High-altitude timing

[Jeff S.]

Moving to Colorado front range (~6000' MSL) from WI sometime in the next few months. Car in question is bone stock, rebuilt 327/300HP base engine w/powerglide. It's currently running very well here (~1000') with 8.5* initial, B-20 vacuum can, main jet size #65 (Holley 4160/List 3367). Is there a 'rule of thumb' to observe regarding advance and/or jet size once in place in CO? Is it necessary to accomplish such changes while en route should I drive the car rather than ship it? Thanks in advance.

Jeff

[William C.]

Re: High-altitude timing

Really shouldn't be too much of a problem, once out there you could try to lean the jets a couple thou to see how it performs, if better, try a couple thou more. Cars were designed to go over mountains without adjustment, but staying might be helped with some tweaking. Timing should be OK.

[Paul Y.]

Re: High-altitude timing

Moving to Colorado front range (~6000' MSL) from WI sometime in the next few months. Car in question is bone stock, rebuilt 327/300HP base engine w/powerglide. It's currently running very well here (~1000') with 8.5* initial, B-20 vacuum can, main jet size #65 (Holley 4160/List 3367). Is there a 'rule of thumb' to observe regarding advance and/or jet size once in place in CO? Is it necessary to accomplish such changes while en route should I drive the car rather than ship it? Thanks in advance.

Jeff

Jeff, I live in Lakewood and I drop a sea level carburator 2 jet sizes then see how it performs. Then I drop one size at a time after that. If it is surging it is too lean. The inspection lets me know when I am close asa you get a read out from it. The timing can be advanced quite a bit compared to sea level but when you drive to a lower elevation you may have to retard the timing. I drive my 63 FI coupe lots of times in the high country. Growing up in Minnesota, I love Colorado. What town will you be living in?

[Jeff S.]

Re: High-altitude timing

Bill & Paul

Not sure where we'll be settling yet - looking primarily in the Monument-Palmer Lake area north of USAF Academy. Stationed at Peterson back in ancient times & have 3 daughters scattered between Arvada & Colo Springs, so we're somewhat familiar with the area.

Thanks for the tips on jetting & advance. I wonder if I'll lose enough manifold vacuum to need a more aggressive can. What is the "inspection" you speak of? Does my 47 year old car has to pass some sort of Colorado emissions inspection to get registered?

Jeff

[Peter L.]

Re: High-altitude timing

Jeff - We moved from the Chicago area to Los Alamos, NM (7200') 13 years ago with our '67 base motor, 4-spd Corvette and finally just before the Albuquerque Regional several years ago we had a friend in Albuquerque who is a fellow NCRS member set up the carb and distributor for the altitude and no other changes and it runs great. I trust there will be someone up there who can help you out because you'll definitely want to get it set up right if you plan to enjoy your car. Pete