The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

64stpside · 05-10-2016, 08:59 AM

lol........guys......I had #6 & #8 plug wires swapped at the distributor!!! Could have sworn I had it right before. I do have another question that's been beat to death. I had it on manifold vacuum and was told to change to ported. When I did that I could NOT get rid of the black smoke not matter what. I even had the mixture screws out only 1 turn. Set the initial timing at 4 to start then to 6 and it's at 8 now and that didn't help. I know I've been told to crank it up but have also been told that due to no egr vale, I will get pinging due to no exhaust gas to cool the charge.My understanding is that ported was done for emissions.......period......but makes the motor run like crap. My question is, if you have a carb issue, will going to manifold vacuum cover up the symptoms? I want to make sure my carb is right and I not using manifold vacuum to make things work.
Regardless of my carb being an issue, I'm going back to manifold vacuum tonight unless someone can give me a reason not to.

From another site about ported vs manifold from a GM engineer:

......(regarding ported vac) "This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it."

05-10-2016, 08:59 AM	#13
64stpside Registered User Join Date: Aug 2015 Location: old hickory, tn Posts: 144	Re: My 64 needs your help..... lol........guys......I had #6 & #8 plug wires swapped at the distributor!!! Could have sworn I had it right before. I do have another question that's been beat to death. I had it on manifold vacuum and was told to change to ported. When I did that I could NOT get rid of the black smoke not matter what. I even had the mixture screws out only 1 turn. Set the initial timing at 4 to start then to 6 and it's at 8 now and that didn't help. I know I've been told to crank it up but have also been told that due to no egr vale, I will get pinging due to no exhaust gas to cool the charge.My understanding is that ported was done for emissions.......period......but makes the motor run like crap. My question is, if you have a carb issue, will going to manifold vacuum cover up the symptoms? I want to make sure my carb is right and I not using manifold vacuum to make things work. Regardless of my carb being an issue, I'm going back to manifold vacuum tonight unless someone can give me a reason not to. From another site about ported vs manifold from a GM engineer: ......(regarding ported vac) "This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it."