1969 BB Idle stop solenoid components

[Steve Antonucci]

If Joe Lucia is out there, can you please comment on the following:

I am currently looking at an "original" idle stop solenoid bracket, clamp,
and two studs that the owner claims were used for 1969 BB THM400 Corvettes
( L-88 & ZL-1 ). Part numbers are as follows: 3967426 & 3940917. The owner
claims that these were used in conjunction with a 4296 Holley for the Corvette
applications listed. I'm a real stickler for original components.

My question is rather simple ( I hope ). Are these not the same components
that were used for L/78 & COPO & ZL-1 Camaro's with THM400's? I believe they
are. The owner further claims that these items are rare in that they were used
in conjunction with the 4296 Holley that featured a unique throttle arm. If
they are indeed ZL-1 related components, would they not be correct for a ZL-1
Camaro? A COPO Camaro? An L/78 Camaro? The problem is this. L/78 & COPO
Camaro's used the 4346 Holley. ZL-1's used the 4296 Holley. Are the arms
that different? 69 Corvettes used a throttle cable, didn't they? 69 Camaro's
still used a throttle rod ( less the L-6 and cross-ram setups ). In my quest
to learn about the use of the idle stop solenoid on 69 Camaro's with L/78 and
THM400's, I have come up across some conflicting information. I know that we
are off Corvettes in general, but I think the ZL-1 & L-88 options might be
able to help me out.

If any member has an original 1969 L-88 or one of the two ZL-1's that has a
THM400, could I possibly impose on you and ask for an image or two depicting
the idle stop solenoid, bracket, clamp, throttle arm, etc.? I want to see
exactly how this setup was configured from the factory and more importantly
the relationship between the solenoid plunger and the throttle arm on the
Holley. As some may recall, I recently found a true hens tooth ( an original
CX coded THM400 used in COPO and SHP applications ) and I only need to get the
proper idle stop solenoid setup and I am good to go.

I was hoping you folks could help.

Steve

[Joe L.]

Re: 1969 BB Idle stop solenoid components

Steve-----

The GM #3967426 solenoid bracket and GM #3940917 solenoid clamp used for 1969 Corvette with L-88/ZL-1 were the same parts used for the 1969 Camaro and Chevelle with L-78 and THM-400. I have no specific information regarding parts application for COPO Camaros; GM never published parts information for COPO cars. However, I'd be VERY surprised if the same parts were not used for the Camaro COPO cars. I'm quite sure that GM didn't have fabricated special brackets and clamps for the few 1969 Camaros with ZL-1 and THM-400. Plus, I see absolutely no reason why these parts would not work for that application.

[Steve Antonucci]

Re: 1969 BB Idle stop solenoid components

Joe,

I'm COPO knowledgeable, but not an expert by any means. I believe that all
COPO cars were L/78's originally. The transmission would have been a direct
carry-over of the one ordered with the L/78. In this case, the CX THM400.
It therefore only stands to reason that the idle stop solenoid setup as well
as the kick-down switch setup would simply be transplanted from the L/78 to
the L/72. Accordingly, the part would have to be the same.

I'm sure this has happened to you and many other restorers in the past. You
think you know exactly what parts you need, then someone pops-up and either
tells you or shows you something different. In my case, I recently saw a 4296
ZL-1 carb with a somewhat strange looking throttle arm. The owner claims that
this was a provision for the idle stop solenoid on Corvettes. Since there
were two ZL-1 Vettes and 69 ZL-1 Camaro's, I have always assumed that they
used the same carburetor. That should explain why I asked about the throttle
arms. If the 69 Vettes did use a throttle cable, there would be a stud on
the throttle arm. As I mentioned, 69 Camaro's used a throttle rod. I started
to consider that possibly there were two different throttle arms on the 4296.

Every 1969 L/78, COPO ( L/72 ) Camaro, Chevelle, and Nova I have seen has used
the 4346 Holley. Less the ZL-1 or course. That used the 4296.

