63 _ Engine dies at idle after warm up

[Steve D.]

63_327_LT-1 cam_B-28 vac can

Doing shake-down runs after work on bottom end (replaced main and rod bearings) and pan leak saga. Starts ok and runs fine but after warm up, idle may slow and then die; or when driving, with clutch in while slowing down it may die. It will restart after dying. It doesn't die predictably every time. In one sleuthing session I let it idle for 15 mins and it did not die. So I went out and ran through the gears a couple of times and every thing seemed ok until I slowed to turn the corner near the house and it died, and then died again when I pulled in the driveway.

Timing is set with 11 degrees initial; at idle (850) with vacuum advance can connected timing is 28 degrees.

Temperature (by infrared gun) at thermostat housing is 185-190 with ambient 80.

The carburetor is an Edelbrock. I have adjusted the idle mixture screws at 11-12 " at 850 RPM. The jets, metering rods and springs are the same as before this problem surfaced.

The fuel pump is mechanical and is new.

One other thing. Prior to the work, it would start as soon as I hit the key. Now it takes a little bit of cranking; not bad, just not instantly as before.

Any ideas?

[Leif A.]

Re: 63 _ Engine dies at idle after warm up

Steve,
Have you checked the float levels in the carb? May be set too low. I had a similar issue with my stock Holley on a L79 engine.

[Mark E.]

Re: 63 _ Engine dies at idle after warm up

Since the problem didn't exist before the engine work, start with what changed.

Replacing bearings means R/R heads, intake, distributor, and maybe the carb. Was a vacuum leak was introduced with one of those new gaskets? Or the vacuum lines not properly attached? Timing changed? Loose/broken/disturbed (causing increased resistance) primary and secondary ignition wires?

[Edward J.]

Re: 63 _ Engine dies at idle after warm up

Steve, sound like the basic's are covered, If you did remove the intake manifold as Mark eluded to, I would say go back and re-check the torque on manifold bolts, I will sometimes make two or three passes around the manifold and then once a few warm up cycles recheck again. another is the carb. base gasket making sure its the same as the replacement, vacuum leaks cause a rough choppy idle.

[Duke W.]

Re: 63 _ Engine dies at idle after warm up

Also check the B28 VAC when hot to ensure that it meets spec and doesn't have an excessive bleed down rate.

Duke

[Gene M.]

Re: 63 _ Engine dies at idle after warm up

Steve,
The wording in your post sounds like you replaced the bearings with the engine in the car. Main bearing r&r is not optimum. If the engine was removed (much preferred way) there would be much more removal and replaced items. Please specify what actually transpired.

[Steve D.]

Re: 63 _ Engine dies at idle after warm up

I was assuming that I don't have a vacuum leak because the idle vacuum matches the cam and the timing fits the vac-can specs; but assumptions are worth what you pay for them.

The engine was removed, disassembled (heads, intake, etc), checked, reassembled with new bearings and gaskets.

I checked the vac-can with a mitey-vac, but it was cold, not hot.

I will check the carburetor base plate and intake for vacuum leaks and check the vac-can again after warm-up.

If I still have a problem, I will start on the carburetor _ check the float levels and .............

Thanks for the input.

[Frank D.]

Re: 63 _ Engine dies at idle after warm up

Assuming the float levels are correct (still worth checking) cold running (choke on) presents a rich condition; stalling when warmed up may indicate a too lean situation as others have stated. You can take an unlit propane torch and pass it around the carb gasket and other likely areas and if your engine speeds up - that's your leak - creating a lean situation..

[Timothy B.]

Re: 63 _ Engine dies at idle after warm up

Get the engine hot and the idle speed set where you want it and re-adjust the emulsion screws for best vacuum/engine speed.

See if that helps, remember that any time you change the idle speed the emulsion screws should be rechecked. What happens is you change the IDLE A/F ratio by opening or closing the throttle blades. Gotta start with the simple things first.

[Steve D.]

Re: 63 _ Engine dies at idle after warm up

Idle is a bit lumpy but pretty good at 850 so I have always used that as target idle. I adjust the idle mixture screws to get max vac of 11-12" at target idle 850. Vac gauge connected to manifold source (not ported source)

[Steve D.]

Re: 63 _ Engine dies at idle after warm up

For my education _ if the dying problem is intermittent and is caused by a vacuum leak, does that imply that the leak is intermittent? If the leak is not intermittent, then what triggers the dying, since the leak is also present during the "non dying" time?

[Frank D.]

Re: 63 _ Engine dies at idle after warm up

The way I read it the 'non dying' time is before the engine is warmed up (meaning choke might be on) so the mixture is temporarily enriched; then when the choke 'pulls off' the too lean mixture (possibly from a leak) is no longer compensated for so the engine dies. Dying under load (e.g. the other symptom noted above) is also indicative of a lean mixture. If the car runs fine above an idle it is on a different carb circuit and also means the fuel pump and fuel delivery are probably fine...

Personally, I'm not an Edelbrock fan, if I want an AFB carb - then I'll get a real Carter AFB and not a 'clone'...

[Stuart F.]

Re: 63 _ Engine dies at idle after warm up

IN discussing this about a 63, it would help to know just which engine you are dealing with here. There are certain peculiarities of certain option engines, and this is of special concern when aftermarket components like the Edelbrock carb are added to the mix. Also, if the engine was a complete rebuild where someone got carried away with the bearing clearances or piston rings used, then you have another factor that might come into play. Short of an engine seizing, back in the old days with old style rear main seals, it was possible to start out with a real tight seal which made the engine almost too hard to start with the starter - rather it had to be push started and then the idle RPM once started had to be continually turned back until the engine had run in for awhile. I know this is not the case here, but I'm just using it as an example of how a rebuilt engine can have some quirks until run in awhile.

Also, I'd check all your ignition re-connects, including the Edelbrock electric choke.

Stu Fox

[Steve D.]

Re: 63 _ Engine dies at idle after warm up

The engine is non-original (65 block, 67 heads etc), but the closest description is quasi L76

[Steve D.]

Re: 63 _ Engine dies at idle after warm up

Further observations _ The original data that I posted is apparently not correct. I started the engine cold (ambient 80 deg) with tach and vacuum gauge connected. Vacuum reading of 11-12" at 850 at start, but at temp of about 160 degrees the vacuum needle began to move down. It will get down to 8" or so before it stumbles. I can restart it without trouble and it will idle around 8" for a while before stumbling again. I can bump the throttle and keep it from dying. As an experiment, I opened the idle mixture screws a turn or so when it started stumbling, but that did not keep it running. Accepting that there is a vacuum leak, while the engine was hot and registering reduced vacuum, I ran a propane nozzle around the base of the carburetor and the periphery of the intake, but observed no RPM bumps on the tach. There are three vacuum connections on the carburetor. The gauge hose is connected to one and the other two have new rubber caps. All of the connections are close to the base and were exposed to the propane.
Even though it passed the propane test, I guess the next step is to pull and reset the intake and carburetor.