What can be said about the 307 small block?

[towbar]

Got a couple 307 stories/experiences. First was my dads 307 2bbl, 3OT 69 C10, bought the truck with 60k on it, he complained about the gas mileage till he sold it about 2 years later, this was mid 70's, I was pretty young and that sticks in my head first and foremost.

Next, in 85, I got a 72 Cheyenne SWB, OG Ochre paint, 307, 3OT....very nice truck. Drove it to high school, lowered it, ran the crap out of it, got 12mpg....for a teenager 12mpg was tough! At about 100k miles the cam went flat, we swapped in a .447 lift L79 cam, 72 4bbl intake and q-jet......wow, woke it up a ton. It then it got 16mpg, was a pretty peppy motor, tougher than nails....can remember floating the valves till it quit from a missed shift /linkage jam a few times....always started back up, never let me down. Later, I sold the truck to buy a 68 Camaro. I have kept track of the truck ever since......today, that same engine is in the same truck, never been apart from the time dad and I put the cam in it and still runs great.

Then I had a 68 Malibu with a 307, PG trans, 1 owner, 90k miles, drank oil horribly, absolutely no power....swapped in a 305 just so I could drive it...planted the 307 behind the garage.

guess the moral is there are good and bad in all.

[garyd1961]

The 307 truck engine is not a low nickel block. It's stamped behind the timing cover 10/20which from what I understand means 1% nickel and 2% tin. They are strong blocks and they are not thin either some have been bored to fit 350 pistons (4 inch bore).I have mine sitting in the shop because I could buy a Vortec L31-R crate engine cheaper than rebuilding the 307. I've seen a lot of 307s worn out but I have never seen one blow with low miles on it.

[68Stepbed]

Originally Posted by leftybass209

Interesting theory your friend holds about the reason for the 305's existence. I would also suggest that there's much more that went into the decision to introduce the 305 other than parts just laying around that would have been specifically for racing applications. Every car manufacturer was looking far ahead of their current model cars, anticipating trends and chasing the most viable options to outsell competitors. They also had plenty of stock for dealers to take care of warranty issues, engine replacements etc. It's not like the supervisors over casting said, "Well we have 12 tons of raw metal, lets just spit out 283/327 blocks, cranks, and rods well beyond the proposed (xxxxx) number of vehicles that are going to be receiving these engines until someone yells, STOP!"

I love hearing from people who used to work at these plants. Their insight is extremely entertaining and often does contain truth that can contradict hearsay. It's also hard to believe that someone had retained an intimate and detailed knowledge database in their head of things that were as routine as working at a factory. I can't remember details of what I did this time last year at my job, so how am I going to remember 50 plus years later? I'm sure it's easier for some than others, but that's why records are so important.

No offense to you, if that sounded argumentative or belittling, that wasn't my intent.

No offense taken. I'm actually hard to offend. lol

Keep in mind, though, that I'm not referring to the 305. I know for a fact the 305 was purpose built in the late 70's to be an economic V8 that would get decent fuel mileage, have good low end torque, and pass emissions. I also didn't say they overproduced blocks and cranks. They just mated the parts leftover from the production of the 302 engine.

There were lots of 307's built, but there may be a partial truth to what the guy told me. My theory is the first run may have been made with the leftover parts, then production just stayed in place to provide and "economy" V8 for base model vehicles.

[697498chevy]

I have my late Father in laws 1969 C 10 that he bought new . Just looked and it has 257,863 miles on it . The original 307 has never been out . Pretty sure I've replaced the cam , lifters , and timing chain . Also probably had the heads reworked . I'm sure it needs rebuilding but it runs fine . For my needs anyway . Just thought I'd put my two cents in .

[leftybass209]

Originally Posted by 68Stepbed

Keep in mind, though, that I'm not referring to the 305. I know for a fact the 305 was purpose built in the late 70's to be an economic V8 that would get decent fuel mileage, have good low end torque, and pass emissions..

Yes, I inadvertently typed 305 instead of 307, as 305's didn't debut until 1976 .

On another note, not directed to anyone in particular...

There's a lot of folklore and speculation being passed off in this thread as fact. Facts are provable, often cited from a credible source. I know we'd all like to trust what "someone else said" but the black and white is what really counts.

307's, in my experience are just as reliable as any other SBC. However, for just as many stories I read that say they last forever, I can find one where a 307 gave up the ghost on someone.

That engine was placed in many pedestrian vehicles, not just trucks. Many 4 doors, wagons, base models and whatnot. It stands to reason that many female drivers (as a basis of the time and not a stereotype) and others not interested in racing or driving fast used these vehicles as grocery getters and A-to-B vehicles. Those engines never wound past 3k often. Easy lives and properly scheduled maintenance mean less wear and tear.

Why did so many 307's live long lives? Simply because they were never a hot rodder's choice of platform. They had enough power to pull the weight of nearly all the vehicles they were placed in, so they rarely struggled. It's no more or less durable than any other small block treated in the same manner, subject to the same conditions. Lean on the 307 and you'll have a paper weight before long, just as with any other small block that got beat on relentlessly.

[mike16]

I think the 010 and the 020 cast into the block behind the timing chain means .01 % and .02%. Its not so much a low nickle content block. its just that it takes a very small amount of tin or nickle to facilitate the casting process and to improve the wear characteristics of the bores.

many blocks , but not all if I understand my resources correctly, many blocks just had the 010, others had nothing, but typically the trucks had both 010 and 020.

some blocks had niether the increased tin nor the increased nickle content. there was never a high nickle content or a low nickle content. it just had nickle or it did not have nickle. According to an article written by David Vizzard on small block chevy's.

[GRX]

The 10 and 20 indicate foundry production lines from what I understand.

Can anyone provide actual GM foundry literature showing the 10 or 20 pertain to nickle or tin content? How about independent metallurgical analysis? It has been done on a few of these said blocks and found to be false. In any case, I am all ears (eyes) to any info to the contrary.