gtorep

iTrader: (18)

This motor was recently assembled and installed- Its a forged 347, eagle 6.125 rods, Diamond Flatops, Steel Rings, Etc.. Motor has roughly 2200 miles on it.

Pulled the heads recently to have them freshened up due to what I thought was valve guide wear and found that a couple of cylinder walls were already showing wear. Especially #7.... Whats this look like? The motor passed a leakdown test but what would cause this kind of wear so quickly?

Pics attached-

bww3588

iTrader: (49)

looks like my cylinder walls.

1000 miles, stock crank and rods, mahle forged pistons...all new bearings...

analysis on tear down, all bearings complety trashed, except the cam bearings, and cylinder walls scored and mahred just like yours...

cluprit...unbalanced rotating assembly.

im assuming your rotating assembly was balanced?

also, something else that would cause that is the bores not sized to the piston properly. just because the piston calls for a 3.903 bore doesnt mean that is what your finished bores should be. each piston should be mic'd and the bore honed to fit with piston manufacturer piston to wall clearance spec.

gtorep

iTrader: (18)

Rotating assembly was balanced, all the bores are showing some sort of wear, #7 was the only one that was bad enough to show on film.

Other Crazy thing, the pistons have a small amount of lattitude movement, they are not rocking up and down, but you can move them side to side about .010 to .015

bww3588

iTrader: (49)

sounds to me like your bores were not finished to the correct size.

gtorep

iTrader: (18)

Thats a disturbing thought... Looks like its coming back out.

bww3588

iTrader: (49)

Define lateral movement. Side to side or top to bottom? The piston should have a little side to side movement. Like maybe a few thousandths.
The pistons are cam ground. Meaning they are eccentric shaped untill they warm up. Usually this is factored into the manufacturers piston to wall spec. which from the wear on the cylinder where the skirt rides makes me think someone tried to tighten things up and error on the short side of the spec, or just didn't go "years of experience" which in my experience...happens way to often with some people.

O2Form

Wow someone doesn't know how to fit pistons! That is classic! bet they doubled the clearance. Take a feeler gauge and check the clearance at top of the piston. EVEN on the loose side the MAX wood be .006, personally I woooood pull the engine and disassemble it then measure everything properly and start over, If the piston manufacturer called for .005 clearance MAX that means TOTAL clearance is .005. Not >005 all around the piston. That means if the bore needs to be no more than .005 larger that the piston. I'm not sure why "MACHINE SHOPS" don't understand this. Try measuring it and see if you find they clearanced it @.010, double the recommended clearance because they were thinking >005 clearance all the way around the piston, when its gotta be less than .0025 or less all the way around or its gonna be noisy and use oil.


Good Luck I hope you get some satisfaction on this, I've seen it so many times in the past its just stupid.

And that hone job is TERRIBLE! Must use ALOT of oil. DId n't you see the cylinders before you put the heads on? Are you sure a REAL machine did this work?

The cylinders look like they were honed with sand paper, Your cylinder walls should not look like that!

bww3588

iTrader: (49)

You know...your problem isint machining...its the green coolant you ran in it. If you had dexcool in it thoes cylinder walls would look perfect.


Sorry I had to

Atleast we agree on something. Lol

gtorep

iTrader: (18)

Not coolant at all, GM Top end Cleaner....

gtorep

iTrader: (18)

A solid Machine shop did the work, and the engine was picked up fully assembled but I did see everything stripped down. Looked like every other engine I have ever had built. I saw no problem with the honing or the finished product. But then again, Im no machinist....

O2Form

well Good Luck, with machine work like that who needs enemies? Any shop ever tried giving me something like this woooood be buying dentures for the shop!

That finish looks like something out of 60's cast iron SBC someone rebuilt at home! The reason you use a QUALITY machine shop is you can make a mess like this at home! why pay for it??????

I wanna tell you something I found a long time ago, good machine shops DON"T install heads...... They do machine work... they don't make excuses AND they are backed up with lots and lots of work for weeks......If I call a machine shop and they don't have a three week wait I know they are not getting my business.

A.R. Shale Targa

iTrader: (2)

Couple of things to point out here....First that bore finish(crosshatch) does
look a little too coarse. Most reputable shops bore to within 6 or 7 thousanths
then finish hone in at least 2 or 3 steps progressively finer, and finishing with
a hand flapper to create a plateau finish( this helps seat the rings and retain
oil for lubricity) I've had great results using Total Seal's Quik Seat powder
in the bores and you can actually see the rings seat during assembly. Also
turquing the head or using a torque plate when honing does distort(pinch) the
bore in as much as .0015. Some machine shops like to skip this labor process
and just add a SAFE clearance which can make a .005 piston to wall slug
more like 6+. Lastly factory pistons use an offset pin bore to lessen piston
rock @ or near TDC for quieter operation, aftermarket slugs center the pin
which when coupled with additional piston to wall claerance can rock the
piston @ directional change w/high rpms. Detonation also weighs in on this
as the spark plug fires from the exhaust side and since peak power occurs
right at the ragged edge you'll notice the piston skirt marks are different
@ the top vs. the bottom of the bore (meaning 12 oclock and 6 oclock)
I see cylinder walls that look much worse than that on 350 hp streetstock
engines with only 1 season on them (approx. 300 miles)dirt roundy round

O2Form

Noway those rings are going to seal on that cylinder wall, I could do better with my monkey and a football. How much oil was this engine using? Qt every 200 miles? more? Ever check how much blowby pressure you had out the pcv system? I can clearly see the cylinder is out of round and has major defects.

O2Form

You a bad mon!

gtorep

iTrader: (18)

Motor had a Vaccum pump, no PCV. But the puke tank did have a mixture of fuel/ oil in it the first time it was drained.

Oil consumption was about a qt a month

O2Form

You do a proper tear down and carefully measure and write down everything and post it up, I'd like to see where you are at. Why did you think it had valve guide wear?

O2Form

Thats normal but over time with this kind of clearance it can only get worse.

I wooood be upset to see that kind of piston wear after such a short run time.

gtorep

iTrader: (18)

Tremendous Smoke at idle!!! Performed a leakdown test and all was good, figured I had a seal or a guide going out. Pulled the headers and the primaries were caked in spent oil! I pulled the heads dissembled them and found a couple of guides were out of whack, and a couple of locks were starting to pull through the retainers... Valve train nightmare was very close to causing catastrophic failure. The scraped up cylinder walls were just a bonus to the first problem.

Whats crazy is oil was in the primarys of #'s 1,2,6 all of which are showing wear but look alot better than old shady #7.

It started smoking and I quit driving it that day.

O2Form

Smart! start over and do it right, please find a new machine shop.

S10xGN

iTrader: (11)

Apologies for the jack.

I've seen this stuff, but never had any inclination as to how it's used, care to give a short tutorial?