Hello

I need some Help! My 91 350 TPI got a rod bearing demage a few months ago. I decided to rebuilt the engine. Its still running but the sounds very bad. Can I just swap the Crankshaft and the bearings to get it run again?
is that the right crankshaft for the car:
http://www.ebay.com/itm/350-CHEVROLE...48e4c8&vxp=mtr

I am not sure about one piece seal or two piece seal?

Thank you

 

If its the org motor your have a 1 piece seal crank.
If you have a rod bearing thats bad, no, it'll have to come apart and the rods will need resized.

 

Ok, do I have to take the Engine complete out? or can I swap the crankshaft/Rods from underneath and maybe just lift the engine a few inches?
Are there some nice instructions somewhere?

 

Motor will be coming out to fix it.

 

Does the engine comes out with the transmission? I just read Haynes and I am confused. It says I have to cut the floor pan. is that true and where?

 

You can take the engine out alone, or with the transmission. There is no cutting involved.

 

Buy a factory service manual from HELM inc.

 

Good lord cut the floor pan?! Really?

Anyway, theres absolutely no need for that. You can pull the engine out by itself or you can leave the transmission attached. Just be careful to support the transmission as you're pulling the engine out.

 

Thanks for the help it worked out. I have a spun bearing on cylinder 8. the one bearing half was pushed over the other half. The surface on the rod has small scraches and I wounder If it needs to be replaced too since there is a bearing installed over the rod. Can I install a cylinder from underneath? without taking out the cylinder head?

 

You sound like you're in a little over your head...

The rod needs to be re-sized - since you spun the bearing and the noise you heard was the rod banging up and down on the journal it's stretched the "circle" on the rod and it's no longer a circle - it's an oval - if you simply put new bearings in there you'll end up with too much clearance (usually on the cap end) as the bearing will want to seat against the rod which is no longer the proper size nor the proper shape. The engine will run for a little while to a few thousand miles tops then you'll have the rod knocking again.

To fix it "for good" you'll have to pull the rod out, have a machine shop "re-size" the rod's big end - that's about as cheap as you're going to get away with. Honestly I wouldn't order one of those crankshafts that you linked to earlier - I would simply take the crank you have and at the bare minimum the one rod you have to the machine shop and have them grind the crank and re-size the rod. However if it were me I would pull all 8 pistons and take them in and have all the rods checked as you could be close to having another one out of spec - then get a re-ring kit for the engine and then do a quick de-glaze honing of the bores and re-assemble with new parts and an HV oil pump (since you're not replacing the cam bearings or tightening up the rest of the engine's clearances the HV pump can bandaid excessive clearances for a long time...) The parts shouldn't run more than $200 for everything and about $100 to grind / polish a crank and my guy charges me just for the rods he re-sizes and measures them all for free so maybe another $20 to $150 to get the rods re-sized.

 

You need to pull the engine out and completely disassemble it and clean it out or it will just happen again, and worse. Depending on condition, you will either hone, bore and hone, or junk the block. Then you will need to have your machine shop grind the crankshaft undersize or get a replacement crankshaft. From there you can maybe get away with reconditioning only the rod that had the failed bearing. Then you need new piston rings, and if you had to bore it out, new pistons also. If your cylinders are out of round and you just hone and replace the rings, it will last a while but you will lose cylinder pressure much sooner than you would otherwise. I think I read that a re-ring will last around 50k miles. If you just replace the bearing and bolt it back together the engine will need to rebuilt again even sooner.

Stop trying to cut corners, it will only cost you more money and time in the long run. Consider finding a cheap pullout 305.