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A locked timing may be okay for racing where you are mostly wide open but I think that you would want variable timing for the street. I know Webers like a lot of timing. I'm not sure about your engine, but for my stroked 427 FE I run 17 deg initial with 21 degrees advance for a total of 38 degrees. The advance comes all in by 2800 rpm. I believe that this will help your popping issue as well.
I have been told that exhaust popping comes from an exhaust leak for sure, but that it is also worse when leaner than when rich. If you are going lean when you decel this will make the problem more pronounced. A lean condition makes for a very poor wave front in the combustion chamber causing an inefficient burn and a fair amount of uburned gas to be left over. This unbured gas hits your hot headers and expoldes causing the pops. Your advanced timing when on the idle circuit (under hard decel with your foot off the pedal) will make the unburned gas issue even more pronounced. |
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UMMMM Deane This locked timing wont be helping in an over run or coast situation ( or even if you try to accelerate particularly if your down below 2500 RPM ). I must repeat that you are asking the carbs & motor to do something it doesnt want any part of ! :CRY: :CRY: :CRY: Jac Mac |
Shirley on the race track you would never be below 3- 3500 RPM?
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Also with 40mm chokes the airflow will fall well short of the heads capabilities on this motor. Jac Mac |
Pat: Dean it is the thread originator, who the hell is Shirley? And why is SHE on the race track? Who's on second:LOL: :LOL:
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Dean: If you are running fixed ignition of 32 degrees on the street you'll knock the ring lands out of the pistons. I've seen it done. Be very careful.
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I have my timing locked at 32 deg. That is correct, but only for the track. I have a switch to change ingnition systems to a computer that will advance the timing up a normal curve. I have another switch to retard total timing 3 degs. I was just trying to tune the race system. I will admit that I haven't tried running hard on the street timing system.
I did up my idle to 1000 rpms and I backed out my mixture screws to 7/8 out. The popping wasn't there. My engine will not idle as low as many due to the very light wieght rotating assembly. If the race idle is set at 1200 for the track, the idle falls below 900 when I flip the timing switch and go to the street system. I think that would be okay. I have ordered some 190 Air correctors and 180 mains just to see what happens. The popping has gotten a lot better, almost gone. I am still lean any time I am close to WOT. |
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the idle mixture screws almost always correct the popping problems. Dean, I would drop the air correctors first before I went up on the mains, this will affect the WOT the most and mid throttle the least.
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Well it is getting much better. However it is really lean from 3000 to 4500 under hard acceleration. It looks like the pump kicks in at 3000 and takes the A/F down until 3500 rpm's from a spike of 18 when the plates open to 14.5 then it looks like the pump shot is over and it goes back up to 18 then gradually back to 12.5 all the way to 6500rpms. It takes 5 seconds for this to happen from the throttle plate opening to get the A/F down to 12.5. It takes 2 seconds for the Pump shot, 1 second to climb back to 18 then 2 more seconds to come back down.
Here is how it was set up 70 idle jet 120 idle jet holder 170 main 210 air corrector f16 tubes .00 exhaust/ float bowl valve 40mm chokes 50 pump shot 380 ci 302 with 8.7 deck, Yates heads with huge CFM numbers. cam - solid roller dur. I 244, E 247 lift 631, 666 110 LCA 106.5 LSA It was way lean at the top end so I went to 190 air correctors and thats when it got the results that I described above. The car seems to run good but I need to fix the lean spot between 3000 and 4500. I was thinking about going to 180 mains and putting my 210 air correctors back in. Any other thoughts? __________________ |
Dean: Who is the maker of these pullies? Part #s?
http://www.clubcobra.com/photopost/d...tle_tight_.JPG Rick |
Rick, I don't know who makes the pulley. Call my engine builder, Lumpy. Reference the Kirkham cobra and he will tell you. 618 664 4767
After plenty of testing i feel like I am getting closer. I switched to an F7 tube and that really helped. My current setup is represented in the first post. I do notice the engine stumbling at around 2500 rpms. Any ideas? I can't really tell if it is lean or rich at this point. It is not popping, just not running smoothly. I tried smaller mains, 65 to 55 and the car was barely drivable. It runs great above 3000. Is this still idle jet holder territory? Remember this is at a constant speed. |
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