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timing.

2K views 26 replies 5 participants last post by  ericnova72 
#1 ·
hi all, i'd like to ask a few questions and ask for some help if i may. i have a 1996 350 vortec completely rebuilt. its .30 over flat top pistons. all new bottom end. roller cam, 540 lift. roller lifters, roller rockers. air-gap cross wind intake. none vac pro billet distributor. with the 1806 edelbrock 650 thunder carb. .... well, timing chain set was installed correctly. point to point. the balancer is in great shape and has a cover with the timing markings for timing. the problem i'm having is... which ever-way i set my timing as far as, both valves on #1 closed in compression stroke at tdc. with the marking at the pointer ether at 12 degrees btdc or at 0 degrees tdc with the distributor positioned in its spot and the rotor firing on the #1 plug. motor will not fire unless i advance the distributor like 20-30 degrees btdc. ones i get it to fire, i retard the distributor at 12 degrees btdc and it revs down, kinda like i want to say not running smooth, and at that setting. if i rev the engine to like 2000-2500 rpm for a little bit, my headers start to glow. if i advance it back to were i can't even see the balancer mark because it way btdc. it runs real smooth without red headers. the confusing part is, why isn't it starting on the right timing setting.
i mean i would think, if the piston is at is at its compression stroke tdc, with the markings on the balancer and timing cover pointer ether at balancer o and pointer at 12 degrees btdc or balancer 0 and pointer at o, with the distributor dropped/installed in with it firing at the #1 plug on the cap.... it should fire right up,,, i would think. but it don't unless i turn/advance the distributor 20-30 degrees btdc. then it fires up runs smooth and if i advance it more it runs even more smooth until of course it starts to run ruff again the i would have to retard it a bit to smooth it out again... anyone have an idea what i'm doing wrong? thank you in advance. ps. the only thing i can think of. its got an aftermarket chrome timing chain cover with a aftermarket timing chain pointer. since it is a vortec motor. maybe i have the wrong pointer on their. not in the right position. ???
 
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#2 ·
Sounds like you have the wrong timing pointer/harmonic damper combination, and/or the balancer ring might have slipped.

There are three different timing pointer locations for the SBC, commonly known as 2:30 o'clock, 2:00 o'clock, and 12:00 o'clock. Three different harmonic damper line locations as well.

Did you confirm balancer and timing pointer are correct at TDC during engine assembly using either a bridge-type piston stop or a dial indicator against the top of #1 piston??
If not, the only way to check now is with a spark plug hole-type piston stop.

A couple of our Wiki articles to help you out:
http://www.crankshaftcoalition.com/wiki/Timing_tabs_and_damper_TDC_lines_SBC
http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center

My guess would be that you have a 12:00 o'clock damper mixed with a 2:30 o'clock tab. That amounts to about the amount of advance(40° roughly) that you seem to be off.
 
#4 ·
just a question. if i put the piston on tdc with both #1 cylinder valves closed on compression stroke, with the balancer and pointer, pointing at each other, with the distributor installed and firing at the #1 cylinder plug wire. how can anything be off? i mean, i would understand if i would bring the piston up to tdc and the balencer and pointer didn't line up. then i can see that something would be off... i'm missing something. i attached some pics of what i have. the cover can only be installed one way. the tdc on the cover lines right up with the balencer tdc. i'm lost or dumb...... or both..lol
 

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#5 ·
The point where both valves are closed is not the correct, or accurate, way to determine TDC. You need to use a piston stop to find TDC. If you think about it, both valves are closed for quite some time during the compression stroke - at least 125 degrees of crank rotation for most street grind cams - just because the marks happen to line up during that 120+ degrees doesn't imply that you are at TDC when the align.

Follow the links that Eric posted.

BTW - it looks like your timing tab completely covers the outside surface of your balancer - if that's the case, then something is out of whack there - I'd guess the timing tab.
 
