Re: IML: '67 Carter carb flat spot

Thanks for the tips David, and of course Dave:

Today I opened up the metering rod caps to try Dave's trick of stretching the springs. One popped out just like it should, the other was stuck down in it's well. Pulled them both out, cleaned the rods, cups, and the wells out properly, and put it all back together without stretching the springs.

Guess what? With only 1 metering rod moving you'll get a flat spot about mid-throttle! Duh!! With both moving right, everything works beautifully now. Decent idle, good mid-range, and she really launches at WOT.

Once again, the IML is fantastic. Thanks for giving me a VERY satisfied grin of accomplishment. Now it's on to more of the detailing, cleaning up, etc.

Advice from the great people on the IML have helped me:

1 - Determine overall health of engine compression.

2 - Clean & flush entire cooling system (Cascade).

3 - Make decisions on freeze plugs, idler pulley, water pump.

4 - Handle proper full brake system rebuild.

5 - Make heat riser and manifold decisions.

6 - Adjust carb properly.

Seriously, she arrived in April 2006 on a flat bed - no brakes, no cooling, etc., etc. Now it's October 2007 and she's a reasonably reliable, 43 year old driver, that turns heads, and gets compliments every day when I drive her to work. Surely couldn't have done it without everyone.

Dan Richardson

300L Family Heirloom

----- Original Message -----

From: David Whitney

To: mailing-list@xxxxxxxxxxxxxxxx

Sent: Thursday, October 18, 2007 4:21 PM

Subject: Re: IML: '67 Carter carb flat spot

Unless you are aware of your A/F ratio you will be fumbling in the dark. Try to find a performance tuning shop that will read the ratios and have a bunch of other stuff hooked up to the engine. Your local Mopar club may be able to point you in the right direction. The tuners will be able to make the proper jet/rod/spring combo recommendations. Once you have that basic setup you can fiddle with it from there. Otherwise any change you make could well send you in the wrong direction. Ten to one they also find some other little things that will help you a lot.

From your initial post about having flatness between 1/3 and 2/3 throttle, it sounds like you are in the range where the secondaries should be opening. So many things are happening at that RPM range that you need to have your A/F ratio correct before trying to adjust anything else. You need to be sure that the linkage to the secondaries is adjusted to spec so they are opening when they should, and then you can fiddle with the adjustable secondary vacuum flap which governs the smooth transition from two to four barrels. There is a delay between when the throttle plate opens and when gas actually starts to be pulled through the secondary barrels. The stiffer your vacuum flap, the longer the delay. That should be just a short bog, though, not a flat spot.

I concur that you are likely running lean, which is not a good thing with today's low octane gas and your high compression engine. When in doubt, run a little rich.

Happy motoring,

David

'91 K-Imperial driver 200,000 miles
'66 LeBaron dual air and every option known to man
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