1963 Carter AFB "No Idle"

[Ray C.]

I fired the 63 340HP for the first time since rebuild. Because of a braking problem I did not take the 63 for a long ride prior to the start of the restoration, but did drive it around a parking lot and loaded it in to my trailer. The engine did idle, but ran poorly.

I have machined and rebuilt the engine (the block was not decked) to original specifications and fired it for the first time the other evening. The engine runs fine above 2000-RPM's, but will stall or quickly quit under 1500-RPM's, no idle. I have tried to adjust idle screws with no luck. I ran the engine for about 30 minutes at variable RPM's to break in the cam, but could not run the engine under 1500-RPM's.

Where should I start to achieve some type of idle, even if a poor idle, prior to completing timing, vacuum test, and the rebuilding AFB carburetor?

The rear intake boss was not drilled or tapped.

As always,

Thanks for all the help and advise!

Ray

[Verne Frantz]

Re: 1963 Carter AFB "No Idle"

Hi Ray,
Is it a little hard to start? Just a hunch, but you might have the timing severely advanced. Loosen the distributor and have someone start the engine. While you keep it running by holding the carb linkage, try retarding the timing (CW) and see if it will idle lower.
You might also want to make sure that the springs are on the mechanical advance weights.
Verne

[Joe C.]

Re: 1963 Carter AFB "No Idle"

Ray:

Is the dimple on the distributor driven gear oriented properly (pointing to the rotor electrode)? Is the static timing set at or near 10* BTDC @ idle? Was your carburetor rebuilt as part of the motor restoration? If so, then was it done correctly? Assuming that all of the above are in order, then the first thing to do is recheck your valve lash. If your lash is too tight, then the engine will not idle. If that is properly set, then you probably have a vacuum leak, most likely along your intake maniold's mating surfaces. If you apply oil to these areas, and the idle increases, then you have found the leak.

Joe

[Joe C.]

Re: 1963 Carter AFB "No Idle"

Ray,

Posted response in the wrong place.

BTW: Engine looks nice!

Joe

[Duke W.]

Re: 1963 Carter AFB "No Idle"

As stated, verify that the dist. gear dimple is pointing the same direction as the rotor electrode and the wires are properly indexed IAW the '63 Corvette Shop Manual.

A Delco "326-16", NAPA/Echlin VC1810 or other brand vacuum can that is stamped "B28" should be installed. (The OE 201 15 can is not suited to the manifold vacuum characteristics of the Duntov cam and will cause idle instability, but not to the degree you report.)

Install the dist and static time it at 10 deg. BTDC and connect the vacuum advance. The window should end up approx. normal to engine C/L.

Set the idle mixture screws 1.5 turns out from the seat.

Is the carb a 3461S or 3721S/SA/SB?

The idle/off idle jets and idle air bleeds are build into the primary venturi clusters, so if it IS a carb problem, this is were you should begin to look if the igntion map is okay. Remove and very carefully inspect the primary venturi clusters for blockage or damage, and be sure correct gaskets are installed that don't block the air bleeds.

Duke

[Ray C.]

Re: 1963 Carter AFB "No Idle"

Hi! Verne and Joe

Thanks for the responses and the leads.

I will follow through with you the information you provided and see where it leads.

I have not rebuilt the carburetor at this time, but have secured a rebuilt kit. It idled OK prior to rebuild, but has been setting for a year and may have dried out causing problems. My plans were to re-build it after first firing.

I did shim the distributor gear and may have changed the dimple location, this will be the first thing I check.

The engine will not run below 1500 RPM's so I have not used a timing light at this time. The points were new when I purchased the 63 and I have not change them. I have a new set of Blue Streak points and condenser and was planing on changing them after first fire. I would like to get the idle close prior to changing the points.

This is the first engine that I have not assembled. I have a very good engine builder/machinist and he assembled this engine for the same price that he charged me for parts and machining on the other engines. He had the valves set cold at 14 and I have re-set them to 16 prior to fire. my plans are to re-set them again after break-in.

I had a coolant leak with the intake on the right rear passage. I sent the intake to Jerry MacNeish at Camaro Hi-Performance. They re-skinned, repaired and machined the intake for correct surfacing, I will do as advised and check along the heads for leaks.

Thanks for the advise!

Ray

[Duke W.]

Correction: "236-16", not 326-16 *NM*

[Joe C.]

Re: 1963 Carter AFB "No Idle"

Ray:".

It is VERY, VERY unlikely that the carburetor is at fault. If it was working properly before, then I would NOT rebuild it until after you have located the problem. As of now, I feel that the carburetor should be a reliable "baseline".

Joe

[DANNY PANTUSO]

Re: Correction: "236-16", not 326-16

Did you change the camshaft and do you put a bigger lift or bigger duration then stock specs. it could keep the the rpm up there also. Danny

[Ray C.]

Re: Correction: "236-16", not 326-16

The 340HP engine was built to original GM specifications, or that was the instructions I gave to the engine builder. I used Federal-Mogul cam and lifters with the 097 cam. The builder did want to reduce the compression, but as advised on this board I told him to build the engine to as it left the factory specifications. The engine seemed to run very well at the higher RPM's.

I am diagnosing the problem one step at a time as recommended in the previous post.

Thanks for all the help!

Ray

[Ray C.]

Re: Correction: "236-16", not 326-16

"You guys are the GREATEST!" I figured the easiest area to attack first was the gear on the distributor shaft. BINGO! when I shimmed the distributor gear for proper clearance I installed the gear with the dimple 180* out of phase. I re-installed the gear correctly, brought up #1 cylinder and re-set the distributor. I was off one tooth, after a couple of tries the engine idles great!! Now on to other small problems, hopefully I will be able to test drive the 63 sometime next week.

Thanks to all for you help!! I owe you a drink of choice when we ever meet.

What a great feeling to here the engine run after all this work.

A HAPPY Ray

[Verne Frantz]

Re: Correction: "236-16", not 326-16

Congratulations Ray! It does feel good when you find a problem and then fix it and enjoy the results. You're pretty good..........less than an hour and a half between posts, and you'd fixed it!!!!!!!!!

Verne