ninetyone

iTrader: (2)

Ok, I have a 91 TPI 350. The car came with a hypertech thermomaster chip and thermostat. I am also aware of the shitload of advance in those chips. Ok, so I found my timing to be at 6 degrees retarded! Actually it was in the next valley down from 0. Ok, so I just moved it up to 2 degrees retarded. Ran better around town and at low rpm, but when I got on it , it just felt like too much advance.Stayed in the powerband too long and took forever to hit 5k rpms! Felt like the engine was going to blow any minute.LOL Kind of felt like it needed more fuel. By the way , the car will knock with the timing set at 0 degrees BTDC. So, i think 2 degrees retarded is the best I can do. So, my question is this: If it does not knock at 2 and it feels zippier around town, then should I just add more fuel with my AFPR? or should I leave the fuel alone and just retarded it back further to about 4 degrees BTDC ? Doesn't run that bad at 4, actually better than it was in the beginning when it was set at 6 degrees retarded!! What do you guys think? I always thought that the idea was to have maximum timing and then add fuel as needed.

JakeJr

Something's definitely wrong with those numbers. Are you sure you're reading the scale correctly; correctly distinguishing advance from retard?

You are checking the initial timing with the EST wire disconnected, right?

The first thing I'd do is verify the accuracy of the timing tab and TDC mark on the balancer. The mark on the balancer could have moved if the elastomer bonding has broken free; happens a lot with older balancers. What you're seeing with the timing light may not be correct.

Best way is to use a positive stop screwed into the #1 spark plug hole to determine absolute top dead center for #1.

ninetyone

iTrader: (2)

Well , what i saw when i disconnected the est and checked the timing the first time was the mark in the center of the valley that is the first valley underneath 0 degrees BTDC. That would indicate to me 6 degrees retarded.

ninetyone

iTrader: (2)

The question I was asking was this though: Isn't the idea to have maximum timing and add fuel as needed? Maximum timing first, which makes the car feel "lean" and then add fuel?? Anyone really know?

JakeJr

I suspect you're mis-reading your timing tab. However, I can't tell for sure because of the words you're using to describe how you came up with 6 degrees retarded.

"Center of the valley"; "first valley underneath 0 degrees BTDC"; it's a vocabulary thing. Those are words we don't use to describe timing.

Maybe someone else can decipher it.

Jake

ninetyone

iTrader: (2)

No, i am not misreading the timing tab. I have settled on 2 degrees retarded timing. If you look at the tab standing in front of the car the biggest upside down v or valley is 0. To the left of that , the first peak is 4 degrees. The next valley is 6 and so on. In between each peak and valley is 2 degrees. So, what i am assuming then on the other side which is retard side, is that the same principal would apply.

TxTtopZ

I think your reading it backwards. I think you think 0 Before Top Dead Center is retard but thats advanced, thus before the piston gets to TDC.
I may be reading this whole thread wrong, but this is what it sounds like....and if so, you are 6 degrees initial, which is not off that much. Also, this timing tab may be inaccurate, post some pics of it.

1991L98G92

On the timing cover indicator....towards the passenger side from the deep vallley (TDC), is BTDC, and to the driver side of the deep valley is ATDC. Your symtems seem to indicate retarded timing. Set to 6 degrees BTDC and try that.

JakeJr

That's the same thing I'm suspicious of. Yep, photos would be a great help.

Verifying TDC with a Positive Stop would be my next step.

Jake

ninetyone

iTrader: (2)

Well, i tried 6 degrees btdc and it pinged like hell. Finally got it set on 2 degrees retarded. I believe this is due to the advance in the Hypertech chip.

hellz_wings

iTrader: (2)

Hypertech chip only advances WOT.. shouldn't change regular driveability..

bobo5084

I am a little further down the street in the crap factor and this is my issue. So I did a rebuild of my L98 on the top half of the motor and have not been able to get the thing to start. I am trying to hear some tricks of the trade on how to fix any and all timing issues. I know my wires are in the correct order but perhaps my distributor is 180 off or perhaps the motor needs to be placed at TDC and then find what ever the advance or retard is for it if any. So I need help with instructions if anyone can spare the time to type it out or send me to a website where they show how it is done properly. Pretty much I need the easiest way to find TDC and where I need to look to find if there is an advance or retard of it. Thanks

JakeJr

Easiest way is to remove the #1 spark plug. Then, if you have a helper, stick your finger in the #1 spark plug hole and have him bump the engine over while you feel for pressure against your finger. No helper, just stick a twisted piece of paper (paper towel, etc.) in the hole.

Once you feel pressure, you'll know #1 is on the Compression stroke. Have him stop bumping when the hash mark on the balancer is somewhere in the range of 4-10 degrees BTDC.

Now, install the distributor with the rotor pointing directly at the #1 spark plug terminal in the distributor cap and the #1 spark plug/wire. Hook up/connect everything else and, if everything is working, the engine will fire and run.

Once the engine will idle on it's own you need to shut it down, disconnect the by-pass (IIRC tan wire w/black stripe near power brake booster) connector and, using your timing light, set the initial/base timing to 6 degrees BTDC (stock setting).

Once the timing is set, lock down the distributor and re-check the timing to make sure it didn't move. If it's good to go, shut down the engine, reconnect the by-pass connector, then disconnect the battery for about 30 seconds or so. Re-connect the battery and you're done.

Disconnecting the battery clears the stored code the ECM sets when it detects the engine running with the by-pass disconnected.

Verifying the accuracy of TDC involves using a Positive Stop indicator screwed into the #1 spark plug hole and is a little more involved - but not all that much.

Jake

ninetyone

iTrader: (2)

Well, i have been doing some thinking and back to this timing question. I have been running the car with the timing at 1 degree retarded for a few months now. I tried setting it to 6 degrees btdc and it pings like hell. What do you think is the problem here? I have all new plugs,cap,rotor and wires too. It will even give me a ping at 0 degrees!!

ninetyone

iTrader: (2)

Could it be because this car was originally a tbi car? I know the guy used a lot of the 305 stuff like the starter, transmission , etc.

ninetyone

iTrader: (2)

Found out later that my swapped 350 has a mis-matched timing cover and balancer, so timing appears like its 14 degrees off.