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engine popping at idle and deceleration
https://www.slantsix.org/forum/viewtopic.php?t=24483		 Page 1 of 1
Author:  daveca5150 [ Wed Aug 15, 2007 6:20 pm ]
Post subject:  engine popping at idle and deceleration
I am finally getting it dialed in. I adjusted and re-adjusted the valves, set the ignition timing to 2.5 degrees advance, new long tip NGKs, new standard plug wires, I rebuilt the 1920 carb, and dissasembled and cleaned my distributor. It runs a heck of a lot better than it did before, but now I get a slight popping sound coming out the tail pipe during idle. It becomes even louder when I am coming down a hill with my foot of the gas. I checked the plugs and they are pretty white already (1 day). I'm thinking I'm running rich with the new jet that came in my Standard kit. It still has a bit of pulsation at idle and I can't get it to idle steady below 750 RPM. Also, when I tried giving it more advance, it idled a bit better, but the engine shook like crazy in 3rd gear and had no low end torque. It runs better with no advance or very little. Hmmm...
Author:  SlantSixDan [ Wed Aug 15, 2007 8:33 pm ]
Post subject: 
Firstly, what is "it"? Model, year, engine, transmission, emissions package.

Sounds like things are not quite right with your carb and/or timing (ignition and/or camshaft). What kind of Standard kit did you buy that contained a new main jet? Haven't seen a mass-market carb kit that contained a new main jet in many, many years. If it did in fact contain a new jet, what was the jet number?

White plugs do not indicate rich running, they indicate lean or proper running, depending on whether they're really white, or rather light tan/grey.
Author:  daveca5150 [ Wed Aug 15, 2007 10:40 pm ]
Post subject: 
Sorry, 63 valiant with the 225. My brain knew white spark plugs means lean, but my fingers typed rich :oops: Also, from working on my motorcycle, popping while decelerating can be another sign of running lean. The main jet that came with the kit was just whatever popped up on the computer at my parts store, it didn't actually come in the same package. I think it was a #54. I hope cam timing isn't out with my fresh engine rebuild, but it wouldn't be the first mistake the rebuilders made (wrong manifold studs, wrong balancer, cut through gasket kit). Is there a way of checking cam timing without removing the timing chain cover and thus the oil band and gaskets?
Author:  1974duster kev [ Wed Aug 15, 2007 10:54 pm ]
Post subject: 
I suspect your not talking of the same thing i'm about to mention but if it helps my car had a miss at idle just put a performance ignition on that went away. but i think your describing popping so i'm probably wrong actually i just was adjusting my valves for the second time in 2 days and i had a lil poppy miss on the left exhaust pipe which was one or all of the front 6 valves since i have dual exhaust i got rid of the miss(slight pop) but re adjusting valves again but now i've got other problems :(. Hope i may have helped


Kevin
Author:  DusterIdiot [ Thu Aug 16, 2007 6:47 am ]
Post subject:  Rejet and try again...
Quote:
I think it was a #54.
I have run into this problem on stock 60's Holley 1920's they were jetted with everything from 54-56... I found with my 67 valiant the stock jet was way too lean (and it will be very lean with the ZFRN plugs), up the jet size to 57 and see if it goes away, the 'max' jet size for the Holley 1920 should be no bigger than 58...

good luck,

-D. Idiot
Author:  daveca5150 [ Thu Aug 16, 2007 10:15 am ]
Post subject: 
I went with the advice of adjusting the valve to .022 exhaust and .008 intake. I'll try the larger jet, but could it also be my valve adjustment?
Author:  SlantSixDan [ Thu Aug 16, 2007 12:47 pm ]
Post subject: 
If your valves were set at 0.008" and 0.022" at anything less than full engine operating temperature, they're too tight. 0.008" is borderline too tight with some engines, even if set hot, and yes, too-tight valve adjustment can contribute to the symptoms you describe.

Unless you are at high altitude above sea level, a #54 jet is probably too small, as DI says.
Author:  daveca5150 [ Thu Aug 16, 2007 5:58 pm ]
Post subject: 
Ok, I'll set the intake valves to .010 and see if that helps. I did adjust them hot, but I had them on the tight side of .008. I went with a #56 jet because it was in stock. If it still seems a bit lean, I'll try a #57 but I'm afraid of losing gas milage.


Cheers!
Author:  DusterIdiot [ Thu Aug 16, 2007 7:58 pm ]
Post subject:  Yep..
Quote:
Ok, I'll set the intake valves to .010 and see if that helps. I did adjust them hot, but I had them on the tight side of .008. I went with a #56 jet because it was in stock. If it still seems a bit lean, I'll try a #57 but I'm afraid of losing gas milage.

Redo a good valve lash, the readjust the carb, 56 might be OK, if gas mileage suffers under a 57, go back to the 56...or it's time to mess with the timing curve a bit....but first things first...basics now, other tricks later...

-D.Idiot
Author:  Aggressive Ted [ Thu Aug 16, 2007 8:00 pm ]
Post subject: 
What has your mileage been with the #54 jet?

I have been running a #57 jet for about 6 months now. It is loads of fun and mileage isn't too bad either. No lean pops either.
Author:  daveca5150 [ Thu Aug 16, 2007 8:33 pm ]
Post subject: 
Ok, a 57 it is. I haven't had enough of a chance to drive with my 54 to get a gas milage reading Ted. Although I did manage to run it out of gas yesterday. I guess E really means E on this car :lol: Luckily I carry a cell phone and I have a nice wife to bring me gas.
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