The Stovebolt Site Forums The Shop Area Engine Shop Is the 1971 250 chevy engine a good engine??

It is in a 1936 Plymouth coupe.

If it has the intake not molded into the head it probably is a good dependable engine if mechanically sound. The later 250 with the integral intake/head combo, not so much.

That series of Chevy inline sixes began production as a 194 cubic inch in the Chevy II compact cars, around 1962 or 63, I believe. The displacement went up to 230, and then 250. The 292 is a "raised block" variant that was used in medium duty trucks. All the engines have 7 main bearings and thinwall castings for weight reduction, and they share the same bellhousing bolt pattern as Chevy V8's. A lot of internal parts are shared with V8 engines, or at least they have a similar design, such as stamped steel rocker arms on individual studs and ball pivots. 307 V8 flat top pistons are a drop-in fit in a 250, replacing the dish top types to get a little compression boost. High mileage 250's have a tendency to wear the #1 cylinder more than the others, sometimes requiring that one to be sleeved on a rebuild instead of boring the whole engine to a large oversize.
Jerry

That's a good question to ponder.

The 250 came out in 1966 and was phased out in the mid to late 80's. As Martin mentioned, the 250 with integral head had issues (cracking etc.). This head design came out about 1975 so the good Chevrolet 250 years are 1966 to 1974. But wait, if you are not happy with engines fitted with equipment to meet EPA, then the years can be shortened to 1966 to 1971. That's 6 years (inclusive) to chose from.

The 250 was one of the 3rd generation I6 engines so it received improvements such as modern hydraulic lifters, newer design rocker arms, spin-on oil filter, and etc. From the aspect of improvements over pervious generations, the 1966 to 1971 250 engines are "GOOD".

The 250 fits well in a narrow engine bay. So for previous generations of cars and trucks that came out with I6 engines, the 250 is "GOOD".

The 250 is designed for torque for hauling, farm work and construction etc. so it is a "GOOD" engine for a working truck.

So why did GM stop making the 250 if everything is so good? The design simply can't be retrofitted/upgraded cost effectively to meet federal emissions and MPG mandates.
That's not good and it's bit sad for us I6 lovers.

Comic relief:

But all is not lost. Jerry (Hot Rod Lincoln) is working up an Atlas I6 conversion kit for AD trucks.
Unfortunately GM pulled the production plug on this I6 generation (2003 to 2009) as well. That is "BAD".

I found a Plymouth listing I thought it said it had a Chevy 250 in it. Now I am not so sure. I did not say the listing and have spent the last 2 hrs trying to find it.

There was a 251 cubic inch Chrysler Corp. flathead six from 1942-1968. Somebody might have been referring to that engine as a "250".
Jerry

This has me 🤔 I have a "70s" 250 in my Suburban. I have often contemplated its value/suitability. I need to double check the casting numbers to see exactly what I have. Good or bad??

It's sad but a lot of them are being replaced by V8s so their value is cheap.

Jerry, instead of an Atlas I6 to AD conversion kit or a 216/235/261 FrankenSix, why not design and build MPFI heads for our I6 engines for $200 each?
Ran out of Pixie dust?

I am sure they listed it as a chevy 250 but at my age who knows what I remember for sure. And they could be mistaken. I thought it strange that they would switch to a chevy because the Mopar is supposed to be reliable.

Like the old chicken nugget commercial used to claim, "Parts is parts!" Individual bits and pieces don't know, or care which engine they happen to get installed into, as long as they fit and work. I'm tinkering with ideas like running pistons for a Ford 223 six in a 235, and adapting 265 Chevy V8 pistons to a 261. Both of those conversions inviolve doing machine shop operations no commercial engine machinist would attempt- - -they're just too time consuming! Being a 76 year old geezer with a bunch of machine tools has its advantages, especially since I don't have to pay rent on the shop they're in! Once I get a prototype of some of these machinists' nightmares running, I'll gladly share the details of construction with anyone dumb or crazy enough to try to build one!
Jerry

Jerry at 76, we are counting on you to keep the ball rolling.
Please allow me to be the first to ask.
After you re-stroke that 261 to 300 CI, will a 400 CFM AFB run good on it like Jon's old Furd?

Probably, but I'm keeping the carburetion a closely held secret for now! There's only going to be one carb- - - - -or maybe three- - - -haven't made a decision yet! That 12 port Furd cylinder head has a lot more going for it, airflow-wise!
LOL!
Jerry

Well just drill holes in that Furd head and bolt it on.
We want to hear that AFB inhaling like a tornado.
How about FSCF (FrankenSixCheviFurd).
If it gets airborne, you can call it:
Found Somewhere Completely Flaming.

I need to stop before I get the moderator slap.

The really tricky project I'm contemplating is grafting a dual overhead camshaft P.T. Cruiser cylinder head onto a Model A Ford engine block. That one ought to raise a few eyebrows on a run stand at an antique car show!
Jerry

Jerry, you have told me that multiple carbs are superfluous many many times.

No, I've said that dual carbs on a stovebolt are lipstick on a pig. If multiple carbs are sized properly for the engine and balanced correctly they can provide a small, but measureable power gain. About 99.999% of stovebolters don't have the technical knowledge or test equipment necessary to make that happen.
Jerry