250 or 350
 

Background: I’ve got a 70 with a 250 3 speed. Engine runs well enough, but it could use a refresh (read: I just want to build an engine). Debating between rebuilding the 250, maybe hopping it up a little, or building a 350.

250 advantages are known “good” engine and it’s a little bit different.
350 advantages are, well, 2 cylinders and parts availability.

Any input?

Re: 250 or 350
 

I'm a big fan of the straight sixes. If it's all original I'd be inclined to keep it that way. If it's a "parts / pieces" truck I'd build a 350. All things equal, cheaper to build / more HP per $. Just my opinion.

Re: 250 or 350
 

I’m in the same boat. Motor is original and truck is in good shape but has been painted etc over the years. Not parts and pieces but not a period correct truck either!

Re: 250 or 350
 

You'll also need to change a bunch of stuff like perch locations and motor mounts for the 350. If it were me and I wanted to keep the truck, I'd put in the 350 because I like more power than the 250 is capable of producing without a lot of work and money thrown at it.

Re: 250 or 350
 

If you are on a budget, go 350. It is not cheap to rebuild a 6, especially if you're wanting to "hop" it up. I'm in the middle of that right now.

Re: 250 or 350
 

It will take deeper pockets to get 400+ HP out of a 6, but the attraction it brings at car shows and the neck snapping sound one makes is very different. Clifford is the 6 guru for performance parts https://www.cliffordperformance.net/

Re: 250 or 350
 

I'd throw the l6 in the trash heap and replace it with a proper V8.
...You asked.

Re: 250 or 350
 

Word.

Re: 250 or 350
 

I hope you're not referring to a 350 as a "proper" V8.

Yes, they are cheap, but they are so bland and common - if you want a 350, just go buy a mid '90's Chevy and drive it until the wheels fall off.

Build the six. If you want more than a 250 can offer, swap to a 292.

Re: 250 or 350
 

Depends on your budget really...

You can spend big dollars on a six and end up with maybe a head turner

What is the rest of the truck like?
Auto or manual?
Brakes? All Drum or Disk Drum?

Re: 250 or 350
 

Love 292's not so much 250's.

Was going to turbo a 292 until I found out how much it takes... then just decided BBC.

Re: 250 or 350
 

Smart man!

454 Mark V...just gotta keep it cool....

Re: 250 or 350
 

Truck is a long bed fleet side, 250 with a 3 speed. Floor shift to accommodate Flaming River tilt column and rack and pinion steering. Front disks, rear drum. Just a cruiser and weekend toy. Sometimes it has to earn its keep hauling a bit

Re: 250 or 350
 

If you want to keep the 3 speed or keep it manual...build yourself a sweet 292....

If you are open to a V8...there is only one choice in my mind...454 and a TH400...

Do the math...the dollars are so close to each other its scary...

Personal preference...:chevy::chevy::chevy:

Re: 250 or 350
 

If you want bragging rights, drop a V12 drive-line in it. Upgrade the fuel system to fuel injection and you will get better gas mileage than you are getting now.

Re: 250 or 350
 

I've built a couple of strong modified inlines over the years. The unique factor is pretty cool. The downsides: Expensive to make any real horsepower and an affordably modified 250 or 292 still pales in horsepower and fun factor to a cheaper mild 350.

Steve weim55 Colorado

Re: 250 or 350
 

What's cheaper about buying an engine that needs to be adapted (radiator, shroud, shift/clutch linkage, exhaust, fuel line) vs what's in it? Who said anything about wanting 400 hp or a big block? I would rebuild the 250 that would fill all your needs. It would be a better conversation piece w/speed equipment than just another 350.

Re: 250 or 350
 

^^^^What he said^^^^^

Re: 250 or 350
 

Special K, that’s kind of how I’m leaning. This isn’t gonna be a go fast truck. Keeping the 3 speed for now, if I came across a 4 speed relatively cheap, I’d probably make the swap. I do like the different factor of the inline.

Re: 250 or 350
 

Look for a Saginaw 4spd. They can be had way cheaper than a Muncie. That Sag 4spd will bolt right in. It would serve you well behind a 250 and be way cooler to drive.

Re: 250 or 350
 

I was building a couple L6 trucks because they are cool and I had no plans but to build a couple cruisers ,Then I fell into a great deal on a 4 bolt 350 that changed everything on one build , The "lowly" :lol:250 came out and was sold for $350.00 to a local guy for his 65 and he was happy to get it . The 350 led me down a different path for that truck with switching the manual cross member to the V8 one and then a lower drop for that truck and then a bunch of chrome to add some glitz and floor shift ...I still have 2-292's and a 250 for my other trucks and they'll get used on more stock style trucks like I had planned from the start.Build what makes you happy and fills your needs . :chevy:,

Re: 250 or 350
 

Input? Yeah. Could fill your screen several times over but won't bore you with a lot technical details.

Back in the day I rebuilt more of both for fleet service and various walk in customers than I care to remember. Saw heck of a lot more 250 over 200k miles than 350s.

A very simple and popular upgrade was the "590" Mercruiser marine cam. Clevite number '1959". Did that to my own monojet carbed 250 in my '69 long stepper. That, good tuning, along with a split header really wakes things up. Sounds good too. As opposed to single exhaust which tends to sound buzzy on the six.

Nostalgia. Inlines are having a resurgence in popularity. Taking my truck to shows a lot of guys will walk past a row of v8s just to look at my grimy old inline to talk old days. 'They last forever' and 'can't kill those things' are common comments. Inline are much easier to service in the vehicle too.

As for rebuilding. Part pricing has changed much in the last few years. 10-15 years ago you could find master rebuild kits for $189. Not anymore. In case you don't know. Master kit has everything. All bearings, pistons, rings, cam & lifters, gaskets, freeze plugs, etc.
Two common oversights I have seen with any engine, not just inline, are reusing old worn valve springs and not checking big end of the conn rods. Have not seen any with with miles on them which were not stretched somewhat.

With above said. V8 is definitely the way to go if you want to build power. Much cheaper and easier to get there. You need to sit down think budget and make a list of goals then decide which way to go.
Hope that helps. :mm:

Re: 250 or 350
 

What rear gear are you running in it right now? If you're thinking of spending money to change to a 4 speed, you should strongly consider looking for a 5 speed from an S10 to get the overdrive. I'm keeping my 3ott steering column, and I'm running a 3.73 out back, so to get overdrive, I bought a 3 speed tranny w/OD. Yeah, it's old school, but that's how I roll. My main point being, if you plan to cruise your truck down any interstates or freeways, that OD tranny will keep that 6 from buzzing you out of the cab. Just my $.02

Re: 250 or 350
 

OK 57Suburb, this is kinda hijacking the thread but, I'm just starting to look into the Saganaw 3 speed OD behind my 72 C20 3OTT 292 coil spring HO 52 4.57 rear end. Would really appreciate any info you have about doing this. How much longer is the trans? How did you mount the cable and the switch? Etc.. Pictures? Thanks in advance.

Re: 250 or 350
 

If you currently have a 7 bolt Saginaw in your truck now, then there is no difference in tranny length. What may be different is the spline count on the output shaft. In your case though , maybe not since your truck is a 72. Earlier models had different spline counts. Factory trucks with this tranny option mounted the engage cable with a bracket on the lower lip of the dash in line with the throttle pedal. They also mounted the switch below the throttle pedal, but I’ve seen some guys make a mount for the carburetor. My only advice for you would be to take your time and find a tranny that has all the components because spare parts for these are rare and expensive.