Rod bearings questions

[turbopac]

I read the faq on this but I need some clarification,this weekend Im going to change my rod bearings. my oil psi@ 6 @ idle and about 20 -25 @ 50mph It sounds like a little knock @ idle, if you put it in gear it mostly goes away.
1.Will the pan just drop down or do I need to unbolt something from the tranny?
2.can I just buy std. bearings?
3.Do I need to plasti guage the old or new bearings?
I havent rebuilt a engine in about 15 years so any help is great!the car is a 87 daytona pacfica t1 auto 120k

[ol"blue]

Quote:

Originally Posted by turbopac I read the faq on this but I need some clarification,this weekend Im going to change my rod bearings. my oil psi@ 6 @ idle and about 20 -25 @ 50mph It sounds like a little knock @ idle, if you put it in gear it mostly goes away. 1.Will the pan just drop down or do I need to unbolt something from the tranny? 2.can I just buy std. bearings? 3.Do I need to plasti guage the old or new bearings? I havent rebuilt a engine in about 15 years so any help is great!the car is a 87 daytona pacfica t1 auto 120k

You'll have to remove the inspection plate from the trans., and I think the triangular brace on the rear of block/tranny. Check the rod caps for undersize marks. You should mic. the rod journals to be sure. Check bearing clearance- old & new. I'd replace the oil-pump while the pan's off.

[dirtyglhturbo]

been there done that. its usually just a short term band aid for it. the clearances on main bearings is what controls oil pressure. if they are scored at all, you are wasting time and money. spend the money on a rebuild. i hear ya loud and clear on the cost,(i'm poor also)but i have learned from the school of hard knocks. you could prolly get a crank kit for it, but then the upstairs, and the rings are still gonna be worn. it's a shitty situation. if you go for it, i wish you the best of luck, and hope it works out. just my opinion.

[22dodge]

couldn't it be possible the knock isn't in the bearings but in the wrist pins. I've only see a ton of worn wrist pins on these engines causing a knock more commonly than rod bearing failures.

[dirtyglhturbo]

Quote:

Originally Posted by 22dodge couldn't it be possible the knock isn't in the bearings but in the wrist pins. I've only see a ton of worn wrist pins on these engines causing a knock more commonly than rod bearing failures.

yes sir. i agree. you just never know. thats why i said to suck it up and rebuild it. it sucks, but at least it will be a permanent repair

[kermit]

If the crank has never been turned before, std. sizes are ok. By the book you should plastigauge, but it isn't entirely necessary. I've had a trusted engine machine shop tell me that too. Reason being is that plastiguage is more of a check of bearing clearance, especially when you are having the crank turned. Obviously you can't go wrong checking it, and it surly would give you peace of mind, but realistically with this kind of "engine refreshing" you are really looking to get better than what you had before, because even if the plastigauge shows them out still it's probably better than what it was with the older worn bearings.

In other words, if you are prepared to do the proper work to machine the engine, then plastigauge the crank, but it you are just looking to get buy, plastigauge really won't tell you much.

[ol"blue]

Even if you are the original owner, the only way to be 100% sure whether the crank has been machined before is to mic. it. On occasion, Chrysler has shipped out a vehicle that for one reason or another has had the crank machined to avoid scrapping an otherwise good engine. Also, many reman. blocks have been installed, either under warranty, or by a previous owner. I wouldn't take something as important as rods & crank journal sizes for granted. It's too easy to make sure.

[phantomrt]

Quote:

Originally Posted by 22dodge couldn't it be possible the knock isn't in the bearings but in the wrist pins. I've only see a ton of worn wrist pins on these engines causing a knock more commonly than rod bearing failures.

^^^ What he said. If you hear any knocking, and it is indeed coming from the rod bearings, you will be able to remove the oil pan and FEEL the play in the rod bearings by pushing / pulling on the rod 90 degrees to the crankshaft centerline. You will notice that the rod will be able to twist a VERY slight amount, and that is normal. But even if the clearances are at .0035", you're not going to hear that. If you're that far, you will want to consider a lot more engine work than band-aid bearing replacement.

These engines exhibit wrist pin knock--its basically the nature of the beast. Usually its a wrist pin noise and doesn't indicate impending engine failure.

[monkeyhead]

Quote:

Originally Posted by dirtyglhturbo been there done that. its usually just a short term band aid for it. the clearances on main bearings is what controls oil pressure. if they are scored at all, you are wasting time and money. spend the money on a rebuild. i hear ya loud and clear on the cost,(i'm poor also)but i have learned from the school of hard knocks. you could prolly get a crank kit for it, but then the upstairs, and the rings are still gonna be worn. it's a shitty situation. if you go for it, i wish you the best of luck, and hope it works out. just my opinion.

I totally aree. I just had to replace a couple pistons and did the rod bearings at the same time. I still had low oil pressure until it finally went away sitting at a stop light. KNOCK KNOCK KNOCK. really sucks to put in all that effort and still have a big lawn ornament.