Head Gasket change on 3.4 - car runs rough after? [Archive] - GrandAmGT.com Forum


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03-25-2006, 02:29 AM
i just finished changing my head gasket on 3.4. The car fired right up but the engine vibrates fairly roughly, the exhaust has a fast, repetitive, clacking/backfire-like sound. the sound comes from the tail end of the muffler. occasionaly.. once every 10-30 seconds there is a clack sound in the engine. all the rockers are torqued to spec and like i said, its intermittent, not repetitive so i doubt it's a rocker. I used a torque wrench on heads, rockers, LIM and UIM. the valves & springs were left in the heads.

I only let it run for about 1 minute then shut it off and ran it for another minute a little later on. it has coolant and oil. i saw no odd coloring in the front valve cover or dipstick. when you change headgaskets does it take a few minutes for the engine to simmer down? i've never done it before and am a bit timid to let it run without seeking advice. .. no codes are being thrown. anyone have any insight?

03-25-2006, 08:47 AM
I assume you had to disconnect the battery to do the work. If so this may be just the computer relearning the engine. I'd say let it run for a little bit and watch your fluid levels closely. If the thing doesn't get worse drive it gently for a little and see if it goes away. That's all I can think of.

03-25-2006, 03:12 PM
I let it sit last night. When i woke up and fired the car up it backfired about 4 times and then quit. i think a valve was stuck open due to low amounts of oil on the rockers after the repair (forgot to lube them up before the valve covers went on.

The engine smokes a bit due to fluids having gotten onto the exhaust mainifolds/heat shields. Does anyone know how long(on average) it takes for oily fluids to burn off a manifold?

03-25-2006, 03:25 PM
There is a repetitive tick coming from cyl 6 tho. What are some of the possible causes of a repetitive tick in the engine? all the rockers were torqued down with a torque wrench and then i attempted to wiggle each rod to make sure it didn't move or have any play.

Do you think i should buy another rocker and try replacing just that?

Do i have to pull the head to replace a valve spring?

03-25-2006, 04:53 PM
It can take a while maybe half hour for all the crap to burn off/out of the exhaust and everything else. Shouldnt really have to lube anything before putting it back together. I havent on any of the head gaskets i've done. As for the tick all the 3.4's have it. Just make sure you change the oil before you start it.

03-25-2006, 05:30 PM
i was talking to a friend and he had the same rough start problem happen to his sti the other day when he put in new injectors. He said it lasted for about 1 minute and then smoothed out. he attributed it to air in the fuel lines. I had a lot of fuel drain out when i depressurized and then even more when i popped the injectors off the rail. i guess logically speaking the system will pressureize when u turn the ignition on, but it will still be containing all the air from when the fuel drained out.

I didn't know about the tick. thanks.