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About distributorguy

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    Senior Member
  • Birthday 09/11/1970

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  • Location
    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. distributorguy

    Engine dieselling ??

    The better solution is to tune away the problem before it leaves you with burned valves. Turning your gas motor into a diesel clearly is a sign of a problem. I find that if your idle mixture screws are set betweeen 3/4 - 1 1/2 turns out when slow idling (under 650 rpm), then you can actually tune the entire range more precisely. Some people will push the idle up to 800+ then tune the mixture, but what you're really tuning at that point is the emulsions tubes. This becomes problematic when you get higher in the rpm range and are trying to get your mains and air correctors properly tuned. You'll tend to go lean more easily - in a difficult way to control - because you've been falsely bolstering the main jets with the idle jets. The ratio is inconsistent, so you "run out" of emulsion tubes and the mixture shifts lean where it shouldn't.
  2. distributorguy

    Engine dieselling ??

    Most of the time, a lean condition is due to vacuum leaks from loose fitting vacuum hoses, loose hardware, bad gaskets, blown vac unit on the distributor, failed check valve on the brake master, etc... Re-jetting lean is also a cause, along with the float height being set too low. Good job fixing it. What did you change?
  3. distributorguy

    Clutch and Flywheel Combo

    We simply use a stock clutch in the Bonneville race truck. It works. We're real close to 200 hp at the wheels. If you find you need mroe grabbing poer, you can have the flywheel step-ground to allow more clamping force. Have an extra .010" shaved off of the surface area where the pressure plate bolts down, outside of the area where the disc lies. Make sure to balance the pressure plate with the flywheel. It only takes once to learn that a clutch imbalance is possible, and extremely unpleasant. Obviously Mike has been lucky so far. It only costs around $10 extra when balancing the flywheel.
  4. distributorguy

    Big Cam????

    No stock head can breathe properly at those lift numbers. Not even in the ballpark. Our full race cam is a little bigger than that, and it required not only a full custom valvetrain to get the geometry correct, it requires different springs and about 100 hours of flow bench work to port it enough to utilize the cam. Literally 2 red Solo cups full of material removed from the ports. That cam wants 12:1 compression or higher to help make up for the drastic overlap at 314 duration. Your cylinder cranking cylinder pressures are what? 110 psi? That'll never draw fuel from the Webers appropriately. The turbulence at 4k will also cause what you're experiencing. Can it be made streetable? Maybe with a custom distributor, and some severe carb rejetting.
  5. distributorguy

    Engine dieselling ??

    If you can run moore initial advance (like 14-16), you can close the throttle plate a little more and reduce dieseling. Lean fuel mixture also causes it, so try setting the idle mixture up more rich - with a little lope to the idle. Also make 1000% sure there are no manifold leaks as the smallest vacuum leak can cause hot spots and run-on.
  6. distributorguy

    Carb advice for 620 w/ L20b

    I hate the argument of a carb being "too big." It always comes from people who have never tried it, yet like to recite crap they read on the internet. On a 620, I've run the DGV, DCOEs, 1 1/2" SUs, 1 3/4" SUs, and 2" SUs. The best drivability on a stock compression engine was the 1 3/4", which is similar in size to running dual 45DCOEs in terms of effective cross section of the throttle plates when wide open. Drivability is great on almost ALL carbs, once they are tuned. Some are easier to tune than others. SUs win that battle. Weber DCOEs lose as the most difficult to tune of all carbs, although persistence can result in an exceptional running vehicle at ALL rpms. Our race truck idles smoothly at 500 rpms with 14:1 compression and launches like a rocket with dual 50DCOEs - when tuned properly. WIth a stock motor the 1 1/2" SUs were great, but it ran out of steam earlier in the rpm band (carbs too small). The bigger the carbs, the higher you can rev. Most people don't have the guts to go past 7k. We go past 10k. 💀
  7. distributorguy

    Carb advice for 620 w/ L20b

    You have the common 1 1/2" carbs. Basically 36/36, which are properly sized for a 1.8 - 2L engine. They are the right size for the motor. In fact the 1 3/4" version are the performance ones. Your choke tubes are worn out, and they are included in the rebuild kit. They need a rebuild. Period. Call Jeff Palya at Paltech regarding the rebuild. Its the easy way to go.
  8. distributorguy

