This one is for all you guys using 3400's with 8mm heads on the rocker bolts, for your swaps.
Monday I get a 2003 grand am GT Im at work with a severe miss. The car only has 52,000 miles, nothing done to it but oil change since it was new. An older fellow owns it, nice guy , uses it to putt around town. So it wasnt abused.
The first thing I was thinking was that , 50k, it shouldnt need anything.
I figured out that it was # 4 cylinder that was missing. Were talking a dead miss here. So I pull the plug, looked kind of wet with something , maybe a little oil. Spark was good to the plug.
Here is where it gets strange.
Compression was nearly ZERO. And that was a big fat zero. On a 50k mile 3400
A little stumped for a while, I decided to pull the front valve cover to see if there was anything strange on the top end.
So when I lift the cover off the rocker arm for the #4 intake is just laying there, the pushrod was sitting just off to the side of the lifter, but still standing up.
It didnt make any noise either.
I pick up the rocker and find that the bolt still has the threads on it, both from the bolt and the head. Yes Im saying that the threads were ripped out of the head.
You know I havent got a clue what caused this. The guy said that he was just driving on the highway and it started missing.
The only thing that I see that is different is that GM quit using the the rocker bolts with the 10mm heads, because these were 8mm heads, and they also had a starter thread tip on the bolt which the older ones didnt have.
My guess is that GM used too long of a bolt, meaning that the thread starter end of the bolt bottomed out before the rocker completely tightened, causing the threads to be stressed.
Before any one ask's if he had any work done to it like a intake job, the answer is no, I already went down that road.
Any way I drilled and helicoiled it, put it back together, runs great again.
Just thought Id post this in case any one ran into the symptoms.
01 cav w/01 3400 gam gt 4t45e
The actual bolt thread is the same(think its 8mmX1.25), the head of the bolt is the difference. the older ones take a 10mm socket and the ones on this particular engine have a 8mm head.
Maybe I wasnt exactly clear in the explanation. sorry.
So if you wanted to you could screw in the old 10mm head bolts in place of the 8mm head rocker bolts. Not sure what good that would do though. That is , if what Im thinking about the bolt length is true then the threads of all of the new ones are stressed from the bolt bottoming out.
That is only a theory about the bolt length, I didnt have an old one handy to compare the newer one with, But I do know that GM has screwed with the bolts specs since the heads are different. They just cant leave things alone, all they had to do with the engine was to fix the intake gasket leak and they go messing with the rocker arm bolts. Geesh.
This would be an important need to know info for you guys running LS1 valve springs. The stronger springs might just pop the threads right out with little effort.
01 cav w/01 3400 gam gt 4t45e
nitros nate has some pics up of his 02 and they look like 10's. Nate if you see this check for us.
01 cav w/01 3400 gam gt 4t45e
03 + Heads have the 8mm bolt. 02 and older have a 10mm stud. They might be more familiar with this sort of problem on 60degreev6.com
Seems like people like the 10mm anyways.
