Messages

1

Maintenance / Re: Survey Request -- Z28 302 Cold Engine Starting Procedure

« on: November 14, 2024, 08:11:48 PM »

Thanks for your info, Tim.  Your info on your L88 is applicable to this survey, given those engines had similarly "long-winded" camshafts and big CFM carbs to those found on the early Z28's.  And thanks for mentioning your engine starting process includes waiting 10 seconds after pumping the throttle before turning the key.  I should have included that as a question to ask in the list of survey questions.

Is the carburetor on your L88 a Holley with mechanical secondaries (meaning, it has an accelerator pump on both the primary and secondary float bowls)?  If so, that may help to explain why you’ve had success starting your cold engine after giving it only 2-3 throttle pumps.  I recently had a 413 small block with a solid roller cam that had the same int/exh durations at 0.050" as the ’67-’69 302 cam.  It had a Quick Fuel mechanical secondary 850 CFM carb with no choke system on a dual plane intake.  Like your L88, it would always fire right up after only 3 throttle pumps when dead cold.  The key thing here is that any mechanical secondary carb puts the same amount of fuel into the manifold with only 3 throttle pumps as a roughly equivalent vacuum secondary carb does with 6 pumps.

I am hoping more 302 Z28 owners respond to this survey.  If they do, owners of these, and similarly spec'd, cars will gain information about how they can best be "coached" to reliably cold start in a more consistent manner.

Thanks to all who respond.
Chuck B.

2

Maintenance / Survey Request -- Z28 302 Cold Engine Starting Procedure

« on: November 04, 2024, 06:58:29 PM »

This survey request is for those owners of well-maintained survivor, or authentically restored, 1967-69 Z28’s having the following correct 302 engine components:  ignition system (Pertronix conversion OK), carburetor and fast idle system, intake manifold, camshaft, pistons, spark plug wires, starter, etc., and is in a proper state of tune, without exhibiting any drivability issues once the engine is running.

If your 1967-'69 Z28 is in this category, I would be interested in hearing from you about the process you go through to start your cold 302 engine in typical summer temperatures (60-80 deg’s F) providing it has been at least 24 hours since the car was last driven.  Thanks in advance to everyone who participates in this survey request.

Could you please answer the following questions:

1. Before attempting to start the engine, have you found the fuel level in the primary float bowl is considerably below the bottom of the sight plug threads, with no signs of external leaking?  About how far below?

2. Do you routinely add any fuel to bring the float level in the primary bowl up to spec, to replace whatever fuel may have evaporated, prior to turning the key? (by way of an electric fuel pump or manually adding fuel to the bowl by another means).

3. Do you pump the accelerator pedal one or more times before turning the key?  If so, about how many “pre-cranking” pumps do you give it?

4. Do you pump the accelerator pedal while the starter is engaged?  If so, have you experienced the engine backfiring while doing this?

5. How far open do you hold the throttle when you turn the key to engage the starter?  Is it just cracked a bit?, about 1/2 of the way open?, all the way to the floor?, or ?

6. When the engine first fires, does it typically run "clean" on all cylinders, or does it need a few seconds and/or some throttle movement before it runs clean on fast idle with your foot off the accelerator?

7. With whatever process you’ve found that works best for your 302 engine, do you find you have to repeat the entire starting process from scratch more than once in order for the engine to start and continue running?

In my ’69 Z28’s case, the 302 engine retains all of its original components, with the exception of my addition of a Pertronix II to the 1111480 Delco distributor about a dozen or so years ago.  I’m the 2nd owner of the car since buying it from a friend in 1979.  It has 28,000 miles since new and it has always required more than just one pump to set the choke and start up on the first attempt.  I have checked the fuel level in the primary float bowl 24 hours after the last drive on a number of occasions and found I typically have to add 1.75 ounces of gas through an upper bowl screw opening to bring the level in the bowl up to the bottom of the sight plug threads.  Whether I pre-fill the float bowl or not, to help ensure the engine starts and continues running on the 1st attempt, I have to give the throttle anywhere from 6 to 8 pumps, crack the throttle a bit, and then turn the key to engage the starter.  Then, if it does start, it usually runs on less than 8 cylinders.  I then immediately open the throttle a bit more and the engine usually “cleans up” after a few seconds and will then run on fast idle at approx. 1,600 RPM with my foot off the accelerator.  Once running, the car has always driven like a dream during the warm up period and, when fully warm, pulls strong well past the 6,000 RPM redline.  Hot re-starting, or after a two hour soak, is always just a quick one pump, turn the key and it instantly starts right up.

