how to set motor to 30* ATDC

[spawn87]

im going to do a boost leak test on my car and i know i have to have my car set at 30 degrees ATDC but i dont know how to do this can some one help?

and i know this is a dumb question but whats ATDC stand for?

 

[Colt4G63 also]

After Top Dead Center. Set it to TDC (Top Dead Center) then turn it about 30 degrees further (clockwise when facing the cam sprockets). That's about 1/3 of a turn at the crank, or 1/6 of a turn at the cam sprockets.

 

[steve]

Look at the marks on the timing cover. See how far the 15 is from the TDC mark? Double it and turn the crank that far past TDC.

It's not a critical measurement, I picked 30* because it's a nice round number and far enough that if your off a bit it won't matter.

 

[spawn87]

ok to make sure i understood right... i turn the crank clockwise to set it to its timin mark then about 1/3 of a trun past that correct?....is there a way to know by just moving the cams ontop?

 

[steve]

A third of a turn would be 120*, that's a little much.

 

[need2boostpsi]

if all you are doing is a boost leak test why dont you just try it where the engine shuts off at,90% of the time you wont get overlap between valves, It doesn't have to be 30* ATDC. If you have overlap all you have to do is pull the MPI fuse and use a wrench and slowly turn the motor over at the crank til you have no overlap. If your still getting air into the exhaust you have a leaky EGR or worn valves.

 

[steve]

why dont you just try it where the engine shuts off at,90% of the time you wont get overlap between valves, It doesn't have to be 30* ATDC. If you have overlap all you have to do is pull the MPI fuse and use a wrench and slowly turn the motor over at the crank til you have no overlap.

This works too. Like he says, you just want to make sure you don't have any cylinders in overlap.

The reason for telling people to use 30* ATDC was prior to that people were all convinced they needed to test at TDC. You don't know how difficult it was to stop all the "experts" from passing that "fact" around.