Thread: Mystery solved !!!!!!!!

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I've been dying to tear into Dan's 455 Olds to find out what caused the scoring on cylinder # 3 and why # 1 and # 3 were oil fouling the plugs so quickly and so badly. Last week we pulled his body off and today we got the engine and transmission out.

We felt we were going to find a broken ring or two, but the two compression rings on each cylinder were fine. We checked the end gap on several compression rings and they all were right at .018, which, from everything I have read, is well within specs. Looking further, I noticed the expander on cylinder # 3 looked odd. What has happened is that the end of one of the tabs has broken off, allowing the expander to compress and not exert any pressure on the oil rings. That also explains what scored the cylinder wall.........that piece stuck under the piston and acted like a scraper as the piston moved up and down.

The expander in cylinder # 1 also was not right. It was not broken, but the ends had overlapped, also not putting any tension on the oil rings. I can only blame it on us not properly butting up the ends when we installed the oil rings on the expander.

So, what we had going on was that cylinder # 1 and # 3 had no oil control rings doing their job, so oil was able to get into the combustion chamber. The rest of the cylinders show excessive oiling, and that was probably due to bad guides (I could wobble every valve in it's guide once I removed the springs). The bad oil control rings were also probably allowing some combustion pressure to get into the pan.

The fix seems obvious. We are going to have the new block totally machined, have the pistons cleaned up, and spend a LOT of time making sure each piston has the rings gapped properly and installed properly. We are also going to bump up his torque convertor to a 3000 stall this time to let the engine get into the cam's operating range. This will give us a chance to fine tune some other issues and hopefully have the car back together in time for Turkey Run at Thanksgiving.

We were relieved to find those issues as it explains a lot of what was going on.

Don

Oh, here are some pictures we took tonight. Picture number one is the oil control expander from cylinder # 3, showing where the end broke off.

Picture # 2 is a picture of the expander from cylinder # 1, see where it overlapped.

Picture #3 is the scored cylinder # 3.