Again, many thanks to everyone who posts a reply.
Chuck B

3

Decoding/Numbers / Re: Part Number Stamp or Sticker on Wiper Motor Assy

« on: October 31, 2024, 12:28:53 AM »

Just discovered this older post on Wiper Motors and thought I'd add my info.  Hadn't realized wiper motors were date code until just recently.  I'm the 2nd owner of this '69 Z28 and bought it from my best friend's older brother in 1979.  I helped him get prices on the car from several Detroit area dealers on his behalf, but he ordered from Snyder Chevrolet in Defiance, OH.  It was delivered to him on 6/9/69.  The car had 5,172 at the time I bought it from him and it had not been licensed since 1973.  I've been very familiar with this car since before Day 1.  Given all this, I'm as sure as anyone can be that this is the original wiper motor that's still on the car today.

I am not sure how this new data gets added to the wiper motor date code chart Kurt has uploaded.  Perhaps someone can do that?

Body Build Week: 05E
Assy Plant: NOR
Vehicle Type: Non-RS
Sticker p/n 5045572
Stamped p/n: Yes, also 5045572
Sticker codes: 106 9 B F
Wiper Plant: Rochester

4

Decoding/Numbers / Re: Part Number Stamp or Sticker on Wiper Motor Assy

« on: October 31, 2024, 12:27:53 AM »

Just discovered this older post on Wiper Motors and thought I'd add my info.  Hadn't realized wiper motors were date code until just recently.  I'm the 2nd owner of this '69 Z28 and bought it from my best friend's older brother in 1979.  I helped him get prices on the car from several Detroit area dealers on his behalf, but he ordered from Snyder Chevrolet in Defiance, OH.  It was delivered to him on 6/9/69.  The car had 5,172 at the time I bought it from him and it had not been licensed since 1973.  I've been very familiar with this car since before Day 1.  Given all this, I'm as sure as anyone can be that this is the original wiper motor that's still on the car today.

I am not sure how this new data gets added to the wiper motor date code chart Kurt has uploaded.  Perhaps someone can do that?

Body Build Week: 05E
Assy Plant: NOR
Vehicle Type: Non-RS
Sticker p/n 5045572
Stamped p/n: Yes, also 5045572
Sticker codes: 106 9 B F
Wiper Plant: Rochester

5

Research Topics & Reports / Re: Original cowl hood photos needed

« on: February 07, 2024, 10:09:28 PM »

If it would help, I have a cowl hood on my car that I purchased new, in primer, that has the original GM Parts sticker still on it, last time I looked before covering the car for the winter last November.  I bought this Parts Dept. hood from a private owner back in the 1980/81 timeframe to replace my '69 Z's flat hood.  Just how old this hood was when I bought it is unknown.  I never procured/attached the matching underhood insulation and would be happy to take and post whatever photos of it are desired -- please let me know if this would help and I'll do that.

6

Maintenance / Re: 302 Z28 Divorced Choke Rod Adjustment

« on: February 07, 2024, 09:45:54 PM »

Thank you, GMAD_Van Nuys, for providing the link to the Holley 4150 repair/adjustment procedures -- very informative.  In reading through it, I noticed there are several carburetor adjustments that require a specific dimensional measurement be achieved for that feature to be adjusted properly.   There is a note in several places that state: "On some models, a specified dimension will be given in the specification table."  Is there a chance you might have this specification table for the 4150 carbs and be able to share it?

