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dpson
04-25-2006, 09:56 PM
I drove home the 62 Lark convertible I bought last month this past weekend. On the open highway it ran just fine, however when stopping at intersections it idled rough and even stalled. The original 259 was rebuilt as a 289 with a Ted Harbit cam (details unknown). It has a rebuilt AFB 4bbl that the previous owner purchased from Dave T and I was told that it might be from an other make (Pontiac?). When the car was shifted into neutral at a stop the RPM's jumped up, but when put back in drive the engine would stumble at idle. This is my first 4 bbl. Any advice on what to check to get the idle situation straightened out?

1960 Lark Convertible
1962 Lark Regal Convertible

GTtim
04-25-2006, 11:01 PM
With the engine warm, adjust the idle mixture screws with the engine idling at about 500 rpms and car in gear. (with wheels blocked and parking brake on of course) Using a vacuum gauge will help you get the mixture right if you are not used to doing this. This assumes that all the other systems are set properly and are functioning well. Timing and points can also cause the problems you mention.

Tim K.
'64 R2 GT Hawk

studebakerkid
04-26-2006, 06:46 AM
Telling a newbie to adjust his mixture screws in drive is just stupid and will get him hurt for no reason. Adjust the mixture screws with the transmission in park and the parking brake on if it is an automatic and in nutral with the parking brake on if a manual.

Once you have the mixture adjusted then adjust the base idle so that when in drive the engine will idle at 500 RPM. If it is a manual then adjust it to idle at 500 RPM in neutral.

You will have to periodically adjust the base idle on these old type carburettors because the idle screw wears as you drive. Every time you close the throttle a misiscule amout of metal is worn off the screw.

If you car is ugly then it better be fast.....

65 2dr sedan
64 2dr sedan (Pinkie)
61 V8 Tcab
61 Tcab 20R powered
54 Champion Wagon

bige
04-26-2006, 07:52 AM
before you blame the carb check your timing. set the timing with all hoses disconnected and the idle set just high enough to keep it from stalling. my guess is that your idle was set while the distributor was advancing itself and once it goes into gear that advance goes away and your idle drops to stall.

after timing is set re-adjust the curb idle so it is about 650 rpm in gear.

Ernie R2 R5388

R2 R5388

Mike Van Veghten
04-26-2006, 03:06 PM
quote:You will have to periodically adjust the base idle on these old type carburettors because the idle screw wears as you drive. Every time you close the throttle a misiscule amout of metal is worn off the screw.

Studebakerkid,
It (the above note) would either have to be made of lead....or driven stop and go miles for....about...maybe....3,000,000,000 miles for the screw to shorten an amount that could actually be measured with normal measuring tools. The spring getting weak and letting the screw back out, the threads get loosened from repeated adjustments/rebuilds, etc. I've never seen one get but the cad plate worn off, and that even was after many, many miles.

And the first comment about adjusting things in gear....do it all the time. As long as the person is carefull. GTTim gave most of the required information...parking brake and wheel blocks. The only one he missed was don't rev the engine.
Lighten up on the guy, have a "Full Throttle" drink or sumthin.

The problem sounds like it could also be misadjusted valves, timing or carburetor related.

Mike

dpson
04-26-2006, 06:37 PM
Thanks for the suggestions. I will check the timing and valve lifter clearance. I did notice some clacking from the left cylinder bank. Any additonal suggestions would be appreaciated.

1960 Lark Convertible
1962 Lark Regal Convertible

studebakerkid
04-27-2006, 07:48 AM
With twenty plus years of experience turning wrenches for a living I can say catigorically that it is just plain stupid to adjust a carb with the transmission in drive. Just like not using jack stands. As for the set screws wearing down I have probably adjusted more because of that alone than most have seen. Strombergs, AFB, Thermoquad, Rochester, Holley ect....doesnt matter when the screw comes in contact at an angle with the fast idle cam or throttle stop and you ajust it sometime you change the allignment so the angle of the screw tip and stop are no longer paralell and you have a tip making contact and it wears off a drops the idle speed. I have to adjust my own once or twice a year just because my newest carbs are thirty years old and the set screws do not line up any more.

If you car is ugly then it better be fast.....

65 2dr sedan
64 2dr sedan (Pinkie)
61 V8 Tcab
61 Tcab 20R powered
54 Champion Wagon

buddymander
04-27-2006, 09:57 PM
I used to adjust idle and misture and even timing while in gear, but I finally realized that as long as I run the vacuum advance to a full vacuum source and retard the timing until it is almost ready to lower the idle, then all I have to do is run the mixture screws in til it lowers or stumbles and bvack them out a half turn.