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Old 03-26-2007, 12:54 AM
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timing without light...

I was wondering if anyone has ever set their ignition timing without using a timing light. I have a 1979 Chevy P/U with a 350 and HEI. A couple years ago my cousin had played with the timing by ear. He would play with the dizzy while idling and and rev the motor. Man...it ran awsome after he played with it. I've been playing with my timing to get my 350 running its best. With my engine at idle, I would turn the dizzy until I got the highest idle speed...and I would rev it to get the best throttle response. Does this sound right to anyone? I really don't know everything about ignition timing. I know the best way is to use a timing light...ain't got the money right now...

thanks,
Mark

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Old 03-26-2007, 12:58 AM
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Before I lost my hearing...I used to do something similar.

That was on old worn engines though. The factory setting is no longer correct with chains stretching and wear on the engine.

I would set the factory and move it as needed for higher idle.

Was it right? Don't know, but on some old worn out engines they will barely run at the factory settings, so it was better than nothing.
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Old 03-26-2007, 01:30 AM
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I"ve done it 2 different ways. on my pull truck, i would hold the throttle at about 4000-5000 rpm and turn the "dizzy" till the engine sounded clear. Or on a street car, you can set it close, leave the hold down a little loose, then take it out for a ride. If you hear pinging or predetonation, then it's advanced too far. Keep turning it down till it goes away. After you think you have it set, your engine should't labor when you're trying to start it. It's worked for me all the time.
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Old 03-26-2007, 01:57 AM
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Quote:
Originally Posted by redline8
I"ve done it 2 different ways. on my pull truck, i would hold the throttle at about 4000-5000 rpm and turn the "dizzy" till the engine sounded clear. Or on a street car, you can set it close, leave the hold down a little loose, then take it out for a ride. If you hear pinging or predetonation, then it's advanced too far. Keep turning it down till it goes away. After you think you have it set, your engine should't labor when you're trying to start it. It's worked for me all the time.
The second way is the way my dad told me how to get it set without a timing light. And if you take it slow you can really dial the timing in that way.Brian
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Old 03-26-2007, 11:48 PM
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re: timing without light...

thankyou all very much for the info. I did once borrow a timing light from a friend. I wanted to set the timing to factory specs.(8 degs. BTDC). Man, it barely idled at all. Like brian_b said, timing chain stretch and my motor has alot of miles on it, ect... Well, anywase, I'm gonna play with it some more and try to get it going good. thanks again everyone,
Mark
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Old 03-27-2007, 05:01 AM
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Timing?

OK, I'm at kind of a lose here. Are you guys suggesting to disregard the factory timing marks and specs, and set the dist (dizzy?) to where ever the engine seems to perform its best at 650 ish RPMS? How do you set the max advance if you do it that way? It is supposed to have a total advance of 32.

I have checked and rechecked the timing on my project 70's model 350 and to set the timing at6~8 degrees BTDC really slows the idle down. Deff. seems like its laboring. The Dist. is a Mallory electronic style but still with spring advance.

The engine was completely rebuilt by a machine shop a couple of years ago and now only has 63 hours on it. It has an RV cam and is in a 6000lb boat.

Inquiring minds,
Jim

Last edited by Speakrdude; 03-27-2007 at 05:56 PM.
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Old 03-27-2007, 06:10 AM
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I never said that. I was strictly talking about a worn out engine which the poster apparently has. When things are not what they should be....the timing may not be either.
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Old 03-27-2007, 06:22 AM
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not at all!! What we are saying is when you are dealing with a semi-worn out engine it can be set best by ear and feel,if you have experience with it. The only way to get experience is to play with it. Now, with your engine your should use timing light to dial it in. You should probably be all in(32* to 36*) by 2800 to 3000 rpm depending on what your set up likes. The best way is to find a dyno tune shop and let them help you check the fuel ratio and timing, they have all the equipment to get it spot on.
Brian
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Old 03-27-2007, 07:23 AM
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you don't know anyone with a timing light you can barrow?
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Old 03-27-2007, 06:06 PM
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I think you guys may have missed my point.

I too have a really good timing light with advance and RPM readout on it.

I have set the timing according to what the shop that rebuilt it told me too which is 6~8 BTDC at 650 rpm's.

