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9/19/11 9:59pm - Original Message: 'ummm.... backfire intermitant'
chronos51
Former Member
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Phoenix, AZ - USA

Vette(s):
1982 corvette crossfire production numer C5101985. Color is silver and claret. All original numbers match. slight mods to crossfire for better efficiancy and power balanced and added fuel pressure assembly between throttle bodies,

Joined: 6/12/2011
Posts: 139
Shocked
82 crossfire injected 74000 miles on it.

just had the oddest thing happen while driving at low in town speeds. I lightly accelerated and my car stalled then backfired. happend 3 times at the same rpm. I checked it at a stop at home and I cant get it to repeat the intermitant backfire. my dist cap moves slightly and Im thinking its time to replace it, timming is correct or as correct as I can get it, no engine codes.
any ideas?
Marcus Confused


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9/20/11 5:17pm - Reply: 'Re: ummm.... backfire intermitant'
chronos51
Former Member
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Phoenix, AZ - USA

Vette(s):
1982 corvette crossfire production numer C5101985. Color is silver and claret. All original numbers match. slight mods to crossfire for better efficiancy and power balanced and added fuel pressure assembly between throttle bodies,

Joined: 6/12/2011
Posts: 139
ok. so I replaced the cap, rotor and the hei ignition coil. seems to have corrected the issue.
Marcus


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9/20/11 5:27pm - Reply: 'Re: ummm.... backfire intermitant'
kwoody
Former Member
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Tucson, AZ - USA

Vette(s):
1982 Black/Tan Leather Build Code C09E Bronze TTop CrossFire Fuel Injection L83 85 Fuel Pump Auto Axle 2.72 Firestone Firehawk Indy500

Joined: 7/11/2010
Posts: 415
Hi Marcus,

I had my dist cap pop up and the rotor made a revolution and left a mark above the contacts. 

What I noticed from the driver's seat was a back fire and jerking motion and the engine stopped. 
I pulled over and found one of the distro clamps loose. I could lift up on that side of the cap.
I secured it and drove home.  I replaced the cap and rotor and made sure that the clip was seated
properly. 15,000 miles later I have had no trouble like that again.

I must not have had the clip lined up on the groove where it seats. 


All the best from Tucson.

Keith


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9/20/11 10:24pm - Reply: 'Re: ummm.... backfire intermitant'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
Take a look at the back side of the old rotor you took off, Marcus....see if you see anything that looks like dark colored lightning bolts running from the center of the rotor out to the screws that hold it on....I bet ya do....

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Joel Adams
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9/21/11 11:26am - Reply: 'Re: ummm.... backfire intermitant'
chronos51
Former Member
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Phoenix, AZ - USA

Vette(s):
1982 corvette crossfire production numer C5101985. Color is silver and claret. All original numbers match. slight mods to crossfire for better efficiancy and power balanced and added fuel pressure assembly between throttle bodies,

Joined: 6/12/2011
Posts: 139
The cap was just loose and the 4 screw clamps would not keep it tight anymore. inside the cap... the contacts were pretty marred up and yes their were black marks on it but more towards the bottom of the cap where. the rotor contact point was pretty messed up as well. the Hei unit that sits on top well the previous owner had sodered the hot wire back on to the metal area that pushes into the dist for contact to the wiring. That was also not making good conection.
It would stall while accelerating, the other day it stalled to the point where it shut the motor down and back fired through the crossfire units.
 
Never Never trust anyone elses work is what I have learned.
 
Marcus


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9/21/11 12:44pm - Reply: 'Re: ummm.... backfire intermitant'
Adams' Apple Lifetime Member
Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
One of the major issues with the HEI system is the rotor, or, more precisely, the composition of the rotor. What kind of plastic/composite is used makes a huge difference. While the OE rotors will still have the same failure issue, the aftermarket replacement rotors are absolutely junk in comparison, with the exceptions of a couple of the High Performance ignition manufacturer's parts.
What happens is the electricity from the ignition system naturally wants to find the easiest way to ground....usually that ground is the side electrode of the sparkle plug. Once the plug electrodes wear, the gap widens, or there is an issue with the plug wires, the ignition voltage wants to find a quicker, easier path to ground. The closest ground there is is the two screws that hold the rotor to the distributor shaft.....and THAT'S where the little lightning bolts on the bottom of the rotor come from, and the blackened look of the center of the rotor. The ignition voltage is literally jumping thru the plastic of the rotor, going to ground. I've seen rotors that were so cheap they would melt a hole right thru the center in about a week of driving.Angry

Anyway, the whole point of this is to use the best quality ignition components you can on an HEI system....it could mean the difference between getting home, or getting a tow twuck...
Also, if you happen to have a violent backfire thru the intake, that can blow vacuum lines off, as well as damage some of the gaskets in the intake tract...and if ya have a Holley sitting on top, you can bet yer booty it just blew the power valve all to smithereens....


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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