Please help. I drive a 76 250 and just recently drove it 750+ miles straight on a new rebuild and have been experiencing various issues. The elevation change was approx 6000ft from where I had the carb dialed in but as soon as I changed elevation my truck went from starting and running perfectly to hard starting (turning over like 7 or 8 times before starting) and bogging down very badly everywhere I try and drive I'm assuming I need to rejet the carb and change the plugs that are more than likely fouled I tried messing with the air fuel mix and the timing with no luck. Also there is standing oil on my intake. Any ideas? Thanks in advance

 

6k elevation change will require a jetting change, and prolly more than just the mains..... Wanna say 1 jet size per 2000 feet, all of your settings will need to be tuned in for 6k increase or decrease otherwise your too rich or too lean.... There are an abundance of great articles on tuning for elevation change, do some reading and avoid the frustration with your engine ..... also, if your running the FE engine that most-likely came with you truck the oil your seeing could very well be from the valve covers, they are a PITA to seal, run your finger around them after warm up and see what you have. If the intake is leaking it will be at the front or rear of the sealing surface and that oil would not be on top of the intake....

FAQ Rejetting Holley Carbs

 

Thanks for the response, I did have to pull over about 9-10 hours into the trip and pull the drivers side valve cover off to tighten down a rocker that was knocking so that very well could be it. If the seal is fine do you think oil overfill could be another cause?

 

Oil over fill could cause all kinds of different symptoms to include an increase in oil volume in the valve covers and more oil leaking out of them. I have never been able to completely seal my valve covers, but have been content with a seep here and there

 

I think some are not fans of the Felpro Permadry line of gaskets but I'm sold on them. Sealed up valve covers and oil pan on my 302.