High Mileage on 350??

[Hawker7]

I’m building my truck on a budget and don’t know what to do about the motor. It is a 350 with 124,000 miles and the one time I started it up it ran and idled smooth with no smoke. Anyone know if 124k is a lot of miles for a 350, or if there is anything I should consider doing to it to make sure it is reliable? I planned on just pulling it and replacing the gaskets on valve cover, oil pan, timing cover, etc.

[grayw0lf]

Originally Posted by Hawker7

I’m building my truck on a budget and don’t know what to do about the motor. It is a 350 with 124,000 miles and the one time I started it up it ran and idled smooth with no smoke. Anyone know if 124k is a lot of miles for a 350, or if there is anything I should consider doing to it to make sure it is reliable? I planned on just pulling it and replacing the gaskets on valve cover, oil pan, timing cover, etc.

I wouldn't think that 124k is a lot for a 350. Unless it came from a 1 ton that was constantly pulling a heavy trailer, I wouldn't worry about it.

Most late model V8's in small trucks are all getting over 200k, easy.

[El Jay]

I'd do what you are planning and run it until it dies, then do a rebuild.

[steelhorse]

A lot of new trucks get 200k plus on their motors with little cyl wear if properly maintained.A fuel injected motor will outlast a carbed one due to fuel wash.I say drive till dead repair/repeat

[chevguy7]

Mine has about 145k on it and I am going to wait until it dies. Other than a small tune up I'm basically ignoring it during my build.

[BlueJeep]

One of my last trucks (1990 TBI 350 3/4 ton 4wd) had 280K before it needed to be replaced. It seemed to have a good amount of power until about 260K, and then it started to show signs of power dropping off.

My last Suburban had 210K when I got rid of it, and I had just returned from a trip from Iowa to Utah and back pulling my Jeep on a trailer (7K total weight). No sign of any lost power at that mileage.

[Hawker7]

Anything I should check when I have it somewhat apart? Any gaskets that should be addressed besides the valves covers, oil, and timing cover?

[68gmsee]

You didn't say if it's the original 350 (year?) but if it is, and has never been rebuilt, you've got a good engine. Most engines of that era didn't last much past 50k, 60K without some problem like worn cam, timing chain, valves, rings or lifters. The engines being made now will last way past 100k, but not then. I think it has to do with the metal alloys being used now.

I'd say do a compression check and make sure all the cylinders are within specs.

Give it a good tune up: timing, spark plugs, distributor cap and rotor, plug wires, filters,etc.)

Replace all the gaskets and seals that you can like oil pan, valve covers and change the oil.

And, as mentioned above, drive it until it won't go...

[Longhorn Man]

you guys are comparing apples to oranges.
Tyhe late model engines, starting around 87, started being built to go hundreds of thousands of miles... the old stuff, in all reality, was made to last A hundred thousand miles.
If you want to do it and do it right (do it once) then pull it, and have it looked at. At a minimum, you'll want to do a cam, T-chain, oil pump, and most naturally, bearings. More likely than not, you'll be getting an overbore and new pistons, a valve job and resurface on the heads. (complete rebuild)
If your plans include lotsa miles, you may want to look into a late model 5.7 block. That roller cam alone will double, if not tripple the life of your engine if treated right.

[68 50th]

In 97 or so I bought a 88 3/4 ton 350/TH700 from the original owner.
It had over 480,000 miles on the clock at that time, it was the original engine in it and it only had a valve job done to it at around 300,000 miles. It ran just perfect but I sold it whitin a year or so. It was very well maintained, the first owner was a newspaper distributor company. Here's a pic of the truck.

[Hawker7]

yes, forgot to mention it is out of my 72 C-10 and is original.

[N2TRUX]

Like Andy said, there is a BIG difference between the early 350's and the 87 and newer motors. Not only did they build them to better standards, the addition of fuel injection makes a huge difference in longevity.

One of the problems with older carb motors is the carbs have a tendency to run rich as the become older. That extra fuel dumped raw in the cylinders washes the oil away and promotes cylinder wear.

As suggested, if she's running good, pull the pan and valve covers. If it all looks clean reseal it and run it till she dies.

[jef5150]

Originally Posted by Hawker7

I planned on just pulling it and replacing the gaskets on valve cover, oil pan, timing cover, etc.

Originally Posted by Hawker7

Anything I should check when I have it somewhat apart? Any gaskets that should be addressed besides the valves covers, oil, and timing cover?

While you have it out, you(someone) should replace the rear main seal.


jeff

[68gmsee]

Originally Posted by Hawker7

I’m building my truck on a budget and don’t know what to do about the motor. It is a 350 with 124,000 miles and the one time I started it up it ran and idled smooth with no smoke....

All of the above responses are correct. But in my humble opinion, the gentleman is on a budget and if the engine is within specs and running smooth, I wouldn't necessarily tear into it. It may go for a few more years with a little tender care and no unnecessary stress like heavy towing, racing, etc...

