[chris929]

*Please only post if you actually know what your talking about*

I just took out my number 1 piston and rod combo as compression was off in that cylinder by about 25 psi so I thought the rings were the issue.

However, we soon found the actual problem....

This explains the loud BOOM and ticking I heard just before I parked my car for the winter a couple months ago.

So there is damaged to the piston aswell as the cylinder wall, here are the pictures:

I took the best pictures I could but as you can see the piston has minor scuffing on the lower side (just on one side) of it aswell on the very bottom where it contacted with the crankshaft (which appears not to have been damaged). There are no cracks or other damage.
The cylinder wall is what scares me the most...if you look carefully you will see a nice nick out of the wall at about 12 o' clock position (right above that dot in the crankshaft).

Now the thing is that the scuffing on the cylinder wall is below where the piston rings lowest point is in their cycle. so what if I smoothed the scuff so that it doesn't scrap the piston? is it salvagable?

So I need to know:
1). Is the piston itself reusable with the minor scraping
2). Is the block toast? or is it okay as the damage is below where the rings go?

 

[slow 2K2GT]

if there are any deep scrapes on the walls of the piston, even some minor ones it will cause damage to the cylinder wall, its hard to tell the depth of the damage to the sides in your pictures, but if its minimal then I would say its ok.

As for the block it will be ok as well as long as the scrapes are not in the area which the rings come into contact.

Seems like you got really lucky there Chris. I personally would not re use the piston in fear of it being weakend or out of line somehow, but then again they are expensive to buy...on the other hand a blown block is too.

 

[chris929]

I'm going to look into coating the piston but more than likely I will just end up replacing the entire piston if I can purchase one seperately.

Its really the cylinder wall that is my biggest concern. My options are to try to smooth it down so that it doesn't scrape the side of the piston, or have that one cylinder resleeved or replace the entire block and have everything re-machined...which would be alot more work and $$.

So the question is could I get away with just smoothing that gouge in the cylinder wall so that it doesn't scratch the piston>?

 

[slow 2K2GT]

you are already running oversize pistons, so depending on how much they need to clean up you may still be within specs for the rings. You may be able to get over sized rings from CP in order to compensate for the larger bore area.

Scratching the piston is not the biggest issue here, you will lose compression and get blow by if the scratch is not fixed.

Were you reving really high when this happened? You rod obviously hit the cylinder wall and bent, I wonder what would cause your rod to float that much so it hit.

 

[chris929]

you are already running oversize pistons, so depending on how much they need to clean up you may still be within specs for the rings. You may be able to get over sized rings from CP in order to compensate for the larger bore area.

Scratching the piston is not the biggest issue here, you will lose compression and get blow by if the scratch is not fixed.

Were you reving really high when this happened? You rod obviously hit the cylinder wall and bent, I wonder what would cause your rod to float that much so it hit.

My best guess is detonation, probablly leaned out because of the design of the Alpine 5th injector. And ya it was reving pretty high- probably around 5K.

Your right, I was pretty lucky because the area on the cylinder walls that the piston rings travels through was undamaged, It was just at the very bottom so there shouldn't be an issue with compression or blow by since the rings don't travel that low. I would just need to smooth out that scrape so that it doesn't scratch the side of the piston.

And of course I will rehone the cylinder and replace the rings.

 

[slow 2K2GT]

Well best of luck with those things, a day or two at the machine shop will sort all that out. Did dmdicks tune you Unichip for your comp ratio? I was reading on the CP site and they say that the pistons will give an 8.8:1 ratio.

 

[chris929]

Well best of luck with those things, a day or two at the machine shop will sort all that out. Did dmdicks tune you Unichip for your comp ratio? I was reading on the CP site and they say that the pistons will give an 8.8:1 ratio.

Ya thanks for your input- hopefully we can sort stuff out here...to be honest i'm not sure exactly how dmdicks tuned it but I did make it clear that i would be running 8.8:1 compression. The tune itself seemed good its just the design of the Alpine kit and its 5th injector that caused cylinder 1 to run lean and detonate. Man i'm looking forward to switching to the secondary rail.

