you install it, do yourself a favor and put the upper bolt in from the outside of the frame, tighten both of them down, and weld the other nut to the new idler arm bracket. Since you need to drop the steering to remove/install the engine, this makes the job a little easier.
  9. Your new plug wires are junk, or you didn't pull the boot back and fully insert the wire into the coil. Plug wires should be under 1000 Ohms per foot. A lot of new ones can range from 2500-5000+ Ohms per foot - junk. New NGK and a lot of the "build your own" wires use good low resistance wire. The only way to know is to test them with an Ohmmeter on the highest setting. 500 Ohms shows up as .5.
  10. Good modern rings use a stainless top ring, ultra-low tension, and about 1/4 the thickness of what you got in a Chev 327, Ford 289, or similar of the era. The 2nd ring is typically cast, oil control rings come in 2 varieties also ultra-low tension. With the quality of Datsun blocks, I'd be surprised if there was ever a ridge present with any amount of mileage, using any style pistons and rings. Its far more likely to see a gouge in the bore wall at the bottom of the stroke. Its not present until you give the cylinder walls a quick hone, and a dead spot appears on the passenger side of the bore from piston tip.
  11. 1. Adjust the float height and drop in your carb. This will help, as the fuel level determines how the emulsion tubes operate, and its CRITICAL. Google "weber float level" and look at the images section for a diagram of how and where to measure. Use a drill bit as a guide for height. 2. Try around 12 BTDC at idle for timing. 3. Where did you buy your new Weber? Not all are real Webers - some are pure crap that look the part but dont work, no matter what you do. Price is a good guide to good or bad. 4. The diaphragm in the carb is the power valve. It works backward from what it should, so if you can lock it from moving it will run better. At least you'll be able to tune your mixture better instead of going len on acceleration and rich on decel.
  12. The 8 mm bolt that holds the clamp to the distributor also has a slot, so there may also be a little more adjustment available there too. When you're at TDC, you should not only see what Mike shows above, but you can remove the 4 main oil pump bolts and drop the pump AND the drive spindle out the bottom. On the oil pump AND the spindle are a couple of staked marks (punch marks) that should line up. If they don, line them up and reinstall. This should provide the timing adjustment you need.
  13. Mechanical advance stops at around 3000 rpm because the dynamic compression of an engine only increase until about 4000 rpm (varies a lot with engine design) and it needs no further advance after 3000 -3500 psi or so. The factory rarely ever set the mechanical and vacuum advance to optimal for any vehicle. If they did, it was for their best performance vehicle (most expensive anyway.) Look at the small block Chevy as a good example. The lighter Camaro which was the first to receive the 350 could have been faster than the Corvette in '68, but they chose to dumb down the timing to make sure it wasn't or Corvette sales would have suffered when the first Vette owner got his doors blown off by a car $$$thousands$$$ cheaper. Trucks and station wagons were further de-tuned. The 620 got an advance curve that made torque, but went "over the top" with advance so horsepower would fall off and the usable rpm stayed a bit lower than was capable. This added durability and longevity to the engine by limiting the rpm range over years worth of use. The light pickup should never be as quick as a 240Z either, not that it could have been, but better timing may have made it faster off the line with its low gears. In later years, advance curves were used to pass emissions - starting in about 1970 changes started. By '74, most import cars had vacuum retard instead of advance to further clean tailpipe emissions and de-tune the engines. Then along came electronic ignitions and all those rules changed. Cars ran better, but not because of the electronics. It was because the timing curve rules changed.
  14. Turbos like 16-20 degrees at idle, then a short advance curve totalling 30-32 degres for a street engine. Our race motor is 13.7:1 (if I recall) and we run 29-32 total, depending on temp and altitude, 110 gas. Our base timing is 24. Ceramic chamber and piston coatings. Your turbo will be less temperamental to tune if you stay at 9:1 or less and have some quench with a closed chamber head. Hog out the plug-side of the chamber and unshroud the valves as much as possible on the quench side. Ceramic coating the pistons will give you significant detonation resistance. A stock A87 head only allows about 62% exhaust to intake flow ratio. Go up a size on exhaust valves and leave the intake stock. Focus on allowing the exhaust to breathe. Scooter's photo will allow for about 85-90% exhaust to intake flow and will go up to about 200 cfm on the intake side. WIth a turbo I'd shoot for about 85-86% exhaust flow since you;re suckingon the pipe. With a supercharger closer to 93%.
  15. The injector bosses barely fit in the 30 mm thick throttle bodies, spraying directly at the head's intake port behind the throttle plates. Given the ideal taper to the intake manifold, there's really no advantage to welding the ports into the manifold closer to the head. Work stalled, as the next step is to test fit the motor in the chassis again. Until I get the shop better organized, there's no way to get the engine hoist to the truck. Hopefully by the time this weekend's snow storm lets up, I'll have a chance to get that done and make the next series of steps forward. We've had some record snowfalls and record low temps this season. I can't wait to be sweating my butt off on the salt in August again.
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