The Stovebolt Site Forums The Shop Area Engine Shop 250 Six: Limitations ?

General question about the 250 six cylinder:

What are its limitations, down-falls, Achilles'Heel ?

IF & when they "blow-up", what goes ?

Have been running my 1972 C-10 w/ 250 & 3 sp for two years now, and am fairly impressed with the 250. Now has 101,000 miles and still going strong.

Just had to run to Valley Forge yesterday to pick up some lawn furniture, which the wife ordered on-line from "Restoration Hardware", about 120 miles / 2 hours from home.
We were on a tight schedule, so I had my foot to the wood most of the way down; while not confessing to "exceeding the posted speed limit", I will say that the engine was taching between 3,500 & 4,000 RPM for most of that two hour trip.
Drove almost as fast on the way home.

No excessive oil consumption, no knocks or valve taps; no driveline vibrations @ speed ( )...
The girl "just seemed to take it".

Long-term ideas for the truck include engine re-build, front suspension overhaul, and better cab-mount repair.

Am thinking about "building" the 250, perhaps going headers & duals, cam, and small 4-barrel, some porting & polishing.

Since my truck feels like it has around 3.73 gearing, this engine is going to continue to operate in the 3,500-4,000 rpm range when the truck is on the highway.

Is this a "time-bomb", or are the 230 / 250 engines "happy" in this RPM band?
(I know this is too much to ask from a stock 235)

When a 250 blows-up, what goes? Thrown rods, spun bearings, what?
(Most engines seem to have a "typical" flaw that finally takes 'em out....)

I really don't want to drop a V-8 into this truck...I'd rather soup the 250 a little, or just rebuild bone stock.

But also want to know if I should limit my cruising speed to 55 for the engine's sake...I know how "John Law" feels about that question!

(Am specifically considering the 250 six from '66 - '72; not going to fool with any "smog motors" or the "integral intake" version.)

Thanks,

Frank McMullen

Cracked head, around the head bolt in the front of the engine, is the only recurring problem I'm aware of... I'm not sure if this is related to the later year engines, or all.

None of the straight sixes like high RPMs, but "high" is a subjective term...

-Boyo

Frank
Downfall of the 250 is the head and manifolds. Prone to cracking, especially on the front corner, that's why the specs for torquing the head was changed for the one bolt. I've ran a few of the 250's, most went over 150,000 miles with one head rebuild, and little oil use. Usually the rest of the vehicle was worn out before the engine. I would get Leo Santucci's book on the Inline Chevy Six, it's a good reference on what to do and not to do. Available at amazon, B&N, and other places.

Santucci's book is a must if you want to build a 194/230/250/292. Another good source of info is the Inliners web site.

Well, I know this is heresy, but if you are going to drive the thing a bunch, and want a bit more power plus reliability, etc, drop a Chevy V8 in. (duckin' and runnin' now, I am) 8-)

Seriously, you'll get more power, economy, and durability from a non-hot-rodded 350 than and over-worked 6.
And there are *plenty* of them out there. Plus it's an easy swap.... I've got a rusty 72 I'd give ya, but I'm too far away for it to be worth it. 8-(

Cheers!
George
53 3600 - being restored
72 GMC 1500 - headed to the recycler

Frank 54,

The limitations are not to the 250, but to all L6, and I can see only the high RPM. I'd rather have the earlier models with the manifolds separeted from the head, and I've seen also the cracking head stuff. Although down here it's not so common. I've also been using a 250 as a daily driver, in a light car called Opala and it's with me for a long long time. Swapped it a few months after almost 6 years of daily pounding and it was still alive.
Considering a mild cam, headders or split cast iron manifolds and a bigger carb (bigger a li'l, do not overdue it) will all make sense, but keep in mind that the 250 will feel somewhat unhappy above 4500/5000 at a continuos use. I see it as part of their nature,and it's not easy to try changing it.

George Grenley

You're stating what's just the clever thing to do. Yes the 350 is really a better option, but the L6 is a great design, and although smaller and waeker than the small V8, is so reliable, sweet and smooth that is just impossible to ignore. Maybe these are one of the reasons why everybody here loves them all so much.

Thanks guys!

I'll see if I can scare up a copy of Santucci's book.

This bow-tie is not my only daily driver, but when it does go out, it spends a lot of time on Interstate highways, so the ability to go at least 65 mph for extended is a must....

Frank McMullen

Frank, I've had a few of them over the years, when I was a teenager, ragged the S**T out of a couple of them and never had a problem. Have one now in an 81 1/2ton with 185,000 mile , runs like a top uses no oil, doesn't smoke has a little valve noise but thats it. The oil was changed regularly and it has hauled boats, trash, broken cars and travel trailers. Wouldn't hesatate to get on the road with it.
If you're worried about the rpm's at highway speed ,try and find a 3speed trans with O/D, it will bolt right in, it is the same size,but you have to find one that is a late model with the syncronized first gear, a saginaw I believe. Look for mid 60's thru mid 70's car, they are kind of rare but you can find them. Think I saw one in swap section couple weeks ago.It will look just like the one in your truck( 7 bolts on side cover) where shifter connects.
Good luck.