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Author Topic: 69Z hard start, backfires on acceleration, stalls when breaking, related issues?  (Read 3015 times)
Steve68
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« Reply #15 on: November 24, 2013, 10:10:14 AM »

Quote
How does one check/adjust the choke? I understand the need for the gap check on the choke plate when closed. It is about 9/32". Are there other adjustments to check? This is the original style choke, not electric.

Place the choke cam on the high step (the end of the screw on the high step) and adjust the screw to around 1500 - 2000 rpm to get your choke set at appropriate engine rpm's in cold weather.
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Steve68
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« Reply #16 on: November 24, 2013, 10:51:46 AM »

Doomer,

Sent you an email with instructions, pics, and additional adjustment info.  To large a file to attach here.

Steve
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doomer
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« Reply #17 on: November 24, 2013, 11:47:59 AM »

You posted as I was typing. .060 is a large gap ,more than we run on the race car.

After a short drive, the backfiring seems to be resolved. This is after replacing the previous plugs with new autolites that were all gapped at 35. Crossing my fingers.

Thanks again to everybody who helped. CRG is definitely my favorite online resource.   Grin
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janobyte
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« Reply #18 on: November 24, 2013, 12:02:52 PM »

Gotta let these carbureted engines "warm up". In todays world of EFI . often forgotten. Glad to see you may have solved it !
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sixt9x33rs
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« Reply #19 on: December 14, 2013, 09:08:05 AM »

Did you get your choke adjusted the way out want it? The adjustment is done manually with a straight slot screwdriver. You manually "bend" the tang that sit on the cam related to the choke assembly. It is simple to do.
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'69 RS Z/28 Olympic Gold, 711
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KERR
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« Reply #20 on: December 20, 2013, 11:00:14 AM »

Mine is doing the same thing,    However i just got the car so i dont know what has been done and what hasent.

When i go to start it in the AM,   It takes for every..  Plan to spend about 5 min just to get it to start.   Its like i have no fuel...    Dont touch the gas it just cranks and cranks,   but you can hold it wide open and it just cranks and cranks..   finally it will start sputtering and come to life..  even when it does start it keeps dying.

Once you make it out of the garage / drive way it  back fires, stumbles a lot...    once the motor is all the way warm it does some what better but its way off.   

Ive ordered a rebuild kit for the carb... i hope to do that saturday.
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JohnZ
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« Reply #21 on: December 20, 2013, 11:55:27 AM »

Dont touch the gas it just cranks and cranks,   but you can hold it wide open and it just cranks and cranks..

Neither of those two methods of starting it from cold are allowing the choke to work - they both leave the choke blade wide open so it isn't pulling the extra fuel it needs to start.

Just push the accelerator to the floor once or twice to set the choke, then turn the key, and it'll start (unless the choke isn't properly adjusted).
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'69 Z/28
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KERR
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« Reply #22 on: December 23, 2013, 10:09:42 AM »

well i had time to look at mine this weeked..  first off i only know a little about carbs,

 #1,  if you take one apart make sure your kids arnt around or it will never go back together!

 Anyway,   i had a freind help me and pretty much the carb needs help.    the choke is electric and has been bypassed.  then for the stumbling he adjusted a buch of stuff with no help.  next it was take apart and cleaned,  no help either.. 

He said from the looks of it,  i need a accelorator pump,  a cam something, and a few other things...    So i think im just going to buy a new carb that isnt a eletric choke and a vacuum secondary,     
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JohnZ
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« Reply #23 on: December 23, 2013, 12:34:22 PM »

well i had time to look at mine this weeked..  first off i only know a little about carbs,

 #1,  if you take one apart make sure your kids arnt around or it will never go back together!

 Anyway,   i had a freind help me and pretty much the carb needs help.    the choke is electric and has been bypassed.  then for the stumbling he adjusted a buch of stuff with no help.  next it was take apart and cleaned,  no help either.. 

He said from the looks of it,  i need a accelorator pump,  a cam something, and a few other things...    So i think im just going to buy a new carb that isnt a eletric choke and a vacuum secondary,     

This is not that difficult. What intake manifold and carburetor do you have?
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'69 Z/28
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KERR
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« Reply #24 on: December 24, 2013, 09:44:57 AM »

to be honest i would have to go look,  I want to say its a holley street advenger? and i think the intake is a Edelbrock.     Its probably a good carb if everything is fixed,  but ive never had good luck with electric chokes, and vacuum secondarys.   I have a Holley 850? double pumper on the vette with manual secondaries.  I never have a problem out of it besides the usual adjustments for weather. 

There is a 850 for sale in the local traiding times,  but thats over kill for the camaro.   
on a side note i did run across a two 4's on a weind manifold and two stage direct port kit with optional fogger set up...   But considering im pretty sure this a stock motor with a cam,  it would go bad in a hurry lol..     

I just dont want to spend a lot of money on the car at this time to get the little problems worked out.   I bought the car for the body / frame to be honest,  and i got lucky that it sorta runs.   Id rather go cheap /used and make it reliable to drive for now,  and save my money for big and better parts,   Then again ive thought about just taking to the lake and putting it into storage until i buy all the parts...       

The game plan is a real real big big block, with a 6 speed and prob a ford 9 inch,     or reuse my current 496ci motor thats turboed,  and 4l80E,  not sure a manual will live when banging gears under boost.
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BULLITT65
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« Reply #25 on: December 24, 2013, 10:51:31 AM »

I think the manual 6 out out of a 4th gen would work just fine. My friend has a 73 Camaro with an LS1 and one of the bigger turbo set ups that i have ever seen and doesn't have any issues. His car is built around autocross and has about 900 hp to the rear wheels
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1969 garnet red Z/28 46k mile unrestored X77
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z28z11
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« Reply #26 on: December 31, 2013, 01:05:53 AM »

A couple of things that have not been mentioned in previous replies -

The accelerator pumps on the stock 4053's typically don't give enough of a shot to prevent stumble on acceleration - plus the combination I ran needed more carb, so I changed mine out to an 850 DP - worked for me - I had this problem back in '75. Cold plugs will give you a lot of deceptive problems (found this out the hard way, too - started my rebuilt 302 in '75 with Autolite A22 racing plugs, was ready to toss in the towel until I changed back to the hotter AC std. plugs and cured it). I was running 12.5:1 Manleys in it, with an Erson HiFlow 2H hydraulic - it would literally fly when it finally got the combo ironed out.

A couple of good backfires will trash your power valve(s). Be sure and replace it with the proper configuration valve, one that matches your original carb's numbers.

Lastly, the Pertronix is a good system, or you can use good HD GM or Accel points if you retain a points distributor. Strong coil helps, too - use a ballast resisitor if you use a high voltage coil so you won't burn your points up prematurely if you do use points. Common sense stuff -

Regards,
Steve
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KERR
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« Reply #27 on: January 03, 2014, 10:22:48 AM »

I havent done anything yet...  i took the kids for a ride saturday and it died,  will not restart..  i guess the fuel pump gave up Sad

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