3.4 runs like crap after head gasket replacement

[safarimike]

just replaced the head gaskets on my moms van (03 Chevrolet venture). the gaskets were fine, but one of the rocker arm threads on cyl. no 5 stripped out. i couldn't fit my drill back there, so i pulled the head to helicoil it. while i was at it i pulled the front head and replaced both gaskets (new intake gaskets and all that jazz). i have everything back together, now its running like crap and it is loud - sounds like the top end. it almost sounds like it did with the stripped rocker arm thread, but louder. when i first started it i thought maybe the lifters just had to pump up, but its definitely missfiring. i thought maybe one of the rocker threads pulled out again, so i pulled both valve covers - all of the rockers are tight and on their pushrods. i turned the motor over by hand. all of the pushrods and rockers seem to be working. i had the pushrods organized when i took it apart because i know intake and exhaust are different sizes, so i dont think there is anyway i could have mixed them up. i checked the oil - there is no coolant in the oil.

i hooked the scanner up to it and im getting a p0300 random missfire code. i double checked to make sure all my wires were in the right place and that checked out.

not really sure where to turn - i guess do a compression test on the cylinders to see if i have compression in all cylinders?

has anyone had an issue like this before?

[glennmac]

Yep I had a problem like that once, swore up and down I had the wires on right, guess what? plug wires on wrong. it took a fresh set of eyes, (not mine) to find it. I never got a code though. Any chance you got something plugging your cat? Try running it with the o2 sensor out, if it improves you got a blockage.

[safarimike]

i have no compression on cylinders 1 and 6. maybe somehow i mixed up the pushrods. or a rocker slipped of the pushrod or spring - though when i had the valve covers off and was turning it by hand everything looked good.

[pocket-rocket]

That sucks. And here I was going to suggest not going by the numbers on the LIM for running wires because the runners cross over from one side of the engine to the other... No matter what is wrong, I hope it's cheap and easy.

[glennmac]

hope you did not bend anything. post your results to educate the rest of us please.

[safarimike]

I am going to work on it tomorrow, Just for my reference the push rods are

rear head - driver to pass side - Exhaust, Intake, Exhaust, Intake, Intake, Exhaust.

front head -driver to pass side - Exhaust, Intake, Exhaust, Intake, Intake, Exhaust.

Is that right?

[Azrael]

That's not right. The order for one one side is opposite the other. The heads are identical but one is spun 180 degrees.

The rear head should be, from driver to passenger: Exhaust, Intake, Intake, Exhaust, Intake, Exhaust.

It doesn't seem like that's the issue though because if that's all that was wrong, you'd have no compression on cyl #3.

And because it's worth mentioning, exhaust pushrods are 6" and Intake are ~5 3/4".

[bob442]

maybe the threads on the other rockers stripped out, we just had a guy who went through that...

[safarimike]

took off the rocker arms for cylinder no. 6 to inspect the push rods and their location. pushrods are not bent and they are in the right spot, go to reinstall, and the threads strip out of the head for intake rocker. this one should be easy enough to heli coil though since its in the front. i don't know of that was the reason for cylinder no. 6 having no compression or what (i didnt look at the bolt threads when i took it off) - but fwiw the exhaust rocker arm bolt was much tighter than the intake rocker bolt coming off - and they were torqued to spec so you would think they would have felt the same comming off.

[pocket-rocket]

That sucks. Rocker arm bolt holes stripping seems to be the thing lately. *goes outside and pats his DOHC*

http://60degreev6.com/forum/showthread.php/47965-3-Misfire-after-LIM-Change

[bob442]

just heli coil every last one, and get a corner drill for the rear, and report back.