Bugey 948 engine rebuild gone wrong - need help

[ichthos]

Earlier, I wrote about my engine overheating and having low oil pressure. To make a long story short, the engine had to be yanked. The oil pump was fine. When the crank was removed though, the main bearings looked as if they had a hundred thousand miles on them - they had actually worn through so that I could see copper! Note that this car has been driven less than 50 miles. This is the first engine I have rebuild. I thought I was very careful in everything I did. I am pretty demoralized by this, but after a couple weeks I know I need to get going again and just learn from my mistakes. So my question is, what could I have possibly done wrong? Any help is greatly appreciated.
Kevin

 

[Trevor Jessie]

Wrong size bearings? Blocked oil feed?

Can a 948 main bearing be installed backward? Blocking the oil feed?

 

[Gerard]

So my question is, what could I have possibly done wrong? Any help is greatly appreciated.
Kevin

You haven't provided enough information to know other than to guess. Trevor hit on a couple possibilities, but I'd like to know if...

• you had the crank resized or just polished... or did you install new bearings without doing either?
• If resized, did the shop have the right journal specs?
• Were both the rod and main bearings destroyed?
• Did you have the block tanked and oil passages rodded out?
• Did you Plasti-guage the journals before final assembly to check tolernaces?
• New or used oil pump? How did you determine it was OK?

 

[DrEntropy]

I'm with Gerard.

A good set of micrometers are a must-have, PlastiGauge is CHEAP insurance... and never take the machine shop's work for granted. Measure, measure and measure everything.

If all that was done, it would seem it to have been oil starved, possibly crud in a galley, pump tolerances too wide or bearing inserts misaligned.

Pics and more info would help narrow the culprit(s).

 

[BugeyeNJ58]

Kevin,
It's always disheartening when something doesn't turn out as we planned with our cars, I know I've made my share of mistakes. (And there's so many more possibilities).

Congrats on your attitude of moving on and learning from the issues. I know I'm not the only one who will learn something when we hear what the possible cause(s) of this problem were.

When you first ran the engine, did it have good oil pressure at startup? Did the engine start to overheat the first time you ran it?

 

[ichthos]

I know it would be helpful to show pics, but I will not be home for a few days as I am on vacation. As far as measuring everything, I had nothing to measure with at the time. I figured I could trust the machine shop to do that - I will take your advice for round 2 and measure everything myself. I have no way of telling a good from bad micrometer. Can you suggest one and tell me what they would cost? What is a PlastiGauge, where do you get it, and how does it work?

A little more background information. I took the critical pieces to a machine shop to have them checked out. I don't remember if they polished or ground the crank, but I had them measure and order the main and rod bearings for me when they were done. I also had them boil out and check the block itself - I don't remember if I had it rodded out. I didn't look at the rod bearings yet. What baffled me before everything came out was that the compression in the cylinders was 170 for all four cylinders, even with the bad oil pressure. I figured maybe it was a bad oil pump (I did put in a new oil pump). I replaced the timing chain and sprocket. I had the head surfaced. The machine shop said my cam shaft was good too. Because this restoration took so long, I forgot what I did in many cases (even though I kept most receipts). Could the crank bolt not being torqued enough cause this? I did not have another Bug at the time to look at, but it seems like the oil pan was way to close to the oil pick up - I am wondering if it was pushed in, interfering with oil flow? I have a second engine I can compare it to when I get home. It was strange that the oil pressure was about 55 when I started it up and then went progressively down as I made a trip across town. Maybe it would be easier to ask if one of you were to rebuild an engine right, what is a list of things you would do? Remember I am a novice. Thanks,
Kevin

 

[DrEntropy]

S'all okay, Kev. We'll go thru this a bit at a time.

Right now, ENJOY your vacation!!!

 

[DrEntropy]

Micrometers ~here~ Cheap doesn't equate with good... I have Pratt & Whitney and Starrett mic's, but I don't think you'll find those easily anymore. The most important thing is to be certain they are correctly calibrated to a "standard".

This is a good Plastigauge explanation.

 

[smaceng]

Sorry to hear of your troubles Kevin,
The compression of 170 for all the cylinders is the good news, in that the rings and head are working fine. Generally speaking, a lack of oil to the crankshaft will turn things badly very quickly. If the rod bearings are bad too, then a good chance there was a lack of oil to the crank. Normally, the bearings will also show evidence of too much heat, i.e., a blue color. If you are still on good terms with the machine shop, I would give him a call and let him know of your problem. Hear what he has to say, and most likely he will want you to bring in the engine. Based on your experience with rebuilding an engine, I would say to take it to him. Let us know what he says. Check the rods first.
Did you put the main bearings in with the holes upward? Or did the shop do that? Did the engine turn over OK prior to putting it in the engine? Which workshop manual did you use?
Scott in CA

 

[nomad]

Well, the first engine I rebuilt went about the same distance!! I've rebuilt several since and had good luck.
I agree with the above advice but wanted to add that if you are using a used cam it should be the one from the engine originally and the same lifter's should go back on the same lobes they came off of. If not I would consider a new cam and lifters. Thats been my experience with other than BMC engines so that may not hold true but I've been overly cautious since my first one. Also, did you make sure you had oil pressure before you started the engine. Bearings should be lubed with assembly lube when installed and engine should be turned over with the plugs out till you are sure you have pressure before starting. New A series engine's and those that have sat for a long time often need the pump primed as well. Make sure your crank is ready to go and your oil passages are clean and unobstucted, use plastigage to check clearances and have at it again! (Machine shop for the crank and the block first!)

Good luck!
Kurt.

 

[ichthos]

That is good advice to take it back to the machine shop, but I had the work done 20 years ago in another state. I started out just wanting to rebuild the engine, and eventually decided to do a total restoration. I actually rebuilt the engine 15 years ago, but I kept it in the house. The engine turned over easily, and started right up last summer. I will take a look and double check that I put in the main bearings correctly. I will also check the rod bearings. I won't get a chance to do this until Tuesday when I get home. I can't remember what manual I used. Thanks for all the help so far everyone.
Kevin

 

[JPSmit]

Without restating what has all been said Kevin, you've caught it and you've caught it early. In the general scheme of things it is an easy and not very expensive fix - you'll be driving again soon.

 

[jlaird]

1. Do not pull pistons, your compresssion is great.

2. Take crank to machine shop have bearings sized or polished and order new bearings for same.

3. Reasemble, check oil pressure.

4. Run it like you stole it.

I know you are really concerned at the moment, but no big deal. A few bearings and a bit of machine work and you are golden, $100 maybe.