Opinion...is a original Chevy 350 engine worn out at 100,000 miles ?

[57NAPCO]

A ol’ mechanic friend made that statement and I was wondering what y’all think.

Is a original 1973-1987 Chevy 350 (5.7) darn near wore out at 100,000 to 120,000 miles, no matter how well kept?

[cadillac_al]

They used to be pretty worn out at 100k miles and the 70's 350's usually had the camshaft replaced by then. My 76 has 180k miles on the original pistons and rods. It has a HUGE ridge at the top of the cylinders but still runs perfectly. It has had a new crank and a couple camshafts and heads over its lifetime. The original heads probably would have made it to 180k too but it was hopped up for part of its life. I think the 80's 305's would last a little longer. If I bought a 100k truck with original engine I would be planning on new crank bearings and a new cam, lifters and timing set very early on.

[vince1]

With a timing set and a new cam it might go farther than that. I don't know what it was with GM but their camshafts didn't seem to last very long. I know of a bunch of them sitting on garage floors for that very reason. I think their valve lifter diameters may have been less than others, so if that had anything to do with it who knows? Too bad because it was otherwise such a well designed engine.

I took apart a 65 352 at 100k miles for a burnt piston (timing too advanced?) and the camshaft still looked good with some sort of a hard surfacing treatment done to it. That's the only time I ever saw that but why couldn't they do it to all of them?

[Tom]

No.

[Thealien]

1970s engines were manufactured with technology from 50 years ago. Machining tolerances were not as good as they are today. If the carb is not tuned correctly and you can be lean (run hot) or rich (gas wash cylinders). I believe these things contributed to earlier engines not lasting as long as their modern counterparts. Just my humble opinion.

EFI and better machining and materials has improved the life span of modern engines.

[57taskforce]

Could be worn out at 100K for sure if the carb and timing have been off for several thousand miles. I believe the better part of today’s longevity is EFI. Keeping the extra fuel out of the cylinders is huge. Gasoline diluted oil effects everything from cylinders to the cam and everything in between.
I don’t believe it’s a safe bet to say that all Gen 1 small blocks are trashed at 100K. So many factors go into that with maintenance being the king.

[mattfranklin]

No. I think machining and materials have continuously improved over the years.

Maybe 4-5 years ago Car Craft did a rebuild on a junkyard Vortec 350 (well, so this is 1990s and maybe 1970s weren't quite as good). Around 180k miles (my memory is foggy). They were planning on doing some machine work, but found that it didn't need it. Maybe they have it a light valve job, ridge reaming, and ball honing.

The only way to know is to take it apart for a good cleaning and inspection.
And that's ok because it's fun.

[geezer#99]

Don’t forget the effect cold temps have on wear.
Starting motors at anywhere below 10F consistently has to produce a lot more wear on rings, piston walls etc.
In those environs motors were lucky to make 100, 000 miles.

[truckster]

In my opinion, no - if it had routine maintenance.

I've had many SBCs go 200,000 and more, including engines built in the 60s and 70s. I used to consider them barely broken in at 100,000 miles.

[Dead Parrot]

If it has been maintained, it should still be in good shape. If one or more of the PO changed oil every 5 years whether it needed it or not and did other upkeep on a similar schedule, then it is probably shot.

A lot of the early post manual choke carbs had issues with the automatic chokes. This caused many a motor to run way rich much of the time. This caused a lot of early cylinder wall wear from too much gas washing the oil away.

Many of the early cat converters had pellets and created a fair amount of back pressure which caused the motors to have to work harder then newer motors with lower back pressure honeycomb cats. More work equal more wear.

My current Hecho en Mexico 350 has about 110K on it and still runs good. I doubt the metal in it is much better then that in the US made 70s blocks.

[Thealien]

Originally Posted by geezer#99

Don’t forget the effect cold temps have on wear.
Starting motors at anywhere below 10F consistently has to produce a lot more wear on rings, piston walls etc.
In those environs motors were lucky to make 100, 000 miles.

And that is where I think synthetic oils really help.

I have been using synthetic oils sins before it was popular and was always asked does it really matter. Synthetic oils flow better in cold weather and withstand higher temperatures.

