Forces Posted February 2, 2007 Share Posted February 2, 2007 When I starat my car cold, it will crank and crank and crank....then it'll fire a few cylindars....more cranking....engine starts finally and runs rough. I drove it around while it was still cold, had been running for about 5 minutes, and if I stab the thottle at all, it backfires through the carb and dies. Once I get it started and warmed up it seemes to run okay, good throttle response at least. I figure it's a/f ratrio is off, timing is off, or both. Any suggestions? Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted February 2, 2007 Share Posted February 2, 2007 I really need to know more, like what kind of dist. do you run? What induction are you running? Etc. Sounds like timming is to retarded to me, but need more info in order to help. Give me a run down on what you are running? John Quote Link to comment Share on other sites More sharing options...
GEMINITWIN111 Posted February 2, 2007 Share Posted February 2, 2007 ^^^agreed Need More Info.may Be A Little Lean. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 2, 2007 Author Share Posted February 2, 2007 Sorry, didn't realize I forgot the basics... 383 small block chev. HEI ign w/ summit brand dist., Edlebrock 750 Manual choke spread bore carb. I fired it up again, same thing. Once it gets hot it runs smooth, but getting there is a battle. It won't idle under about 1300 RPM without shaking the car off it's wheels, but I figure that's just cause the rings aren't set. The engine literally has about 2 miles on it, if that. I'm gonna weld some O2 bungs in for a wide band, but I gotta DRIVE it to my buddy's house in order to do that, and the Z is in no condition to leave the garage, let alone the neighborhood. Quote Link to comment Share on other sites More sharing options...
Paz8 Posted February 2, 2007 Share Posted February 2, 2007 Is the choke connected and working? Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted February 2, 2007 Share Posted February 2, 2007 A few things to check: vacuum leaks will cause high idle, when it gets hot it might be closing the leak. Timming needs to be checked, could be to much retard. Check the valve adjustment, you did not state hyd., solid, roller. I tend to think it is a vacuum leak / timming. John Quote Link to comment Share on other sites More sharing options...
endurorider Posted February 2, 2007 Share Posted February 2, 2007 Sounds like vaccum. spray some brake clean around the carb base plate and intake and see if it smooths out. Just don't catch it on fire. stay away from the ignition. Put a vaccum gauge and see if it is low or the needle is fluctating fast. cover your hand over the carb to make it go rich and see if it cleans up. check you inital timing with a timing light. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 2, 2007 Author Share Posted February 2, 2007 Tappet cam, hydrolic lifters, solid non-roller rockers. I don't HEAR any vacuum leaks, but that doesn't say much. What is a good place to set the timing at? I have it at 10 degrees advacnced now. Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 2, 2007 Share Posted February 2, 2007 A fresh motor, if timing and fuel are close, should fire up and run within 5 revolutions. If it doesn't start and run smoothly, then something is wrong. Check for vacuum leaks (like the brake booster hose you may have forgotten) and also check to see where your static ignition timing is set. If the choke is not working, it will generally run like crap cold...but should clear up within about 20 seconds or so on a well tuned motor. Set your timing at about 10 degrees (good starting point). Does pumping the throttle a couple times during cranking help the cold starting situation or not? Are you running a mechanical fuel pump or electric fuel pump? Do you have your vacuum advance hooked up to manifold vacuum or ported vacuum. Quote Link to comment Share on other sites More sharing options...
Michael Posted February 3, 2007 Share Posted February 3, 2007 Mine had similar problems (454, stock HEI, 750 vacuum Holley on a Edelbrock Perf rpm, choke mechanism removed, moderately healthy mechanical roller cam). First it ran OK, then on successive attempts (days, weeks) it would run worse and worse. Then I realized that the distributor hold-down bolt was not completely tightened, and over time the distributor had rotated counterclockwise! Not sure about vacuum leaks in my case, butI did observe that if I blocked the carb venturis with my hands - even slightly - the engine would cough and sputter; if anything, it was starving for fuel. And when cold, it would need 1-2 minutes of ~1500-2000 rpm operation before it could settle into a stable idle. Once settled, it idled fine at 800 rpm. Fuel leaks from the venturis at idle (incorrect float level). My next step, since parts of the combo are definitely weak links, is upgrades; capacitive discharge ignition system and aftermarket distributor, 850 CFM mechanical-secondary carb (probably Barry Grant mighty-demon). I'm looking at a system that could communicate with manifold vacuum (below the throttle blades, not above) with dial-back. But this is for a fairly aggressive engine; if yours is more mainstream, then throwing money at it is probably an ill-advised solution (as, indeed, in may also be in my case...) Quote Link to comment Share on other sites More sharing options...
