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.

Sorry you found an assembly issue, but thanks for sharing the details and pictures. It's a shame you have to go to the expense of prepping another block vs cleaning up the two cylinders and reworking the guides.

Thanks Roger. Yeah, a couple of machinists have said they could just rebore everything to 60 over and save this block, but we just want to start with a totally clean slate this time and put this one behind us. He will push the old engine into a corner and save it in case he needs it some day.

The other issue is that we have lost a little confidence in the machine shop that did the engine machining originally. I have used this guy for over 25 years and the talk around town is, if he personally does the work it is fine, but if his guys do it you don't get as good of a job. The galley plugs (2) that blew out of my 331 also came from that shop, and we used him to do machining for the marina I worked at. Twice we had valve jobs fail within 15 minutes running time when the ground valves mushroomed. He never takes responsibility for anything, always blaming it on "spikes in oil pressure" or other factors.

Now that I am learning more about machining, it occurs to me that he has never asked for any pistons when he bores out an engine. The new machinist insists on having them there to bore each cylinder specifically to fit that piston. Pan, Jerry, and the other guys on here seem to agree that is the only way you can do it properly.

So maybe it is wise not to trust the rest of the machining he did on the old block either. Plus, this will give us a chance to change a few parts and make this engine a little stronger than the last one.

Don

nows the time to think about getting that stock rocker arm set up off... its a pos and going studs .that too bad about the oil rings hasting is abit better to work PC are crap with the hastings they do not over lap as EZ .the new engines have gone to a thinner oil ring and are very easy to over lap or bend .i just did a mark 6 bbc were the guy bent the oil ring when he put it together it happens

This is just a thought. When I bought my KB pistons, one was smaller that the rest. So they had to make another one to fit the specs. It pays to measure.

There is no question we are going to take your advice on the Hastings rings, Pat. I looked at the ones we have on there last night and the way they butt up is not that impressive. What do you think about the .018 end gap on the top rings? The gaps on the oil rings looked wider, is that normal?

I also saw that on piston # 3 we inadvertantly put the two ring gaps in line on the 2 thin oil rings. Don't know how that happened as I always stagger the gaps, but it must have been late at night.

Don

Just some things I wanted to share here.

Don-you might want to take a hard look at the ring compressor your using.It doesn't take much,but a slight nick on the edge would cause you a problem going in.

As your putting in the pistons the walls are oiled up.Your turning the engine over by hand to put in the next piston.I suggest you watch the oil pattern on the wall of the last piston you put in.If you see anything weird like a line in that oiled cylinder,you stop and take out it back out to check it out.Not fool proof,but it might help catch problems.

That is a good point about watching the oil pattern, I'll do that. My ring compressor is a SnapOn that I have had for years. It has something like 4 different collars that fit different sizes of pistons,and a clicking plier setup that squeezes the collor tight around the piston. I will take a look at the collar to make sure it hasn't gotten nicked or otherwise damaged.

Don

Glad you guys found the problem. Knowing what went wrong makes it a lot more reassuring rebuilding it this time. I had a 289 in high school, that the parts shop sent a 302 crank for. When we rebuilt it in the shop, nobody caught the difference(myself, my shop teacher, and my friend who helped rebuild the engine)We all were frustrated at the noise it made running, but could never figure out what was going on. I must have taken it apart and reassembled three or four times. I finally talked to the local Ford dealership, who had me bring all the parts down. The measured the crank and figured out that was the mistake, but by then it was over a year later and the parts company had gone out of business. I was graduating from high school, and didn't have time or money to fix it! It still kills me 30 years later! I loved the 68 mustang until the engine failed repeatedly, I just gave up on it. Glad you guys found the problem and have the resources to fix it up!

Yes, we were relieved to see those oil rings like that, Steve. Up to that point we hadn't really seen anything that looked like it was out of place or broken. The other thing is that the engine is FULL of ground up carbon pieces, I mean the oil is gritty. It looks like all that oil getting into the combustion chambers was forming carbon that was breaking off of the valves and being ground up by the pistons into chunks. The oil was also turning black after only a little while of driving.

I think if we install the rings correctly this time and have a good valve job (including guides) done on the new heads, we will be ok.

Don

same tool i use every week to put pistons in many years ago i ran a flap wheel in side my bands then wet sanded them with Wd40 to get the hi spots off the in side of the band .were they stamp the band size on the outside it was pulling steel down on the inside . after boring i break the edge with the boring cutter or a drum sander made for the job or by hand which way i do it has alot to do with how big the bore is to size of the fire ring is on the head gasket i use on the job. breaking the edge helps get the pistons down the hole and make sure there is no sharp edge at the bottom of the bore is this cut the piston skrits up so i sand the bottom edge of the bores as well after a bore and hone . .018 is the lest to use 016 is the lest for 2 ring .oil rails end gap can be very big 040+ as for getting one piston small out of a set i seen more then one its not hard to see 4 out of 8 that are under 001 that why i never bore and hone a block till pistons are in hand . i allways number the pistons for bores and bore the block to each pistons real size i hold less then .0002.5 and i allways check and fit the ring gap

You know, Pat, I will have to look at my ring compressor because I know that size stamp you are talking about. I will also wet sand mine, I have used them for so many years they might have gotten nicked or scratched. They nestle together inside the box, so maybe the one inside scratches the one placed on the outside of it.

Tonight I removed all the rings from the pistons and cleaned them up with a scotchbrite and some solvent. They all look good, but there is some scuffing on that black stuff they put on the skirts. Is that normal ?

I also want the machinist to look at the connecting rods and crank. The bearings seem to generally look good, but some have a little more wear on the outsides of the bearing, and some look like there is only wear on part of the circle, as if the crank journal is not contacting the entire circumferance of the bearing. Maybe the rod ends need honed to true them ?

The one piston, number 3 where the expander tip broke off, shows some scratches on the area above the top ring, that smooth area right at the top. It is only on about 1/2 of the piston top, and I think it was caused by the fragment of the expander or carbon getting lodged in there and scratching the piston. Should that cause any harm ?

Don

you have to make sure there is no steel stuck in the piston skrits shinny black specks is steel/iron. top part of rods bearing is load side so this can show wear .more then lower .i check rod lineament if rods are bent a small amount they can show off side wear marks in the bearing or a real bad rod recon the 12:00 and 6:00 are the small size of the rod bearing has you get to 9:00 and 3:00 the bearings get thinner so if the bearing show wear this hi you need to check whats out of size