Well upon removal of the heads last night I found some galling in a cylinder. It seems to be about .0010 to .0015 deep and im sure theirs a little more on sum of the other cylinders but I think this is the only really bad one. I could use some second opinions on this one. What I wanna do is carefully hone it out and get some over sized rings. Normally I would take it to a machine shop but im breaking the bank as it is and theirs more than one way to skin a cat. lol I may go .0020 over and just get the over sized rings. Other than using up some stones does any one see any other problems? Ive done this before on aircraft recips but their a little lower compression and a lot looser tolerances.

 

oops too many 0s .010 and .015 and i wanna oversize .020

 

 

If I am reading this correctly you want to hone (Bore) the cylinders .020 oversize and get oversize rings but use the stock size pistons? If that is what you want then my answer is you cannot do that and expect it to work. The cylinder wall clearance would be too high and the pistons would rock too much in the bore.

 

X2 He would have one noisy engine when it was done, Cylinder sizing sould be done with a torque plate then you know the exact piston to cylinder wall clearance is once the heads are bolted on!!!!!!!!!!!

 

I dont know, if its only out .010 and I can just use a .010 oversize ring I dont think the piston rock would be that much if any really. Plus the expansion of the piston when the car heats up is gonna take out some of that .010 anyways not by too much mind you, but never the less help close up some of that cylinder to wall gap. but I can see what you guys are saying if its much more than .010 I may have to bite the bullet and get new pistons and take the block in and have it bored.

 

I can tell you I seen a guy put .030 over pistons in .040 over bore it wasn't long before he took it apart cause it was makeing alot of noise!!

 

You have an engine with many miles on it, correct? If so you already have considerable wear in the cylinder. Furthermore, it isn't linear wear. It's greatest at the top and diminishes toward the bottom. (ice cream cone)

The effect this has on your piston rings is that they are constantly opening and closing. The higher the rpm, the poorer the ring seal will be.

If boring is out of the question, do as little as possible.

 

If it's an 85, just go buy a good used short block out of craigslist for $150 that looks good, and put in another set of rings and bearings, and call it good.
The 85 is a plain vanilla 350 with 2 bolt mains, but has forged pistons. in 86, they determined the forged pistons weren't necessary, and put cast ones in from then on.
just use your cam with a new set of lifters and a new timing chain, and plenty of cam lube.
Take everything else off your original engine and use that stuff over.

 

Better yet, just bolt the used block in and run it. It'll last longer than what you are planning with yours and will be less work.

 

x2!!!!!!!!!!!!!!!!!!!

 

x3!

 

I wouldn't want to fly in a plane that has mis-matched pistons/rings/bore.

 

You might want to find out what caused the galling before you reuse your old heads. On my 85 I found galling on one cylinder caused by a head gasket leak allowing coolant into the cylinder. You could barely see the "rut" from the coolant passage to the chamber in the head. Your original heads are probably 624 heads which have a reputation for cracking.
If you hone a couple of the cylinders on the original block .02 or .03 bigger with the original pistons please post an audio clip of the engine running on this forum.

 

Well heres the deal im stuck between a rock and a hard place, im outa cash so basicaly im just trying to get this thing running now. 427c4 I think your right. it did have the leaking head gasket and thats probly what caused the gauling yes and as for heads im using a set of 186s with 1.5 rr, so no worries thier. No, im not goin to run over sized rings with std pistons after all the heads up. A 350 chevy is higher comp. than a 320 lycombing out of a cessna and its air cooled, typicaly its within spec to run up to .015 over on the ring size of an 320 but the piston is about 1/3 larger in D than a 350sbc also, and like I said befor a lot looser tol.
So now the only options I have...and on second look with out using boar gauge (cuz thier locked in my box at school and its spring break)...the spot seems to me to be about .002-.005 deep.

So due to being a poor student I can either

A. leave the bottom end alone and put the new heads on an drive it untill I can afford a crate motor end of summer or...

B. I have new std rings and rod bearings I could put in and just try to clean the cylinders up and conture the galling into the cylinder a little bit.