Forces Posted February 3, 2007 Author Share Posted February 3, 2007 I haven't adjusted the choke, it's hooked up, but set to what ever it is out of the box. It's a 750cfm Edlebrock manual choke. That could very well be PART of the problem. I know that the air fuel screws were turned ALL th WAY out from the box....it ran really bad then. I have the fuel pressure set to 6.5 PSI, per edlebrock's suggestion. Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 3, 2007 Share Posted February 3, 2007 Spin the mixure screws all the way in, then back them out 2 full turns. It doesn't seem to matter what engine or what carb, that is always a good starting point. If its a manual choke carb, it can't very well come pre-adjusted out of the box. Make sure that the choke is open when the control is open, and closed when the control is closed. you'll need to open the choke gradually for the first minute or two of running the motor, or you'll have an engine that runs like crap. With the engine stone cold, try this: leave the choke open, pump the throttle 3 times, and with your foot applying about 15% throttle, the engine should light off within 5 revolutions. If it doesn't, but it still cranks strong, your ignition timing is retarded. Kick it up a bit and try it again....without all the pumps. Fuel pressure looks good. The only thing I can think of that may not be right, if everything else is, if the float level in the carb, but edlebrock should have set that correctly. It might also be a good idea, once you get it started, to let it idle for a couple minutes and then shut it off and pull a plug. If its black, you know you have plenty or too much fuel. If its white, you have not enough fuel (or too much air...vacuum leak), if its a tan or brown, you are doing fine....and should go after timing. Also, see if you can get your hands on a vacuum gauge. Manifold vacuum (measured below the throttle plates) should be 20 in/hg or better with a mild cam. Long duration cams will have lower vacuum readings. Quote Link to comment Share on other sites More sharing options...
endurorider Posted February 4, 2007 Share Posted February 4, 2007 Once you get it running long enough. at idle block off the secondarys to make sure your not pulling air with them closed. make sure your pcv valve is intact. remove it with the engine off and shack it and listen to see if it rattles. Just had a honda in the shop the other day that would not idle and failed smog at a test only . pcv had no insides. well it had a bad cat gross polluted for nox, but that was not the drivability problem. The easy test is when its cold just block off the carb with your hand partly and see if idle smooths out and picks up speed, thats telling you your to lean and you most likey have a vaccum leak. You say it runs fine once it warms up? Quote Link to comment Share on other sites More sharing options...
Forces Posted February 6, 2007 Author Share Posted February 6, 2007 Spin the mixure screws all the way in, then back them out 2 full turns. It doesn't seem to matter what engine or what carb, that is always a good starting point. If its a manual choke carb, it can't very well come pre-adjusted out of the box. Make sure that the choke is open when the control is open, and closed when the control is closed. you'll need to open the choke gradually for the first minute or two of running the motor, or you'll have an engine that runs like crap. With the engine stone cold, try this: leave the choke open, pump the throttle 3 times, and with your foot applying about 15% throttle, the engine should light off within 5 revolutions. If it doesn't, but it still cranks strong, your ignition timing is retarded. Kick it up a bit and try it again....without all the pumps. Fuel pressure looks good. The only thing I can think of that may not be right, if everything else is, if the float level in the carb, but edlebrock should have set that correctly. It might also be a good idea, once you get it started, to let it idle for a couple minutes and then shut it off and pull a plug. If its black, you know you have plenty or too much fuel. If its white, you have not enough fuel (or too much air...vacuum leak), if its a tan or brown, you are doing fine....and should go after timing. Also, see if you can get your hands on a vacuum gauge. Manifold vacuum (measured below the throttle plates) should be 20 in/hg or better with a mild cam. Long duration cams will have lower vacuum readings. I tried that, and it fired up a whole lot easier. 3 pumps w/ choke off. fired up with choke on. I advanced the timing to about 20, and that got rid of a lot of the backfiring...still doesn't run quite as smooth as I would like it to though. Just to see how the engine would respond, after it was at opperating temp, I put the choke on at idle, and it killed it. I am a little worried now, I heard something knocking. Sounded like the valves chattering a little. It wasn't very loud but enough to concern me. It probably wouldn't be a bad idea to check 'em anyway. