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3/13/12 11:46am - Original Message: 'backfiring with Edelbrock carb and intake...ideas?'
VikingVette
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Greer, SC - USA

Vette(s):
1978 Black with Viking mural painted under hood AM/FM/CB radio, T-top and a 2013 Cyber Gray Grand Sport Coupe, 2LT for my daily driver

Joined: 3/13/2012
Posts: 264
I am new on here.  I have a 1978 with a ZZ4 engine.  For showing, I had a Edelbrock endurashine intake manifold and matching endurashine carb installed.  The car is at the local Vette doctor as I type and he is trying to trouble shoot why it backfires.  The car backfires when it up to temperature and just cruising in town (30-45 mph).  The car doctor called me yesterday and told me that when the engine was swapped, the mechanic installed tapered thread plugs.  The standard ZZ4 cylinder heads are aluminum and require the old style straight thread plugs (oh...and of course they sell for $9 each compared to $2 each for the regular plugs...sheeeesh).  I am surprised that I did not blow one right out of the head.  They have been in there for 6-7 years!
 
Does anybody have any suggestions that I might pass along to this mechanic, he is new to me, but between him and his dad, they have over 60 years of corvette mechanics. 
 
Keep dem phiberglass chariots rolling,
David da Viking
 
My last name is Urke and my grandfather immegrated from 'Urke' Norway in 1905 when he was 6 years old.  So I truly am a Viking.....I was also born and raised in Minnesota and I will ALWAYS have 'purple' blood.  I work in engineering and have to visit different project sites.  This past Christmas, my oldest daughter gave me a hard hat painted like a Minnesota Vikings helmet...I get a lot of grief, but I am NOT a fair weather fan


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Warning: The surgeon general has declared that it is NOT unhealthy to smoke your competition AND I just discovered that my corvette is a hybred.  It burns gas and rubber! 
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3/13/12 12:06pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
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

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Welcome to C3VR!! Clap
Lottsa things come to mind with a backfire, but a little more info is needed:
Does it backfire/pop thru the carb, or the exhaust?
Is it a constant backfire, or very random?
Did it do this before the intake/carb swap?
Does it start and idle ok?

If this problem only started after the swap, my first thought would be a lean carb mixture. It could also be that one(or both) of the intake gaskets slid out of place, and is now just a vacuum leak source. Could also be the timing, but, from the description, I would think it will probably be something causing a lean fuel situation. Your "Doctor" should be able to read the plugs, even if they are the wrong ones, and see if it appears to be running lean, or if only one or two are lean.
Might just give the guy a little time, and see what he comes up with.Thumbs Up



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Joel Adams
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3/13/12 1:18pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
VikingVette
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Greer, SC - USA

Vette(s):
1978 Black with Viking mural painted under hood AM/FM/CB radio, T-top and a 2013 Cyber Gray Grand Sport Coupe, 2LT for my daily driver

Joined: 3/13/2012
Posts: 264
Thanks fort he input Adam.  We had a cat JUST like the one in your photgraph....he just showed up one day and we named him Casper. 
 
The car just started to do the back fire thing.  It ran OK (not great) before last fall.  It goes pop...pop...pop....way back by the mufflers, but never constant.  When I am slowing down, I like to down shift it (a 3 speed automatic) just for the sound, and ever since I had that engine dropped in, it popped when I down shifted.  This mechanic has dropped LOTS of ZZ4's into vehicles and he told me that for some reason, this was a recurring issue with just about every ZZ4 he has ever installed.  Even though he is new to me, I think that he knows his stuff.  He did inform me that the Edelbrock would never allow the maximum power out of the ZZ4 compared to a Demon or a Street Avenger, but I wanted the show, more than the go.
 
Slight point of interest, we have a motor home and we keep it at a campground in Maggie Valley, NC for extended periods of time.  In that campgound, David Pearson has a permanent trailer set up, so I did have him autograph the under side of my hood.  I don't care much about famous people, butto have the "silver Fox" on my car.....wow.  I see him a local car shows too.


____________________________________
Warning: The surgeon general has declared that it is NOT unhealthy to smoke your competition AND I just discovered that my corvette is a hybred.  It burns gas and rubber! 
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3/13/12 3:12pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
cthulhu Lifetime Member
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Hot Springs, AR - USA

Vette(s):
69 Conv #'s Match 427, TKO-600, 3.36HD-Posi, T/T, PS, PB, PW, SP, Lthr, Comp Mag 270 & Pro Rlr Rockers, Edel Air-Gap RPM, BG SD 750 MS, MSD 6AL+Tach Dist+ Blaster SS+Wires, Hly Bl Fuel Pump, K&N, Jet-Hot Hkr Side-Pipes,Steeroids, Al Rad, Spal Fans

Joined: 4/24/2004
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i thought there was a fairly common burnt exhaust valve problem with stock zz4's

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3/13/12 3:57pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
VikingVette
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Greer, SC - USA

Vette(s):
1978 Black with Viking mural painted under hood AM/FM/CB radio, T-top and a 2013 Cyber Gray Grand Sport Coupe, 2LT for my daily driver

Joined: 3/13/2012
Posts: 264
Thank you CT..I will pass that along.  The mechanic is also replace the valve covers at this time, so he can easily check that as well!

