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Discussion Topic:
Popping out the tailpipes
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DVW |
06-26-2010 @ 6:18 AM
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Member
Posts: 5
Joined: Jun 2010
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I completely rebuilt a 48 factory relieved engine in a 48 Ford convertible, bored out to .080, Isky cam #77,Johnson adjustable tappets, Offenhauser heads, Edelbrock intake with 3 97's. The front and the back are blanked off. I have changed over to 12 volt,I have a Mallory dist.I have a lot of Stromberg 97's and have tried several.The valves are straight. I used the original valve springs. When I first started this engine, It ran perfectly.It has gotten progressively worse.Popping out the tailpipe.Any suggestions?
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37RAGTOPMAN |
06-26-2010 @ 6:30 AM
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Senior
Posts: 1961
Joined: Oct 2009
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when does it pop out the tailpipes ? going down a hill with the throttle off, or at idle? midrange? did you ad a TOP OIL ? valves sticking ? did you have the valve springs tested,and were determined that they had good tension,and were useable ? also check the intake gasket and the carb base gasket for air leaking in causing a lean mixture, also any EXHAUST LEAK will cause this when backing off the throttle., ignition wires are good? no cross firing ? let us know, 37 RAGTOPMAN KEEP ON TRUCKIN,,,,!!!!!
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DVW |
06-26-2010 @ 7:02 AM
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Member
Posts: 5
Joined: Jun 2010
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It pops some while idling, but if we rev it up , it pops continuously. I did not check the tension of the springs.New spark plug wires. adjusting the carbs seems to make no difference.I did not add a Top oil.It loads up with black smoke coming out the tailpipe.It has done the same no matter what carb is installed.
This message was edited by DVW on 6-26-10 @ 7:06 AM
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flathead4rd |
06-26-2010 @ 7:48 AM
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New Member
Posts: 169
Joined: Oct 2009
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You don't say if you have a fuel pressure regulator for your 97's. If you getting black smoke your carb is probably loading up. Strombergs need 2-1/2 lbs of pressure or less.
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DVW |
06-26-2010 @ 8:13 AM
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Member
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I am very slightly less than 2 lbs.
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37 Coupe |
06-26-2010 @ 10:01 AM
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Posts: 362
Joined: Oct 2009
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Before you worry to much or get to involved in tearing things apart or adjusting remove aircleaner and drizzle MMO ( Marvel Mystery Oil) down both sides of carb. This will get into both sides of valve chamber and loosen up what is probably a slightly stuck or sticking valve. The Ethanol gas is creating a lot of this remember they make corn syrup out of it too. If this is the problem it will cure quickly and then you can just add 4 ounces to every 10 gallon fuel in the tank to maintain free valves.This is not an old wives tale nor is MMO "snakeoil" it works.
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supereal |
06-26-2010 @ 10:54 AM
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Senior
Posts: 6819
Joined: Oct 2009
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With that cam, you need new valve springs to compensate for the "ramp" of the grind, certainly more than the 40 pound stock closed tension. We never reuse valve springs in any rebuild, as the tension decreases with age. Often, popping is due, or increased, by an initial advance setting that is too high. Aftermarket ignitions can exceed the usual 4-5 degrees. Setting timing on pre-'49 engines is hampered by the lack of a marked crank pulley, and is often "by guess". I have yet to see much discernible advantage produced by Mallory, or any other conversion, over the stock system in good condition on a flathead. I'm not among the MMO fans, as it doesn't take much to produce spark plug fouling.
This message was edited by supereal on 6-26-10 @ 10:55 AM
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DVW |
06-26-2010 @ 11:55 AM
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Member
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Joined: Jun 2010
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This has become very frustrating. I am 74 years old and have forgotten what I once knew. I built this car the way I wanted it when I was 17 but could not afford it then. I want to thank all who have responded, I welcome all suggestions.
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supereal |
06-26-2010 @ 1:49 PM
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Senior
Posts: 6819
Joined: Oct 2009
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At 75, I'm in the same boat, and sometimes "popping out of MY pipe" too! I'm fortunate to have two mechanic sons at our shop who are patient with the "old man". Frustration is built into the old car hobby, I've found, at any age, and while my mental gears grind a whole lot slower, at least they are still grinding!
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DVW |
06-27-2010 @ 5:10 AM
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Member
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Joined: Jun 2010
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I checked with Mac's and Dennis Carpenter and all I find is stock valve springs, where do I get stronger ones?
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