I used to prove this by leaving a quart of conventional oil and a quart of synthetic out overnight on a cold night. Pour out the oils (into a container or?) out at the same time. The synthetic always poured out much faster. On a cold start up which oil would flow through the engine on a cold day better?

With that being said the additive packages of both conventional and synthetic oils have greatly improved over the years. I still prefer a good synthetic and regular oil changes.

[garyd1961]

If it was well maintained it should be a good one to rebuild but back in the day a 100,000 miles was something to brag about.

[Ziegelsteinfaust]

Originally Posted by Thealien

1970s engines were manufactured with technology from 50 years ago. Machining tolerances were not as good as they are today. If the carb is not tuned correctly and you can be lean (run hot) or rich (gas wash cylinders). I believe these things contributed to earlier engines not lasting as long as their modern counterparts. Just my humble opinion.

EFI and better machining and materials has improved the life span of modern engines.

The worst offender is oil. All those contribute, but long term would make drivabilty pretty difficult.

Plus also long points of sitting, and cold starts. Do the most wear. As when a engine is warm, and dialed in. The wear pretty much stops.

I had a few very low mileage late 60's engines, and they were worn out by 120k.

I have built a few 60's vintage engines that made it to past 200k, and a fairly presicion 307. That was reputed to make it to 275K. It was a for a friend who installed cell towers, and he drove the wheels off it. He gave it to me after pulling it out to put in his hot 350 after a change in careers. When i pulled it apart it was worn, but still had acceptable cranking compression. Along with reasonable ring wear, and ridge. I put it back together for kicks, and gave it to my friend who's 350 was dying. He got a few years before it was to worn out.

It was to long ago in the 50's that engines were worn by 75,000.
The 30's and roughly 40,000 a engine was worn.
In the area of 1900-1920 roughly. A engine needed a valve job, at 4000 miles. A oil engineer put graphite oil in his Dusenberg if i remember correctly. He was at 15,000 miles with out needing major repairs as of yet.

Not to deny manufacturing technology, and material quality. But I don't believe rebuilder series garbage is wholly better then 1960's stuff

[b454rat]

Changing the oil when supposed to helps tremendously. I was stationed in Canada, drove a 78 Malibu for bout 6-8 months, can't exactly remember anymore. But it had a 400 in that I got from a buddy when his junkyard was open. It was tired then. Think it was a 72 or 74, was so bad I needed vise grips to get the lifters out. I put in a new cam/lifters, timing chain, high volume oil pump, rebuild 883 heads and some intake that was on the car when I got it. Inside was disgusting. I don't think the oil was ever changed. I drove it 5 hours each way, from Ottawa to lower NYS by the PA border. Only reason I pulled it was for a 454 I built for the car. It still ran great before I pulled it. I needed the crank for another 400 I built, and it was virtually spotless on the inside. IMO, its maintenance and a proper tune to make em last. If it's dumping fuel, then your washing the pistons/bores of oil, also thinning the oil. I had a Tahoe with 257k on it, and would still lite the tires up putting ur foot into it. I have another one now with 203k and runs great. I need to change the oil but holds 25lbs or so hot at idle. Over 50 going down the road.

[BigRandy]

I vote "NO." Not if they are kept clean and tuned.

My 77 Silverado had a mild cam swap at 36,000 miles, headers, a B&M shift kit and would still lite up the tires when I sold it in '87 with 168,000 miles. Other than the cam swap the engine was never opened, but I was a fanatic about 3000 mile Castrol GTX oil changes. I replaced a valve cover gasket at around 110K and remember the inside was the color of honey. I'm sure that made a big difference.

Toward the end of my ownership it would puff some blue smoke at startup after sitting for a few days but that was it. Oil pressure was still good and,to the best of my recollection, only used maybe a quart between changes. I figured most of that was from the valve guides.

I've got a 74 C10 with a 454 that has 112,000 on it and I can stand a nickel on the air cleaner at idle. Oil pressure is 50 on the highway and it doesn't smoke - ever. I don't know if the engine had any major work done before I got it so that 112K may not be a fair yardstick.

