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1500 rebuild - some questions

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tosoutherncars

tosoutherncars

Jedi Knight
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Hi all,

Got the top half back together today. Valve guides good, valve stem seals, valves adjusted, head skimmed, new head gasket and assorted seals.

Fired right up... somehow seems more rev-happy, does that make any sense given the raised compression? (approx. 9:1)

Anyhoo, a couple of questions... On start-up, it billowed a cloud of light blue-gray smoke, which increases on accelleration / revving. Since I know it's not valve guides, I assumed it had to be rings. Got out the compression tester... again.

150 / 150 / 150 / 130

So I think at this point I can safely say I need to do the rings? (I can't think of any 'easy' reasons for the smoke, or loss of compression in #4)

If the rings on #4 are gone, would this have caused the blown head gasket btwn 3 & 4?

The rings are doable with the engine in the car? from underneath? But I need to pull the head again, to get the pistons out? (I know it's easier with the engine out, but I really, really don't want to do that. I already have a 'project' car, this one is supposed to be the driver!

And finally, on an unrelated (?) matter... Every time I pull the plugs, #2,3 and 4 look fine, #1 is black, and twice now the porcelain has shattered. After only 3 minutes on brand new plugs, here's what I found (in order, 1 2 3 4, L to R)

headrebuild017.jpg


What the heck is going on here? How can I be way rich in only one cylinder? Perhaps it's oil? Ways of telling?

TIA for any suggestions...
 
Looks like 2, 3, 4 are too lean and 1 is blowing oil.
 
Like I say, that's only after about 3 minutes on new plugs Jack, don't assume the rest are lean... but something is definitely up with #1.
 
Check to be sure you have the intake sealed well and tight. Our 77 midget revved like that and we couldn't get the valves adjusted because we thought we had the intake tightened down. We had converted from a side draft to a downdraft and the new intake wouldn't seat because of the exhaust manifold.
 
To be sure, you should really do a leak down test. It will let you know exactly where that missing 20 lbs. of compression is going.

Also, if you don't feel like doing rings right away, there is a product called Restore that many people I trust swear by.
 
Yes, Morris is right. Do leak down to see if it is really valves, rings or whatever. You can buy a low cost tester from Harbor Freight or Northern Tool

And be sure that your PCV system isn't fouled up. Othewise you could be sucking oil into the intake manifold and burning oil that way. If nothing else, leave the hose off the valve cover and vent valve cover to the atmosphere temporarliy. Plug the area where hose goes into the intake manifold.
Try to drive it for at least 5 to 10 miles to get out any residual oil and see if smoking stops.

In a pinch a cold/hot compresssion test can help spot compression problems.
Let the car sit for at least a day or two. Do not start. With cold engine, do compression test and record numbers. Then start engine and warm up fully. Do second compresession test. If you have any big differences from cold to warm, it's usually rings.
 
Hi Nial,

Good point. Yup... the valve cover hose was either open, or routed to the air cleaner.

I'll get the electric fan connected and take a longer drive today, see if the condition persists.

1) Any safe remedies to try to un-stick rings, before I pull the darn thing apart?

2) If I've got blowby on at least one cylinder, am I likely to blow my new headgasket?
 
So! Grabbed a leakdown tester ($79.85... ouch). Using about 50 PSI, I get losses of about 15% on all cylinders except #4, which is closer to 40%. With the valve cover off, escaping air is clearly audible in the pushrod passages, which confirms that it's getting past the rings. Right?

Head's coming back off, pan's coming off, and we'll do the rings (and rod bearings) as discussed previously. I'll pull it all apart today, and take piston #4 out so I can do some examining & measuring.
 
Head back off, oil pan off, piston #4 out... doesn't look too bad, to my eye! Minor roughness on the cylinder wall. Rings all free & able to rotate. I'll take some pictures...
 
Well. I think I was expecting to find the rings seized, or some other similarly obvious fault. No such thing... the walls are stained, but it looks much worse than it is... none of the marking on the cylinder wall is deep enough to catch a fingernail.

