Lt1 spun bearing
 

While running at Summit Point raceway with my 94 auto I had an overheating and loss of power issue. I limped it back to the pits with decent oil pressure and when I removed my helmet I heard the sound. Today I confirmed my suspicion that I have a spun rod bearing. I just had the tranny rebuilt in March and now I have to take it out again and remove the engine and rebuild. Does anyone know of a good source for a crank kit? I just want to take it apart and thoroughly clean everything, install a new crank kit and reassemble. I am not interested in upgrading the motor because I will probably sell this car and look for a manual trans Vette. Any advice that your guys can give me to help with this job would be greatly appreciated.

just curious what did it sound like?

Been there!!
 

Whump WHump Whump...

Any parts store should be able to order you a crank kit. They used to be pretty reasonable but I haven't bought one in years. I've got a couple of good, standard LT1 cranks laying around. Let me know if you'd like one and we'll work something out. I wouldn't be looking for much out of one due to shipping costs.

How many miles where on it, and what RPM's were you taking it to?

Sorry to read about the misfortune.

I'd like to ask if you can mention what kind of oil pan
was on the engine.

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Second that. Sorry to hear it, I went thru a rebuild but it was the aftermarket timing gear that caused it, although 1 rod bearing did look a little worn so this would have happened eventually.

Was this a stock motor or heads/cam set-up, and what was the max rpm?

For the rebuild, since you are selling, I would get the used LT1 crank offered here and a bearing kit (rod&mains), clevite 77 standard size (not oversize). Plus of course, all the seals. Not sure if the rods themselves will be ok or not, should inspect.

Stock pan, Stock engine, I always overfilled by a quart of oil. Never lost oil pressure that I know of.

80,000 miles are on the car


Will the motor have to be totally disassembled to clean and flush out residue?

If you were 1 qt over, I'm surprised you spun a bearing...
Although my LT4 now has much more start up knock than it did 3 years ago. over 5000 track miles now. So I may be seeing a spun bearing soon.

:iagree:

I have an odd knock on startup at the very front of the engine. Goes away when warmed up. Maybe 6800rpm shift points for the last 3 years are giving me an indication that it's time for an all forged 396?

Just to clean it, flush it, and put new rod & main bearings in can be done with the engine in the car. If the crank is very mildly scored, it can be polished lightly in the car.

However, if the crank has to come out, then the engine has to come out and I would totally disassemble it at that point.

I just pulled the cap off and the crank does not look very good. I guess I will learn how to pull the motor.

Most likely piston slap ... and from what I hear a common problem. I'd go easy until the engine warms up and quiets down before you give it a normal workout.:smash:

Go start your car and rev it in Neutral.

If you get the knock / rattle sound under DECELERATION it's most likely a rod bearing. You can R&R that with the motor in the car. However, if the crank is scarred badly then you need to pull it out and machine it, anyway.

If it's under ACCELLERATION then it could be a main bearing (although I've seen this with rod bearings, too). You have to pull the motor. You can't get the end caps off with the motor in the car.

What is your target for the rebuild? If you want to go cheap there are several options. When I spun a rod bearing last fall I bought a stock 40K mile LT1 motor from a local builder (he had about 30 of them, B-body motors), cleaned it up, slapped my heads and cam on, and was back in business. Cost me $650 for the motor and some more for gaskets and such. I did all the labor and paid my buddies with beer.

It's really not that bad to pull the motor from a C4, I can do it now in a few hours. Of course I don't know how much time having an auto trans would add, if any.

I just had the tranny out in March and I still have the borrowed trans jack in my garage. It won't be bad to get out the second time now that I know the ropes. After that is out I'll just have to disconnect the other stuff holding the motor in and pull it out. I have an engine crane lined up to borrow and I will need an engine stand. I just priced a crank kit so it should not be too bad in cost. I will just chip away at the project as I have alot of other things to do right now. This car probably won't see the road for a few months. I'll have to drive the C3's for the summer.

Normal operating temps on all fluids before a thorough thrashing is SOP in my book. Guess that's why it takes so much abuse ;)