A little background first.

Recently I replaced the 1 inch open carb spacer on my 428 with a much thinner Boss 302 spacer from NPD. I did this to get better alignment with the transmission kickdown. The boss spacer is the same thickness as the original 1966 spacer, but it also has a PCV fitting.

After replacing the spacer, i spent some time adjusting the idle mixture screws.

Initially I set both adjusters out 1.5 turns. It idled like crap. It would idle, but with lots of engine shaking and rocking. Tried small adjustments in both directions, multiple times. No luck.

Finally found that for best results, both adjusters needed to be turned out a total of about 3 turns. Seems like a lot to me. But it idles super smooth now.

For some reason, this is bothering me.

With them turned out that far, is it telling me that I need to look at something else that may be out of adjustment (float level, etc.)?



Tim


1970 Boss 302
1972 F250 Crew Cab (powered by 66 Super Marauder 428)

But what bothers me is it should not have changed significantly from just changing the spacer......unless you have an air leak around the spacer.

Big problem with those ford spacers is they warp from being tightend (overtightened).

If the engine is happy with three that sounds good, but I would check it out with a vacuum gauge and RPM meter rather than use your era (common problem). Shouldn't need three but if the engine is responsive to minor tweaks and 3 evens its out and gets you those most vacuum with the lowest RPM its really not a problem.

Again I am more concerned with the lack of response (indicates air getting in someplace or passages blocked) and the difference between settings (indicates air leaking someplace). Sounds like an afternoon with some ether (starting fluid) is in your future.


Good Luck,

Bill White
White Automotive

I did not check what the settings were prior to "resetting" them. I just turned them in to the stop and backed them out 1.5 turns to start the adjustment process.

For all I know, the settings didn't change.

I did use a vacuum gauge and rpm meter.

I also used half a can of carb spray looking for a vacuum leak after I first fired it up, but I didn't find a leak.

Thanks for the feedback!

Tim

Again I would not be so concerned with backing them out to 3, sounds like you did it correct and just what the engine wants.
FYI for inquiring minds, I always bench set my idle screw to 2 turns rather than 1 1/2. I have had engines not run or stay running at 1 1/2 whereas I have never had a problem at 2.

And again my biggest concern is if you are not getting a response to even minor adjusting of the screw.

Bill White
White Automotive