____________________________________
Warning: The surgeon general has declared that it is NOT unhealthy to smoke your competition AND I just discovered that my corvette is a hybred.  It burns gas and rubber! 
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3/13/12 5:09pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
DaveM Lifetime Member
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Flanders, NJ - USA

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1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Joined: 1/27/2004
Posts: 2530
I never had any problem with backfiring with my ZZ4. Good luck with it, I hope they get it worked out for you.
Dave


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Lifetime Member #116
Dave's '82


   
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3/14/12 10:50am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
philip
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Marana, AZ - USA

Vette(s):
1982 Silver Blue

Joined: 4/8/2010
Posts: 104
I never had any problems with my ZZ4 with an Edelbrock carb. Ran fine and had plenty of power. Actually had more power than with the Holley 750 that was on it originally. If the tech can not find the cause of the backfire maybe it is time for a new tech. I know of mechanics with lots of years of experience that can not do any more than change parts until the problem goes away.

The backfiring occurs when you are slowing and pull the trans into a lower gear. This will cause a rich condition and there is a hot spot in your exhaust that is igniting the fuel in the pipes/mufflers. Usually there is not enough oxygen in the exhaust system to promote burning so look for an exhaust leak allowing O2 to enter the pipes.


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3/14/12 11:27am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
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
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philip said: The backfiring occurs when you are slowing and pull the trans into a lower gear. This will cause a rich condition and there is a hot spot in your exhaust that is igniting the fuel in the pipes/mufflers. Usually there is not enough oxygen in the exhaust system to promote burning so look for an exhaust leak allowing O2 to enter the pipes.

With the complete description of the problem now, I agree with Phillip...you prolly have an exhaust leak, most likely somewhere up around the junction where the pipe meets the manifold. If you still have the AIR system on the car, check all of that, too...a leak in the tubes, or a bad diverter valve can also add more O2 to the exhaust stream, and cause a backfire on decell...



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Joel Adams
C3VR Lifetime Member #56    
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             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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3/14/12 11:29am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
VikingVette
Former Member
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Greer, SC - USA

Vette(s):
1978 Black with Viking mural painted under hood AM/FM/CB radio, T-top and a 2013 Cyber Gray Grand Sport Coupe, 2LT for my daily driver

Joined: 3/13/2012
Posts: 264
Thanks Philip.  That was good information.  I had wondered why the popping was way back by the mufflers.  That is probably where the 'hot spot' is.  This mechanic did tell me that he would check the exhaust system for leaks.  I was also VERY pleased to read that you have had GOOD luck with an Edelbrock vs the Holley.  That gives me hope.  Again, you ARE right about your assement about mechanincs.  I have HAD (past tense) one of those too.  He was VERY good at re-building engines though!

____________________________________
Warning: The surgeon general has declared that it is NOT unhealthy to smoke your competition AND I just discovered that my corvette is a hybred.  It burns gas and rubber! 
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3/14/12 11:33am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
VikingVette
Former Member
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Greer, SC - USA

Vette(s):
1978 Black with Viking mural painted under hood AM/FM/CB radio, T-top and a 2013 Cyber Gray Grand Sport Coupe, 2LT for my daily driver

Joined: 3/13/2012
Posts: 264
Adam,
I have always had a problem with one of the header bolts.....right now I can hear a ticking at idle and I know that one header (hooker headers) bolts is not as tight and the ticking is exhaust (I think).  I do appreciate all the input that I have received. 


____________________________________
Warning: The surgeon general has declared that it is NOT unhealthy to smoke your competition AND I just discovered that my corvette is a hybred.  It burns gas and rubber! 
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3/14/12 11:58am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
DaveM Lifetime Member
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Flanders, NJ - USA

Vette(s):
1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Joined: 1/27/2004
Posts: 2530

I have Hooker Headers (side pipes) and I'm always tightening the header bolts, I check them every couple months and there is always one or two that have loosened up.

Dave


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Lifetime Member #116
Dave's '82


   
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3/14/12 4:57pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
Jaws79 Lifetime Member
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Sykesville, MD - USA

Vette(s):
1979 Corvette Coupe Corvette Light Blue Midnight Blue interior Mirrored Glass T-tops

Joined: 4/27/2008
Posts: 4211
I remember they used to have have some header bolts that had a locking piece to keep them from coming loose, but I don't know if they're still around
 
Barry
 
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3/14/12 6:07pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
danascar
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Germansville, PA - USA

Vette(s):
1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. 1999 Covertible, 6 speed, Atomic orange, Oak interior

Joined: 1/28/2010
Posts: 763
You can get locking bolts at Summit....http://www.summitracing.com/parts/STG-8911A/

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3/14/12 9:28pm - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
DaveM Lifetime Member
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Flanders, NJ - USA

Vette(s):
1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Joined: 1/27/2004
Posts: 2530
I looked into those Dan, I don't have any room beyond the head of the bolt.

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Lifetime Member #116
Dave's '82


   
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3/15/12 11:14am - Reply: 'Re: backfiring with Edelbrock carb and intake...ideas?'
philip
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Marana, AZ - USA

Vette(s):
1982 Silver Blue

Joined: 4/8/2010
Posts: 104
The stage 8 bolts have another nice feature besides the locking ring, they have an Allen and a hex head. Fot the areas that it is hard to get a box wrench on the Allen wrench will fit.

http://s80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/exhaust/?action=viewĄt=P1010002.jpg


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1977 Nova 1982 Corvette   

The Toy Box
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