Suspect Posted May 20, 2011 Report Share Posted May 20, 2011 I have a L16 with a dogleg 5 speed in my 73 620. Ever since I swapped this motor from my other 73 620, it just hasn't ran the same. I swapped everything, intake, exhaust, carb, all the wiring harness, coil, points, everything. The only difference is the 5 speed and the truck body. When I drive down the road, I can run 55mph fairly comfortably, when I try to reach highway speeds or take on any hill, it just won't pickup. I've messed with the timing and points, and got no where. I also took apart the carb, cleaned all the jets, This motor in my other truck would run out of gear with the speedometer pegged (had someone sideswipe me on the highway and I ran them down). I can usually figure this out but I just don't know. Quote Link to comment
herculesinwyoming Posted May 20, 2011 Report Share Posted May 20, 2011 dirrerent gear ratio in the rear diff maybe? Quote Link to comment
68Datsun510 Posted May 20, 2011 Report Share Posted May 20, 2011 Diff tranny ratios too, and are you getting full power to the coil? Quote Link to comment
datzenmike Posted May 20, 2011 Report Share Posted May 20, 2011 Are you trying to do this in 5th gear? 5th isn't for carrying heavy loads, accelerating, passing or climbing grades... always downshift to 4th. The dogleg has slightly lower ratios 1 through 3 and is the same as the 510 sedan 4 speed but with an overdrive 5th gear. It won't accelerate as fast as the original 4 speed but will be identical in 4th. All 4th gears are the same 1 to 1 in all trannys. Quote Link to comment
Suspect Posted May 20, 2011 Author Report Share Posted May 20, 2011 It seems doggy in all gears. 1st and 2nd, if you rev the piss out of it, it seems almost normal. 3rd gear and above it just won't go, hills especially. I can hit the bottom of a medium hill at 65mph and kick it down to 4th and it will lose speed down into 3rd and still keep losing speed. It struggles to keep 40 on a hill. This same hill in the other truck, I would enter the hill at 60mph, put it on the floor and pick up to 75 by the top. On the highway, there is a steady barely noticable hill and it struggles to stay above 50. Its weird, maybe my motor is just getting too tired, has over 300k on it. I might make a video of how it is to kinda give an idea of what its doing. Quote Link to comment
datzenmike Posted May 20, 2011 Report Share Posted May 20, 2011 Well you'd better go through it. Check confirm timing Check plugs. Are they white? A sign of running lean. Quote Link to comment
D52E Posted May 20, 2011 Report Share Posted May 20, 2011 Possible items to look at: Restricted exhaust bad tank of fuel Camshaft timing off Quote Link to comment
DISLEXICDIME Posted May 21, 2011 Report Share Posted May 21, 2011 Gear. Ratio and tire size? Disconect the y pipe get some ear plugs and go for a test drive. Make sure the fuel pump is not weaping . Quote Link to comment
DISLEXICDIME Posted May 21, 2011 Report Share Posted May 21, 2011 I wonder if yout t chain stretched in the accident. Is the vac avance working you could have a cracked or sticking advance weight Quote Link to comment
Suspect Posted May 21, 2011 Author Report Share Posted May 21, 2011 The sideswipe wasn't that bad, not bad enough to cause any damage. I drove the old 620 for a couple years after that and it was fine. I've had every fuel line off and made sure it was clean, from carb to taking out the tank. I didn't find anything wrong there. I took apart the reman carb and found a little dirt but not bad at all. As for the exhaust, it has 2.5" with a glass pack, don't see any possible problem there. My guess its either bad plugs, wires, or points. the vacuum advance works. Quote Link to comment
Suspect Posted May 25, 2011 Author Report Share Posted May 25, 2011 Its started to run a little better but still not what it used to be... Yesterday I pulled the carb and put a secondary jet into the primary. It seems even better yet but I still think I have a timing issues or something. I do have a few more motors, lots of L16 used short blocks, complete L18, and two complete L20bs, I might swap in a L20b. Another question... the carb on my L16 is an older carb, I believe its a 69 510 carb with a manual choke. It is quite a bit smaller barrel bore size. Can you swap the small bore bottom of the carb to the larger one off a L20b? Quote Link to comment
DAT510 Posted May 25, 2011 Report Share Posted May 25, 2011 i dont have any clue as to where the problem might be, but im just going to throw this out there, maybe fuel pressure? if you put another jet in the carb and it got better, it has to do something with the fuel or carb Quote Link to comment
datzenmike Posted May 25, 2011 Report Share Posted May 25, 2011 Swap another carb on it. Quote Link to comment
dacaulker Posted May 25, 2011 Report Share Posted May 25, 2011 I'd go weber and pertronix, call her done... Quote Link to comment
Suspect Posted May 25, 2011 Author Report Share Posted May 25, 2011 I had a L20b carb on it and I didn't get to test it much... it had an air leak in the plastic base and ran bad. I was going to try it without the base but I've been too busy driving it. The carb on my truck was one I bought re manufactured, only been using it a couple years. Quote Link to comment
dacaulker Posted May 25, 2011 Report Share Posted May 25, 2011 I gave up on those carbs. nuthin but problems. Use a vac gauge and make sure you have good pressure when you tune. after your done pulling your hair out out, look at getting a Weber 32/36 is very versatile. and will work on any Lmotor(if jetted correctly). I also got rid of those temperamental points and went electronic.They will usually solve any ignition issues. also gives you a hotter spark and better ignition. With the simple Pertronix unit you use your stock coil(make sure it's good) and distributor. Quote Link to comment
hoopty Posted May 26, 2011 Report Share Posted May 26, 2011 Can I get an AYMEN to a 32/36 with an electronic dizzy? AYMEN is right! If you have room in your budget do yourself a favor and take the easy way out... you'll save yourself the time and the headache. Quote Link to comment
Suspect Posted May 26, 2011 Author Report Share Posted May 26, 2011 Can I get an AYMEN to a 32/36 with an electronic dizzy? AYMEN is right! If you have room in your budget do yourself a favor and take the easy way out... you'll save yourself the time and the headache. I've been driving these trucks with stock carbs and point distributors for years, most of the problems I've had were to do with the points being cheap now days and not lasting long. I did have a short in the distributor once. I usually ran the vacuum advanced unhooked and this is the first time I have it hooked up. I'm about to unhook it and see if that helps. I do have a brand new Weber 38/38, cannon intake, and long tube header just waiting to be put on my LZ motor..... Quote Link to comment
banzai510(hainz) Posted May 27, 2011 Report Share Posted May 27, 2011 points wear out fast if you have the incorrect coil in there. Point coils are about 1.6 ohm with a 1.6 ohm ballast. Or close to it on both. Dizzy bushing wear will also kill performance Ck cam timming(timming light) and electrical timming(timming light) incase your off a tooth on oilpaump shaft. Quote Link to comment
dacaulker Posted May 27, 2011 Report Share Posted May 27, 2011 Yeah, I had a 38 on mine at first but it was just to rich (was installed on a stock 1600). Ended up back at the smaller 32/36. It gets better mpg and has plenty of power on demand. Good luck let us know if it fixes your issues.... Quote Link to comment
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