3.0 rebuild started. Have a few questions. PICS

mcguiver7 · mcguiver7's Garage

Hi everyone. I started my 3.0 tear down the other weekend. All went smoothly till the last flywheel bolt. I attempted to remove it with heat and vice grips, but no dice. In the end I welded a cheap 8mm allen wrench to it. It came out with ease. I have a few questions related to disturbing discoveries found inside the case. All and all the crank and bearings looked great minus the main bearing which had a slight score. It's deep enough that it should be replaced.

Is this normal? It appears to be apart of the thermostat channel.

Piston 2 had a chip at the base. If this still weights out fine then can I use it? No idea how it happen. My guess is it happened sometime during head stud removal.

When I got the motor the chain housings and tensioners were off and i'm guessing at some point the chain got bound. It's just the one tooth, but I have a feeling it should be replaced. Worst case it shears off at some point?

main bearing

cylinders are all in good shape

flywheel bolt removal

Can anyone give me advice on what to do about the cam chain gear, piston, and unusual crater near the thermostat channel?

Matt

mcguiver7 · mcguiver7's Garage

Are the pictures displaying ok?

longhornchris04 · longhornchris04's Garage

I can see them... Can't answer any of your other questions, but I can certainly see the pictures.

Its only a matter of time before one of the experts show up. I'm sure one of them will chime in when they can.

mca · 09-25-2009, 09:05 AM

First two pics ... that is normal. I asked the same question during my rebuild. Leave as is.

mcguiver7 · mcguiver7's Garage

Thanks MCA. Thats good news.

I think i'm going to replace the intermediate sprocket regardless considernig it's only $54. Anyone have any idea about the piston?

mca · 09-25-2009, 09:16 AM

Quote:

Originally Posted by mcguiver7

Thanks MCA. Thats good news.

I think i'm going to replace the intermediate sprocket regardless considernig it's only $54. Anyone have any idea about the piston?

I believe that the consensus is that you should replace both IS chain sprockets.

I didn't though ... only replaced one (towards front of engine) because the other one looked brand new. If I could do it over again I would replace both.

If you have a shop replace the sprockets, have them clean out the IS shaft too. Lots of crap came out of mine.

Also, enjoy the journey. It is a blast.

OldTee · 09-25-2009, 05:14 PM

You might be able to file out the piston but I would replace it. Consider the stresses on the piston during operation you will never know until it comes apart. Replace the gears.

mcguiver7 · mcguiver7's Garage

Would you suggest deglazing the cylinders. They don't seem to have the yellow glaze that everyone talks about. Am I wrong?

mcguiver7 · mcguiver7's Garage

Also the cylinders showed no ovalness at all. Though they were slightly under spec in diameter, but still well within spec when it came to piston to cylinder tolerance. Thats the most important part is that the gap between the piston and cylinder is not too great right?

Eagledriver · 09-27-2009, 03:47 PM

Personally I'd not be afraid to use that sprocket. In fact I usually keep the old chain unless it's worn out. I'd clean up that piston with a file and use it too. The case area is normal. You should check the outside of the case in that area and cover any defects with JB weld. This prevents oil leaks there. The bad news is you have Alusil cylinders. The good news is that many have had success reusing them. Personally if the old rings are in spec I'd keep them. If not then you'll need to go through a deglazing procedure on the cylinders and put in new rings. The most critical measurements are the cylinder to piston clearance and the top ring land clearance. These numbers are in all the books but basically the top ring cannot have more than .004 inches clearance and the piston to cylinder cannot exceed .004 inches either. If you re-use the old rings then you could cheat a little on the top ring number.

Keep in mind that I'm not a professional rebuilder and I mostly work on my and my friends race engines. I try to save money but still get a reliable engine that has good compression and doesn't burn excessive amounts of oil. If you want a "zero time" engine you might need to replace the pistons and cylinders.

-Andy

mcguiver7 · mcguiver7's Garage

thanks for all the advice Eagledriver. I'll check the top ring landing clearance next. Can you tell just by looking at the walls which metal it is? These have Mahle 95ZN1W3 stamped on them. I hope they can be reringed. I already pitched the old ones.

mcguiver7 · mcguiver7's Garage

11 fins for an sc cylinder means nikasil right? I think I might be in business for reringing these bad boys.

tom1394racing · 09-27-2009, 08:23 PM

Mahle=Nikasil for SC cylinders.

Eagledriver · 09-28-2009, 05:39 PM

I was basing my call on the color of the cylinders. Usually the Nickasil looks much more gold colored and the alusil looks like the picture you showed. Nickasil is magnetic....

-Andy

Eagledriver · 09-28-2009, 05:43 PM

Look at the pictures in the thread "scotchbriting the cylinders" and you'll see what Nickasil looks like.

-Andy

mcguiver7 · mcguiver7's Garage

I'll check to see if they are magnetic or not. I am positive that they have 11 fins and no fin support brace. I read in one of those threads that a 3m 7447 pad should be used which is a 1 grade. The only one I can find locally is a 00 grade (less abrassive). Would this be sufficient for deglazing?

777joee · 777joee's Garage

If can use a very small magnet on a string and bring it close to the inside cylinder wall it should swing over and attach itself to the cylinder wall. If not you lost the lottery and have Alusil not Nikasil cylinders.

That is the sure way to check.

hdbmw · 10-01-2009, 02:05 AM

Hi, How's the crank look on that main? Your using new main bearings I'm sure and your probably all right on the crank (they're so hard) but you've got to look or have the shop check it when it's micropolished. The guys are right that removing and then polishing the nicked area on the piston should be fine, people have been modifying and shortening piston skirts for along time, just make sure there are no cracks and you leave no sharp edges that could become stress risers (that area does see some loads). Ditto on the gear (but prudent advise seems to be to replace). The point made above about clearance is more important than the nick. Tom's right Mahle= Nikasil's for SC's. There's really no "bad" news in the pics.
Signed the "eternal optimist"...LOL

OldTee · 10-01-2009, 04:52 AM

Eagledriver and others have a point. Polishing the piston might work, and is low risk. But doing so is on the wrong side of the risk/reward curve. A used piston is maybe $25-50. A destroyed engine priceless. Then there is the nagging thought that the piston is flailing away at 6500rpm just as you exit turn one. There is a cost to that too.