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#28624 03/14/2004 2:06 PM | Joined: Mar 2004 Posts: 3 Junior Member | | Junior Member Joined: Mar 2004 Posts: 3 | We are working on our 51' Chevy 3100 that was setting out in our to decay for 2 years. We got started on it, and started with the engine.The engine is a 1954 Chevy 235, not the 219. We replaced the coil, points, condesor, spark plugs, and also rebuilt the carb. When it fired up though, it had a rough idle and backfire. Even after letting it run, adjusting the lifters, still no luck. When you turn the choke off after letting it idle and give it gas, it wants to quit, however the fuel pump is working perfect. Whats wrong with our beloved truck? Any help would be appreciated. Thanks! | | |
#28625 03/14/2004 2:39 PM | Joined: Jul 2003 Posts: 33 Apprentice | | Apprentice Joined: Jul 2003 Posts: 33 | U problably need to check the ignitiontiming, and possible leaks around carb. | | |
#28626 03/14/2004 5:08 PM | Joined: Mar 2004 Posts: 3 Junior Member | | Junior Member Joined: Mar 2004 Posts: 3 | I disconnected the vacuum line at the carburator, but I didn't plug the line.
Tim | | |
#28627 03/14/2004 6:57 PM | Joined: Aug 2001 Posts: 78 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2001 Posts: 78 | Clean the mouse nests out of the exhaust pipes. You never know it could be that easy. 
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Rollin' Hard
1946 Chevy 1/2 ton
1959 Phord 1/2 ton
2001 Chevy 1/2 ton
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#28628 03/14/2004 11:07 PM | Joined: Mar 2004 Posts: 3,068 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 3,068 | You may have a sticking or burnt valve. Any valve noise? Backfiring usually means ignition getting back through the intake. | | |
#28629 03/16/2004 1:38 AM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | If you disconnected the line at the carb and did not plug the carb, you adjusted it with a massive vacuum leak. I usually just tune mine up with the line connected idling at 500 RPM. Since the distributor is connected to ported vacuum there is no advance at that RPM anyway.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#28630 03/16/2004 3:29 AM | Joined: Jan 2003 Posts: 32 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2003 Posts: 32 | Make sure that you didn't cross a pair of plug wires. Make sure you have them in the correct order. | | |
#28631 03/16/2004 3:44 AM | Joined: Dec 2003 Posts: 510 Shop Shark | | Shop Shark Joined: Dec 2003 Posts: 510 | The one thing I haven't seen mentioned here is checking the points gap (or dwell.) If the gap is too small, it can result in backfiring thru the exhaust...and possibly thru the carb.
I'd take a look at the points (and look into the possibility of replacing them with a Pertronix Ignitor) as well as making sure that the firing order is correct and that there are no vacuum leaks. | | |
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