[C10-Driver]

I have 175K on the 350 in my 1990 Chev. Had to do the valve seals recently but it still runs great and has tons of power. If it ain't broke, don't fix it???

[grayw0lf]

My next door neighbor has over 350k on the 4.3v6 in his S-10. It obviously smokes a bit, but runs great.

[PanelDeland]

My $0.02 .If it runs good and you're on a budget,pull it,gasket it ,paint it and tune it.While you are running it til it dies,buy a junkyard core and a smallblock rebuild book.Start tearing it down and planning/building the replacement you really want.As time/funds allow buy/build that engine.When it's done you can swap as needed.The bst thing about doing it this way is that you get to drive the truck until you can plan a weekend for the swap.It's really hard to get pumped up about a project you can't drive, and more so when you're waiting on fundage.This makes even more sense if it's your DD.

[Gray Ghost]

Originally Posted by Longhorn Man

you guys are comparing apples to oranges.
Tyhe late model engines, starting around 87, started being built to go hundreds of thousands of miles... the old stuff, in all reality, was made to last A hundred thousand miles.
If you want to do it and do it right (do it once) then pull it, and have it looked at. At a minimum, you'll want to do a cam, T-chain, oil pump, and most naturally, bearings. More likely than not, you'll be getting an overbore and new pistons, a valve job and resurface on the heads. (complete rebuild)
If your plans include lotsa miles, you may want to look into a late model 5.7 block. That roller cam alone will double, if not tripple the life of your engine if treated right.

Andy's right on this one....I had 124 on the clock when the motor went south and from my experience that was a lot of miles. Newer motors are lasting over twice that with no problems. Our S-10 4 banger has over 240k on it!

[Southpa]

I've checked the numbers on my motor. ie. suffix code stamp and embossing on pass. side, both tell me the block is a 1970, so I can assume original motor. Since I've owned the truck (13.5 yrs now) I've put 164,000 miles down. The odometer read 000,598 when I bought it and I've watched it zero out again and then some. I've literally taken this truck to hell and back (well, almost literally ) I've run it w/ a bad rad for a while and watched temps exceed 260 deg. F Its been continuously driven on some of the roughest logging roads and has hauled some of the heaviest loads and has never run better.

I have yet to do any major engine work. Compression test back in 2001 averaged 155 lbs all around. I have a slightly used Competition cam to go in and asked my mechanic buddy about putting it in. He asked me, "Is your truck broken and/or not running right?" I said, "no" and his response was, "then why mess with it? Wait 'til it dies or stops working within your needs". The truck has never run better and I can assume 364,000 miles on the clock.

I'm pretty sure the compression is a result of a good buildup of carbon. But a well-maintained engine should last a long time. I've replaced valve seals a couple times and do regular oil changes. I live in a moderately mild climate (Vancouver Island) and temps rarely go below freezing so I've been using 20W50 oil. This is an original Van. Is. truck, even better than a California truck because paint doesn't fade as fast.

[ChevLoRay]

I decided to go with a crate motor, because my block has been built once and has at least 213K miles on it. It could be 313K because I just don't know for sure. It was used to tow a 26-ft camper and whatever else may have been asked of it.

I weighed the costs of doing a proper rebuild, with the possiblities of a bore meaning new pistons, etc. Being sure the total package would be reliable and still money-smart lead me to the decision I made. Luckily, I have found a new crate 350, still wrapped and palletized, for $1K. Yeah, it's a bargain, but I'd still do it for more money. Machine work and parts could easily run $800. The new engine has a warranty, the rebuilt one would not.

[mrein3]

I respectfully disagree with those who say tear into it and rebuild it.

At 124k you probably need a timing chain. If you have no record of it ever being replaced, now is a really good time to do it. Since you are planning on replacing the timing chain cover gasket, you should plan on doing the chain too.

How long an engine lasts is DIRECTLY related to how you maintain it. If you keep the oil fresh, keep it in tune, and don't constantly and consistantly buzz it to high R's, 124k is nothing.

New gaskets, new chain, spend your hard earned cash on other items in your restore.

One more thing, change the front oil seal in the timing chain cover. If you have a groove in your harmonic balancer - which you probably do, this can leak. You have 3 options to stay ahead of this potential leak.
1. Buy a new balancer and replace the oil seal with a stock replacement one.
2. Buy an offset seal and replace the stock one - use your current balancer.
3. Buy a sleeve that you whack over the snout of your current balancer.
I have done all three of these and all three options work.

[72 CustomCamper]

My dad's 84 truck has about 350,000 on a 350 we rebuilt in our basement...


Chuck

[Hawker7]

Since I'm on a limited budget I can't afford to rebuild, but can devote my time to pulling the motor and cleaning everything up on the motor itself, and the engine bay. I want to replace all the seals as I don't want anything leaking and making a mess of my driveway, or the engine bay that I'm cleaning. Since this will not be a DD, I will probably only put a few thousands miles on a year, and hope to have the motor last for some time.

[72 CustomCamper]

Letting them sit for long periods is what dries out seals...


Chuck