    Carb advice for 620 w/ L20b

    From my experience, the 38/38 with a manual transmission on a 2L engine is a good solution, but takes additional tuning FAR beyond the sub-$400 price tag. If you think the SUs are hard to tune, the 38/38 confronts you with a far more significant learning curve. The 32/36 is used on any 4 cylinder from a 998 cc Mini up to a 2.4L Ford. One size fits all? There's no such thing. I think its too small for anything bigger than 1500 cc if you're looking for drivability more than economy. If you want easy, learn to tune your worn carbs and call it good. Personally I'll take the old SUs over HIFs any day. The fuel bowl and floats are accessible at all times - which helps diagnose drivability issues when they arise, plus they are further away from the exhaust.
  9. distributorguy

    Carb advice for 620 w/ L20b

    You will never get the truck to run as well with a DGV or DCOE as it will with SUs. They are very simple, and a re-bush job with rebuild kits that you can install are cheaper than buying a DCOE setup. Or call any one of the pros who can rebuild them, such as Joe Curto (.com), Z-therapy, Paltech, etc... Its worth the money and time to rebuild them.
  10. distributorguy

    What lowering blocks?

    You don't flip them over. You get a spring shop to make a new top spring, and they fold the bushing eyes the other way so that it lowers the truck. Depending on how much you want to lower the truck with the spring, they can make the spring shorter in length, so that the rear shackle still has room to function, rather than resting against the frame. You can't completely change the direction of arch without making the spring wavy and weak. In the end, you can go lower yet with blocks if you wish, but you'll have to C-notch the frame as the springs alone can nearly run you out of room for suspension travel if you go far enough.
  11. distributorguy

    What lowering blocks?

    If you buy the "better" lowering blocks, they are cut with a taper to correct angle changes. 👍
  12. distributorguy

    New user, new car, super excited

    Gorgeous! As for tuning, take an Ohm meter to those plug wires. You want lower than 5000 Ohms, and those older NGKs run 7000+. Run non-resistor spark plugs and low resistance plug wires.
  13. distributorguy

    What lowering blocks?

    Didn't say that. I'm saying I sorted through it and check pinion angle, which did not change throughout raising or lowering the the rear end, or when I lifted the huge "kink" out of the center of the driveshaft. Normally the carrier bearing is supposed to reduce the driveline angle by half. If you can place it in a position to reduce all U-joint angles, its doing its job. My worst U-joint angle is 2 degrees from straight. No vibration on the chassis dyno at 204 mph. I'd say that's proof enough that we're in good shape. And yes, I "eyeballled" it - with a 4' construction level and a cheap magnetic angle finder from China Tool (aka Harbor freight.) My whole point is that the pinion angle was correct to start, and it didn't change throughout the process.
  14. distributorguy

    What lowering blocks?

    There's nothing blind about raising the center/carrier bearing on the driveshaft when you raise the rear axle. Its line-of-sight. Since the truck can't axle-wrap, you have 3 degrees (or more) of flex in where the pinion angle can land. In essence, since you're not changing the pinion angle by raising the axle (moving it in a parallel plane) you shouldn't even have to check it. The driveshaft will however "dip" in the center if you don't raise the carrier bearing, putting more stress on the U-joints. Duax was right about that. Our race truck drivehsaft sits level, and we had to raise the carrier bearing 1" to do that, using custom springs and 1 1/2" blocks.
  15. distributorguy

    What lowering blocks?

    I'd have to guess when you raised your truck by going axle-under-springs you didn't have straps around the springs. That would have eliminated most of your axle wrap by using ALL of the springs as a traction bar, instead of only the shortest ones. Normally, only the front of the springs would be strapped, but the rear is where you'll experience lift issues and axle wrap with the axle under the springs. My truck has close to 200 hp at the wheels and with a rebuilt spring pack I have no discernable axle wrap. If I did, I'd build the caltrac style traction bars Duax posted above, as that setup actually increases downforce at the rear wheels by utilizing axle wrap to add traction.

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