There is a slight ridge, on the rear half of the cylinder wall only, about 2/3 of the way down. Visible in some of the pictures. Damage from a failed thrust bearing in a previous life, perhaps?

cylinderandrings004.jpg


Rod bearings were down to the bronze, and will obviously be replaced.

Some skirt wear on the pistons, a little bit of carbon buildup above the rings. My only other observation is that the gaps on all the rings were lined up, although I can't imagine *that* was causing all the compression loss.

Thoughts?

Hone, re-ring and away we go?

I don't have a good dial guage, so I haven't been able to measure the bores. I'm guessing that's my next purchase? Check for round, etc.?

Also, took pic of ring gap. Looks fairly tight to me, what is spec?

OK, links...

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings009.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings007.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings006.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings005.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings003.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings002.jpg

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/cylinderandrings001.jpg
 
Measure, and maybe hone, re-ring and away we go?

Let the experts figure it out along with mic'ing the crank.
 
lining up all the gaps on the rings will hurt your performance sugnificantally. Ive seen just rebuilt engines loose much compression just for that reason alone. Cant tell you if they burned excess oil as that was back in my 2cycle engine rebuilding days. What is that funk all over the cyl wall? Water stains from dissembly? judging by all the carbon so far down the piston I d say your getting some excess blow by for sure.
 
If I was not clear, a full overhaul is in order.
 
blkcorvair said:
lining up all the gaps on the rings will hurt your performance sugnificantally. Ive seen just rebuilt engines loose much compression just for that reason alone. Cant tell you if they burned excess oil as that was back in my 2cycle engine rebuilding days. What is that funk all over the cyl wall? Water stains from dissembly? judging by all the carbon so far down the piston I d say your getting some excess blow by for sure.
Click to expand...

The funk is actually discoloration of the cylinder wall... perhaps over-rich mixture washing out the oil and causing the rings to scratch it, or traces of coolant from the head gasket being blown? I suppose it might even be from the time one of the exhaust valves broke & danced around in the engine for a while, although it doesn't look like impact marks to me.

I'll pick up a 3-stone hone tomorrow, and a bore gauge. Anyone have the specs for max bore size for a re-ring?

And... I can hone it with the crank in? How do I stop the metal shavings from contaminating the crankcase?

(Why do I get the feeling I'm about to pull the engine?)
 
Yank it out. Bore and crank machining should be done by a machinist. Very difficult to be accurate with a stone and a hand drill. NO way to be accurate with the crank without the proper lathe & tools.

The mark around the circumference of the bore down low is usually from condensate rusting it as it sat unstarted for some time in its life.
 
Yes, yes and yes. do as Doc suggests and you will be good to go for many years.

This is the heart of your LBC, make sure it is strong and happy.
 
My $00.02: If you don't want to rebuild the motor, don't hone it. If you want a short-term solution: clean and oil the old rings, clean and oil the bore, keep your crankcase well vented and drive it until it dies.

Speaking from personal experience, a halfway overhaul is a great way to blow some time and money before you do the real thing.

Driving it until it dies isn't really gonna cost you anymore than overhauling it now.

I think getting the rings unaligned and moving will fix your problem, but if it doesn't, in the grand scheme of things 130 psi on one cylinder isn't really that bad... but if you can't live with it rebuild the motor right.
 
Good point, Morris...

An additional wrinkle... since I've had the head milled, if I go oversize, I'll have to use low-comp pistons. Of course, they're like hen's teeth, since most rebuilds would switch to flat-tops.

I'll grab a bore gauge tonight, and mic it. If the bores are within spec, I'll just clean, slap in new rings (if they're available locally) and drive it until it dies. If they're too far over or oval, it'll be major overhaul time.

Anyone know the bore spec +/- for the later 1500s?

Doc, Jack... when I get to the point of a rebuild, I'll certainly follow that advice. But I'd rather buy a used engine (pennies) and rebuild it in the garage, while I drive... particularly if I'm not going to be able to keep my existing head, when I overbore!
 
yep, a second engine is priceless.
 
That is one good point about the 1500's. Second hand engines are plentiful.
 
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