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  #1  
Old 05-14-2000, 04:40 AM
csp475230
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I have a 230 gas from 1975. I set the dwell to 48 where the shop manual said to set it. Now when I first start up it back fires a little bit out the carb. I believe there was water in the tank so I used a gas treatment. Would a bad fuel filter cause this. Once I give it some gas and it back fires a few times it runs good.
Thanks for your help in advance.
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  #2  
Old 05-14-2000, 12:06 PM
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Location: Gainesville FL
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I read your other post and almost jumped the gun with an answer. Then I reread it and saw that you had checked the timing. My first jump the gun answer was you were changing the timing with your two dwells. BUT, it was the wrong direction. The lower dwell would result in higher timing (more advanced), which should make it run better.

When I realized that I didn't reply. The M115 Stromberg carbed 4 cyl is very picky about timing. Be sure you are at least at factory setting or above. (I would recommend 5 degrees over factory settings). By factory settings I also mean proper operation of both vacuum advance/retard and centrifical advances.

Based upon the back fire issue I would say you are either retarded (or deficient in secondary ignition capabilities/coil/rotor/etc.) or lean. On the Stromberg the choke was a constant problem and the oil resevoir needs to be full of oil. The main diaphram (easily removable by removing the top (three screws if I remeber correctly)should be checked before adjustments are made.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 05-14-2000).]
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  #3  
Old 05-14-2000, 01:07 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
As stated, the higher dwell reading is a closing of the point gap which advances the
timing.
You will notice a felt oil res. on the dist. shaft when you remove the rotor. These
sometimes never get oiled as they are hidden and the results is wear and slop on the shaft. This shaft is the lobe and advance plate and wear affects the dwell and timing to the point where the points are too close and can cause your backfire. Look for drifting dwell and erratic timing with a light on the timing marks.
i have had excellent results with point conversion kits for these older ignition systems. Mechanical switching has many wear drawbacks and is easily replaced with improved performing electronic ign. for short $$$.
Arthur
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  #4  
Old 05-15-2000, 02:06 AM
csp475230
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Thanks so much with the info you provided. Do you know where I can purchase a conversion set? The problem goes away after a couple minutes can this lead me a certain direction in trouble shooting?
Regards,
Chris Patko.
quote:
Originally posted by Arthur Dalton:
As stated, the higher dwell reading is a closing of the point gap which advances the
timing.
You will notice a felt oil res. on the dist. shaft when you remove the rotor. These
sometimes never get oiled as they are hidden and the results is wear and slop on the shaft. This shaft is the lobe and advance plate and wear affects the dwell and timing to the point where the points are too close and can cause your backfire. Look for drifting dwell and erratic timing with a light on the timing marks.
i have had excellent results with point conversion kits for these older ignition systems. Mechanical switching has many wear drawbacks and is easily replaced with improved performing electronic ign. for short $$$.
Arthur



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  #5  
Old 05-15-2000, 01:23 PM
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Join Date: Aug 1999
Location: Florida / N.H.
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Crane has an optical one I like at www.cranecams.com
Check the XR-700 series. Fine for the street. No need to change the coil.
Petronics [sp??] has a hall effect one .
Simpler , but not as good at cranking speeds [starting].
It is preference and both types are a major
improvement over mechanical switching points.
Both under $100.
Arthur
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  #6  
Old 05-16-2000, 03:42 AM
csp475230
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Arthur, Thanks for the help I put a conversion kit in. It runs better but did not fix the problem. It still backfires out the carb when I first start the car. Once driving everything is fine. Any other ideas on nwhat it may be?
quote:
Originally posted by Arthur Dalton:
Crane has an optical one I like at www.cranecams.com
Check the XR-700 series. Fine for the street. No need to change the coil.
Petronics [sp??] has a hall effect one .
Simpler , but not as good at cranking speeds [starting].
It is preference and both types are a major
improvement over mechanical switching points.
Both under $100.
Arthur



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  #7  
Old 05-16-2000, 11:23 PM
Larry Delor's Avatar
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Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,077
I thought that if your timing was too far advanced, you would backfire, especially upon accelleration. But, the backfiring goes away once warm...at least with the old ign. it did. Is there anykind of thermostatic device (like the kind that initiates the preheating of intake air by passing it over the exhaust manifold) that could have a vacuum leak--but only when cold?

my 2
-Larry

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