Survey Request -- Z28 302 Cold Engine Starting Procedure

[COPOZ/28]

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

[GMAD_Van Nuys]

I hope some Z28 owners reply to this survey as I go through a similar process starting a vintage vehicle which has a Holley 4150, but it is not a Camaro.

[jwbavalon]

I would classify my 1968 Z28 as authentically restored and is in a proper state of tune and no drivability issues.  I have a Progression distributor.

As per your questions, the following are my observations on starting after 24-48 hour since last driven.

1. Fuel level is lower but did not check

2. Do not add fuel .

3. Pump the accelerator one time to set the choke then 1-2 times to before turning the key

4. I do not pump the accelerator pedal while the starter is engaged

5. I do not hold the throttle when you turn the key to engage the starter

6. When the engine first fires, it does not typically run "clean" on all cylinders but needs a few seconds and/or some throttle movement before it runs clean on fast idle at 1500 rpm with foot off the accelerator then further drops to 1300 rpm on a light tap of the accelerator pedal.

7. By not adding fuel to make up for the evaporation, I use the starter to build up oil pressure before the engine starts.  Usually it takes 2 starting process of 3-5 second key turns till it fires.

Once running, no problems restarting after a 6-7 hour stop at Car Shows with only one pump of the accelerator.

[Brew14u]

My 1969 Z28 has the original drivetrain, original distributor, date correct recently restored 4053 (not original), original intake and heads.  I assume the internals are original, but I have not verified.  I try to drive it once a week or at least once every two weeks.  The more frequently I drive it, the easier it is to start and it seems to run and drive better. 

To specifically respond to you questions:
1.   I believe the fuel level in the primary float bowl is low, but I have not checked the level, there is no detectable leakage
2.   I do not add fuel to the primary bowl other than with the starter and mechanical fuel pump
3.   Yes, 5 pumps @ 100%
4.   I do not touch the accelerator when the starter is engaged to avoid backfiring (yes, I have experienced backfiring if I operate the accelerator while
        the starter is engaged)
5.   I do not touch the accelerator when the starter is engaged to avoid backfiring
6.   It does not run “clean” when it first fires, pump accelerator about 50% 2 or 3 times until it runs “clean”
7.   Brief stops to get fuel, I only turn the key and it fires up and runs “clean”, for several hour stops 2 pumps @ 100% before turning the key, for next
        day starts I use the 5 step procedure below

After much trial and error, here is the starting procedure I use:
1.   Crank the starter for 5 seconds, turn the key to stop for a second
2.   Crank the starter for 5 seconds, turn the key to stop, adds fuel to the primary fuel bowl and begins oil circulation
3.   With the key in the off position to avoid operating the cowl solenoid,  pump the accelerator 100% 5 times
4.   Without touching the accelerator, turn key to start, fires up but struggles
5.   Pump accelerator about 50% 2 or 3 times until it runs “clean”

Based on the 55 year old dash tach, fast idle is about 1,800 and normal idle is about 1,100.  I rarely take it to 6,000, but pulls hard 3,000 – 6,000.  One problem I have is the exhaust has an extremely strong smell of unburned fuel to the point of making your eyes burn and clothes reek even though cylinder compression and spark plug appearance are normal.

[NAPA68]

I'll respond survey prefacing the fact I do NOT have the requested car. Although, I find the procedure applicable to most any collector car I own.
1. Crank the engine until it shows oil pressure
2. Once it shows oil pressure, I stop cranking and depress the pedal to the floor 2-3 times
3. Wait about 10 seconds
4. Crank (no thottle) and most often the car jumps on high idle (or in the case of my L88 I hold it up there).

I find cranking the engine until there is oil pressure is enough to fill a low fuel bowl. Pumping twice and waiting allows the fuel to atomize in the intake.

Tim

[COPOZ/28]

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.