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That about wraps it up -- thanks Kurt and Bryon.

Encouraging info -- thanks to all who responded.  A friend took my question to a Corvette forum and received very similar responses to those here.

What about the possibility of the new-for-1969 head casting p/n 3927186 being introduced early, as a running change during the last 3-4 months of the '68 model year?  If introduced early, and if Flint didn't spend tooling $'s for drilling/tapping the alternator mounting holes, were these new head castings ever used on later '68 engines with their left side alternator mounting provision remaining in place until the actual 1969 start of production, when the change over to the right side alternator location took place?

If that is unlikely (or never documented by anyone in CRG as having taken place on an engine), I would have to agree it is most likely explained by a digit that got "buggered up" a bit during the mold making/casting process.

My 05E Norwood '69 Z28 has a pair of the 3927186 cylinder heads on its engine and both heads have the bosses and 3 drilled/tapped holes for a right side alternator mounting location that was adopted for the start of the '69 model year.  Right side head has a casting date code of E79 (May 7, '69).  Left side head date code looks much more like E78 (May 7, '68) than it does E79 -- see photos.  The engine build date per my P-O-P is 0513 (May 13th).

Has anyone observed a 3927186 head with a casting date as early as May 7 of 1968?

August 2026 Update:

While having my '69 Z28 certified/appraised at Jerry MacNeish's shop in Maryland last month, he had laid out a couple of his original '67 Z28 Holley List 3910 carbs (date codes 751 and 753) for me to measure various air/fuel calibration hole diameters (PVCR, IFR, etc.) -- info I was missing in my database of the three different Holley carbs used on '67-'69 Z28's.  That completes the list of all calibration spec's on two of the three unique carbs for these engines, the '67 List 3910 and the '68 & '69 List 4053.

Jerry also gave me contact info for someone he knows very well who owns one of the incredibly scarce Holley List 3911 carbs that came only on the few '67 Z28's built for sale in California.  I've contacted that person, who luckily lives only about an hour and a half from me, and he agreed to let me review that carb once we agree on a mutually acceptable date sometime in the next few months.

Stay tuned!

August 2026 Update:

While having my '69 Z28 certified/appraised at Jerry MacNeish's shop in Maryland last month, he had laid out a couple of his original '67 Z28 Holley List 3910 carbs (date codes 751 and 753) for me to measure various air/fuel calibration hole diameters (PVCR, IFR, etc.) -- info I was missing in my database of the three different Holley carbs used on '67-'69 Z28's.  That completes the list of all calibration spec's on two of the three unique carbs for these engines, the '67 List 3910 and the '68 & '69 List 4053.

Jerry also gave me contact info for someone he knows very well who owns one of the incredibly scarce Holley List 3911 carbs that came only on the few '67 Z28's built for sale in California.  I've contacted that person, who luckily lives only about an hour and a half from me, and he agreed to let me review that carb once we agree on a mutually acceptable date sometime in the next few months.

Stay tuned!

I found this one, loose, hex head screw wedged between the upper rounded edge of the washer reservoir and the  radiator closure panel on my '69 Z28.  It's 1/4"-20, non-full thread, 7/16" hex head, 13/16" long with a small hole drilled through each flat on the hex and a larger dia. blind hole, about 1/8" deep, in the center of the head.  Anyone recognize it as a legit Camaro fastener?

At first blush, it resembles the two fasteners that attach the left side radiator support to the radiator closure panel, into well-nuts, but the those screws have a flange head and do not have their hex flats thru-drilled, per the AMK website -- unless I'm wrong about that.

Thanks for the help.

Thank you!

That's one less thing to do (three times!) for my trip to and from the Camaro Nat's in Morgantown, PA, next week, with a side trip on the way home to Jerry MacNeish's shop in Maryland for an appraisal/certification.

I will be trailering my '69 Z28 in an enclosed trailer very soon.  Although I am an experienced trailer user (boats, 5th wheels, utility, etc.), this will be my first time using an enclosed car hauling trailer.  The trailer has an electric winch to pull the car into the trailer, rather than having to drive the car in.  I plan to attach the winch cable to an axle strap looped around the center of the front suspension crossmember and then pull the car up the ramp with the winch.  I'm hoping others have determined if it is advisable to remove the front spoiler and support rods before loading the car into the trailer. 

If I don't remove the spoiler and support rods, is it possible these parts would contact the loading ramp's surface as the car begins to make its way up the ramp?

Thanks for your help.

Thanks Jim.

Does anyone know the hex size and thickness of the pair of 5/16"-18 adjusting nuts (GM #9417954) on the front parking brake cable?

Are they the standard 1/2" hex for a 5/16"-18 nut or are they the oversize 9/16" hex?

They could also be thicker than a standard nut to permit an open end wrench to hold the one nut (the nut that is against the cable guide) while the 2nd (locking) nut is tightened.

Also, I've found conflicting info on whether these nuts are phos/oil coated or zinc plated.

Thanks for the help.

Like many before me, the correct speedo cable clip is a difficult part to find.  Some cars have 2 holes in the tunnel and use 2 clips in the tunnel area, while others have one hole in the tunnel.  In addition, there is a hole behind the ignition coil on all cars for another clip, close to the cable's grommet, just before where the cable enters inside the car.

