Robertv34

I have a 1993 gmc sierra 1500 that I just replaced my heads on! But now when I start the truck it has rough idle it shakes alot and black smoke comes out the exhaust? Also when i step on the gas it turns off on me? My question is could the timing be off?

Robertv34

Im going to check out the vaccum leaks but timing is out of my reach! any more suggestions would help! Thanks.

mudmaniac

Are you saying that you replaced your heads with all of the associated work to go along with that and you don't know how to check the timing?

Robertv34

Yes lol I just dont have a timing light so I put the distributtor back in the same direction! But you never know a tooth off could mean alot!

mudmaniac

Yes it does, even without being a tooth off your timing can be off a good bit. A timing light is fairly cheap to buy and be sure to disconnect the ECM link when checking the base timing. It should be a brown wire under the glove box that has a connector you need to unplug.

therewolf

Hi Robertv34,

Welcome to the Chevy Forums.

When you say you "Changed the heads." does that mean you pulled the old heads off, threw a new set of head gaskets on, then used new heads? Rebuilt heads? Reconditioned the old heads?

I recall some guys with the same problem a few years ago pulled the heads off an engine, saw it was metallic-looking on the block, so they assumed the head gaskets came off with the old heads. After a lot of troubleshooting, they found they had placed a set of new head gaskets and new heads over the old head gaskets, which had never been removed. That extra set of head gaskets seems to bog down performance a little.

If you saw the old head gaskets hit the trash can with your own eyes, please disregard this post.

jeffs_62

Even without a timing light you should be able to get it close enough to run.
Like gary said, Roll it over to TDC, look at where the dist. is pointing, that is your new number one, firing order starts there.
Are you sure the firing order is correct?
18436572 if memory serves.

piccdragblazer

sounds like the timing is off you dont need a timing light to get the timing correct you can always remove the sparkplug from cylender number 1 and you have 2 choices you can so buy a timing whisle or if your on a budget you can just put your finger over the sparkplg hole and turn the crank. your going to feel air rushing out and one you feel the air stop rushing out it means your at the top dead center or at least pretty close than remove your distributor and than reinstall it so that the metal prong on the rotor is pointing in the derection of cylender number 1 then reinstall the distributor cab so that the cyclender number 1 spark plug prong is the first prong that the distruputor rotor hits when you start the engine up than reinstall all your spark plg wires and your spark plugs and fire it up

Deteoni

Or you can put a long screwdriver in the #1 cylinder and watch it for the piston to top out.

mudmaniac

Lots of great shortcuts listed here guys, yes these methods will find TDC for you and get you close to the correct timing, but do we really want to argue that a timing light is not the best method for accurately setting the timing?