What the ....!!!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Hugger · 01-13-2004, 06:58 PM

I got new dual exhaust put on today...Looks great, Sounds great, but on the way home it's not running right???

Seems like timming, but I can't figure out why it started now. I havn't drove it for several months, but on the way to the shop I didn't notice it running bad.
On the way home it was backfiring, missing you name it.
I havn't had time to look at it close yet, hopefully It'll be something simple.
Any guesses??

By the way I got MagnaFlows with an H pipe, exiting back corners (Hidden Turndowns)...Looks great!
Thanks.

JayDubBlazer · 01-13-2004, 07:01 PM

You now have different back pressure and you are going to have to retime your engine.

724x4a/cchevy · 01-13-2004, 07:03 PM

What size exhaust did they put on it? That will definately have an effect on the engine's performance. And it might not run right.

Hugger · 01-13-2004, 07:04 PM

That's what I was thinking but I didn't know it would make that much difference...
First thing I thought of was the cross over...
Thanks, for the quick reply.

Hugger · 01-13-2004, 07:05 PM

2.25" pipe

Hugger · 01-13-2004, 07:35 PM

I will get the timming light out tonight and see what I can see..

I tried to time it once before, and finally had to take it in to the shop...The guy told me it was 180 out????
I don't see how this is possible and have it still run at all, but what ever he did made it run better.
I guess I'll try again.
Thanks.

cdowns · 01-13-2004, 08:11 PM

if it's been sitting for awhile now might be a good time to change air and gas filters and throw a couple cans of drygas in the tank

jhow66 · 01-13-2004, 09:28 PM

New pipes would not make it backfire or miss .Did they have your plug wires off for any reason? If so a couple could be crossed.

stelth2002 · 01-13-2004, 09:31 PM

I agree with the wires. New exhaust wont make that much difference in timming. The main thing i would worry about if you have headers too is the fuel mixture will need to be richened. Which is carb. An engine will not run 180 off either so i guess im confused.

**old Rusty C10** · 01-13-2004, 09:31 PM

not only off make sure that they didnt make any of the ignition wires or any of the harness touch the manifolds or pipes that will short it out or cause a miss too

Longhorn Man · 01-14-2004, 12:20 AM

I'll asume the headers were new. If so, look for a primary tupe that still has paint on it...that will be the cylinder not fireing.
If they all have paint burned off, then I would go over the fireing order...the 5 & 7 get flip flopped quite easily, and it'll run about like you describe.

djracer · 01-14-2004, 12:25 AM

also make sure they didn't put the mufflers on backwards!

Hugger · 01-14-2004, 12:39 AM

I checked the timming, and it was about 14 BDC, I adjusted it from 4 to 16 and all in between. I think it should be at about 8. It runs better at about 14, but the problem is there through out all adjustments.

I swaped the cap with my daily driver, no difference.

It has that da....da...da..da.da.dadada sound when you get on the throttle, missing!!!
Checked all wires, didn't see anything bad.

It has the original rams horn exhaust manifolds, so I can't tell which cylinder is the culprit witht the paint trick. I tried pulling a plug wire off here and there, but it doesn't seem to change it?

I put the timing light on all the wires, and all appear to be firing, but I don't think that is a good test.

Will try again tomorrow.

Thanks, for all the replies. It just realy pisses you off when you fianally spend the money for new exhaust and it won't run to hear and feel it....

Thanks.

Hooter · 01-14-2004, 12:46 AM

hmm does it have HEI? hows the distributor cap? firing order right?

onelow69 · 01-14-2004, 01:05 AM

I had a simlar problem after I had exhust done. This might sound weird, but the guy that welded my exhust used a mig welding machine. Well as most of you know welding with a mig uses high current between the neg or ground and the mig tip of the gun. Well come to find out what had happened is that the electic current from the welder shorted out the HEI unit, and that what was causing the mis-fire. So word of caution, always disconect the ground from the battery or disconect the dist from all of your electric system before you have any welding done.

Longhorn Man · 01-14-2004, 01:08 AM

You can spray water onto the manifolds after a few min of running to get the same effect as the paint deal.

Hugger · 01-14-2004, 01:20 AM

That is wild Onelow69, but I have points....thinking about going HEI maybe will befire I get this problem resolved.

I will try the water deal tomorrow.
Thanks Longhorn Man

doughby82 · 01-14-2004, 05:17 AM

Quote:

Originally posted by onelow69
I had a simlar problem after I had exhust done. This might sound weird, but the guy that welded my exhust used a mig welding machine. Well as most of you know welding with a mig uses high current between the neg or ground and the mig tip of the gun. Well come to find out what had happened is that the electic current from the welder shorted out the HEI unit, and that what was causing the mis-fire. So word of caution, always disconect the ground from the battery or disconect the dist from all of your electric system before you have any welding done.

holy crap your lucky thats all that shorted out.yeah i never weld when the battery is connected

01-13-2004, 06:58 PM	#1
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	What the ....!!!! I got new dual exhaust put on today...Looks great, Sounds great, but on the way home it's not running right??? Seems like timming, but I can't figure out why it started now. I havn't drove it for several months, but on the way to the shop I didn't notice it running bad. On the way home it was backfiring, missing you name it. I havn't had time to look at it close yet, hopefully It'll be something simple. Any guesses?? By the way I got MagnaFlows with an H pipe, exiting back corners (Hidden Turndowns)...Looks great! Thanks. __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

