I need some help with my '65 C10. In my very long process of bringing this truck back to life, I now have the new (rebuilt) 230 straight six in the truck. I have gone through the break-in process, done some troubleshooting and have been running the truck for several months. Here are the engine items which are not original: - cam - slightly more aggressive - hardened exhaust seats for unleaded fuel use - block is actually from a 250 All else is original stuff from the 230 and new or rebuilt. The one problem I cannot seem to solve is an irritating "stumble" I get when accelerating. This is not noticeable at high speeds, mostly just when starting out. Or if I am at idle and hit the pedal, there is a hesitation before the engine "kicks in." I have two original carbs and rebuilt them both - no change. I have checked and re-checked the timing and am pretty confident that it is correct. PCV valve is operating correctly. All things seem to point to the accelerator pump, but like I said, I've rebuilt two carbs and it hasn't helped. I will point out that the pumps in the new carb kits appear to be of very low quality compared to the original ones. Could this be a problem with the vacuum advance? Anyone know an easy way to test this? Any other ideas about what might be causing this problem? Thanks for any suggestions!!
[updated:LAST EDITED ON May-30-03 AT 10:15 AM (CST)]It "could" be the vacuum advance. Is the vacuum module on the distrib the original? Try replacing the module. If you are spot on sure that the carb jetting and the rebuild went right, look into a distributer rebuild. With a hotter cam you may be needing a different curve in the distributer advance. New weights and trying different advance springs may help to dial in that 6. Hotter coil ? Plug gap ?? Good luck getting it dialed in. I love it when folks hop-up these motors ! DValentine
I had a similar problem when I rebuilt the rochester bc on my boat. the accelerator pump was working, just not very well. Fortunately I had another rebuild kit that I had bought previously just for one gasket. I compared the original pump with the two from the kits. one of the kit pumps was missing a spring that ran around the inside of the diaphram to help keep fuel from blowing by the pump. I put the "better" pump in and it worked great.