Does any of your reference material indicate that the 4346 Holley used a
different throttle arm when THM400 was ordered? That is essence, is the
crux of the issue.

Steve

[Mark #28455]

Ask Jim Stubbings

at Heartbeat City - he knows a lot about the ZL1 cars, has owned several of them, and reproduces parts like the crossram intake, etc. I bought a repro of that bracket from him a year or two ago.

By the way, are you sure the ZL1's really all had the 4296? I don't recall a 4296 dated before about March 1969 and some ZL1's were built in January, I think. If you've seen an earlier dated 4296, please let me know.

Thanks,
Mark

[Joe L.]

Re: 1969 BB Idle stop solenoid components

Steve-----

The "throttle arm" was never available seperately for a Holley model 4150 carburetor. It was supplied only as part of the throttle body assembly. The throttle body assembly for the Holley 4296 used for 1969 L-88 and ZL-1 applications were the same regardless of transmission application. That's exactly as I would expect it to be. The Holley 4296, aka GM #3955205, was used for ALL 1969 L-88 and ZL-1 applications. If there had been a carburetor with a different "throttle arm" (and, consequently, different throttle body assembly) it would not have been a Holley 4296, aka GM #3955205. It would have been a carburetor with a different number in both Holley and GM systems. There was no such carburetor, though.

I can't find a reference for the throttle body assembly for the Holley 4346, aka GM #3959164. However, it does not really matter. As described above, the Holley 4346, aka GM #3959164 was used for ALL 1969 L-72 and L-78 applications. Therefore, by definition, there was no difference between the carburetors for manual transmission or automatic transmission applications. So, there was no difference in the "throttle arms" for the same reason described above.

[Dick W.]

Re: Ask Jim Stubbings

Mark, I have seen one 4296 dated Dec 1968. Do not believe it was a restamp as why would one date one that early for a Corvette?

[Jon S.]

Re: 1969 BB Idle stop solenoid components

Hi Steve,
I have an original L88/M40 car with (as far as I know) the original bracket and solenoid. I'd be happy to take some photos over the weekend and send them to you. Send me your email address.

By the way, are you sure about the CX coded trans? I have my original transmission with vin and, if memory serves, it is a CY code.

Thanks,
Jon
jstrac@cox.net

[Dick W.]

Re: 1969 BB Idle stop solenoid components

Steve, Jons car has the bracket and solenoid that you are looking for. I have seen his car and a couple of more L/88 automatic cars. They all have the setup that he does.

[Mark #28455]

Thanks! *NM*

[Steve Antonucci]

Re: 1969 BB Idle stop solenoid components

Excellent Guys !

As always - many thanks!

Steve

[Steve Antonucci]

Re: 1969 BB Idle stop solenoid components

Jon,

While on this topic, what actually activates the idle stop solenoid? Does it
always come on at idle? Or, does it activate in cold weather, or ...?

Lastly, while the solenoid is energized, what is the increase in RPM's?

Steve

[Clem Z.]

these idle soleniods were used for different

reasons,some kick up the idle speed when the A/C is on and some were use to close the carb butterflys down to prevent engine run on when you shut off the ignition. i never owned a corvette with one so i have no idea what purpose they served on a corvette

[Jon S.]

Re: these idle soleniods were used for different

I believe Clem is correct, and going from memory (not a good thing, lately), the idle stop solenoid on the L88s is actually called an "anti-diesel solenoid" in the books. I don't recall what book, but that does ring a bell.

Jon
#10673

[Clem Z.]

that makes sense since L-88s had no A/C *NM*

[Mark #28455]

since we're talking L88's

Has anyone looked at the fuel distribution "Y" block? I was originally told that 1969 L88's all had a block with an attached support that bolts to the intake manifold, yet I was recently told that the ZL1 Camaros did NOT have this support and that person was under the impression that the support did not come out until June 1969 (too late for the Camaros).

Any thoughts?
Mark