7

Maintenance / 302 Z28 Divorced Choke Rod Adjustment

« on: January 28, 2024, 12:01:05 AM »

The '69 Chevrolet Service Manual provides information on how to adjust the divorced choke rod on Z28 302's (and other Holley 4 barrel equipped V8 engines) on pages 6M-3 and 6M-7.  As written, the procedure is unclear.  On page 6M-3 it says:

    "On all engines except L6 and 2 barrel V-8 engines, hold the choke valve closed and push the rod downward to contact stop -- the top of the rod should be even with the bottom of the hole in the choke lever.  On L6 and 2 barrel engines, hold the choke valve closed and pull rod upward to end of travel.  The bottom of the rod should be even with the the top of the hole in choke lever."

There is no specific reference to Holley 4 barrel equipped engines in the 6M-3 page write up.  Therefore, should the choke rod be adjusted (bent) in the same manner as the above description for the L6 and 2 barrel engines, so that the bottom of the rod is even with the top of the hole in the lever?  I ask this because the 302 choke rod operates similarly to the L6 and 2 barrel engines -- namely, the choke rod is pulled upwards to hit the end of its travel.

Then, on page 6M-7 it says:

    "With Rochester 4MV and Holley Carburetors, install the choke rod and adjust as necessary.  Be sure choke valve moves freely from full open to full closed position."

I assume the instruction on page 6M-7 refers to the procedure on page 6M-3 which, unfortunately, does not mention Holley 4 barrel equipped engines.

Is the L6 and 2 barrel V8 procedure the correct choke adjustment procedure others have used on faithfully restored 302's that results in clean starts when the throttle is pumped just once to set the choke, without having to pump the throttle multiple times, before turning the key to start the engine? 

If anyone can shed more light on this maintenance/adjustment procedure for 302 z28's , I would be very grateful.

8

Originality / Re: Ignition Coil Primary Wire Connections -- Guide, Support, etc.

« on: December 24, 2023, 06:56:07 PM »

Hi Mitch,

Thanks for looking.  I was a bit surprised to see there are three upturned flanges and one long, narrow tab on the part.  I was expecting to see only two upturned flanges on opposite sides.  Perhaps my memory is failing me.  Is the one you found definitely the style Chevy used in the late 60's?
Chuck

9

Originality / Ignition Coil Primary Wire Connections -- Guide, Support, etc.

« on: December 22, 2023, 09:17:08 PM »

Does anyone know where to obtain the thin, stamped "guide" (or support) that go onto the ignition coil + and - primary terminals?  If I recall, GM used these items on each terminal of the ignition coil for most of their cars from the mid '50's thru the '70's.  These "guides" are the first thing that go onto each coil terminal, followed by the negative wire (from the distributor) and the positive wire (from the harness), and then followed by the #10-32 nut and lockwasher.  These "guides" were made from thin sheet metal (~ 0.020" thick) and had two opposite ends turned up as flanges (about 0.035" high).  These two upturned flanges on the "guide" served to prevent the legs of the wire harness terminals from spreading apart excessively when tightening the #10-32 nut.

I've tried AMK Fasteners and various restoration parts suppliers of replacement coils and they do not have these "guides".  Any help would be appreciated.  Thanks.

10

Originality / 1969 Z28 302 Engine Oil Dipstick Tube Orientation

« on: March 14, 2022, 08:09:41 PM »

There is information on the orientation of the oil dipstick tube in the block published in my copy of the '69 A.I.M. (in UPC 6, Sheet B1). It shows the curved portion/dipstick handle pointing forward and slightly outboard per a notation in View A that reads: 7 deg's, +/- 5 deg's, or roughly towards the left front headlight.  However, I've come across many underhood photos of  supposedly original cars that show in most cases the tube is oriented nearly vertical, such that the upper end of the tube is positioned between the cylinder head and the air pump distribution tube assembly.  Could this be one of those cases where it doesn't really matter how it is oriented as there are many documented examples showing a variety of orientations?

