LS TDC

[pbreaction]

Hey this is my first of many posts i am sure but i am about to start my wiring of my MS3 pro and i wanted to ask what is the easiest way to find TDC with a fully assembled LS engine. When i got my LS2 rebuilt into an LS3 i asked the builder if he had marked TDC and he told me No that its built timed based on the cam sensor and the "computer would keep it timed". Now if that's true do i really need to check the timing and if so what kind of accuracy do i realistically need. So far i know cycl 1 is on the compression stroke and using a chop stick i was able to figure out when the piston stopped going up (although it would kinda pinch it) so i know the vicinity of TDC even though i am sure that isn't then most practical way of doing it. Now i have seen some device you can screw into your spark plug hole that will stop the piston, you would mark the balancer then spin it the other way and then TDC is half way between those marks... is that going to be the easiest way?

So after reading the manual a few times it seems to really highlight the importance of insuring your engine is timed. Now is that just a generic statement that mostly applies to older carb engines that are now getting retrofitted for EFI or it applies to all engines no ifs ands or buts.

Thanks in advance,

-Mark

Just a little background. 6 months ago the only thing i knew how to do on a car was change the oil. Since then i ve bought a v6 2000 firebird, tore it apart, and after getting a ls2 of craigslist and getting it bored into an LS3 i ve installed it. Now i am about to start the wiring and soon to be ignition. I have read the manual a few times and the book they recommended on the DIYautotune site.

[jsmcortina]

Verifying the timing really is important - even though the LS engine should be timed right. Making "before" and "after" timing marks on the damper is the way to go.

James

[pbreaction]

ok cool i will look into getting one of those spark plug things.

Also i had i question i was kinda boucing off a few co workers. When wiring up the coils can i short the signal ground and the power ground to together? i was also considing puting a 1 ohm resistor between the short.. or i guess the other option would be to run the signal gnd to the ms3 and the other ground to the block(seems that would be ultimatly the same thing since i am assuming its not a differential output. And on the noise reduction should i put a decoupling cap near coils on the power or is there one built into the circuitry within the MS3 Pro.

[old guy]

If you plan on using a positive stop that screws in the plug hole be real careful.It is real easy to bend a valve if you have never done this before.
Here is the way that I do it.
1 Make sure you are at tdc of the compression stroke(both valves closed)
2 Rotate the engine about 45 deg in either way from tdc.
3 Install your stop insuring it is screwed all the way down.
4 Rotate the engine back towards tdc, until you contact the stop and put a mark on your damper that lines up with your pointer.
5 Remove the stop and rotate the engine back towards tdc and continue to about 45 deg past tdc.
6 Install the stop again making sure it is screwed all the way down.
7 Rotate the engine back towards tdc, until you contact the stop and put a mark on your damper that lines up with your pointer.
8 Remove the stop.
9 Measure the distance between the two marks and divide by two.
10 Put a mark between your two marks on your damper at this distance and you have found tdc.

Whatever you do don't make a complete rotation of the engine with the stop in place, or you risk a chance of bending one of the valves.
If you want to know how far apart the degree marks should be on the damper.
Measure the diameter if the damper,multiply by Pi ,divide by 360 and this will give you the distance in thousandths between each degree mark.

As far as your question about the LS coils.People have ran them either way , but I would just run both grounds to the block.
A lot less wiring.