flatheadjim Posted July 8, 2009 Report Share Posted July 8, 2009 My 48 P15 has had the exhaust manifold split and Blue Streak Glasspacks installed for Mufflers, and when I use the engine backpressure to slow down on hills I get a lot of Afterfiring thru the pipes. Is this normal? Could it be a timing problem or maybe to rich of a fuel mixture? Hope it's nothing to worry about. The engine runs fine and makes decent power otherwise. Any comments? Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted July 8, 2009 Report Share Posted July 8, 2009 Do you have an exhaust leak in the manifold or where the pipe connects to the manifold. Such a leak will suck oxygen into the hot exhaust system and this oxygen will ignite any unburned fuel causing a bang ot two in the tailpipe. Quote Link to comment Share on other sites More sharing options...
flatheadjim Posted July 8, 2009 Author Report Share Posted July 8, 2009 I just replaced the exhaust manifold to tailpipe gaskets and everything looks good up against the block. I'm not talking about a few pops or bangs, this thing sounds like machine gun fire when I'm coming down a hill. It really sounds kinda cool but not at the expense of burned valves or whatnot. Everything is tight at the manifolds, all the noise is at the rear of the car. Late ingnition might be the culprit but at this time I can only static time my ignition until my 6 volt timing light arrives. I have it set at three degrees advanced right now, any other ideas? Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted July 9, 2009 Report Share Posted July 9, 2009 As long as your engine is not pinging nor running hot enjoy the sound of your glasspacks. Quote Link to comment Share on other sites More sharing options...
flatheadjim Posted September 2, 2009 Author Report Share Posted September 2, 2009 I removed my exhaust system from the Manifold back and had a shop redo the whole thing. I had dual pipes just running willi nilli under the car and way too many bends for my likes. Now I still have duals but there as straight as I could get them running side by side out the right rear. I reused the Bluestreak Muffs as they were in good shape. Now my engine does not Afterfire at all on down hill runs and sounds much better than before. I do belive that the system was sucking air somewhere as suggested and causing the popping. No more machinegun and A better tone. FYI. Flatheadjim Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted September 2, 2009 Report Share Posted September 2, 2009 lots of people have problem understanding the burning of fuel rich exhaust fumes in the exhaust system, all it needs is a tad of oxygen as the fuel and heat are already present.. glad you got it fixed..I like the rich sound of a throaty exhaust but the popping...does not add anything to the nature of the beast.. Quote Link to comment Share on other sites More sharing options...
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