: Northstar threw a rod, hole in lower block. Rebuildable?



alexrex20
06-10-05, 06:38 PM
Hey guys,
I pulled a 4.0 Northstar out of an Oldsmobile Aurora. It threw a rod and punched a hole in the side of the lower half of the block (not the pan). I know the lower half also serves as the main caps, so does this mean the block is complete trash? Or can the bad half be replaced (in conjunction with align boring the main journals and fitting oversize-OD bearings)?

I'd really like to save (and use) this engine. The cylinders are nice and clean, with some crosshatching still visible, and I've checked for taper and out-of-round, etc. and it all looks to be OK. Is it worth it? Or even possible?


Thanks,
Alex

Spyder
06-11-05, 05:20 AM
...doubtful... ?

eldorado1
06-11-05, 05:42 PM
Ha!

I wouldn't. Just buy a rebuildable core for like $200.

BeelzeBob
06-13-05, 01:32 PM
Technically it is "possible" to obtain another lower crankcase, mill .010 off of the mating surface, install it to the block and re-linebore/line-hone the mains....but.....all that is going to cost you more than another engine in all likelyhood. And, since the LCC isn't serviced separately, you'll have to buy another engine anyway just to get the LCC. If the block were something really special with a lot of time/money in it for modes it could be saved but a stock crankcase would be hard to justify saving for all the grief it will take.

Besides, it is hard to believe that it actually threw a rod and punched a hole in the lower crank case and didn't hurt one of the bores at all...... have you got it apart completely to inspect all the bores all the way to the bottom??? Amazing that the block would be OK with a hole in the LCC...!!!!

dkozloski
06-14-05, 08:10 AM
Many years ago my boss's wife chucked a rod in her '54 Caddy when a rod nut unscewed from the bolt. The big end stapled the pan to the block. The hole in the block was pretty clean so I rounded it up with a rat tail file and threaded the hole with a pipe tap. I plugged the hole with a big pipe plug and welded up the hole in the pan. The crank had a ding that I cleaned up with a file and an oil stone. I had to pull a head off to change the rod and piston but it all worked out and ran fine. My boss took the failed rod, nut, and bolt to the dealer and about two months later the dealer told him to come down and get his new engine. The factory replaced the engine even though the car was six years old. I guess the nut was not supposed to come off the rod bolt.

Concourson20s
06-14-05, 06:21 PM
My boss took the failed rod, nut, and bolt to the dealer and about two months later the dealer told him to come down and get his new engine. The factory replaced the engine even though the car was six years old. I guess the nut was not supposed to come off the rod bolt.

How times have changed. Come to a dealer today with a rod and bolt in your hand and they will ask you, if you are going to shove it up your arse, or if you want them too.

alexrex20
06-16-05, 01:05 PM
Technically it is "possible" to obtain another lower crankcase, mill .010 off of the mating surface, install it to the block and re-linebore/line-hone the mains....but.....all that is going to cost you more than another engine in all likelyhood. And, since the LCC isn't serviced separately, you'll have to buy another engine anyway just to get the LCC. If the block were something really special with a lot of time/money in it for modes it could be saved but a stock crankcase would be hard to justify saving for all the grief it will take.

Besides, it is hard to believe that it actually threw a rod and punched a hole in the lower crank case and didn't hurt one of the bores at all...... have you got it apart completely to inspect all the bores all the way to the bottom??? Amazing that the block would be OK with a hole in the LCC...!!!!


Well, the machine work would be NC so the only out-of-pocket expenses would be materials - the bearings and the LCC. But you're right: It's not worth the trouble. The reason I wanted to keep the Northstar is so I could drop it in my FWD Bonneville, with a pair of turbos thrown in for good measure. There weren't many V8 FWD options when I came up with the idea, but with the new LS4 in the Grand Prix's (with the 4T65E?), there's now a direct Gen-III swap for my purple granny sedan. Stroked LS1 would be nice. I'd deal with the manic torque steer once I got the sucker in.

As for thrown rods... Last year, I bought an old Chevy 454 dually for $500. It had a bad carb and the owner was desperate for cash. My buds and I threw in a Corvette cam and Corvette HEI, plus a Holley 750, and the Tank was decently quick in the first 2 gears. Anyway, we later ghetto-rigged a small shot of nitrous: A 125 dry shot. It lit up all four tires shifting into 2nd gear, and pieces weren't falling off the truck, so we threw in some bigger jets (what we calculated to be upwards of a 600-shot), and blasted the 454 to hell. After the first hit, we bent pushrods, flattened the main bearings, but surprisingly the block held up. The second hit we floated and snapped some valves, and thus a piston and then the rod. No biggy, we just dropped the pan, pulled out the culprit along with its piston, and fired it up on 7 cylinders. (Actually, with all the bent pushrods, it was probably only firing on maybe 5 cylinders.)

After tearing down the engine, the main bearings were shot to oblivion, but the crank was still straight and true, as were the cylinder bores.

alexrex20
06-16-05, 01:08 PM
I guess the nut was not supposed to come off the rod bolt.

:rofl:

alexrex20
06-16-05, 01:09 PM
So anyway, what's a huge hunk of scrap aluminum worth these days?

eldorado1
06-16-05, 02:37 PM
So anyway, what's a huge hunk of scrap aluminum worth these days?

I got $30 for my block at a scrap yard... Would've got more, but the cylinder liners made it "mixed metal", so instead of $1/lb, I got like 50 cents...