Rebuildable Block?
 

Just tore down my old 951 engine and found scoring on the wall of cylinder 3 (and smaller similar marks in cylinder 2). The long mark is deep enough so you can just catch your fingernail. Can I hone those marks out and use the block without sleeving?

And what is the likely cause?

http://www.mikepellegrini.com/Graphi..._1921small.jpg

The engine has about 185K miles. It was running great when I took it out of the car. The only problems were valve guides and the bottom end felt kinda "loose" - like it needed rod bearings (which at 185K is probably a safe guess).

Compression was good -

1. 120 PSI
2. 140 PSI
3. 140 PSI
4. 125 PSI

And the leakdown test was decent:

1. 5% loss - intake leak
2. 20% loss - rings and intake (both) leaks
3. 11% loss - both rings and intake leaks
4. 11% loss - rings leak

Whadaya guys think?

I'd like to use this for my son's car.

I would go ahead and hone it out. Most of the very light marks will probably disappear. The larger mark (The gouge/scratch that catches a fingernail) may very well not be worked out, but may not be noticeable under city running conditions. Not being there and accurately gauging the gouge/scratch it's hard to say if the motor will be a perfect runner or not. Under high boost it may be that if the scratch does not hone out, or not hone out enough so that it causes blow-by, so therefore it may never be a perfectly smooth running engine.

Rebuild this one or find a good used block and work on it.

Cause: Almost to many to name them all - Cracked ring, debris introduced through air intake, broken or bad spark plug, hard carbon deposits breaking loose, etc.

Side Note: When a bug hits your windshield at speed, do you know what is the last thing that goes through it's mind ??



It's butt


Have pfun, Ed.

Thanks. Would you put new rings on?

If the bottom-end felt "a little loose" when you checked it earlier, then I would do a complete tear down to investigate the crankshaft and rod bearings. IMHO

Personally, I would not put in new rings until I could make a determination as to why the scoring on the cylinder wall appeared in the first place. If this engine has 185K miles on it, and, has not had a lower-end job there is a possibility of having something fail.

Good luck, and...btw, this is just my opinion. I am no expert, just a little concerned for you right now.SmileWavy

Thanks.

My son figures to use it in his car. His head is in really good shape, but the block appears to be toasted.

It's gonna be a somewhat critical application so we gotta get it right. His car is modded all to heck:

Lindsey Racing Stage 2 MAF with a piggyback controller
3 Bar FPR
951Max Chips
75# injectors
Lindsey Racing Super 65 Turbo
Open Tial 38mm dual port wastegate
Innovate LC-1 Wideband O2 sensor and digital AFM gauge
Lindsey Racing Manual Boost Controller
Lindsey Racing 3" cat-less, muffler-less exhaust with a resonator
Koni adjustable struts with adjustable ride height with 425# springs and solid strut mounts
Koni adjustable shocks with 550 # Rear Coil-overs (torsion bar delete)
KEP Stage 2 clutch and pressure plate

If I remember correctly, he runs up to around 18 PSI in boost.

His old engine has a problem with No. 3 cylinder:

http://www.mikepellegrini.com/Graphics/LDTest.jpg

The compression leak in No. 3 caused oil to back up in his turbo (we think) and destroyed the oil seal in the turbo - when he boosts, it produces a James Bond kinda smoke screen. But the plugs are good, there's no oil in the hard pipes, and the car runs really great.

We figured with nearly a 30% leak to the crankcase, his block must be toast, and that it'd be easier and better to use my old one (after re-doing the bearings).

But if it's gonna be marginal, maybe it'd make more sense to keep looking...

We haven't pulled his engine apart yet, so we're not sure what kinda damage there might be...

Well now we know - There is no way a scored block will hold up to all those mods - So go with another good block. Hone the new to you block, rings, bearings and seals, belts and rollers, and a new water pump if not a newish one there already.

if it's a tolerance group 0 or 1, bore it out to remove the scratch :)

Hone (by someone who knows how to hone these blocks) and go with aftermarket pistons, or find another starting point. From my experience you can get an entire engine for about $500.
Honeing will run you $400-500 and another $750 for pistons/rings. If you are trying to make big power I would go the hone route.

Could it just be the rings on #3 on his engine causing blow by?

Your getting good sealing with the 2 caps of oil.

Not sure if that would or wouldn't occur if you had some block issue.

Either way it looks like you're going to pull that engine out and look at it --
see if there is something obvious with the rings or cylinder wall there.

M

No, my son's car doesn't smoke except when he boosts - and then, it really is intense. The plug looked in good shape - no big carbon deposits. The boost hard pipes and the intercooler are relatively oil free.

But he goes through a tremendous amount of oil - maybe a quart a day!

It's gotta be the oil seal in the turbo.

I found this really great thread on honing by HondaDusteR: http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/487924-project-924-s-engine-replacement.html

He reused his old pistons. I think this may be more in my ballpark.

We have yet to tear down my son's engine. It could be he just has a broken ring or something and that his block would be easier to use than mine.

It sounds like your son's Turbocharger is cooked (Internal seals burnt out and coked) rather than the piston rings - possible - Son's motor may be an easy rebuild.