OMF

So... It's the first time I've had my car down here, and I noticed it as we were passing through Flagstaff. The engine was rattling like a snake as we were climbing the long hill approaching Flagstaff.
I shook it off as my distributor coming loose and advancing a few degrees.....not so, I checked it today and the timing is spot on at 34 degrees @ 2800.
I went and bought a timing light from everyones favorite store Harbour Freight, and had to back off the timing 6 degrees to get rid of the rattling.
I still have some light throttle rattling, so I'm going to have to make some adjustments to the vacuum advance too.
So whats with the fuel down here? I only run premium fuel, and back home there isn't any ethonol in Premium. is that so down here???

Somthings good about the high test back home

694speed350

A better question is what is the altitude difference between home and there. also what is the temp. difference?

COOLTED

Google says Flagstaff is 7000 ft., and that Edmonton is 2021 ft. That might be why. How dare you insult our fuels!!!

Mike21175

Edmonton - 2201 ft above sea level

Flagstaff - 7000 ft above sea level

I think that is the problem.

Mike (Love Google!)

Wee

I just bought a HF timing light this weekend...Haven't used it yet....How did it work....? Did you get the unit that has the advance ****...?

Brian

sagebrush rebel

The higher the elevation, the smaller amount of octane you need. I run my 65 chevelle when I worked at Crater Lake National Part on regular at 7000+ elevation and it run fine, but when I went to visit the girlfriend at Medford, 1000- elevation it would really rattle. This was on 11 to 1 compression

RockyL32

There is ethanol in all grades of fuel here unless you find a station that advertises "ethanol free"

7T1vette

11:1 compression at 7000 feet gets you the same amount of oxygen in the cylinders as if you had about 8.5:1 compression at sea level. Air is a lot 'thinner' at 7000 feet. That kind of altitude change is a big deal for a non-computerized engine system.

OMF

Yes same one....worked like a charm

OMF

Well hate to rain on your parade......but i'm in Surprise AZ at around 1150' ASL now, and when I went out this morning she was still doing it. So the altitude is about 1200' less than home, Oh and the temp is relatively cool for this area @ about 85 degrees. I wouldn't think that would make such a difference.......must be the gas

mikep3

I had a similar problem that made me retard the timing from 32 to 28 degrees to get the rattle in the distributor to stop. This was at highway speed of 65 or higher. I disconnected the vacuum advance to stop the problem.
I checked the timing with a light and found that I had 56 degrees total advance with both mechanical and vacuum at 3000 rpm.
I modified the vacuum advance and now I have 48 degrees at 3000 rpm with both mechanical and vacuum. This is with 32 degrees total mechanical advance at 3000 rpm.
I think with Vortec heads you can go with 34 degrees but I get too much nock when starting.