I'm going to have to make a big decision soon. My car is in the shop with some serious issues. Seems one of the pistons has too much play btwn it and the cylinder wall, causing the knocking that I was hearing. On one of the other cylinder walls, there is noticeable scoring indicating the overall assembly was not as solid as I thought. This hybrid was done two years ago this month, and was bored .5mm at the time. Now I have to make the decision to try and save this block, or downgrade to a new/used stock SVT engine. I would probably sell my car if it came to that. I searched but never found a definate answer to the limitations of how far these can be bored. I know someone said 3.5, and 3.2. But how does this convert to mm's? What bore can be done on top of the .5mm that was done originally? Does it then become difficult to find pistons/rings to fit the custom bore? Or can a machine shop simply remove the sleeves and replace them along with the pistons/rings? I don't want to do a straight 3L, because I really want to keep the look of the stock SVT UIM, and the shop didn't seem too comfortable with the idea when I mentioned it. I am obviously no mechanic, but I took good care of my car. I was always cautious on long sweeping right turns and that kind of thing, so I'm very surprised to say the least. But I must take the next step to get my car back. Should the 12,000 mile warranty on a new/used SVT engine even be a consideration? I really don't want a stock SVT engine. Any input would be greatly appreciated. Thanks in advance.
I've really only seen 4 causes of piston/cylinder wall scoring:
1) No/poor chamfer at bottom of cylinder bore. At bottom dead center, the piston protrudes of the the cylinder a bit and it rocks a little. If there isn't a proper chamfer there, the piston will become scored.
2) Poor cleanliness during assembly of the pistons or installation of the pistons into the engine.
3) Handling damage to piston during assembly or install.
4) Material in intake tract sucked into cylinder scoring walls. Material can also come into the cylinder from the exhaust system as well due to natural overlap of the valve timing. I have seen failed cat. converter material in cylinders before. It is very gritty and wears down the bore and rings in no time.
As far as additional boring goes, going past 0.500mm oversize poses lots of potential problems. The liner starts to get thin. The head gasket starts to overhang the combustion chamber. The existing sleeves are cast in and have ribs on their backside. They cannot be simply pulled out.
If you want to find out what 3.2L or 3.5L equals in oversize, do a little searching for the stock bore size and stroke and do the math. It is fairly simple.
The 3.5L was suppose to be a stroker engine that SHO Shop never made.
A very simple solution is to replace the block with a junkyard 3L block. Probably can do that for $500 and do the work yourself. Only a quality machine shop can determine the situation with your current block now.
It sounds like it will just be a better idea to get another shortblock. I'm still unsure of the reason that this happened but am very curious, being that it's two years old. When this is rebuilt, should I be very sceptical of the hybrid's reliability? Or is this most likely something that could have been avoided, such as cleanliness of the assembly as posted above? On the bright side of things, I can now get my Spec flywheel installed for free. My last question is...should I have the new block bored or leave it alone? I read that boring can cause longevity issues, or is that mostly with extreme situations with boost and such? Thanks again.
I just got back from the shop. The owner handed me a shop rag, with something wrapped up in it. I opened it to see about fifteen pieces of one of my pistons. He said they were sitting in my oil pan and oil pickup. Note I got no metal flakes or pieces from my oil change. Anyway, he is going to take the block to a machine shop and see if they think it can be bored even a miniscule amount just to reshape the cylinders, that at least one of is egg-shaped from the busted piston. I told him it probably wasn't a good idea, based on info I got from this site. He said he'd take it anyway, and not charge me for it, just to see what they say. But if I end up just finding a used shortblock, am I correct in thinking that it must be older than '01? The oval-port 3L block is not compatable with the SVT heads, or is the 3L shortblock the same regardless of the split/oval port? I searched but only found that an oval port hybrid can be done with 3L heads, and SVT UIM. I don't know enough to know how the ports do or don't affect the shortblock. Reason I ask is because shortblocks are slim-pickins 'round here.
Not correct. You can use the 01+ block just plug off the two oil returns and the oil feed hole that feeds the head under the timing cover. when you place your 2.5L heads on the new block you'll see the passage that needs plugged. A couple years back there were a lot of writeups on this very issue and how to safely do it since the front feed is under pressure.
Thanks a lot. I have done a lot of searching but keep coming up just short of what I'm looking for. I would like to give a printed out How-To of the hybrid build. The one that I have from an old PM won't link anymore. And with all due respect Tom, your's just doesn't seem very detailed in regards to the actual build, at least compared the muiltipage version that I remember printing off the first time I went through this. Same with the one from the Neco forums. All I could come up with from searching was a straight 3L build. If anyone has a link to the extremely thurough 3L hybrid How-To, I would appreciate it. Otherwise I'll just keep searching. Thanks again everyone.
It's the same as a 2.5L. You just fill a couple oil drain backs and hack off some ears so the alt etc can bolt up. Just pull the heads and bolt them it to the block.
http://airknight.wnysportriders.org/3LFAQ.html
http://www.geocities.com/svt_mondeo/3L.html
Thanks, I got the key points I was looking for. One question though... at one point Dave talks about boring up to 2mm, which directly contradicts what I'm hearing from others. It would be easier to bore this block another .5mm rather than buying a new/used block, but who should I believe?
Because machine shops suck unless it's a Chevy 350. Looks like you found that out already.
I wouldn't use anything that doesn't use a stock Ford piston and ring.
