I just bought my kids a 72 C-10 as a project. I have never seen this issue and am not sure were to start. The truck is way over carbed and back firing. I tried to adjust timing to compensate a bit for the bigger carb, but had no such luck. A new carb would do this truck a great deal of good, but after buying the truck I was left with just enough cash flow to buy gas for the trip home. I had noticed that the wires were old as well and would need to be changed, but seem to be taking care of the job for now. I checked the firing order and found that I have #6 and #8 swapped. When I changed them to the correct position the truck won't start. Switch them back and it fires right up. Any ideas what is going on. Just not seeing the solution
350 wires not in order but engine starts and ideals
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zora
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assuming you have a stock cap, not a corrected cap, that makes no sense. Recommend you carefully retrace the wires and the firing order 1,8,4,3,6,5,7,2 clockwise
Can you be more specific as to what carburetor you are referring to make and model number? Backfiring is usually ignition related, if this is a points type distributor did you adjust the dwell angle before the timing?
A corrected cap has all even wires on the passenger side of the cap and all odd wires on the driver side of the cap. It does this with internal brass connectors and is purely for appearance. These are some HEI examples.
http://www.jegs.com/p/Accel/Accel-HEI-Corrected-Distributor-Cap/1503636/10002/-1
Can you be more specific as to what carburetor you are referring to make and model number? Backfiring is usually ignition related, if this is a points type distributor did you adjust the dwell angle before the timing?
A corrected cap has all even wires on the passenger side of the cap and all odd wires on the driver side of the cap. It does this with internal brass connectors and is purely for appearance. These are some HEI examples.
http://www.jegs.com/p/Accel/Accel-HEI-Corrected-Distributor-Cap/1503636/10002/-1
SWHouston
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In addition to Zora's good info, but before you check the FO, pull the #1 Spark Plug, roll the engine over to get it on the Compression Stroke and Timing Mark, where you know exactly where they have the Distributor stabbed for #1 Cyl.
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Thank you for the reply. I am not sure what size Holley Double pumper it is. But it seems to be way bigger than what is needed for this application as I am smoking the neighborhood out in carbon monoxide. I have an A/C Delco factory style HEI. I know this sounds like I am out of my mind. But I am not crazy, I rechecked this issue when getting home from work this evening. I have consulted with 3 other Mechanics and they all asked me the same questions. I am afraid that this is an internal cam degree problem based on the fact that when correcting the wires it won't start. I will be starting over from scratch and running a compression test on all cylinders and pulling #1 plug rolling engine over till I have TDC and re-arranging wires. I sure hope this works and takes all other guess work out of the equation. Again thank you very much for your help. If anyone has any other ideas please let me know. I will most defiantly keep you posted on results.
zora
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Holley's have their list number stamped on the front side of the air horn. It will be a number like 4779, 4780, etc. Depending on the age of the carburetor you may have a blown power valve which will cause full rich at idle. In addition you dont indicate whether you have an automatic or manual, double pumpers tend to work better with a manual or an automatic with a high stall convertor. I'm sure you're not crazy and your approach of determining TDC on #1 is the best way to sort this out.
Am not sure as to the carb size. It does have an auto and no stall. I do appreciate the help. I will check the horn and let you know. The power valve is high probability. I know that with that as an issue any tuning would be out of the question, but when all else fails start over. The thing about it all is it just makes no sense. Again thank you.
zora
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Another thought in addition to the power valves are the float levels, too high and you will have the issue you are experiencing. Not sure how familiar you are with Holleys but there should be a plug on both the primary and secondary float bowls. With the engine at idle remove either one and the gasoline level should be even with the bottom edge of the hole.
Got it all fixed up. Found that the truck was timed off #8 Cyl. have since adjusted the carb and am still running rich, but have plans to replace the power valves and check floats. Runs much better. Thank You for Your Suggestions.
Thank You
Thank You