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Old 03-01-2006, 10:13 AM
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350 backfire

I have a 68 chevelle i bought off of someone. It is not the original engine, it has a 350. Anyway the problem I having is, I installed a new intake manifold on it. I finally got everything back together. The only parts i have to take of was the distrib. air filter and carb. Once all of them were put back one. I have had to mess with the disb and spark plug wires and I installed new spark plugs. I got the firing order set up and the #1 piston set at TDC. Then i took the distrib cap off and pluged in the #1 plug wire where the rotor was pointing. And then put the plugs in the firing order on the distrib. cap. I went to fire it up and BOOOM the loudest back fire i had ever heard it came from both exhaust and carb. I then rechecked everything and tried it again. I backfired once again. I do not know what else to check or if i did something wrong anyhelp would be appreciated.

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Old 03-01-2006, 10:24 AM
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Sounds like your distributor is where it needs to be by you saying that you have checked it twice. Just in case I would check it again, you need to be on TDC on #1 on the compression stroke, then the firing order is this 18436572 (just in case you didn't know). If that is all good. what intake did you have and what is the new intake you installed? What size carb are you using?

Steve
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Old 03-01-2006, 11:18 AM
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Yep! Sounds as if your not set on compression stroke of #1 cylinder. Recheck and let us know how it goes please.
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Old 03-01-2006, 11:36 AM
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Same exact thing happened to my 'stang. Make sure that you're timing isn't 180 degrees off =) I timed it to the wrong stroke. After I got it fixed, fired up and ran like a beaut. Now my tranny is a whole other thing...
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Old 03-01-2006, 03:36 PM
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I had an edelbrock torquer, but it was old nasty so i bought a edelbrock rpm performer. I am Not sure about the carb, its four barrel eldelbrock. Looks like a 600 cfm to me.
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Old 03-01-2006, 03:49 PM
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Sounds like number one was not on the compression stroke and therefore you are 180 degrees out of time.
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Old 03-01-2006, 04:01 PM
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Doc here,

Number 1 cylinder TDC compression, Timing marks aligned, Both intake & Exhaust valves closed , no pressure on the lifters (not too much slack either..) If you can't co~ordinate these, you have timing chain/gear issues..

Drop the dizzy in, and watch the rotor, It will advance clockwise a bit, this is because the gear teeth are diagonal cut, It will go about a tower in a half in some cases..Note the amount of change and then withdraw the dizzy.

Line the oil pump shaft up to that location with a large screw driver, and reset the dizzy, for number one plug tower, allowing for advancing as the gears seat..

The easy way to do this is make magic marker lines on the base of the dizzy, for exact #1 plug tower, and the difference of rotor movement as it seats..due to the cut of the gears..(I.E...#1 and the amount of distance BACK required to make it sit on #1 plug tower when bottomed out..)

#1 plug tower in the stock location for SBC's is 5 to 7 O'clock, (depends on year, and obstructions) 7 is usually good.

Direction of rotation is clockwise.

The F.O. is 1 8 4 3 6 5 7 2..

Put on your hold down just tight enough to hold it but enough to forcibly move it by hand, and start it up..set your static and total timing..

Static 10 to 12 is a good starting point advance defeated and vacuum line plugged.

Total around 34 to 36 is usual on a stocker with advance hooked back up..

Tighten down the hold down, set your idle for 650 Manual trans, 950 Automatic, and drive it .. hammer it on the freeway, If it pings or runs hotter than usual, retard it a few degrees..If it dogs, advance it..Try also lugging it up a steep hill highest gear as slow as it will pull, If it pings check the timing again.

That's it.

Doc
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Old 03-01-2006, 04:30 PM
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hey, just for the sake of it, with nu 1 on com, if your wires were long enough you could put nu 1 anywhere on the dizzy.if you move your rotor ,right or wrong??
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Old 03-01-2006, 09:26 PM
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hehehe

Long time a go I had a gal brought in a car that her hubby had changed from points to HEI, it needed a tune up and he was to busy with other things to mess with it. When he put in the new distributor he put #1 plug wire where ever the rotor was pointed when he dropped it in.
I didn't pay any attention and pulled the plugs, wires, cap and rotor and chunked em. Got the new stuff outa the box and put it all on the way your supposed too. Broke the starter on the first hit. I always check it out if I don't know the car.

Yes, you can move the wires but it makes ya look like an idiot if ya do.
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Old 03-01-2006, 09:28 PM
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Yeah. ALWAYS do it right the first time. If you do it right, then someone else touches it, they will do it right if they know what they are doing, and if you do it your way, fail to let them know, and they have their way with your car, you're lookin' at more repairs... It's a good way to test if that's your problem, though.
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Old 03-02-2006, 12:54 AM
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Quote:
Originally Posted by Da Tinman
Long time a go I had a gal brought in a car that her hubby had changed from points to HEI, it needed a tune up and he was to busy with other things to mess with it. When he put in the new distributor he put #1 plug wire where ever the rotor was pointed when he dropped it in.
I didn't pay any attention and pulled the plugs, wires, cap and rotor and chunked em. Got the new stuff outa the box and put it all on the way your supposed too. Broke the starter on the first hit. I always check it out if I don't know the car.

Yes, you can move the wires but it makes ya look like an idiot if ya do.
Doc here ,

Amen Bro..

If you set your Fire order other than stock, THEN MARK all the towers and plug wires..(So even Ray Charles could figure it out..) THEN PUT a sticker on the hood that Say's Fire order has changed: etc..etc..etc..

The next owner, or next wrench to work on it won't have a Clue..

Just think having to pay $100 several times in a row for a smog check because the #1 cylinder was actually 5..and the timing didn't square with the techs standards..AUTO FAIL...too bad ... too sad..

Doc
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Old 03-03-2006, 04:34 PM
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I have no idea what the people before me did. I really hope that the case isnt that the #1 didnt change. I dont know a whole lot about cars, just enough to get me around on them. Anyway I heard that there are four strokes to the engine the comp, power, intake, exhaust. I think that is the order they go anyway if I am wrong please tell me. So basically from what I heard from here, and other people their are 2 TDC's, so I turned it until it went all the down and came back up again to the next TDC. So I tried to fire it up again and it started to do the same thing it did last, never started and had some sputering after I turned it off, so I stoped because I didnt want it to explode (backfire) again. I want to know if there is a way to tell if it is at the comp TDC.
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Old 03-03-2006, 07:12 PM
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Pops term

Pops alway told me four strokes are:
Suck, Push, Pow, Putuwee.
Intake, compression, power, exhaust.

Check the firing order,, or maybe the plug wires are routed in the wrong direction.
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Old 03-03-2006, 09:29 PM
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Odd #'s on the left. even#'s on the right.
#1 on the dist usually points to the front.
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Old 03-04-2006, 08:21 AM
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I thought the #1 is where ever the rotor is pointed distrib. Beings that I am having to redo the entire order #1 is where ever the rotor is pointed then just run the plug wire to the #1 cylinder front of motor on drivers side, correct right. Then Just run in order. From what I hear that the the rotor should be pointed to the #1 cylinder thats how you determine, it is just a wives tale. I am just making sure that where ever the rotor is pointed right at the time of redoing what I was doing is #1.
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