So now that I feel dumb for asking about the .010-.020 oversize rings.(forgive me I come from a land of air cooled engines) lol

Whats your opinnions on options im left with. Though not ideal.. I know but you play the cards your delt and ill make it up to the poor car end of summer.

 

HEy, this is a corvette, not some old beater ford......treat this car to some intelligence.

Leave the pistons in the cylinders as is. The pistons are supported by approx. 70% - 80% of the cylinder wall the way they are now. If you screw with it, you will only mess it up, the new rings won't seal, and you will be putting in 2 quarts every week, and plugging up your catalytic converter...
your oil pressure should be something like 30-50 psi hot at idle. if so, leave the bearings alone as well, they are fine.......
The oil consumption is probably the one cylinder and valve seals . Change those valve seals, and reassemble it and continue time. It will just use less oil after that.

Also, on an 0320 lycoming engine, there is an overhaul manual that gives you the spec's to which you can refurbish the engine to. The airframe also has a maintenance manual with an engine section as described in ATA code chapter 72.
I am sure that cylinder galling is outlined as a cylinder replacement candidate condition.
But you know that's just the beginning of a top overhaul.
Fits and clearances you mentioned are for air cooled cylinders with airflow over them. not water cooled engines without a propeller.
If you were to rebuild the engine in your car, obtain an overhaul book such as you would for that aircraft engine.....which I personally wouldn't screw with oversize rings in a std. bore for liability and comon sense reasons......ring end gap clearance , and worn out cylinders just to start.
Come on, your an aircraft mechanic, not a tractor mechanic. People's lives are in your hands.
Live up to the standard!!!
The book store has probably 20 of them you can either peruse with a pen and paper, or purchase. The chilton's down at the autozone has the same info as well as the other "how to hot rod small block chevrolet engines" books...Lingenfelter had a good one as well.
Student, do your homework!!!!

 

Haha, yes I do have a chilton and no thier nothing like modern aircraft mantinace manuals with thier ata codes unfortunatly. And yes in a cessna I would most definatly change a cylinder if had signs of gauling. 1. Its the customers cash and if it isnt within tolorances its grounded. 2. Your right lives are on the line and you would be an idot to sing off a plane thats otherwise unairworthy. I was trying to get across that the std piston can infact use up to .015 over size ring if need be due to normal wear. but yet again thier air cooled and subjected to more expansion and contration. Where as your liquid cooled engine's not so much....but come on now be honest did you google that ata code? lol

O and by the way it wasnt me who treated the car like ****. Ive only had the car for a month and its been in the garage for three weeks now. Im just a broke *** trying to put a lil life back into a dieing car any way I can with the funds I have for now. If I would have owned it since new the poor thing would have never ended up in this shape.

 

Sounds like your tring to bandaid your problem and in the end your not going to be happy and will have to do it over again to get it right. I am sure if this engine has a lot of miles on it the ring lands will show alot of wear.

If that block needs to be bored then do it and also I am a big advocate of plate honing I have leaked down some new engine builds and have found up to 40% leak down because the block was not machined correctly and the owners were not very happy because of dirty oil in less then 100miles.

If your going to change pistons and if the new ones are not the same weight it will need to be balanced the crank may need to be turned, Rods should be resized or at least be checked for sizing.

A good rebuild is not cheap and a cheap rebuild may bite you back.

Agains this is not a tractor!!!!!!!!

 

If the piston skirts aren't totally used up and the piston clearance is still within reasonable spec, you'd be better off just rough honing the cylinder and throwing on a fresh set of rings. Then again, you didn't post pics, but a couple of vertical scratches won't stop it from running, but if it is a mess and that cylinder is missing, you can't do anything with it short of over-boring to a new set of pistons and rings.

I've done some band-aid overhauls before- it was successful about 1/2 the time.

 

Here is a quote from another site.