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 14, 2007 Author Share Posted February 14, 2007 I Set the A/F at 14.6:1, and advanced the timing to 14 degrees, vacuum off. There are no vacuum leaks. Idle is set at ~1000, and It is still backfiring like crazy when it's cold, and when it's under a load when I get on it a little. If I floor it, it sputters out and wants to die. Something isn't right, the car doesn't have near the power that it should have. The back firring is coming out of the exhaust, and it's LOUD, must sound like a drive by shooting when I'm cruising in my neighborhood......I'm thinking the edlebrock carb is junk (although it is BRAND NEW!). I have heard that the holley is a much more streetable carb, and easier to adjust. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted February 14, 2007 Share Posted February 14, 2007 I may be way off here, but I've seen too many problems blamed on fuel that were actually ignition/timing related... Even down to a couple plug wires reversed/ in the wrong. OR (this one has plauged me TWICE now..) a bad coil, or coil-dizzy wire. I had an old truck that would do the shot gun backfire out the tail pipe, seamingly out of the blue.. (quite a sound isn't it!) It took me getting a HUGE shock on my finger to figure out the main coil wire was grounding out (small crack in the boot I discoverdd with the motor running, and checking the plug wires.. ) When I floored it and the motor torqued over, it moved just enough. My Z also did this when the coil quit (stock 75) and I messed with the carbs for days... replaced coil, and it was god again. ALSO.. my buddy's 454 dualy had THE SAME problem... with a brand new coil that 'went bad' for some reason.. ? Oh.. here's a thought too, are you SURE the dizzy is lined up right? Obviously 180* out is a no brainer, and it won't run worth crap, but I've had them out by a few teeth and it will cause the backfire/bog you describe. You can try rotating the plug wires on the dizzy around one position, then turning the dizzy back slightly. (theory here is if the firing order is off, and you're out of rotation on the dizzy, it gives you more rotation to get in into proper timing) You'll be able to tell pretty quick if this is the case. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 14, 2007 Author Share Posted February 14, 2007 hmmm. I suppose that could be the issue...I AM running a summit brand HEI dist. Never have cared for summit brand stuff, one day I will learn my lesson on trying to save money on cheaper parts. This is a stupid question, but I have to ask...I am somewhat familiar with the HEI, and some ignitions. The coil, on a SBF is eay to point out, but as far as an HEI, There is the desi., the rotor, the plug wires, and vacuum advance. When you say 'coil', are you refering to the rotor?? Quote Link to comment Share on other sites More sharing options...
gvincent Posted February 14, 2007 Share Posted February 14, 2007 The "coil" in a HEI distributor is in the Cap top. There is an insulator rubber piece and a spring and center pin conductor that has to touch the rotor, the pin should move up and down with the spring. Remove the top of the distributor cap and check that the rubber insulator is there and that the spring and pin move up and down easily. Some electrical gel is usually used to coat the insulator. Greg Quote Link to comment Share on other sites More sharing options...
Forces Posted February 15, 2007 Author Share Posted February 15, 2007 I checked the coil, its fine. Let me elaborate on the issue here. I have a 750 CFM manual choke carb, #1407. it is on..... SBC 383 stroker w/ forged flat top, dual valve relief pistons Airgap intake 66 cc RPM perfoormer heads w/ 1.5 rockers HEI vacuum advance distributor Here is the problem.... Very hard cold starts, will not start with choke shut. I should note, that it does start a little better, no much, but a little better with the choke 80% closed. Once running at operating temp (and it's a battle getting there, believe me), it spits and supters, and BACK FIRES like crazy. With the glass packs, it makes it pretty damn noticable. It is advanced to 14 degrees, vacuum off. No vacuum leaks. When I stab the throttle in nuetral, vroom vroom. at idle in nuetral 0% thorttle rrrrrrrr....pop pop..rrrrrrrrrrr. pop. When it's under a load, its a whole new ball game. Idle drops from 1000 to about 800, which I assume to be normal. A few things happen a part throttle that are not desireable. 1. AFR goes pig rich at 10:1 (set to 14.6 at idle) 2. More backfiring, not as bad, but still not acceptable 3. The thing is a DOG. If I stab it in gear, it backfires through the carb, or just bogs down and trys to die, unless I lay off the throttle. It's got no power. Now I have read that the secondaries only open up when under a load with edelbrock carbs. This leads me to believe that there is a problem with the secondaries. The fact that it has such a hard time starting leads me to believe that there is a problem with the choke...duh. I just don't know where to start looking in the carb to hunt these issues down. The only things I have adjusted are the AFR screws, the idle speed, and Choke Idle speed. *EDIT* I have done a good amount of reading about edelbrock carbs, and have not found ONE SINGLE SHREAD of positive feedback about the EDL 1407. Not user friendly, dyno tested to kill power, everyone who buys onbe has to re-jet it right opff the bat. Anyone want to buy a 750 cfm performer series edelbrock? Beat your head against the wall if your considering it. Quote Link to comment Share on other sites More sharing options...
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