65milano

Thank you again. The 383 option wasn’t on my radar screen: would you know if it will fit under my small block hood or would it need a stinger hood?

road pilot

It would look like your old engine if you use the same size intake and carb. Its just bored out 350.
Yes...you can use your old hood.

Westlotorn

Actually a true GM 383 is normally a .030 oversize 350 block with a 400 crankshaft in it which is a 3.75” stroke and a 4.030 bore size. There are a few other combo’s but this one is very popular. The reason people buy the 383 is for the torque increase, a good 383 feels almost like a big block while still fitting in the original small block space.

Your factory rebuild 327 should have been good to run at 3,500 RPM for months straight with zero issues as long as you did not overheat or run out of oil so as others mentioned the RPM did not hurt the engine something else did. Most common, overheat or lack of oil. If not overheat or lack of oil it was not assembled correctly. In the old days the Nevada freeway did not have a speed limit. Cars like Corvettes would run across Nevada at 100 MPH plus and run that speed for a couple hours. RPM’s had to be 4,000 + the entire time. I had a cousin buy a 1966 Corvette brand new and took the first trip from California to Salt Lake City just to enjoy the no Speed Limit road in his new Corvette. As you get close to every city you pass Nevada does have speed limits. He was a slow learner. Got three tickets going and two coming back. Nobody thought he was damaging his new car running 4,000 RPM + for most of the combined 20 hour trip.

hdrider1

A whirring sound sounds suspiciously like a bearing going bad.

65milano

Hello all. The shop opened it up and sent a . The diagnostic is that the crankshaft bent (it had not been changed in previous engine rebuild) and a connecting rod broke. They say they don’t need to re-bore the cylinders.

Thoughts appreciated!

65hihp

Crankshaft bent? At 3000 rpm? You said you were not sure the tach was accurate.. I think you're onto something there.

joe1148

My two Centavos. Assuming it's a numbers matching block that wasn't decked to remove the numbers. I wouldn't give this a second thought. I'd rebuild it and put it right back in place. Additionally, I'd send out that tach for a rebuild and new tach cable.

Dad's '66 427

We have blown up our fair share of motor stuff with the Blown Alcohol Car, but...... for the experts here, how do you bend a crank in a street car???

pop23235

My $0.02, crank may be bent, but how do they know yet without removal of the crank? Spun bearing in my opinion started this damage. Nothing to do with RPM.

bauto

I believe it spun a rod bearing and then the rod broke a short time after , the crankshaft is probably damaged beyond repair. I am sure you can still buy a recondition crank kit with bearings
pretty reasonable . No way to tell if it is bent without removal
Bob

pop23235

Second thought: When a shop tells me this, I get my parts and leave. They either are lying or don’t know what they are doing.

Easy Rhino

I was thinking the same thing.

6T7L71CPE

Maybe I'm missing something, but if a connecting rod broke wouldn't we see some major damage to the block?

bbxlr8

WOW, You were already getting there in this post above:
Hate to be a pessimist but the third-party part makes me feel like they are not going to stand behind this. I don't do rebuilds as much as the more experienced people here, however, it seems that they surely should have examined and measured everything they reassembled. Bent crank out of the blue sure doesn't pass my BS test as the root cause...

Stay calm and give them a chance to see if they will make up for it in some form or another. Usually, this type of situation ends up in a pissing contest and chances of $ recovery are slim to none even if you prove it i.e. it still becomes a lost cause financially.

I would not have them do anything else if it is rebuildable.

bbxlr8

You don't need a tach to tell the difference between 3K vs 6K on the freeway for 10 minutes (or even 10 seconds) - No chance it was that off

ruxvette

Jeez, I'm no mechanic but all/most of the bearing journals look horrible. What was in the crankcase? Anything? Oil? Oil/gas? Oil/Gas/water?

mudbone64

Wouldn't you also see a damaged rod? I watched the video several times and I think the only rod bolts I couldn't see clearly were the #5 cylinder rod bolts. All of the other rod bolts appear to be intact and undamaged. Also, the mechanic states "don't ask me why, but it happens". That statement is unacceptable. If that were my car/engine the whole shebang would already be back at my house. That mechanic is a waste of time. If you can't find a competent, trust worthy engine builder/mechanic then I think you should go the crate engine route. There are so many better options out there than trusting a supposed engine builder that says "don't ask me why, but it happens".

65milano

Thanks everyone for your comments and suggestions. I will head over there tomorrow and take a look myself - and ask smarter questions thanks to all of your contributions!
It seems to me like the spun rod bearing hypothesis is on the right track - i’ve looked at a few videos online where this is an issue and in some of them there is whirring/chirping noise consistent with what I heard before it failed. As to additional damage to the block, my guy says there is none. What should I be looking for? Should any damage be obvious to the naked eye or is there any special equipment needed?

silver837

Their (the shop ) scenario smells if you ask me. You should be able to repair or replace everything with new parts.
If it were me I would be looking for a new shop .

Westlotorn

I just found your note and wanted to offer help. I was an engine specialist for Federal Mogul for 30 years. In my job I called on the major rebuilders in the Western States. We supplied Federal Mogul Engine Bearings to these major rebuilders. Several Hundred times we would be called in to help diagnose engine bearing failures so this is not new for me but your pictures don't show enough to really see what may or may not have happened. I will share what I see and give you a couple things to study when you visit the shop.
You can share this with your shop owner if you wish. This is industry known information.

