Engine lunched itself...need advise

[AyWoSch Motors]

Sorry to write a book, but I'm in need of some advise and some insight. First time I've ever had this happen to me personally.

This morning, on my way to work, cruising along at 50, listening to the radio, actually going to be early to work for once, my truck desides "nope, dont wanna run today".
Started it this morning, sounded good, took off, was running great as always, and suddenly started going tick tick tick, and within a few seconds of that happening, started knocking and banging loud, and spuddered to the side of the road.
I tried to start it, started right up, but started knocka knock knocking again pretty loud so I shut it off quick.
Ended up trailering it back home.
Got home, and started investigating. I checked the oil, and it was pretty low, (which is odd because I check all my trucks about once every month, and it doesn't leak a drop, and it doesnt smoke whatsoever), but it wasnt so low that it should've self destructed. I then looked to the bottom of the pan thinking maybe something popped up and punched it, but saw nothing. Did notice that the bell housing is oddly oily, so maybe the rear main seal is gone which would explain the oil disappearing.
I took the valve covers off hoping it to be something simple like a rocker nut fell off or a bent push rod. No luck there. So I drained the oil. Magnet on the plug is complety clean, no metal, but when I poured the old oil out, there were a few flakes of brass in the bottom of the pan.
At this point I'm thinking it spun a bearing or a wrist pin or something. Gave me no warning either. Been using it everyday, with no signs of it about ready to give out. I'm lost.

The the engine is question is a 305 sbc, which is the original numbers matching engine for my 86 K1500 Seirra. Always been a great engine since I've had it, strong runner.

First question: what do you think happened? what went wrong?

Second question: is it going to possible to fix this engine, or am I gonna need to get a new one?

Third question: How important to the value is a numbers matching engine?
And if something terrible has happened to it, would it be more money wise to get it machined and rebuilt, or to just buy a new long block 350 for $1,500?

Any thoughts at all would help, thanks

 

[PrairieDrifter]

I'd say it shredded a rod bearing. It can happen that fast, that "brass" you saw was probably the copper bearing material. It could be rebuilt easy, the crank may need some work, which would be extra.

Personally I wouldn't save a 305. If it was numbers matching I definitely wouldn't scrap it or sell it, I would just tuck it in a corner. But that's just me, kinda depends how nice the truck is too.

 

[Grit dog]

I agree, blew the babbit right out of one of the rods.
Personally I don’t think numbers matching means much of anything unless maybe it was an all original pristine truck.
But what year did GM trucks start matching engine numbers?
I know there’s no such thing as a truly matching numbers truck in the 67-72s.
Bottom line if you need it for transportation, dropping an engine, any decent small block in it is likely first priority.
Quicker than rebuilding and what do you do with an old 305? Spend the money to fix the rod or crank and keep running an antique engine, tear it all the way down and end up with a 305 again when you’re done?
Personally the only GM engines that have seemed the least bit unpredictable (going back 30 years now…) were 80s 305s. I think every blown GM engine I replaced back in the day (only a few, but lots of 350s around)was a 260 or 305.

 

[PrairieDrifter]

I agree, blew the babbit right out of one of the rods.
Personally I don’t think numbers matching means much of anything unless maybe it was an all original pristine truck.
But what year did GM trucks start matching engine numbers?
I know there’s no such thing as a truly matching numbers truck in the 67-72s.
Bottom line if you need it for transportation, dropping an engine, any decent small block in it is likely first priority.
Quicker than rebuilding and what do you do with an old 305? Spend the money to fix the rod or crank and keep running an antique engine, tear it all the way down and end up with a 305 again when you’re done?
Personally the only GM engines that have seemed the least bit unpredictable (going back 30 years now…) were 80s 305s. I think every blown GM engine I replaced back in the day (only a few, but lots of 350s around)was a 260 or 305.

Engine numbers can come on dealership sales cards and info. I believe that's what he means.

I've got the engine number on some of the info for my grandpas 79,

 

[Octane]

Sorry to write a book, but I'm in need of some advise and some insight. First time I've ever had this happen to me personally.

This morning, on my way to work, cruising along at 50, listening to the radio, actually going to be early to work for once, my truck desides "nope, dont wanna run today".
Started it this morning, sounded good, took off, was running great as always, and suddenly started going tick tick tick, and within a few seconds of that happening, started knocking and banging loud, and spuddered to the side of the road.
I tried to start it, started right up, but started knocka knock knocking again pretty loud so I shut it off quick.
Ended up trailering it back home.
Got home, and started investigating. I checked the oil, and it was pretty low, (which is odd because I check all my trucks about once every month, and it doesn't leak a drop, and it doesnt smoke whatsoever), but it wasnt so low that it should've self destructed. I then looked to the bottom of the pan thinking maybe something popped up and punched it, but saw nothing. Did notice that the bell housing is oddly oily, so maybe the rear main seal is gone which would explain the oil disappearing.
I took the valve covers off hoping it to be something simple like a rocker nut fell off or a bent push rod. No luck there. So I drained the oil. Magnet on the plug is complety clean, no metal, but when I poured the old oil out, there were a few flakes of brass in the bottom of the pan.
At this point I'm thinking it spun a bearing or a wrist pin or something. Gave me no warning either. Been using it everyday, with no signs of it about ready to give out. I'm lost.