Thanks for the help.

11

Maintenance / Re: Head Gasket Steel Shim Style

« on: February 25, 2021, 12:12:45 AM »

My pistons all mic'd out at 0.022" +/- 0.001" down the hole.  The piston skirts were treated to the abradable coating from Line2Line in Clarkston, MI for a thumb pressure "push fit" into the cylinder, so that should reduce any piston rocking to the least possible amount and contribute to good, long term ring sealing.  Will follow their recommended dyno break-in cycle to optimize the skirt to wall fit.

12

Maintenance / Head Gasket Steel Shim Style

« on: February 24, 2021, 09:08:03 PM »

This is a head gasket preparation question.  I've received all my OEM '69 302 parts back from the machine shop and the block decks required about 0.008" to clean up, with the resulting deck height coming in at 9.011".  For head gaskets, I can choose between the modern Fel-Pro 0.038" composition part, the Chevy p/n 10105117 0.028" composition part, or the '69 OEM 0.016" steel shim part.  Knowing a tight piston to head quench distance (i.e.: "squish") of 0.036"/0.038" helps to fend off detonation, the 0.016" steel shim gasket gets me to this nice 0.038" squish, but the final actual compression ratio comes out to 11.08:1.  Stepping up to the thicker 0.028" Chevy '117 gasket drops the true CR down to 10.8:1 but increases the squish to 0.050".  Since I have used (and plan to continue to use) ACES IV mixed with 93 octane fuel successfully, I believe I can tolerate the 11.08:1 CR the steel shim gasket gives and plan to use it for this assembly.  My question has to do with how best to prep the "old fashioned" steel shim head gasket to avoid long term future coolant leakage.  Back in the day, the only steel shim head gasket prep I am aware of was spraying a light coating or two of aluminum paint on each side of the gasket, letting it dry and then installing/torquing the heads, followed by a retorque after it's first hot start/cool down.  I've heard of some folks laying on a very thin coating of Perma-Tex Gasket Maker (p/n 51813) around the gasket's coolant holes in addition to the aluminum paint spray.

What have others found that work long term for prepping the old style steel shim head gasket?  Thanks a bunch!

I forgot to mention all the "internals" are OEM '69 302 -- the cam, pistons, intake, carb, etc.
Chuck B.

13

Decoding/Numbers / Re: Oil Pan Ident/Date Code Stamping?

« on: April 08, 2020, 11:18:20 PM »

I stripped the paint off the timing cover today and found an obvious month/year date code: 4  69 (see pic's) which seems to make sense for my V0513DZ POP Engine Code.  I'm a bit surprised that the timing cover is date stamped but the oil pan is not.  There is a possibility that my oil pan is not original to the car as I know the 1st owner installed a deeper sump oil pan in 1970.  What I can't recall is whether he had the original oil pan modified for a deeper sump, or he bought a new 'ready-made' deep sump pan.  I seem to recall the deeper oil pan was on the engine when I bought the car in '79.  What I don't recall is whether or not I bought a new, correct replacement 302 pan or he included the original pan (if he had it) at the time of the car's transfer to me.

Have others found a month/year date code on their timing cover and/or oil pan?

14

Decoding/Numbers / Re: Oil Pan Ident/Date Code Stamping?

« on: April 05, 2020, 09:42:28 PM »

There is a possibility this number/letter stamping could possibly be the last 4 digits of the base (before any of the internal baffles are spot welded into it) oil pan stamping part number, along with the change letter of the engineering drawing in effect at the time it was stamped.  If this is correct, then the number/letter combo has no relevance to indicating it is a 302 pan as opposed to any generic small block pan without the internal baffles.

15

Decoding/Numbers / Oil Pan Ident/Date Code Stamping?

« on: April 04, 2020, 11:24:15 PM »

While in the process of refreshing the 302, I stripped the paint off the oil pan and discovered these characters - 2252W, located on the underside of the pan, about 2" back from the front face of the pan.  Does anyone know what this code refers to?