However, I also agree with Mark that it seems to labor at the specified mark but if I time by ear, it smoothes right out and the idle speed greatly increases.

Now granted, This is a 1970's model block. Who knows how old the timing chain and sprockets are. The rest of the componets are new, pistons, RV cam, oil pump etc.

I dont want to cause any damage by trying this but I could be causing damage if it is laboring, right?

So, Should try to time by ear? What do the experts say?

Jim
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Old 03-27-2007, 06:12 PM
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You can always vacumn time it......If you do not have a timeing light or if you harmonic vibration damper has creeped ( outer ring slipped on inner ring) you can set your timing using this method. Adust your carburetor, air/fuel mixture and idle. Then hook a vacuum guage to a vacuum pot on your intake and slowly turn distributer back and forth ( retarded and advanced untill you achieve the highest vacuum reading then turn distributer and reduce reading by two increments and lock distributer down. For example if your highest vacuum reading is 18 turn distributer untill it reads 16. This will get your timing very close. I still reccomend the use of a timing light but if one is not available or your damper has slipped this will do the job.
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Old 03-27-2007, 09:31 PM
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I just got my 76 Chevy 350 1/2 ton back from my mechanic who this week just installed a brand new rebuilt ATK / VEGE crate engine in it..Naturally, no timing cover came with this engine..When we put the accessories on it prior to installation we conveniently found and used a left over harmonic that was an inch bigger diameter , and according to ATK tech support , was not in concert with the sharkteeth timing marker that would normally be used ( and that normally sets at about 1:00 o-clock ( 70's chevy 350's) on the timing cover). So, now , nobody says that it can be timed with a timing light until we locate TDC and then fasten the sharkteeth accordingly . So, we did the
" hear and feel" technique as described in today's threads. Wouldn't the
" hear and feel" technique be better with a vacuum guage and a a tach ? I was really having a tough time finding TDC poking little things thru the splug hole. I found the top of the piston 3/8" below the bottom of the splug hole and got puzzled as to why , when the piston was at that point, the rotor was pointing at # 8 distributor lead . If the timing was that far off it would seem like the engine would not be running. That 3/8" space , that may be equal to 9 degrees on the harmonic , might have been on the exhaust phase ( assuming the piston rises all the way , and comes dangerously close, to the plug) . The rotor I thought was way too close to # 8 .. I think all you guys have something to offer and appreciate your comments. Keep in mind at 6000 foot altitude here we're at 14 degrees BTDC right from the git-go at 700 rpm's
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Old 03-27-2007, 09:47 PM
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I tried timing an engine by ear once. It ran well at idle and sounded good but the timing was way out, 45 degrees out. As far as I'm concerned, a timing light is a must have tool. Short of tuning the engine by vacuum as Henry Highrise suggested, it's going to be very difficult to get it close.

Colorado Mark, there will always be two pistons at TDC at the same time. One on the exhaust stroke, one on the compression stroke. They're called companion cylinders. If you had #1 at TDC then the #6 cylinder (next to #8) will be at TDC as well. It's possible that the #1 cylinder was on the exhaust stroke.

You can come pretty close to #1 TDC compression by pulling both valve covers and watching for both rockers on #1 to be loose and both rockers on #6 to be in overlap (intake valve just starting to open and exhaust valve almost closed). You can also feel inside #1 and feel when the piston reaches TDC.

Last edited by Blazin72; 03-27-2007 at 10:32 PM. Reason: clarification
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Old 03-27-2007, 10:15 PM
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I was turning the engine by hand when I found that 3/8 " gap which meant the top of the piston was either on it's way up or on it's way down and my harmonic goove was pointed at 1:00 o clock plus or minus.. Keep in mind when I declare that 3/8" measurement I am assuming that the piston ascends all the way to the bottom of the splug hole....The rotor was stopped dead looking at #8 on the distributor which lead me to believe that the timing was radically advanced to the tune of maybe like you say 25-30 degrees too far , which I never thought was possible without experiencing a wacky idle along with other obvious performance problems. Your thoughts alerted me that an engine will still seemingly run what sounds to be OK but in fact could be way off. Thanks , B-72....
Mark in Pueblo , Colorado ...
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Old 03-28-2007, 05:08 AM
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Can I use this square plug behind the carb. to perform the vaccum test?




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