The the engine is question is a 305 sbc, which is the original numbers matching engine for my 86 K1500 Seirra. Always been a great engine since I've had it, strong runner.

First question: what do you think happened? what went wrong?

Second question: is it going to possible to fix this engine, or am I gonna need to get a new one?

Third question: How important to the value is a numbers matching engine?
And if something terrible has happened to it, would it be more money wise to get it machined and rebuilt, or to just buy a new long block 350 for $1,500?

Any thoughts at all would help, thanks

Longblock 350 is the way to go.Put that 305 in storage,just in case an original is ever desired

 

[Octane]

I agree, blew the babbit right out of one of the rods.
Personally I don’t think numbers matching means much of anything unless maybe it was an all original pristine truck.
But what year did GM trucks start matching engine numbers?
I know there’s no such thing as a truly matching numbers truck in the 67-72s.
Bottom line if you need it for transportation, dropping an engine, any decent small block in it is likely first priority.
Quicker than rebuilding and what do you do with an old 305? Spend the money to fix the rod or crank and keep running an antique engine, tear it all the way down and end up with a 305 again when you’re done?
Personally the only GM engines that have seemed the least bit unpredictable (going back 30 years now…) were 80s 305s. I think every blown GM engine I replaced back in the day (only a few, but lots of 350s around)was a 260 or 305.

I know of an 1980s blazer with a 305 that the crank snapped at highway speed.The lady said one second all seemed well,and then a bump and it was gone!

 

[75Monza]

My 383 stroker snapped the crank off right behind timing gear in a wedge so that it could still turn over but ran like total dog turd. Only thing that kept it in place enough to run was gear drive and aluminum timing cover. Drove the thing 20 miles home with a car trailer behind after that happened, lol.

 

[Kurnacopia]

Dont let that brass throw you off. Check the crank for issues. Make sure you go over that valve train in detail and look for anything loose or bent. If all of this passes the test, start looking at bearings. Are there any other symptoms? Smoke or water leaking? Think outside the box and double check everything until you find the exact issue.

 

[Bextreme04]

I wouldn't keep or rebuild the 305 if it is hurt and worn enough to require any machine work. If it is in decent shape, you can probably get away with new bearings and mild machine work for a few hundred dollars. The reality of it being an original engine though, is that it is probably worn enough that it will require an overbore and therefore new pistons... which would put the cost right at what you gave for a new 350 long block. If you have this as a daily and don't have weeks to have it down, that will be your best option. Get a 350 long block, pull the old engine and transfer everything you need to over to the new long block, drop the new motor in and off you go in a weekend or less.

 

[peats]

i don't know what your budget is but that 305 has little value. i bet you can find a good running 350 on craigslist for $1,000 or less.easy peasy.

 

[DoubleDingo]

Get a crate engine (350), swap over the accessories, put the 305 in a corner, and drive the truck. Then you can tear apart the 305, mic the bores and journals, and rebuild it if you want to, or if it turns out to be completely unrebuildable, then you can toss it or make a coffee table from it.

 

[cstew47]

Longblock 350 is the way to go.Put that 305 in storage,just in case an original is ever desired

Try to source a 383 if possible. Same block with way more torque. The price shouldn't be much different.

 

[Raider L]

Oh, but what about the 307??!! What a wonderful motor!! It was even more worthless than the 305. All those late '70's and '80's engines like that are what I call EPA engines. They were built to satisfy the government for cheap and complied with the Clean Air Standards of the day. You might save the heads only because of the closed combustion chamber of 64 cc's. Some people have used them to race but you can't do anything to them other than polish the combustion chamber and re-valve them but then you throw them away.

Get a 350 and you won't have anymore problems. Heck, put a 2 bbl. on it if you want it to save gas.

 

[AuroraGirl]

Oh, but what about the 307??!! What a wonderful motor!! It was even more worthless than the 305. All those late '70's and '80's engines like that are what I call EPA engines. They were built to satisfy the government for cheap and complied with the Clean Air Standards of the day. You might save the heads only because of the closed combustion chamber of 64 cc's. Some people have used them to race but you can't do anything to them other than polish the combustion chamber and re-valve them but then you throw them away.

Get a 350 and you won't have anymore problems. Heck, put a 2 bbl. on it if you want it to save gas.

Wouldn’t a small cfm 4 barrel spreadbore be a better economy carb if you adjusted the secondaries properly or just practiced good pedal discipline

 

[75Monza]

Wouldn’t a small cfm 4 barrel spreadbore be a better economy carb if you adjusted the secondaries properly or just practiced good pedal discipline

In theory, yes. But, the first time you get the "bwaaahhh" of the secondaries opening, that thought gets thrown behind the seat for emergency use only.