| What are the telltale signs of a restricted exhaust [message #264509] |
Sun, 19 October 2014 16:10  |
budworks521
Messages: 137
Registered: October 2013
Location: Grand Rapids MI 1974 Pain...
Karma: 4
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Another sad story after supposedly fixing my issue. I was wondering if anyone ever experienced a steady reading of 18 inches of vacuum for a minute or so and then the gauge slowly descends to zero and the engine shuts down?? My vacuum gauge has notes that state a restricted exhaust. I had no problems with the engine two weeks ago after finally eliminating my carb from flooding. Now I can't keep it running? My number 7 plug looked gassy. All the others burned fine. Sounds great until until the engine stumbles. My exhaust looks sketchy. New mufflers might be in order??? Thanks for any insight.
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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| Re: What are the telltale signs of a restricted exhaust [message #264514 is a reply to message #264509] |
Sun, 19 October 2014 17:30  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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If it is that restricted, it should only take a few seconds to build back pressure to the point of killing the engine. Not a few minuites. In that first minuite where it runs does it respond to throttle normally? Running out of fuel delivery would also cause vacuum to reach equilbrium with atmosphere as no pumping action.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: What are the telltale signs of a restricted exhaust [message #264537 is a reply to message #264509] |
Sun, 19 October 2014 21:31 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Normally, even at idle, if you put your hand in front of the tailpipe exit, you can feel distinct pulses. If the exhaust is restricted, the flow will seem steadier, and also very weak. A very slight breeze instead of distinct puffs.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: What are the telltale signs of a restricted exhaust [message #264540 is a reply to message #264509] |
Sun, 19 October 2014 21:43 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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I think I agree with John L. IMMEDIATELY after it dies, if you pump the gas, do you see it squirt into the carb primaries? If not, you have a fuel delivery problem. If you see gas then it's something else. I'd doubt it's plugged exhaust for the reason John mentioned. Plus it'd probably still run somewhat if one muffler was plugged. What would cause both to be plugged at once? That said, I'd lean down and check for a crushed tailpipe somewhere.
An old mechanics trick is to tape (or wire) a piece of toilet paper over the tailpipe and watch for fluctuations in movement. You can spot misfires pretty easy.
Is your choke on too much and causing an over rich stall?
I had a catalytic converter get plugged on a 2001 GMC pickup. Would NOT go over 50 mph. Got louder but would not go faster. Drivers side cat was plugged. Not a rare problem as it turns out. Mufflers are harder to become plugged than cats.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: What are the telltale signs of a restricted exhaust [message #264562 is a reply to message #264509] |
Mon, 20 October 2014 08:20 |
budworks521
Messages: 137
Registered: October 2013
Location: Grand Rapids MI 1974 Pain...
Karma: 4
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I still need to get my choke to open fully either with an electric choke or "farmer's choke" I did dial back the fuel mixture to spec and it was running fine two weeks ago. This issue is a new issue after I supposedly solved my carb flooding a bit (vapor canister line or container being plugged) I got it running and it stopped flooding at the accelerator pump area. All of these issue seem to be on the same side (driver's side) Maybe my exhaust was bad all along and it finally gave up. I didn't have a fuel problem two weeks ago. My tanks are at 1/4 full though. It is not miss firing either. If I pulled the pipe off the donut area on the driver's side and ran the coach to see if it helps will it hurt the engine? Thinking of just dropping the pipe from manifold to muffler and see if it helps??? I'll dial back the choke/fuel mixture to it's previous lean reading and see if that is it. I could keep the coach running period without the choke fully open and fuel mixture moved a bit to the lean side or at spec. Thanks. I suspect running the engine with the exhaust off the manifold would be loud but not hurtful to the engine right??
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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| Re: What are the telltale signs of a restricted exhaust [message #264565 is a reply to message #264509] |
Mon, 20 October 2014 09:02 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Have you leaned out the carb and it needs the choke to idle now? Trying to understand your post. Idle mixture is set choke wide open fully warm for best max RPM gain and then reset base speed and recheck. You should then lean each screw to just get to the best lean idle --a drop of not more than 25 RPM per side. It won't hurt the engine to disconnect pipe for test only. Watch for backfire fire hazard with extinguisher handy
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: What are the telltale signs of a restricted exhaust [message #264589 is a reply to message #264509] |
Mon, 20 October 2014 17:43 |
budworks521
Messages: 137
Registered: October 2013
Location: Grand Rapids MI 1974 Pain...
Karma: 4
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I leaned the carb to three hash marks from spec mark ( I think ) and installed the farmer's choke per Dick Paterson directions. Afterwards, the beast fired up much easier and ran fine for much longer. No stalling and had a reading on 17 inches of vacuum behind carb. It did jump a little and wanted to drop to 15 inches. I decided to recheck my timing since I advanced it a bit prior to doing the new adjustments. I am at 15 degrees TDC and I have not tested my rpm's yet. I decided to throw the vacuum gauge in front of the carb and it looked awesome .. steady eddy for quite awhile. I then decided to slowly increase the rpms and watch the gauge. It dropped a few inches at first and then shot up to 22-25 and back to 18. From my research a restricted muffler might be the culprit. I will check the rpms this weekend and see if I can better dial in the carb and ignition and see if my vacuum gauge performs better. At times with the gauge it states a healthy engine with a need to adjust timing and carb so I am hoping for the best. Thanks again for any input as this learning curve is quite high for this rookie!
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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| Re: What are the telltale signs of a restricted exhaust [message #264592 is a reply to message #264509] |
Mon, 20 October 2014 19:16 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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I think the instructions on your gage are for idle, or at least steady throttle conditions. If you open the throttle, the vacuum will be lower, as there is less restriction to create the vacuum. If you let off the throttle, the vacuum will shoot up as the intake restriction is increased, and then back as it stabilizes.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: What are the telltale signs of a restricted exhaust [message #264789 is a reply to message #264509] |
Fri, 24 October 2014 19:07 |
budworks521
Messages: 137
Registered: October 2013
Location: Grand Rapids MI 1974 Pain...
Karma: 4
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Senior Member |
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It takes about 5 minutes for the choke to fully open since all I have for now is a farmer's choke setup. It does work though considering. This weekend I am going to dial back the distributor to 10 degrees TDC and see how it idles. I need a new exhaust so.... I doubt highly if I have a gas issue. More of a choke, idle speed, and tweaking I hope. I might pull one exhaust off driver's side since that side of the manifold has had the most trauma signs! Carbon buildup in the intake, semi flooding, etc... What a chore!!
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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| Re: What are the telltale signs of a restricted exhaust [message #264794 is a reply to message #264509] |
Sat, 25 October 2014 06:13 |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
Karma: 0
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Sir,,, just repaired a 2005 Taurus with 200k miles. Had codes,,,runiing lean. Drove ok but a little sluggish at 65-70. Installed an exhaust backpressure gage in the first O2 bung. Reads bad,,, to much backpressure. installed after the cat. To much backpressure. No bung aftsr the 2nd cat. Was it the 2nd cat or the muff. Drilled hole in ex. pipe after the 2nd cat before muff. Reads good. Welded up 3/8 hole in pipe and replaced all 3 cats. Gage is cheap. If you don't have a welder,,,, take to muffler shop after repair or screw in a plug. goodluck,,,PL
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