Specs: 4800lb 66 Electra, HEI conversion, new plugs (stock .035" gap), spiral core 9mm leads. Stock manifolds and cam, free flowing dual exhaust, 800cfm 1975 Q-Jet, switch pitch TH400 (manual switch), 3.07:1 rear gears, moderate weather, at or near sea level. I'm getting a ping when I floor it from normal road speed (35-40mph) in low stall. I don't get it when I floor it from a standing start and I don't have it when I'm near or at the top end so my initial or maximum advance isn't the problem. I use the best fuel and the highest octane boost I can find (5-7 points) so I don't think poor fuel quality as a reason. My guess is that I have a lean spot in the quadrajet in the mid level operation. My secondaries are set quite rich with a B Hanger and AX rods. My distributor is a brand new HEI conversion from Dave so that can't be the problem either. I have new plugs and new spiral core 9mm leads. What I notice is that the 401 loves a lot of initial advance and the more I give it the more it wants (at 12-13 degrees it's a completly different engine). I'm sure that I could run near 14-15 initial (mechanical) and it wouldn't complain. Of course it would be too high on the top end. Currently it's set to 10 degrees with 8 degrees of crane adjustable advance set to full manifold vacuum and in low stall if I plant it it really growls and takes off. The reason I don't think it's the advance is that at the revs it occurs (1600 - 2000 rpm) the advance weights wouldn't be all the way out yet (max advance is 2800) and the vacuum has just dropped right off because I've just floored it. The only thing I can think of is a lean condition caused by primary jest being too small. I don't know what they are because I'm loath to remove the main body as it's a brand new carb. It is a replacement 800cfm unit for a 76-79 Pontiac Big Block (so my research tells me) so I suspect that during those years lean tuning was all the rage. The problem is that my mechanic/'restorer guy' says he's never heard of such a condition as "Lean Ping" and he gets really upset when I keep mentioning it. He wants me to lower my initial timing and start driving more sensibly (who ever heard of such a thing!). Can someone please confirm that there is such a condition as pinging caused by too lean a mixture? I know a dyno and mixture sniffer would settle the condition but these dyno tests are really taking their toll on my wallet. Also, what size primary jets and rods should I have for a leadfoot in a heavy car? I know that this isn't a performance application but I get a real buzz out of going fast in a heavy car (anyone can go fast in a lightweight car - no offence to anyone in this forum - please). So, please help this crazy guy go fast with class.
I know its real. I had an intake manifold gasket that leaked on a dirtbike i had and the lean condition caused it to ping pretty bad. ________ APARTMENT FOR SALE PATTAYA
Thanks Jake, was your dirt bike a two or four stroke engine? Anyone else have any input on this condition?
This is my point Dave, I'm not sure if it is or not. The plugs are showing no signs of lean conditions. No whitness anywhere. In fact the front two on each bank are a bit blacker than the rear two on each bank. I just get this pinging in the midrange when I floor it from low speed in low stall (i.e. under extreme load). Can a lean condition cause a knocking in the engine? I'm trying to diagnose the knock. If it wasn't for the knock I'd say the carb was doing it's job perfectly. Good power - no hesitation, slightly rough idle occassionally (which you are dealing with in the other thread). I guess there is no way to really tell without putting a diagnostic 'sniffer' and running it through the dyno. I'd like to see how much your distributor has added anyway because it feels like an extra 10% to me - at least.
Wrong taper on the needle can give richness in many places, dead lean in others. I do believe a fuel curve analisis on a rolling road would be a good thing on this one.
I don't know abou the lean ping condition, but i do know that i wish BuickStreet would come over to the states and visit me in Idaho and tune the 401 in my GS for me....:Brow: :Brow: :laugh: :laugh:
Hey, I'm with you on that one. My first visit to the States was a doosy and I can't wait to come back. I'm not too sure how much of a tuner I am but I know that I've managed to squeeze a few extra horses out of this 'little' Nailhead - and I'm sure there are a few more to come. My Dual quad Offy intake arrived last night. I'd say that will cure any lean issues I'm battling :Brow: I'm saving my pennies for my next visit and if I'm in your neighbourhood I'll certainly drop in. Looks like a cool car you got there "Kid". Dave, I'll book a dyno tune.
Well.. Your offy's arrived in good shape, and with anyluck and the postal service, you should have the carters by next week.. :bglasses: I'd hate to see the faces on the locals when they see you comming with that setup.. LoL Humor me here and try this.. Take the allen wrench and turn the screw OUT a turn or two on the vac canister.. Go out and test.. And Lean Ping is a real thing... Tell them 'pros' they have more to learn.. :gt:
Ditch the dyno time, save your money. Ever see anybody drive a dyno around? Doesn't happen, and since both timing and jetting settings go artificially larger for dyno use, you don't need to waste time and money on that. You can go a lot farther by simple seat of the pants testing/changing. Leave all that dyno crap for the hero worship, OOH-AHH, Wow, Dude sect. If both carbs are aftermarket and have idle systems in both, you have to run the carbs straight on, not progressive linkage. This will make for a bit harder tuning, but should work out somewhat well. You may have to lean the mani jets and the idle size orifaces down to make the idle and low speed OK. Let's tackle the vacuum booster leakage issues first, then go for the carbs. Remember, you are in a place that is up-side-down to us here! (hahahahaha).
