Not so good first drive of the year. UPDATE 9/12/14 VIDEO

Sorry for your loss ! it amazes me with all the information on this site and people (not you) will still assemble a double chain with a tensioner I've read more then once this happens on here .it looks like they spent a little money on the block with the steel caps hope you can save the block ?
 
The last 2 cars I've bought with built motors are now both on engine stands. The 474 in the trans am had the Butler Performance goodies in it but the clearances where horrific when we checked them after I pulled the motor for a rear main seal. Total tear down and start over.

Now the GN, this motor was built back in 2004 and I have the build sheet from the machinist. They machined everything properly and did most of it right minus the $5 tensioner. The other thing I scratch my head on is why spend all that money like they did with the heads, intake etc etc and run a cast piston? I know it works but from front to back on this car it was set up for street/strip. For the difference in the price of pistons why skimp there? One never knows? Maybe that was the thought process back then.

At any rate I didn't really want to spend the money on this car, that's why I bought it already modded but it wasn't running the number and I probably saved myself from a catastrophic failure catching it on a cruise and not at the 1320 mark.

I think the block will be ok from what I've seen so far.
 
Yup you are right. Why do all that and run cheap pistons?

Anyways, looks like the parts can be saved and the motor can go back together with a few changes and it'll be a good piece.
 
This is very unfortunate. This sucks that you're having issues. The only bright side of this is that when your engine is built, you'll know exactly what is in it.
 
And here we have the thrust bearing! The rod bearings were scratched but the center main bearings had a lot more wear. This is the worst one.

 
:eek:From the looks of that brg and the parting faces, the engine has had SEVERE, repeated detonation issues...
 
hiboom said:
that cap looks to have a lot of fretting and is no good IMO
Click to expand...

What is fretting? So the billet main cap is no good anymore?

The crank is scratched pretty heavy, you can catch the scratches on your fingernail.

I bought this car off this forum and I went back and read all the PO threads. He had what he thought was false knock several times while he owned it. I also had knock issues when I bought it but after checking the knock sensor I found it was not even hand tight. So I torqued it to proper specs and I didn't see anymore knock.

I'm not sure when the motor got hurt but I have only put maybe a 1000 miles on it. Who knows but it is what it is.

I won't be using this crank rods or pistons again so as long as my block is serviceable we are good to go.

My pistons are .020 now so I might have to go .030 over to clean up the cylinder walls.

I'm leaning toward the stroker kit right now. Just waiting on the machine shop to tell me what we need to do from here so I can get the parts ordered.
 
"What is fretting? So the billet main cap is no good anymore?"
My $.02........
Fretting is the result of movement between two parts, resulting in transfer of material from 1 surface to the other.
In this case, detonation looks to have been the cause. The hammering on the piston rod caused the cap to move on the block parting face.
That hammer effect cracked and broke up the layer of brg material on the main brgs.
Reuse of the caps will depend on how much they must be cut, in order to true the faces. Cutting too much necessitates moving the center line of the mains up so far, the block becomes junk..
 
Some tried methods to prevent fretting came to me from a machinist in Ft Wayne. Evidently a Cummins engine has the problem of fretting on the mains. While we know detonation causes this a preventative measure is to add a locktite gasket maker to the bottom of the main caps. Torque to spec and ride on. Im sure people will advise against it but I figure if it works and wont harm anything why not. Just my .02

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Clean up everything as best you can and check the main bearing bores with a dial gage if you have one.
Many machine shops think there competent enough to install caps but in reality results may vary.
Just something to think about.
AG.
 
I have a local machinist here in town that is very good. Both him and his son. His son has an 87 GN.

They will be handling this for me when the time comes. Right now they are doing a 474 for my 78 Trans Am. Just need to wait my turn in line at this point.

I will bring this thread to their attention. Thanks for the info.
 
Yes it can. I had a converter failure last summer. I lost lock up and broke the Sprague. As mentioned earlier in this thread detonation is also a factor here.

I have basically zero movement in the crank now. This motor had knock issues documented by the previous owner in threads on this board. I also had weird knock issues and found a loose knock sensor. Tightened it and my knock issues went away.

One thread by the PO mentioned him running too much boost without alky and he thought he maybe hurt the motor. Then he added alky later. That may have been the catalyst?? I also have a broken cam chain tensioner? Could that be the catalyst with material going though the motor? Who knows at this point but I will definitely check things over before I put it back together.
 
Go with the stroker/roller engine. You won't regret it!
 
Well the time has come to get started on the engine rebuild. The machinist picked the block up last night. He is going to take some measurements and decide if we can stay at 20 over or bore to 30. Once I have that answer then I'll be ordering the 4.1 stroker rotating assembly Tuesday. I'm opting for new billet center caps just to be on the safe side.

We never really found a smoking gun as to why the motor ate itself up? The tensioner was still on the block when we took the timing chain cover off, what had happened is the tensioner arm broke and the shoe just flipped back and laid there. The chain was super loose which I expected. The 3rd main cap bearings where in much better shape than the other bearings and the bearing itself didn't fit the cap like the others. That main cap also had a lot more heat in it than the rest, that's why I'm just going to get new caps for the line hone. We're thinking the 3rd main cap was installed improperly and the motor was severely detonated prior to the previous owner installing Alky. That was probably the catalyst and it was just a matter of time before melt down.

So the tentative plan for now is Billet 4.1 stroker, full roller set up. I'm going to have my Champion heads gone through. I did find out that I have a Champion intake as well that's been ported. I'm getting my advice and parts from Dave Husek so I'm letting him decide on the cam based on my goals. He's going with a custom grind of some kind. We are also going with an Earl Brown timing chain cover.

Dave and I are talking a little about a turbo upgrade for me. I'm currently running a TA60 so we'll see how that shakes out as we go along.

On a different note take a look at this video I shot this morning of my other car. This is a 474 Pontiac Stroker I just finished up. This is why I've been waiting to start the GN build.

 
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