One restoration parts supplier offers two versions of this clip p/n 3772324, one of which is described as "assembly line correct" at a higher price.  I've tried installing this "assembly line correct" clip and find that one of the short locking fingers breaks off when trying to get it into the sheet metal hole and/or when expanding the locking fingers.  This happened with two of these clips.  Reviewing posts from others on these clips, it is apparent no one is making a workable version of it.

In the meantime, I've found another style clip that does a great job of supporting the speedo cable, in any of the 2 or 3 locations for a speedo clip and securely fits into the existing approx 5/16" drilled hole in the sheet metal.  The clip I found is actually a MoPar brake line clip for use with armored brake tubing (measures approx. 5/16" dia. over the armor/spring material).  It was used extensively on 1960's and early 70's MoPar cars.  This clip not only fits the existing sheet metal hole nicely, but also gives a secure fit to the Camaro's speedo cable.

Until such time as I can find the correct style Chevy clip that actually installs, expands the locking fingers properly without them breaking off, and stays put, this MoPar clip is going to be used to keep the speedo cable properly routed.  They are available from any of the MoPar restoration parts suppliers.

I have also used Sta-Bil for a few decades with good results.  About 10 years ago, I switched over to the ACES IV stabilizer and octane enhancement product from BND Automotive.  It equals the performance of Sta-Bil when it comes to keeping fuel fresh over long periods of storage.  But the ACES IV product has other other significant advantages over Sta-Bil.  It does a very good job of enhancing the octane level of unleaded gas, something Sta-Bil does not do.  It also reduces ring/bore wear.  Both of these advantages have been documented by Automotive Engineer/Racer/Tech Writer, David Vizard, in extensive A/B dyno tests he has run.

I was rooting around in the trunk of my 05E Norwood '69 Z28 recently and I discovered this small pad tucked up close to the rear seat back.  Does anyone recognize what this may be, assuming it came with the car?  If it did, could it be a protective pad to prevent the bumper jack from scratching the chrome on the bumper?

April 2026 Update:

Good news!  A fellow CRG member, known to many of us, has volunteered to offer their original '67 Z28's List #3910 Holley carb for me to gather needed information that will help me to complete a forthcoming database of fixed and changeable tuning orifice diameters, and other features, on 1st Gen Z28 carbs.

I will be visiting this volunteer in July, 2026 and complete the List #3910 portion of the database later that month.  This will leave the very low volume List #3911 carb, used exclusively on California bound '67 Z28's with the K19 A.I.R. smog control system, as the only missing data.  I suspect my chances of having anyone step forward with one of these List #3911 carbs, complete and in its original unmodified condition, are about nil as only fraction of the 602 total '67 Z28's were delivered to California.

There is a possibilty that the List #3910 & #3911 carbs were identical as far as certain drilled orifice dia's are concerned, but whether this is true or not is unknown to me at this time.

The primary metering block used on the List #3911 carb is stamped with the ident no.: 5462 on its top surface.  Does anyone have one of these 5462 metering blocks they would allow me to measure various hole dia's, or agree to let me send various size numbered drill bits to you for you to measure these few holes?

Maybe someone out there has a List #3911 main body that would yield the air bleed hole dia's?

Thanks for your help.  It is still my desire to have the CRG publish the data on the website when it is completed.

Again, if anyone with a List #4053 carb (used on all '68 & '69 Z28's) would like to confirm the dia's of any tuning holes in their carb have been drilled out or not, please send me a PM and I will respond.

Chuck B.

April 2026 Update:

Good news!  A fellow CRG member, known to many of us, has volunteered to offer their original '67 Z28's List #3910 Holley carb for me to gather needed information that will help me to complete a forthcoming database of fixed and changeable tuning orifice diameters, and other features, on 1st Gen Z28 carbs.

I will be visiting this volunteer in July, 2026 and complete the List #3910 portion of the database later that month.  This will leave the very low volume List #3911 carb, used exclusively on California bound '67 Z28's with the K19 A.I.R. smog control system, as the only missing data.  I suspect my chances of having anyone step forward with one of these List #3911 carbs, complete and in its original unmodified condition, are about nil as only fraction of the 602 total '67 Z28's were delivered to California.

There is a possibilty that the List #3910 & #3911 carbs were identical as far as certain drilled orifice dia's are concerned, but whether this is true or not is unknown to me at this time.

The primary metering block used on the List #3911 carb is stamped with the ident no.: 5462 on its top surface.  Does anyone have one of these 5462 metering blocks they would allow me to measure various hole dia's, or agree to let me send various size numbered drill bits to you for you to measure these few holes?

Maybe someone out there has a List #3911 main body that would yield the air bleed hole dia's?

Thanks for your help.  It is still my desire to have the CRG publish the data on the website when it is completed.

Again, if anyone with a List #4053 carb (used on all '68 & '69 Z28's) would like to confirm the dia's of any tuning holes in their carb have been drilled out or not, please send me a PM and I will respond.

Chuck B.