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#12 ·
well, i don't really think the keyway is sheared. the balencer is a 8" one and the cover was bought for a 8" balencer. the the (0) degrees on the cover lines right up with the (0) degrees on the cover when put on. this **** is kicking my ***. this is all new to me and is kind of confusing to me to understand somewhat... i mean, when you do this a few times then i guess its easily understandable but for an old-school fart like me, its more of an on hands type of soul.... but i'm trying. i guess i'll have to keep reading erics links til i get it...lol i do strongly think that tab is wrong. weather its self or the position in which it is placed. the balancer? well, its the stock one to that motor. the chrome cover? not sure if its a problem. what i do know, if i set everything to even get it close to 12 degrees btdc or at tdc firing at #1 plug, it will not fire up. only if i turn the distributor ( advance ) will it fire.. once it fires and i have it running smooth and revving great. i put a timing light on it and try to bring the balencer (0) degrees on the tabs 12 degrees btdc at idle. it really revs down and revs real laggy. AND. if i give it a steady rev at that setting for a bit.....here comes the red headers....:nono:
 
#14 ·
OK guys, some good updates and some weird updates. had a good friend over that is a mechanic at work and also races like every weekend. so, he has ALOT more knowledge of the issues I've been having then i do. but. today i made me a piston stop tool. super easy. just to make sure that i was working with tdc with my marks on my balancer and pointer. which after doing the test i was dead on with my marks. one thing that he did was installed the distributor at (0) tdc on balancer mark and pointer (0) mark. set the distributor. guess what. it started right up. i guess i might have been a tooth off. not sure. thats the good update. now for the weird update. i have two marks on my balancer, one at (0) tdc and one at 35 degrees btdc. after we started the motor up and let it warm up. we went to set the initial timing at 12 degrees btdc. and the 35 degrees mark was that was showing, not the (0) mark. that was to the left of the balancer. we can't understand that. meaning. it will start at (0) to (0) marks but right after it starts the 35 degrees mark is whats showing with the timing like. almost as if its advancing itself right to 35 degrees at startup... wth... you can imagine, if he was stun you can imagine how lost AGAIN i am. lol i mean, its running real good. but how can that be?????? but, we left it at that for now.lol
 
#22 ·
pingging

ok guys, well, since the last time you guys were helping me. as far as timing and pinging. motor runs real strong when i get the timing were it runs real good. BUT, it seems to ping and miss if i advance it too much and if i retard the timing to try to get rid of the ping. the miss go's away but the pinging stays no matter which way i time it. i'm running 93 octane. so not sure what i'm doing wrong. any ideas? thank you much.
 
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#24 ·
well, their is a spot were its running good. but still pings. its not a stock distributor, its a new msd 85551 mechanical distributor. we did re-curve it. as for the bushing. we installed the small red one giving us 28 degrees. and we removed the two heavy springs that came installed with the distributor and replaced them with one silver (light) and one blue (light) one. now, do i know why he did these changes? well. he explained it and i just went with it. it was getting late so he had stated to play a little with the timing just to see were we where with it. and this is the gentlemen that is a mechanic at my work and races for a hobby. all this is all new to me. but i added some pics to show what am talking about. maybe its the wrong setup. not sure. i do know it pings no matter were i set the timing.:confused:
 

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#23 ·
Have you gotten it to a point where it times on the timing tab and you can use a timing light to verify the setting??

If not, you're just shooting in the dark and have no way to verify the timing curve and total mechanical timing produced by the advance mechanism in the distributor.
 
#25 ·
now for the weird update. i have two marks on my balancer, one at (0) tdc and one at 35 degrees btdc. after we started the motor up and let it warm up. we went to set the initial timing at 12 degrees btdc. and the 35 degrees mark was that was showing, not the (0) mark. that was to the left of the balancer. we can't understand that. meaning. it will start at (0) to (0) marks but right after it starts the 35 degrees mark is whats showing with the timing like. almost as if its advancing itself right to 35 degrees at startup... wth... you can imagine, if he was stun you can imagine how lost AGAIN i am. lol i mean, its running real good. but how can that be?????? but, we left it at that for now.lol
 
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#26 ·
ok,,,,so let me get this straight, because i can use ALLLLL the help i can get and i am willing to try anything to make this dam motor run and timed right. dam complete fresh rebuilt motor and this little issue is kicking my butt bigtime. sooooo, i should leave the silver light and blue light springs on. change the small red bushing to the 18 degrees black one and the set the initial around 12 and see what happens? plus i am running the

autolite
( app605 ) double platinum finewire....
 
#27 ·
I agree, most likely the Black(18°) bushing will be the best but you might try the Blue(21°) at a later date once you get things under control.

May also need to switch to the two Blue springs together.

fine wire plugs are generally not the best for performance use. Better to usea plug with a fat center electrode that won't have a tendency to overheat and act like a glow plug, which the fine wire can do because it doesn't have a large enough area to transfer the heat away from the electrode.
 
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