Backfiring problem - Team Camaro Tech
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post #1 of 21 (permalink) Old Sep 2nd, 08, 08:34 AM Thread Starter
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Ron
 
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Backfiring problem

OK, my engine (327 2-bbl) had been running fine but I checked timing, dwell, rpm's and adjusted everything to specs. My first mistake, the timing was way off and when I brought it to 2 degrees BTDC the engine stalled and backfired through carb and I couldn't get it started until I rotated the distributor back where it was. It is now running like crap so I moved the dist back to about where it was and it starts but still runs funny. Also, the hold down clamp for the distributor has to be really cranked on to keep the distributor from moving. I can't imagine this nut has to be tightened this hard.
I am also getting a lot of blue/brown smoke from the exhaust. The car hasn't been started in at least a few years. What is the right thing to do here? It's all original. Looking for some guidance.
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post #2 of 21 (permalink) Old Sep 2nd, 08, 09:20 AM
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Steven
 
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Re: Backfiring problem

I would start with fresh gas and fresh plugs if car has been sitting a long time ... Also, do the basic tune-up work. It is also possible that your carb is gummed up from sitting too long ... May have to rebuild that. At least start by changing the gas filter in that. It wouldn't hurn to change the oil .... I would ... Like I said, do the basic tune-up stuff, but certainly start with fresh gas and fresh plugs, properly gapped and see if that doesn't get you running ... The backfire could be a pop because the carb is not squirting when hte accelerator is pressed, or, it can be a backfire from incorrect timing ...
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post #3 of 21 (permalink) Old Sep 2nd, 08, 10:17 AM Thread Starter
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Ron
 
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Re: Backfiring problem

I've already done that; replaced the entire fuel line, cleaned out the tank as best I could, fresh gas, new fuel pump, filter, plugs, wires only thing I haven't done was the points which I'll be doing shortly. Like I said it was running fine until I changed the timing to the spec. I plan on getting a Holley 4 bbl Street Avenger carb 670 cfm, was going to ask what manifold would work best with this carb and a cam but that's a winter project. I just want to get it running good enough so I can take it down the street. Gas has bubbled out of the carb so I believe its gummed up.
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post #4 of 21 (permalink) Old Sep 2nd, 08, 10:44 AM
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Tom
 
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Re: Backfiring problem

I would almost bet that the balancer has slipped on its hub. And if gas is bubbling out of the carburetor then there is something holding open the needle and seat.
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post #5 of 21 (permalink) Old Sep 2nd, 08, 12:18 PM Thread Starter
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Ron
 
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Re: Backfiring problem

How would that happen and is there a way to tell for sure and how do you fix that, please don't say the crank has to come out.
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post #6 of 21 (permalink) Old Sep 2nd, 08, 01:24 PM
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Tom
 
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Re: Backfiring problem

The balancer is a weight attached with rubber. The rubber deteriorates allowing the weight to slip on the hub. If it is not visibly loose or the rubber isn't falling apart, about the only true way to check it is to find actual top dead center. You do that with a piston stop. You pull #1 spark plug and install a piston stop in its place. You then turn the engine over by hand until it stops. Mark your balancer. Then you turn the crank the other direction until it stops and mark it again. The space between the 2 marks is TDC. DO NOT CRANK THE ENGINE WITH THE STARTER WHEN USING A PISTON STOP! And it is an easy fix (if thats your problem). You just need to replace the balancer with a new one, no crank removal necessary.
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post #7 of 21 (permalink) Old Sep 2nd, 08, 01:45 PM
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erik
 
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Re: Backfiring problem

On engines that old you can pull the bolt out that holds the balancer on and with a light and mirror look at where the keyway is on the crank, the mark on the balancer should be in the same place as the keyway. If it isn't it has slipped! By the way how are you adjusting your timing and dwell? The dwell setting will affect the timing and visa versa.
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post #8 of 21 (permalink) Old Sep 2nd, 08, 03:10 PM
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Re: Backfiring problem

Quote:
Originally Posted by rjg67rs View Post
OK, my engine (327 2-bbl) had been running fine but I checked timing, dwell, rpm's and adjusted everything to specs. My first mistake, the timing was way off and when I brought it to 2 degrees BTDC the engine stalled and backfired through carb and I couldn't get it started until I rotated the distributor back where it was. It is now running like crap so I moved the dist back to about where it was and it starts but still runs funny. Also, the hold down clamp for the distributor has to be really cranked on to keep the distributor from moving. I can't imagine this nut has to be tightened this hard.
I am also getting a lot of blue/brown smoke from the exhaust. The car hasn't been started in at least a few years. What is the right thing to do here? It's all original. Looking for some guidance.
Well there's your problem. Thats 4 degrees initial. shoot for 8-10.
Who on Earth said 4* btdc? I haven't looked at stock 327/210 specs but i'm almost positive that it would not be that low.
You don't need the distributor so tight to where it will not move, mine is not, it can be turned by hand an no, the timing does not change. The nut won't get tight unless it is slipped towards the distributor, hints why there is a slot to move the collar back and forth.
Right thing to do.
New plugs, wires, coil, new distributor parts. They are cheap if you still have the points type.

