The Stovebolt Site Forums The Shop Area Engine Shop Issues with Ethanol (quadrajet)

Just moved from Alaska (no ethanol) after 42 years to Oregon (10% ethanol). Using 92 octane in my 1960 quadrajet 283 in a 65 Suburban. Acceleration is smoother when engine is good and warm. When I get to 55 running rough for 5 or 10 miles then smooths out. Same if I run up to 65. New plugs, timing check, vacuum good. Any additives that might solve this? or changes to needles/jets. Was running great before the ethanol.

Paul

What is the difference in elevation from where you came and where you are now?

What elevation were you at in Alaska vs. the elevation in your new location?

52Carl, you must have ESPN!

Anchorage at sea level. Cottage Grove 600'. Shouldn't make much difference. I did change out my 195 thermostat for a 180. Put new plugs in just before leaving Alaska. Was running a little on the lean side, now a little on the rich side. Carb was rebuilt for ethanol use.

78Buckshot and Carl are onto something.

Mr Google says Cottage Grove, Oregon is 650 feet above sea level. If you lived in the mountains, your carburetor needs to be adjusted for the heavier air at low altitude.

Also, are you sure you have a Quadrajet? They weren't introduced until 1965.

I wonder about the difference in humidity in between Oregon and Alaska. The QJet on my 1980 truck was horrible on damp days. Edelbrock AFB clone was better.

my last reply doesn't seem to have posted. Anchorage at sea level. Cottage grove 600'. Still in dry summer conditions here. I did change out the 195 thermo for a 180. Was running a little lean in Alaska, now running a little rich. yes, quadrajet.

You were still in moderated status. I approved your most recent posts and one more will get you full member status.

The altitude difference is only 550 feet. That really shouldn't cause too much disruption to driveability but I would still tune the carburetor.

A lot of "Carburetor" problems are actually ignition-related. I'd try a new set of spark plugs, plug wires, and possibly a distributor cap and rotor.
Jerry

I agree. The Ethanol should not have made that much difference in the running. Sounds like you are running a little rich.
Remove a spark plug or 2 after you run around slowly for a time & see if they have black carbon on them. If it does
that is what is making it run rough till you get out on the road & burn it off.
If it is timed to specs you could advance it a few degrees & try it.

George

I agree, the elevation difference should have no effect, PO noted new plugs and carb rebuild. I would pull the carb apart and inspect the spring loaded power valve, if it is stuck in the "UP" power position the main jets are flowing maximum fuel. Also double check the float level. I have had 180 degree t-stats that run too cold, might want to go back to the 195 for a test as the warmer engine will help with the rich a/f ratio.

Both the old 4-Jet (square-bore) and newer 4-M (spread-bore) are referred to as "quadrajet" in original Rochester literature.

"Standard" jetting is sea level to 4000 feet with no changes.

Rebuilding to ethanol specs should only mean a leather accelerator pump instead of modern man-made material, and possibly, a few misinformed individuals will use the old monel steel needles instead of the "rubber" tipped needles. Ethanol will cause the monel steel to rust.

Did the issue occur PRIOR to the carburetor rebuild?

If yes, maybe need to look elsewhere.
If no, maybe take the carb apart and check float settings.

Sounds to me like you are having choke issues, as you state it smooths out after warming up, but think about the timing of the issue (when it started).

Jon

Thanks for everyone's input. Going to start by reinstalling 195 thermostat. Went to 180 because I knew getting through Portland Oregon on my way to Cottage grove there would be a lot of stop/go/wait and area temp might be high and my truck would get hot in the waiting. I think then come down on my jet size from 74 to 72.

carbking can confirm, I think the #68 - #72 jets would be standard for that era and cubic inch, do you know what year the carburetor is? Is it a spread bore Q-Jet?