78Marquis

Hello to everyone. I just joined which makes sense as we have a 96 Explorer, a 78 mercury Marquis and an 04 Lincoln Town Car and have been Ford people since 1972 and a 64 Mercury Comet.
My question is: We bought another 78 Mercury Marquis last year which spent all its life near the coast in South Carolina & we live at 6,000 ft altitude in Colorado. Can I just adjust the carb's jets for our altitude or did Ford use different sizes for sea level vs. high altitude? This Marquis is number 5 of the 78s for us but we've never had one from near sea level. Thanks!

Hoggy

Yes my friend you will have to re jet your carb. Does it smell rich?
My sugestion to you is to finf a guy that spesialises in carburetors here in Colorado( I know a good guy in Evergreen) But any reputable shop in your area that is good on emmissions just might be a place to look. Having the tools to check you exaust gas is key. Dony listen to the bar room experts who say a certain sizs jet is the ont that works ata certain altitude.

Be methodic about the changes you make to your carb as you tune it ,and write down EVERYTHING you change on it . Most important of all- read your spark plugs with every change you make. they tell ALL.

I run a 460 with a 600 cfm Holley that was dialed in using an exaust gas analizer. My van passes emmisions and pulls real well. I think it could use more carb when I'm pullin a grade. The spark plugs look grey and not too hot.

I believe it is a myth that at altitude a bigger carb jetted down will compesate for altitude( meaning more air flow and fuel leaning). Meaning a bigger carb to gulp the air and lean jets to not make it too rich.

The thing to watch more than anything is how well a signal is working with ignition timing. Big cfm will not mean squat is the air do'es not flow fast enough and the mix is wrong. Can I be more vague?

I'm sorry, I didnt help a bit.
Long story , short, consult a proffesional.