 

[slow 2K2GT]

Yeah me too, are you keeping the Unichip to run your secondary rail or will you be upgrading to the SMT like me? I have no one around to tune the Unichip so even though it cost a little more its the best sollution for me I think.

Let me know how things work out.

 

[dmdicks]

Chris,

Are you sure its the number 1 piston? Did you ever install a wideband or EGT probe on your car to monitor things? The tune I gave you was really rich and timing was retarded. With that said running with one subinjector tends to lean out the #3 and #4 cylinders.
I can't really tell from your pictures but it looks like the piston and cylinder have been ovalized, meaning they are not perfect circles anymore. You would need to get a micrometer and measure the size of the cylinder wall from top to bottom. If it is indeed ovalized then most like your combustion temps got too high and warp the piston causing it to get stuck in the cylinder which caused the rod to bend. Then when it got unstock the bent rod contacted the end of the cylinder wall on the up stroke. If this is the case then the neither the block nor piston are salvageable.

 

[JonGTR]

Get a new motor. End of story.



At the least, you will need a new rod AND piston. Do not reuse it. You will also have to hone the cylinder, which means new pistons anyways. That's the least to say.......

Again, start over with a new block.

 

[JDOGG]

+1 they'res a block at car bashers that you should be able to use. Just need to have the bore remachined. hopefully you can get just 1 new piston.
New block FTW.

 

[chris929]

well one other option I might look into is to have that particular cylinder resleeved.

It is definately cylinder 1- the cylinder closest to the timing belt and furthest from the subinjector. I have a micrometer and will take a close look at the cylinder walls. I have a wideband on my car but no EGT. A/F was stable.

 

[JDOGG]

well one other option I might look into is to have that particular cylinder resleeved.

It is definately cylinder 1- the cylinder closest to the timing belt and furthest from the subinjector. I have a micrometer and will take a close look at the cylinder walls. I have a wideband on my car but no EGT. A/F was stable.

what was the A/F stable at wot?

 

[dmdicks]

Can't resleeve a cast iron block. There are no sleeves to begin with. Sleeves are only used in Aluminum blocks. Strange that it happened on cylinder 1. It also looks like the rod moved on the wrist pin making it off center.

 

[chris929]

what was the A/F stable at wot?

Cruising= 14.0-14.5
WOT= 11.5-11.6

I'll try to measure the cylinder wall tonite and we'll see how things look.

 

[JDOGG]

Perhaps check your injector on the # 1 cylinder??

 

[Midnightsky]

Brutal man, sry to hear about this......I agree with DM about it looking ovalized, that can't be good.

 

[chris929]

I think i found the problem....

There are no wire locks on the sides of the wrist pins so the rod moves freely from side to side. I'm thinking that because of this excess movement the piston seized thus causing the rod to bend.

I just checked the box that the cp pistons came in and the orginal wire locks are still in there.....why the hell wouldn't my mechanic have installed them?

 

[grumpy1]

some engines dont use wrist pin locks. i dont know for sure but i would guess the tib is like that.. they press the pin into the rod and the pin floats in the piston. i dont know your set up. are those 1.8l rods and piston? you can get the block bored and sleeved. a junkyard block might be cheaper just from the pictures it looks like it might be a oil problem.it is all burnt and hot looking. i would pull down the main cap on each side of that journal and make sure it didnt spin a main bearing, how was the rod bearing?
those were my first thoughts from the pictures. good luck to you!

 

[chris929]

Okay we closely examined/measured the cylinder wall tonite and there is no warping or ovalizing- the pictures might seem decieving but believe me seeing it in person is another story.

After quite a bit of research I feel okay about the notch out of the very bottom of the cylinder wall and I believe it will be okay once we carefully smooth it out.

Still looking into a replacement piston but already have honing equipment + new set of rings.

I'd still like to know about the wrist pins though...can they simply be pressed in- or do they need the lock wires to secure them properly? Is that side to side movement normal?