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post #9 of 21 (permalink) Old Sep 2nd, 08, 05:05 PM
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Re: Backfiring problem

4 was spec on a bunch, but 4 sucks. 4 was for emissions purposes. 4 won't run worth a hoot. SBC's LOVE advance....
read this a few times, then read it again. post 7 by JohnZ
https://www.camaros.net/forums/showth...01#post1004627

tumper said it well, just look at the relationship of the balancer keyway to the tdc mark on the outside ring. Some are 10 degrees off from the factory though to mate w/ a different cover. But the keyway is always oriented to dead center of #1 rod journal. You can eyeball straight down from the center of the deck surface to your timing tab and crank, to see if your tab is 10 off or dead on with tdc. It's not precise but it works.

And yup, set dwell before you set timing. When you adjust points you are altering the distance of the rubbing block to the distributor cam, and moving the block delays or advances when the points short out voltage supply to the coil. Dwell is how long in degrees the points remain open, or how long the coil is allowed to charge. A dwell meter is sweet, but you can also do this with a matchbook cover..

Most of them were around .018" or around 30 iirc. Those #'s will run pretty good anyway. I haven't fooled with points in years. Was gonna put my old points unit back in the 283 for play purposes but forgot to. Stole a bunch of stuff like headers and a starter off it to make a pink 305 run so now I can't do the points play for awhile. Hey I ought to stick the points unit in the pink 305. Teach that thing to have a roller cam and vortec heads yup that's what I'll do hehe.

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post #10 of 21 (permalink) Old Sep 2nd, 08, 05:57 PM
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Re: Backfiring problem

The reason why it backfired in the intake is because the intake valve was still open causing a flame front into the intake manifold and carburator. This can be dangerous. The timing was retarded if what you say is true. If you ignite the chamber and the intake valve is open well...guess what happens to the gaskets mounting the carb to the intake and also the intake manifold gaskets. They can blow out and will cause a vacuum leak. Set the timing to 15 degrees before the piston has reached terminal lift.

Last edited by Autoteck; Sep 3rd, 08 at 03:31 AM.
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post #11 of 21 (permalink) Old Sep 2nd, 08, 06:31 PM Thread Starter
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Ron
 
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Re: Backfiring problem

Well, just took off the cap and low and behold my points are loose, move all over. May explain the problem. I'll check the balancer alignment anyways.
I have a timing light and analyzer to check dwell. I did check dwell first then looked at timing. When I did check the timing mark it was about 12'o clock, way off the tab. I'll put in new points, rotor, cap, etc. then see what happens. I'll keep you posted because I may need more help.
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post #12 of 21 (permalink) Old Sep 2nd, 08, 07:28 PM
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Re: Backfiring problem

12 o'clock is about 45 btc, should have been pretty happy. Most of mine think 45 is cool beans at idle.

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post #13 of 21 (permalink) Old Sep 3rd, 08, 10:23 AM Thread Starter
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Ron
 
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Re: Backfiring problem

OK, are you kidding or are you serious about 45 degrees being good. I always thought if it was off the tab then something is wrong but I am a believer if it runs good then don't screw with it.
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post #14 of 21 (permalink) Old Sep 3rd, 08, 04:48 PM
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Re: Backfiring problem

Quote:
The reason why it backfired in the intake is because the intake valve was still open causing a flame front into the intake manifold and carburator. This can be dangerous. The timing was retarded if what you say is true. If you ignite the chamber and the intake valve is open well...guess what happens to the gaskets mounting the carb to the intake and also the intake manifold gaskets. They can blow out and will cause a vacuum leak. Set the timing to 15 degrees before the piston has reached terminal lift.
sorry for hijacking the thread but I am alittle confused on this. Can someone straighten me out! If the timing is more on the retarded side wouldn't both valves still be closed on the downstroke of the compression stroke and then the exhaust valve would be the next to open. How would the intake valve be open and backfireing up through the intake if the timing is alittle retarded? I am confused on this? I would think that the only way to backfire up through the intake is if the cam timing is off, the distributor is installed wrong or the timing is way far advanced, but thats why I need someone to set me straight. thanks for the help.

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post #15 of 21 (permalink) Old Sep 3rd, 08, 05:07 PM
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Re: Backfiring problem

Quote:
Originally Posted by rjg67rs View Post
OK, are you kidding or are you serious about 45 degrees being good. I always thought if it was off the tab then something is wrong but I am a believer if it runs good then don't screw with it.
No, I am serious. They usually run fine at 45, at idle. Depends how hot it is. And sometimes they don't like to start with that much advance. You wouldn't want to be at 45 under load, might detonate.

As for staying on the tab,,,,,,have you ever revved your engine while looking at the timing? It goes way off the tab. Edit: tabs only go to like 12 or 14btc, and that's where the damthings are just beginning to run right.

I run a locked out distributor(not recommending this to you, just making you aware such a critter exists) on my car. Timing is at 38° starting, idling, and full load. That would be real close to vertical.

I also have a zz4 that I don't use vac advance on because I think vacuum hoses look like *** and the engine doesn't need it anyway, just centrifugal advance. I have it about 20something at idle and 30something at speed. Not recommending that to you either, just making you aware there's more ways to play.

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