01-13-2004, 07:01 PM	#2
JayDubBlazer go cyclones Join Date: Jun 2003 Location: Ames, IA Posts: 1,885	You now have different back pressure and you are going to have to retime your engine. __________________ Wes PROJECT OLE GREEN 1972 Blazer 4X4 350/700R4 2017 Silverado LT

01-13-2004, 07:03 PM	#3
724x4a/cchevy Self-proclaimed LED man Join Date: Nov 2003 Location: Harrisburg, Missouri Posts: 1,021	What size exhaust did they put on it? That will definately have an effect on the engine's performance. And it might not run right. __________________ My LED Website My Photobucket Album of LED's Ask me about hand-made custom L.E.D brake and reverse lights. <- LINK I also do LED: -Third Brake/Cargo -Brake (truck and burb) -Reverse (truck and burb) -67-68 Front Turn Signals -69-70 Front Turn Signals -71-72 Front Turn Signals -GMC Front Turn Signals I can also do custom lights for other vehicles....i did a set for a AMC Gremlin once Norwood Survivor

01-13-2004, 07:04 PM	#4
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	That's what I was thinking but I didn't know it would make that much difference... First thing I thought of was the cross over... Thanks, for the quick reply. __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

01-13-2004, 07:05 PM	#5
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	2.25" pipe __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

01-13-2004, 07:35 PM	#6
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	I will get the timming light out tonight and see what I can see.. I tried to time it once before, and finally had to take it in to the shop...The guy told me it was 180 out???? I don't see how this is possible and have it still run at all, but what ever he did made it run better. I guess I'll try again. Thanks. __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

01-13-2004, 08:11 PM	#7
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	if it's been sitting for awhile now might be a good time to change air and gas filters and throw a couple cans of drygas in the tank __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

01-13-2004, 09:28 PM	#8
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	New pipes would not make it backfire or miss .Did they have your plug wires off for any reason? If so a couple could be crossed. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

01-13-2004, 09:31 PM	#9
stelth2002 Young Gun wth Fast Inline Join Date: Jan 2002 Location: Idaho Posts: 1,475	I agree with the wires. New exhaust wont make that much difference in timming. The main thing i would worry about if you have headers too is the fuel mixture will need to be richened. Which is carb. An engine will not run 180 off either so i guess im confused. __________________ 1967 Chevrolet LWB with built 292! 415 ft. lbs of torque, 4 speed :O with 27% overdrive too, 3.73 Posi. Frame and body done... getting painted!!!

01-13-2004, 09:31 PM	#10
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,294	not only off make sure that they didnt make any of the ignition wires or any of the harness touch the manifolds or pipes that will short it out or cause a miss too __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

01-14-2004, 12:20 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I'll asume the headers were new. If so, look for a primary tupe that still has paint on it...that will be the cylinder not fireing. If they all have paint burned off, then I would go over the fireing order...the 5 & 7 get flip flopped quite easily, and it'll run about like you describe.

01-14-2004, 12:25 AM	#12
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,891	also make sure they didn't put the mufflers on backwards! __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

01-14-2004, 12:39 AM	#13
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	I checked the timming, and it was about 14 BDC, I adjusted it from 4 to 16 and all in between. I think it should be at about 8. It runs better at about 14, but the problem is there through out all adjustments. I swaped the cap with my daily driver, no difference. It has that da....da...da..da.da.dadada sound when you get on the throttle, missing!!! Checked all wires, didn't see anything bad. It has the original rams horn exhaust manifolds, so I can't tell which cylinder is the culprit witht the paint trick. I tried pulling a plug wire off here and there, but it doesn't seem to change it? I put the timing light on all the wires, and all appear to be firing, but I don't think that is a good test. Will try again tomorrow. Thanks, for all the replies. It just realy pisses you off when you fianally spend the money for new exhaust and it won't run to hear and feel it.... Thanks. __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

01-14-2004, 12:46 AM	#14
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	hmm does it have HEI? hows the distributor cap? firing order right? __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

01-14-2004, 01:05 AM	#15
onelow69 Registered User Join Date: Jan 2003 Location: Central Cal Posts: 124	I had a simlar problem after I had exhust done. This might sound weird, but the guy that welded my exhust used a mig welding machine. Well as most of you know welding with a mig uses high current between the neg or ground and the mig tip of the gun. Well come to find out what had happened is that the electic current from the welder shorted out the HEI unit, and that what was causing the mis-fire. So word of caution, always disconect the ground from the battery or disconect the dist from all of your electric system before you have any welding done. __________________ 69 Chevy Truck, 350, 400trans, Lowered 3.5/6, Disc brake conv, All early classic stuff. 62 Chevy Nova 350, 700R4, 2400stall, F9in, 3.70gear, AlburnPosi, Chevelle Disc Brakes, ect.



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01-14-2004, 01:08 AM	#16
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	You can spray water onto the manifolds after a few min of running to get the same effect as the paint deal.

01-14-2004, 01:20 AM	#17
Hugger Registered User Join Date: Mar 2003 Location: Wichita, KS Posts: 137	That is wild Onelow69, but I have points....thinking about going HEI maybe will befire I get this problem resolved. I will try the water deal tomorrow. Thanks Longhorn Man __________________ 72 LWB - Hugger Orange 350/350 3.73 Next; 335hp GM Crate

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