Crankshaft, it is not bent at least through the Main saddle. We can only see the Main surface on your crankshaft for #1,2,3 and 5 and they look perfect ready to go back in and run again. #4 is probably the same but they left the bearing sitting on the crank so you can't see the bearing surface on the crank for #4 Main Bearing. A bent crank running in an engine will quickly wear the main bearings in the tight areas. It is very obvious on tear down if you know to look for it.

Connecting Rod Surfaces on the crankshaft. The very good news is I see no Heat marks. The crank is not discolored at all showing it had full oil flow at all times. When a crank is starved for oil it shows up first on the rod bearings, running without oil they would self destruct quickly but also heat up the bearing surface and the crank throw on that rod surface usually will dis color along with the failed bearing. Blueing of the crank is common, as it gets hotter oil burns to the crank surface in the extreme heat and leaves it blackened. I see no crank discolor marks so you had oil flowing properly as the engine failed.

Connecting rods hold the bearings in place with crush, crush is defined as the rod end when torqued is slightly smaller than the bearings you install. As you torque them into place Crush holds the bearing so it does not spin in the rod end over the life of the engine. The Tangs on the bearings are only there to help you assemble properly, a tang offers zero help against a spun bearing. If a bearing spins in the rod cap the engine is done and needs a rebuild or at least that one rod repalced or rebuilt. Knowing this you need to look at each Rod and each matching bearing for that rod. Keep all bearings and rod parts matched together just like they came out of the engine for analysis. So Cylinder #2 Rod appears to have been a problem. You want to study the #2 rod and the #2 rod bearings. With the bearings removed from the rod cap and rod study the rod looking for cross hatch in the area the bearing is intended to press into. So cross hatch on the big end of the rod bearing surface and on the rod cap bearings surface. IF a bearing spins in the rod end the cross hatch will be gone and circular wear marks will replace the cross hatch in that rod because the bearing was spinning in place. The bearings will also show clearly if they have spun. After being torqued in place the bearing back will show cross hatch markings from being crushed into the rod cap surface. Even after 200,000 miles a rod bearing will show this cross hatch, if not the bearing has been moving in the cap which means it did not fit correctly on install, no proper crush. Study the inside of the rod end looking for the cross hatch or marks from a spinning bearing. Study them hard.

Work your way down the crank, study each rod, rod cap and matching bearings for the same issues. Record what you see, written notes, pictures and video if you can. Look at the rod bolt threads also. #2 threads look shiny? From Nut moving maybe?

Now study each Rod cap and its matching rod for proper fit at the parting lines, If you remove the rod cap the parting line is where the rod and cap meet. If the rod bolts were not torqued and left loose you will see signs of movement where the cap was moving on the rod. There will be shiny spots where metal was moving on metal on these rod and cap ends. If you suspect one rod of being loose compare that rod to the other 7 rods in the block. All 8 rods should a have similar visual markings when you remove the caps. This process is new to you so look for things that do not look the same.

Check the part number and manufacturer on every rod bearing, record the size. Part number and size are stamped into every bearing. You might need a magnifier glass to see the numbers. If a rod bearing spun the numbers usually are worn off.
The Bearing part number should tell you what material the bearing was made out of but you will need to look that up by the number on the bearings.
Measure the crank shaft Rod Journals and verify the size, Std, .010, ,020 or .030. As they grind a crank for a new surface the surface gets smaller so your crank may be .010 undersize and that is fine and normal as long as the bearings match.

Look at your rebuild receipt from the engine build, you should have either received new connecting rods or your old rods should have been reconditioned, either way there should be a billing for that service on your receipt. Record what was actually done in your block.

Again very hard to see details in the quick video but something is very odd.

Possible causes: my guesses
-Rod left loose Not torqued properly on install
-Rod bearing installed but wrong oversize
-Oil break down due to coolant entering the oil supply, cracked head, bad valve seat, cracked cylinder, leaking head gasket
-Original engine had a rod failure and the rod was not resized or replaced at the rebuild. This type previous failure always results in a spun bearing at low miles use.

On assembly when you torque the Crankshaft Main Bearings in place you spin it. If it is straight it spins freely with just a little bearing drag. Any assembler will need to spin the engine after crank install as he installs pistons, rods, timing etc. A bent crank will have a hard spot as you rotate it. Hard spot defined, as you rotate and engine with no heads on the effort to spin the engine is exactly the same all 360* of rotation. If you find a hard spot where it takes more effort to spin the crankshaft you have a problem, either the line bore of the bearings is not straight or the crank is not straight. Any qualified assembler would catch that right after crank install so either your crank was not bent or a rookie that did not know any better assembled your engine.

What is the white colored stuff on the crankshaft at the rod bearings. Did they use a paste lube when the engine was built? Might just be a trick of light in the picture but it looks odd? Was there antifreeze in the oil?
What material were your rod bearings? Aluminum bearings can gaul to the crankshaft on failure, copper lead tin rod bearings usually scratch up the surface on failure.

It is your engine, make a cheat sheet and take notes so you do not forget to ask questions or verify items listed above. Once they start working on it all the information needed will be gone forever.
If your installer is not an engine builder they won't have the tools on hand to properly measure and odds are they do not have the expertise to properly examine what they see.

I have met some wizards in the field that knew incredible amounts of engine information and could have taught it at a high level. For every one of those I met hundreds that did not have a clue. A lot of guys turning wrenches are just doing their job and don't have the experience to analyze a failure like this even though they may have a ton of experience on other areas of car repairs.

Hope some of this helps.
Mark