cnorgaard

'96 LT1 175,000 miles. Spun the #8 connecting rod bearing and gouged the crank journal. Definitely a new crank, but is it possible to drop the crank without having to pull the block? Anyone ever done this before? Thanks. - Carl

THE 383 admiral

Even harder is the trans.. but if I could change a crank in a F body.. the C4 has much more pan clearance..
The opti & balancer are a pain
With that mileage I would really consider a low milage swap.. or a complete re-build

NuckinFutz93

At 175k miles, you really should do a complete rebuild or low mileage swap like Admiral said. When you spin bearing, there is no way to know where all the damaged bearing pieces go. IMHO, if you just throw a new crank in without a rebuild, you'll be throwing good money away.

cnorgaard

So what about the original question: Can the crankshaft be dropped without pulling the engine? If so, what's the trick(s)?

cv67

yes you can

Converter/clutch, that pita balancer timing cover (chain has to come off opi etc

You could pull the whole motor in that time.
Can only hope for the best but if your bearing is spun your rod is probably history,pretty much every metal surface has the potential to be fubarred from all the metal being forced through it.

zr1fred

It can be pulled without pulling the engine but it is a LOT more work. First, the transmission must be removed , or at least pushed back about a foot, which is a LOT more work than removing it. Than you need to remove the flywheel, front engine accessories and timing cover, remove the suspension cross braces, and remove the oil pan. You will also need to remove the drivers side cylinderhead to remove the piston and rod in order to re-size the rod. Probably need to remove the passenger side cylinderhead to remove the #7 rod which shares the same throw on the crank. This is a VERY abreviated discription. All this and you have a 50/50 chance that contamination will immediately take out the new crank. In sumnation, you will have spent three to four times the work and energy to just F**k up the job. Does that answer the original question?

cnorgaard

OK, now this is the answer I was looking for. Both #7 and #8 connecting rods look OK. Going to mike them just to be sure but there's nothing obvious so for now I'm going with crankshaft, oil pump, Opti, plugs, and plug wires replacement. If I can get it running without the knock it's sold ASAP. Time for us to get a grown up's car.

cnorgaard

So you did this on an F-body without pulling the block?

zr1fred

If the bearing spun, which generally preceeds the knocking sound, it's almost certain it opened up the rod.

cnorgaard

Could very well be, and if I have to pull that head to pull the piston and replace the rod I can live with that. Pulling the block is what I'm trying to avoid. I have plenty of time but I don't have a real shop and hoist.

cv67

Youll need to pull the head on that side, too in order to drop the piston back in.

383vett

Feel sorry for the next owner. Maybe sawdust in the oil will get rid of the knock without all the hassle.

THE 383 admiral

YES.. its very tight on a f body.. I also have years of experience.. to help me out..

PS it was a high milaege motor I wanted to pull any way.. this bearing spun about 120mph
I only removed the crank.. it was wasted.. and rod 5.. I already had my built 357 waiting.. to go in.. when I had a f body 2 years ago.

Let us stress the fact.. its very easy to pull the crank.. but putting back in while the block is in the bay.. is completely different.. the crank is about 55 pounds.. you need to be perfect installing. In tight quarters..without hitting the journals.. passing each rod.. this is assuming.. you have no internal damage or debris..

PLRX

Engine is toast. Pull the whole thing and get it re-done properly. Time to inspect those cylinders for a proper 4.030 bore, and now that you need a new one, buy a 400 crank (3.75) for a 383 SBC stroker.

Paul Workman

Having gone that same cheap way before ... and suffering the consequences a couple months later, AND since it is a high mileage motor, I can't agree more with the recommendations to pull the motor and overhaul it!

However, you may not need a new crank, necessarily. Depending on how bad it is, turning it 0.010 or so might clean it up. Then using over-size bearings on the rods connected to that crank journal may suffice. You will want to replace all the bearings tho. And, then why not have the bores checked and bored if needed - start over with a fresh motor, rather than a bandaide fix??

Hate to see you go through the trouble - thinking you're saving some time or effort to avoid pulling the motor. For little more effort, rent the cherry picker and motor stand and have a lot of fun while your refreshing your toy!

P.

RollaMo-LT4

True, but he's just wanting to get it running.
Then he will dump to POS on the next guy.


Real classy of you.

cnorgaard

OK, lighten up guys. Since it's never burned oil the rings are obviously good. The tranny and everything else about the car is AOK so with a new crank/bearings, oil pump, timing chain, and Opti I would say it's far from a lemon. We have other reasons for needing to sell it that have nothing to do with its current state of repair.

But there is one question remaining: The #8 connecting rod. Some say since the bearing spun the rod is automatically toast which means pulling the head and either replacing the rod or having it machined to spec. Others say to reassemble the rods & caps without any bearings, mike them all, and if there's no difference between #8 and the others just go with 8 new connecting rod bearings on a new crank. What's your experience?

zr1fred

To do the job right, you should re-size the rods, at least the one with the spun bearing (about $20-$30 at a machine shop). You can buy crank kits (crank and bearings) at most parts stores, Autozone, etc. about $150, and the gaskets needed for about $100. There is nothing wrong with just changing the crank, I think what most of us are saying is that it is far easier to pull the engine and it is hard to do the job right on your back, a lot of little things can bite you in the ***. You can pull the heads in the car and then just pull out the shortblock if you are worried about getting the engine out. With everything disconnected including the trans, there is no need to remove the hood, if that's a concern. If you haven't had any other problems, the rings, cam/lifters, timing chain and heads should be fine. The piston sometimes hits the head with the bearing out, so that can take out a head gasket.

lt4obsesses

If you have to sell the car anyway, just sell it as is. This way the new owner, knowing full well the issue, can repair it, mod it, upgrade as they see fit. You won't really be losing any money as you would have to buy the parts anyway.

There might be someone right around the corner looking for just a project like this. Just a thought