honing the cylinder

[itstippy]

There's a terrific thread out there already called "honing the cylinder". Great stuff.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=028330#000000 <br /><br />I understand that glazed cylinders will cause lost performance due to lack of oil seal between the cylinder surface and the rings. I can live with a loss in horsepower. Will glazed cylinders hurt the longevity of the motor? <br /><br />I've got a 1961 Johnson 18HP FD15 mostly disassembled. I have NOT opened the case and I'd like to be told that it's not necessary. The cylinders DO need to be honed - they are glazed like pottery. If I do not hone the cylinders will the motor quickly wear out due to friction, or will I simply have lost performance but no further harm done?

 

[lark2004]

Re: honing the cylinder

no, you won't lose performance. If you only break the glaze and don't change your bore size (by honeing to much) you will just need to put new rings in. The whole reason for honing is to give the new rings a fresh bore to seat into. You should actually pick up some performance, and if you do it right, no, you won't wear out your motor more quickly. <br /><br />Good luck with it.

 

[rodbolt]

Re: honing the cylinder

but the pistons do have to be out and take care with the hone. only break the glaze dont try toremove scratches. by scratch rub a copper penny over it. if the copper sticks in the scratch its to deep. and remove all covers for cleaning. if you think a hone removes stock you should see what the abrasive does to pistons. after honing take the block to a machine shoptohave the bore measured. the measurement method and specs are in the service manual. itwill run ok with new rings and slightly out of spec as long as there are no major vertical scratches(see penny trick above) and the rings are still square. the most important thing is cleaning after honeing. seethe post on piston failure in this post.

 

[OBJ]

Re: honing the cylinder

I'd like to add a little to rodbolts post....I don't think it can be stressed enough how important cleaning the block is....something not much talked about here on the forums.<br /><br />Getting the gasket surfaces clean and removing all the residue from boring/honing can't be stressed enough.<br /><br />After boring/honing, get a tub full of hot water and liquid detergent and scrub the crap outta' it. Blow it out with a hose and dry throughly. After it dries, get some oil into the holes....there rustable and will rust real quick if they aren't lubed right away.

 

[itstippy]

Re: honing the cylinder

Can I get away with NOT honing, or will I be killing the motor by running it with glazed cylinder walls? I'd like to not open the case. I had exactly 95#'s compression per cylinder when I tested the motor before starting this project. The pistons are slightly scored. Cylinder walls are not scored but heavily glazed.<br />I will have everything very very clean before reassembly. I'm a clean fanatic - I clean worn out parts before throwing them away just to get a really good look at them. The surface on the block where the head gasket goes looks imperfect - it's not a mirror finish like I'd expect to see. It's almost like it was cast or machined imperfectly; kinda rough. I'll post a picture if I can get the lighting right. I've Scotchbrited all the gasket residue off.<br />I'm afraid of messing things up by cracking open that case - I'm not a machinist and if I can leave well enough alone and run it with glazed cylinder walls I'll put up with loss of horsepower. As long as I'm not killing the motor.

 

[Tinkerer]

Re: honing the cylinder

itstippy<br /><br />If you hone it the cylinders are still going to glaze again. It's unavoidable in any motor. If the compression is within specs and if you were happy with the way it was running, why bother? <br /><br />If you do de-glaze it I'd second OBJ's opinion about the importance of cleaning.<br /><br />The other thing that is critical and not emphasised enough is to clean the ring grooves on the piston properly. Don't fall for the old trick of cleaning them with a broken ring. Get a groove cleaner and do it right. If the rings don't seat right you can end up with a lot worse problems than normal glaze.

 

[itstippy]

Re: honing the cylinder

I'm hoping that a thorough decarb with Seafoam will help clear deposits in the ring grooves, once I get this back together.<br />I'm not happy with the way it was running - it was a basket case when I got it and I've never seen it run. I bought it for parts for my FD21 and, of course, decided to fix it up rather than junk it. 95#'s compression top and bottom, plus reading the iBoats forum inspired to give it a try ("fix 'em don't junk 'em"). <br />It's been run hot. The guy I bought it from said he got it with a blown head gasket, which he replaced, but he never got it running. He bragged that he was good at fixing things and never uses a manual, so you know the type. Amateur job replacing the head gasket. Thermostat was almost unrecognizable, must be original. Exhaust chamber so caked with carbon it looked like someone packed a bag of Kingsford in there. Rubber mounts broke. Two lower units in a box, which I will turn into one decent one (need a short shaft driveshaft though). Everything utterly filthy. I could go on and on. I've been pulling this old girl apart in my "spare time" and cleaning everything with a toothbrush and Mean Green as I go. Just having a blast with my manuals and wrenches, asking for advice as needed. But I'm afraid to open the case as I might be in over my head there.<br />I'm going to try to post a picture of the block where the head goes. It's rough. Will a new head gasket work, I hope? Experienced eyes will tell me what I need to know.

 

[itstippy]

Re: honing the cylinder

Here's the pic. Wish I could find a free hosting site that would let me store more than one at a time. Click on thumbnail pic and wait to load - it's slow. What do you guys make of this? Finish cleaning it and put on a new gasket torqued to specs, or am I doomed? Thank you all!<br />

 

[Tinkerer]

Re: honing the cylinder

itstippy<br /><br />In light of your last post I'll change my opinion.<br /><br />For all the work you're doing, and given the poor condition of the motor, it'd be best to open the case and hone it. And fix anything else that needs attention in there. <br /><br />It's not that hard. Just bolting and unbolting. You can get a machine shop to hone it. Or maybe bore it. If you can't measure the bores yourself pull it apart and take the block to a machine shop and get it measured to see if you need standard or oversize rings. Then see if you can find the rings you need.<br /><br />You need to be sure you can get or make a gasket set or it ain't gonna work.