Carb solenoid/bracket for BB/3x2?

[Steven C.]

I've been following Kurt's thread on carburetor solenoids and brackets, and after seeing some of the photos, I remembered that I have a similar animal in my parts bin.

I pulled it out last night, and holding the bracket up to my carbs ('69 L71), it appears to mount on the front and center carb mounting studs, and the solenoid would move the throttle lever.

Here are some questions:

1. I'm fairly certain that these parts don't have an original place on my L71 -- is this correct?

2. Showing my ignorance, were 400-hp BB available with air?

3. If so, did they have a carb solenoid, with a bracket that spanned the front and center carbs? '67-'69?

4. Does this bracket have any other applications?

Thanks in advance.

Steve

[Dick W.]

Re: Carb solenoid/bracket for BB/3x2?

One of the applications for this bracket is L-71 with M-40 transmisssion.
Two. Yes 400's were available with A/C
Three. Yes
Four. Yes 400,s with A/C and or M-40

[Steven C.]

Why on L-71, M-40?

Thanks, Dick.

What energizes it, and when (what conditions?).

Looks like I need to keep it, and put it back in place...

Steve

[Steven C.]

Re: Why on L-71, M-40?

More info: My car is '69 L71 with THM (LX engine code). I thought these solenoids were "AC idle-up" solenoids, what does it do when no AC; as on L71 w/M-40?

[Jack H.]

Re: Why on L-71, M-40?

There were several uses for carb idle solenoids and one WAS to boost curb idle when A/C was active with the compressor loading the engine. But, that wasn't what the solenoid was used for in '68-69.

Another application was to provide two curb idle profiles: (1) when the engine was running boost idle, and (2) relax the solenoid on engine shut down to drop engine RPM and 'starve' it to prevent run-on or dieseling.

Beginning in '71, still another application was invoked. Marry the idle solenoid to the distributor's vacuum advance. Give the engine full vac advance + higher idle RPM when the car's operating in high gear(s) and deny it distributor vac advance + lower the engine RPM when the car's running in low/no gear range.

What this did was give the car max 'pep' for passing on the highway, reducce tail pipe emissions (sensitive to RPM differential) when the car hit a freeway exit (compression braking), and retard spark timing for max burn efficiency for during periods of sitting at a traffic light idling.

Typically, the theory of operation for these systems is detailed in the Chassis Service Manual for a given year car and you can read up on them there.

[Steven C.]

Thanks, Jack!

Very clear and helpful information. I have a '69 L71 with M-40. I've added a later GM HEI distributor instead of the TI ignition. For my 12v to the HEI coil, I used what I thought was a convenient orphan wire from the IGN fuse...that must have been the idle solenoid feed!

Key on, idle solenoid extended to boost RPM, key off solenoid retracted to prevent run-on, it sounds like from your information. I think I'll see how it goes without the solenoid, I'm still wrestling with an overly high idle.

Again, thank you very much.

Steve

[Chuck G.]

Re: Carb solenoid/bracket for BB/3x2?

I remember going round and round on this subject with the JG revision.

Solid lifter 3x2's with automatic used the solenoid.

Hydraulic lifter 3x2's with automatic did NOT use the solenoid.

Hydraulic lifter 3x2's with AC and automatic used the solenoid.

This follows the info provided in the various parts books regarding usage. Chuck

[Steven C.]

Re: Carb solenoid/bracket for BB/3x2?

Thanks, Chuck.

I guess that can explain why Dick called it $5000 bracket/solenoid in another thread.

Usage seems to have been limited to '69 L71 with automatic (255 produced) and '67-69 L68 with AC and automatic (presumably a small number).

But, this confuses me in light of Jack's response. It seems like it would function as an "AC idle-up" on those cars so equipped, else why wouldn't L68 with M40 without AC not have it.

His explanation as an idle-down for the L71 w/M-40 makes sense.

Anyway, today I've gone from thinking I had one for someone who needs it, to learning that it is for my car...and I'd better keep a close eye on it.

Regards and thanks,

Steve

[Chuck G.]

Re: Carb solenoid/bracket for BB/3x2?

I'd take a wild guess that manual trans cars give us the capability of blipping the throttle at idle, whereas automatic cars do not.

I'll have to go back through some of the old parts books and refresh my memory. Chuck

[Jack H.]

Re: Carb solenoid/bracket for BB/3x2?

The theory of operation write-up on the CEC (combined emissions control) system used one-year only in 1971, makes a rather 'vague' reference to one aspect of the solenoid solving the problem of the increased throttle angle required by AT and A/C equipped cars. You can interpolate this to mean the extra drag on the engine caused by the AT or the A/C compressor was intended to compensated for by 'tweaking' the normal curb idle RPM up to compensate which 'could' result in dieseling or engine run-on during normal shut-down....

[Steven C.]

Thanks, Jack *NM*

[Dick W.]

(Message Deleted by Poster)

Message Deleted by Poster

[Joseph T.]

Re: Thanks, Jack

Red X and no site connection

[Dick W.]

Re: Thanks, Jack

Oh well, back to the drawing board.

[Dick W.]

Re: Thanks, Jack

We try agian