I'll give lots of credit to the FI and ignition systems in late model cars for easily reaching 200K and beyond.

[Ziegelsteinfaust]

Originally Posted by b454rat

Changing the oil when supposed to helps tremendously. I was stationed in Canada, drove a 78 Malibu for bout 6-8 months, can't exactly remember anymore. But it had a 400 in that I got from a buddy when his junkyard was open. It was tired then. Think it was a 72 or 74, was so bad I needed vise grips to get the lifters out. I put in a new cam/lifters, timing chain, high volume oil pump, rebuild 883 heads and some intake that was on the car when I got it. Inside was disgusting. I don't think the oil was ever changed. I drove it 5 hours each way, from Ottawa to lower NYS by the PA border. Only reason I pulled it was for a 454 I built for the car. It still ran great before I pulled it. I needed the crank for another 400 I built, and it was virtually spotless on the inside. IMO, its maintenance and a proper tune to make em last. If it's dumping fuel, then your washing the pistons/bores of oil, also thinning the oil. I had a Tahoe with 257k on it, and would still lite the tires up putting ur foot into it. I have another one now with 203k and runs great. I need to change the oil but holds 25lbs or so hot at idle. Over 50 going down the road.

Stationed in Canada?

From the story you were to late for the Vietnam draft by 4 years atleast.

[b454rat]

I was stationed in Ottawa 97 to 99. US Navy, they didn't have a base there, was called Personnel Exchange Program. They got some of us, we got some of them. It was a good time, wish i did more, but oh well...

[LS short box]

Another thing to consider is how the vehicle is or was driven. Mostly highway driving at 60 mph will wear less on an engine than lots of stop and go in city.

[b454rat]

I remember back in the day reading the classifieds in the paper, 95K "highway miles" lol. If a vehicle had 100k on it was junk, with that many miles beat to death. Now hardly hear of anything with that low a miles. I will say my 96 Yukon only has 68k...

[twinsemi]

I can post with some authority on this, having been a Chevy-Olds dealer mechanic back in the day. (1979-1980) Also worked at an engine rebuilding shop back then, too. There were two weak points that Chevy built into the SBC by the late seventies. The first was that they had cheapened the build by using cast rather than forged crankshafts. The second was that they didn't do a very good job on the EGR. Cylinder heads (speaking about valve seats on #8) were a major failure point in the day.

[twinsemi]

And I forgot to add that nobody has yet chimed in on synthetic oil. Biggest change in the lifetime of engines in my lifetime. Because if you weren't running it, everytime you either delayed changing the oil after 3K mi or simply floored it, you were killing the engine. so if you are asking about some generic engine from back in the day, you have to assume the worst, namely it's toast after 100K.

And if you say that it's tolerances and metallurgy, well, I saw engines from the fifties hit 500K. They were single owner and maintained as carefully as a Swiss watch. For our modern times, and for my money, the one game changer has been the oil. Pop Science back in the sixties, did an article about a Ford VP of engineering who was curious about synthetics. He took delivery of a brand new '65 Lincoln. He broke it in on regular oil for 5K, changed to Amsoil (the only game in town at the time) and drove it for 100k miles. He did not do even one oil change. he changed the filters every 5k and topped up the oil as required. He took his family on all sorts of car vacations in addition to his daily commute. After two years and 100K miles he had the Ford engineers tear the engine down and inspect every detail for signs of wear. Their measurements showed nothing out of original specifications. They could still see the cross hatch on the cylinder walls.

[ctandc]

Didn't see this mentioned........

Bearing materials and design were greatly improved by the middle late 60's.

Oil - sure - tons of improvement.

Tooling improvements (engine parts castings) played a part too. A lot less likely to see so much variance in blocks / heads / cranks etc...

But one thing to consider is whether or not the engine in question came with hardened valve seats designed for unleaded gas. If memory serves, GM started using them in the early 70's. Running unleaded in the old engines without hardened seats will cause a ton of wear.

Me personally? Why overthink it? You can do this and that, research this or that....or you could run a compression check and a leakdown test on the engine and know for sure. Odds are most 30 year old small blocks will suffer more from leakage issues (rear main, dried out valve seals, gaskets etc) than anything else.