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.

[NAPA68]

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.

Hey there Chuck,

Yes, the carb on the L88 is a double pumper.

Tim

[GMAD_Van Nuys]

While not a 1st generation Z28, my Mustang has a factory Holley 4150 780 cfm carburetor and I use the following procedure to start the car after it has been sitting for several weeks:
1).  Pull manual choke.
2).  Pump accelerator three times.
3). Engine usually starts after cranking the starter three times.
4).  I'll let the car idle with the choke on before driving the car for a couple of minutes as I've had it stall when I immediately drive it.

If the car hasn't been drivien in a month, it is difficult to get it started.  After multiple attempts, I'll let the car sit for 10 minutes or so and then it will start easily.  The Mustang has a Shaker Hood and I would have to remove the assembly to inject gasoline into the fuel bowls, so I haven't had to do this yet.  The BOSS 302 was rebuilt by the prior owner with replacement TRW pistons, aftermarket camshaft with Crane rockers, Stinger electronic ignition, and Hooker Super Competition headers.

[Dave69x33]

Interesting topic and one I deal with on occasion.

My '69Z is stock restored.  If I do not drive the car for an extended period of time such as during winter storage, the fuel in the float bowls does evaporate.  I use a small 7 - 9 ounce clear plastic bottle filled with fuel (approximately the same total amount contained in the float bowls), with a tapered extended tip (from Hobby Lobby) that fits inside the primary and secondary fuel bowl vent tubes. It works well to control an squeeze fuel down thru the vent tubs to prime the float bowls.  I then use a couple squirts of starting fluid down the carb, mash the throttle once to set the choke, then start the car.  The engine may sputter on the first attempt but then I mash the throttle once again and the engine typically comes to life.  Remember that once the float bowls are filled and fuel is supplied to the Holley accelerator pump, mashing the throttle sprays raw fuel down thru the carb. If you continue to full pump the throttle, you run the risk to flooding the engine...not a good thing on a cold engine that has not been started for an extended period of time.  Too much raw fuel can soak the cylinders and plugs, and leak down into the oil.  Pull the dip stick and smell the oil if you think this has happened...which might be time for an oil change!

During winter storage, keep your fuel tank full and use a few stabilizer such as Stabil 360.  Unless you use non-ethanol race fuel, a few stabilizer during storage is a must.   

Once my 302 has been run, warmed up and driven, then turned off and sits overnight, the next day with one mash of the throttle to set the choke and shoot some fuel down in to carb typically allows my engine to start with no issues.  If the car sits for about a week, I mash the throttle once and start the engine which may sputter a bit, but with light feathered foot taps on the throttle (not full full mashes of the throttle), the engine comes to life.  The engine may stumble a bit if the choke is not set right (to maintain about 1500 - 1800 rpm), feather the throttle for a few minutes until the engine (and intake manifold) begin to warm up and atomize the fuel.

P.S.  I have a 10 mile road trip that I will take my Z28 on during the winter after 6 - 8 weeks, if the roads are dry, to help keep the car running well, powertrain seals lubed, and prevent the hard starts after sitting for months!  I may even "bark" the tires one or twice on those trips...LoL!

[COPOZ/28]

Dave69x33:  Very interesting.  Of the responses posted to this survey request so far, your Z is the only one that actually fires up (even though it may not be "clean" running right away) with just one pump of the pedal after sitting for a day or two.  You mentioned your car is "stock restored", so I assume it has all the correct carb, manifold, camshaft, distributor, etc. pieces for a '69 302.  The rest of us stated that we have to go through multiple pumps before we turn the key to get it to fire up on the first attempt when cold.  If I were to give my car just one full pump and then turn the key, it would literally crank without firing for as long as I chose to keep the starter turning.  Has your car always behaved this nicely for you on cold starts, or is there something regarding its tuning spec's that you've done to enhance its ability to cold start on just one pump?

[Dave69x33]

COPOZ/28:

I should clarify that my 302 does not always fire up with one press of the accelerator peddle. It may require 2 - 3 try's to get the motor to fire to life after an extend down time. I just prefer to not pump the throttle numerous times before the first attempt to start the cold motor and spray too much raw fuel down the carb and into the cylinders.  Again, for me I found using starter fluid helps get a cold engine to fire if it has not be run for an extended period of time.

Modifications: I did upgrade my valve train and cam to a full roller Comp Cams #12-770-8, called out as the CSXR274 R-10 cam.  Gross lift is 0.564 Intake and 0.570 Exhaust, Duration @0.50 236 Intake and 242 Exhaust with lobe lift 0.3770 Intake, 0.3810 Exhaust and 110 degree lob separation.  Since my DZ 302 motor is not the original for my car (was in the car when I purchased it), I took a few liberties to upgrade the valve train s if the modifications could be hidden and not obvious. The idle characteristics are a bit more aggressive than the stock 30 - 30 cam but has a much more useable power band in the 2200 - 6200 RPM range. I really like the throttle response from the cam from 1500 - 6500 rpm.  The rest of the Comp Cams valve train include: Rocker Arms: Comp Cams CS 1.5 Ratio, 7/16” Ultra Pro Mag XD #1804-16, Lifter Kit: Comp Cams Roller Lifter, CS Super #818-16, Valve Springs: Comp Cams Spring, #977-16 for #972-973. along with custom length push rods to assure a proper sweep path in the middle third of push rod tip.  I posted a sound bite on YouTube. If you search "Soundbite of 1969 Z28 Camaro with Comp Cams XR274R Cam No. 12-770-8: you can here the cam.  Its a LeMans Blue Z with white stripes.  I can believe I did this in April 2012...wow, where did the time go!?!


Timing & Vacuum Advance: I run the initial timing at 12-degress BTDC, idle speed between 900 -1000 RPM, but prefer to set the total mechanical with a dial-back timing light with the RPM set at about 3000. This is per Jerry MacNeish's recommendation who restored and reset the advance curve in my stock restored #1111780 correct date coded distributor. If you search CRG, there is good discussion on setting timing and how to make sure all the mechanical advance is in by 2400.  I also run full vacuum advance to the distributor from idle. You need to swap the vacuum lines between AIR (smog) system diverter valve and the dist vac advance. You need the dynamic vac advance to the distributor to get the 302 to run optimally and for best drivability. CRG chief contributor JohnZ has a great tech article explaining this. The "stock" vac advance was set up for emissions with the smog system and not performance.

Carb & Jetting: I also spent considerable time dialing in the jetting in my stock restored #3923289, correct date coded Holley model 4150 780 cfm carb.  My carb specs: jets are #68 primary, #76 secondary, #6.5 primary power valve and replaced the secondary power valve with a block off plug.  I use #28 discharge nozzle with the extended tubes (for improved direct fuel flow) and white accelerator pump cam in the #1 piston.  My secondary spring is the yellow color code designed to open at 1635 rpm and be full open at 5750 rpm.

Spark Plugs: I run AC Delco hotter R45 plugs. The stock R43 are rated too cold for the 302 driven as we drive our cars.

All told, my intent is not to say this is how we should all start our cold 302 Z28's but this method has worked well for me!

Hope this helps!