Tweet
Don't rule out the harmonic balancer. I am assuming that the engine is stock and you don't have a wild cam in it now. If you can get confident about the firing order and wiring and still cannot get it to run correctly when reinstalling the distributor, I would time it by ear and see how far off the mark on the balancer is. I recently replaced one on a car that was about 180 degrees off. Trying to get it to run on the timing mark caused severe backfiring and within days my marginal muffler gave it up. A balancer may be over $100 rebuilt but would be easier to replace than the timing chain. If you cannot get the engine to run right even after timing by ear then I may suspect the timing chain.
-
-
Re: Sliped Harmonic Balancer
So you recommend I double check the distributor first and reinstall if necessary? -
Re: Sliped Harmonic Balancer
Someone may correct me, but if you are able to get a smooth idle within the range of adjustment that it is in, I do not think repositioning the distributor is going to help you much. (assuming you are not rotating the thing 90 deg or more). In my case, it was so far off that I ran out of room to adjust the distributor base due to interference with other parts because of the vacuum advance diaphram and due to the slippage, I was trying to force the timing mark to line up correctly. I ended up going back to my original position and timing by ear, ignoring the timing indicator. Then I went looking for the reason why the indicator was not lining up properly. It may be tough to detect if it is only off by a ten degrees or so but you may want to check the actual #1 piston TDC against the indicated TDC on the crankshaft. In my case it was obvious when I pulled my rocker cover, that my valves were not in the TDC position and sticking a screwdriver in the spark plug hole confirmed it was not TDC. Something else to confirm may be the #1 cylinder location. Seems to me I remember different numbering conventions on GM motors, but that may have been on engines from the 60's. I know there were some differences between my Vette and my old Fords.Comment
-
Re: Doug, How do you "slipe"....
...a harmonic balancer? (just kidding) :-) TBarr #24014Comment
-
Re: I think you do it your right pinkie finger....
Unless you are a two finger typist. There also may be a disconnect between the brain and the little finger.Comment
-
Re: I shouldn't "pinkie" attention....
...to anyone else's mis-types since all my brain-disconnects are out in the open to be seen as well. :-) TBarr #24014Comment
-
Re: Sliped Harmonic Balancer
Hi Michael. It makes absolutely no difference where your distributor is installed, as long as you have the firing order correct..1-8-4-3-6-5-7-2. The rotor spins in the cap. It doesn't care which tower it touches, or which tower you designate as #1. Of course, objects such as the vacuum canister, etc. which allow you to adjust the timing come into consideration. Changing your distributor to the correct factory position will not correct your timing.
If the balancer is the problem, the timing will still be incorrect no matter which wire you designate as #1. I would bring #1 up to TDC...pull the spark plug and remove the valve cover to be sure. Then check where the balancer mark lines up with the timing tab. It's also possible that the timing chain cover or timing tab are incorrect for your car. The tab could be bent, or it might have been welded on incorrectly in the past. Hope this helps. Chuck1963 Corvette Conv. 327/360 NCRS Top Flight
2006 Corvette Conv. Velocity Yellow NCRS Top Flight
1956 Chevy Sedan. 350/4 Speed Hot RodComment
-
Re: Cylinder Numbering Convention
I may not have been clear on what I meant about confirming cylinder #1 location. It seems to me some engines had the #1 cylinder on the left bank and some on the right bank. Some manufacturers numbered the cylinder bank 1234 and others went 1357. Hooking the timing light to the wrong cylinder bank would make it appear as incorrect timing when it is not. Sometimes you are lucky enough to have the #1 cyl marked on the intake manifold.Comment
-
Re: Sliped Harmonic Balancer
Michael, If memory serves me correctly, checking the timing on 79 motors required looking down behind the waterpump. I may be wrong on the year, but if I am correct it is possible someone put the wrong timing cover on the engine. If I am wrong about the position of the timing tab, then maybe you have the wrong damper. Your statement that the engine runs OK with the timing mark at 12 o'clock seems to confirm at least one of the two problems.Comment
-
Re: Cylinder Numbering Convention
#1 cylinder on a chevy small is the left front cylinder. A imprecise way to determine TDC is to pull the spark plug, rotate the the engine by hand until you feel the cylinder pressure,out of the spark plug hole, peak. It is pretty easy. Then you know that within a degree or two it is at TDC. GaryComment
-
Re: Sliped Harmonic Balancer
I've seen balancers with TWO timing marks on them, about 15 degrees apart. You should hear how bad it runs when you pick the wrong one.
Mike
Quebec NCRS ChapterComment
-
May be a bad distributor gear install.
If the above notes about checking for original/matching timing chain covers and balancers don't provide the answer, here is a possibility: Lots of people with Chevy engines take the distributor apart to clean or overhaul it. It is possible to put the gear back on with the teeth out by 180 degrees. There are an odd number of teeth, so the timing will be off and it will be necessary to move the wires in the cap one hole to get the cap under shields. Anothe reason to pull the gear off is to replace it with a bronze gear that is compatible with steel billet cam shafts (originals are not). If this engine has a "wild" cam, it is possible someone got the distributor gear on backward when they worked on the distributor. - DaveComment
-
Re: Correction to Cylinder Numbering Convention
After looking trough some texts, I think GM used the same numbering convention in all makes and I am not sure if it ever varied. Ford and GM do number the cylinders differently. What GM did do was produce distributors that rotated different directions in the different divisions. They also produced different model caps that varied the position of the #1 terminal with respect to the mounting screws or adjusting windows.Comment
-
Re: Sliped Harmonic Balancer
Once bought a 71 LT1 because of that. The owner couldn`t get it to run and sold it cheap. About 10 min. set on the correct mark ran like a dream.Comment
Comment