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250 l6 potential

blazin_blazer

blazin_blazer

1/2 ton status
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with all the tech and advancements in engine components, they claim its easy to get a hp per cubic inch of displacement w/the 350-454v8, can the 250 l6 be built reasonablly to produce 250hp?

how much hp/torque can you expect from the 250 6 w/cam,headers,intake&carb?

anyone have any links to l6 buildups?

and does anyone know what this engine weighs or where i can find the factory specs for this motor? supossed to be an 80 model.
 
The link I was looking at while back was saying that a fully dressed 250 I-6 was 100lbs lighter then a dress 350. I recently picked up a 250 I-6 shortblock (oil pan, block, crank, pistons) by myself to get it out of the back of my truck and into my sideyard storage area. I am a big person but I could lift it. I guess it weighed about 250lbs.

250's and 292's can be made to have a healthy amount of power. They are not known as huge HP motors but they are torquey as heck, and with even normal mods should be able to approach 1hp/CID I would think. There are guys that are running wicked fast 1/4 mile times with turboed & supered I-6's.

Harley
 
250's rock. I had one in an '81 SWB and it got 18 mpg on the highways.
 
I know you can repeatedly run them out of oil (until they start clacking and make NO power), and they will always survive. I remember seeing an article about a tubbed nova with a 250 inline six, so it must have been at least a little bit healthy.
 
I have built a few inlines. It is fairly easy to get 1 Hp per CID. But the more you modify them the more gas they suck. I have found it is cheaper in the long run to build a 350. A built 250 with 4 barrel carb, intake , headers and cam, 9 to 1 compresion ratio is going to get about the same MPG as a mild build 350.
I have always wanted to fuel inject a older inline and see what they could do. A stock GM TBi out of a 4.3L would be pretty sweet on a 250 6.

If you want to build a inline here is a good link for parts and tech help.
http://www.cliffordperformance.net/
 
I am planning on putting a 250 I-6 in my buggy project I am planning. I am just planning the basic upgrades to it to get some good lowend grunt but I have the crazy idea to try and put a little forced induction on it but I don't know if I will or not.

Here is a vid of a Brazilian Opala with worked inlines. It runs a 9.4/qtr. They said the orange one has run down to 8.9 before. Apparently they are quite popular with the Brazilian drag racers.

http://www.youtube.com/watch?v=fS55f7HIh9U

Harley
 
Why?

The 350 small block Chevy is lighter, and more importantly there are a gazillion performance parts made for it. Not only that, but they (performance parts) are less expensive for a small block Chevy than for any other application (that I'm aware of).

Is it possible to make a 250 I-6 more powerful? Sure, but it will cost you considerably more and have less power than a 350 with the same dollar investment.

Again, why?
 
Wasatch K5 said:
Why?

The 350 small block Chevy is lighter, and more importantly there are a gazillion performance parts made for it. Not only that, but they (performance parts) are less expensive for a small block Chevy than for any other application (that I'm aware of).

Is it possible to make a 250 I-6 more powerful? Sure, but it will cost you considerably more and have less power than a 350 with the same dollar investment.

Again, why?
Click to expand...

The figures I've seen all said the L6 was lighter than the SBC...

Some guys (myself included) think they're cool motors. I'm planning a 292 buildup at some point. The idea of building a torquey little beast with under 300 cubes is cool to me.

Horsepower is not everything.

blazin_blazer, check into the forums on inliners.org. It's about the only place to get the straight info on these motors. I've been spending time there lately, not posting, just reading.

BTW, there's a company that makes new heads for the Ford inlines. They're working up a new head (finally!!!) for the Chevy Sixes. It'll be a true 12-port head, making things like MPFI much more viable for this motor. Oh, it's an aluminum head. :woot: :saweet: :pimp:
 
Oh yeah... from what I'm reading, the Offy intakes are better for low-end torque whereas the Clifford stuff is geared more toward higher-RPM horsepower (ie: nothing you'd want out of a truck motor). Check out the Offenhauser products.
 
I have more experience with the Toyota 2F engine, as used in the FJ-40 Land Cruisers, than the Chevy I-6.

Many, many FJ-40 owners have pulled their 2F (or the previous version, the 1F) engines in favor of a small block Chevy. The small block Chevy's are about 200 lbs lighter than the stock Toyota I-6 engines. I really doubt that Chevy's cast iron 250 or 292 engines weigh 300 lbs more than the Toyota cast iron sixes.

Certainly, to each, his own. If that's your desire-go for it. I should not "Rain on your parade" so to speak.

The 1978 FJ-40 I bought had a seized 2F, which was perfect for my use. It now has an LS-1 Corvette engine hooked up to a NV-4500.
 
Wasatch K5 said:
I have more experience with the Toyota 2F engine, as used in the FJ-40 Land Cruisers, than the Chevy I-6.

Many, many FJ-40 owners have pulled their 2F (or the previous version, the 1F) engines in favor of a small block Chevy. The small block Chevy's are about 200 lbs lighter than the stock Toyota I-6 engines. I really doubt that Chevy's cast iron 250 or 292 engines weigh 300 lbs more than the Toyota cast iron sixes.

Certainly, to each, his own. If that's your desire-go for it. I should not "Rain on your parade" so to speak.

The 1978 FJ-40 I bought had a seized 2F, which was perfect for my use. It now has an LS-1 Corvette engine hooked up to a NV-4500.
Click to expand...

I'm fascinated with the idea of doing more with less, which is one reason I like the sixes... The 292 Chevy is especially interesting, since no body seems to understand it.

I predict better pulling power and fuel economy than I had with my stock 305.
 
Why?

The 350 small block Chevy is lighter, and more importantly there are a gazillion performance parts made for it. Not only that, but they (performance parts) are less expensive for a small block Chevy than for any other application (that I'm aware of).

Is it possible to make a 250 I-6 more powerful? Sure, but it will cost you considerably more and have less power than a 350 with the same dollar investment.

Again, why?
Click to expand...

X2
Altho Ihave built inlines to perform very well. I spent a bunch of money on them and ended up with an engine that performed like a V8 SBC or SBF and got worse or at best the same fuel milage.
Look at the in line 6 jeep used for so many years. Even with modern MPFI system they got no better fuel milage in a smaller lighter Jeep. Than a full size Blazer with a TBI 350.
 
Thunder said:
X2
Altho Ihave built inlines to perform very well. I spent a bunch of money on them and ended up with an engine that performed like a V8 SBC or SBF and got worse or at best the same fuel milage.
Look at the in line 6 jeep used for so many years. Even with modern MPFI system they got no better fuel milage in a smaller lighter Jeep. Than a full size Blazer with a TBI 350.
Click to expand...

I'm still pretty confident that a L6 built for the application will do as well as a V8 of similar displacement (comparing a 292 L6 to a 305 V8).


Actually, I'm kind of betting the 292 would do it better than the 305.
 
A 292 will make a lot more torque down low than a 305. But I doubt if it will match it in fuel economy. They are known as notorious gas hogs. I had one in and old work truck with a utillity bed. Even with the stock 1 barrel carb it only got 14 MPG if you drove it easy.

The last 6 I built was a 300cid in a Bronco. 4 barrel manifold. Holley 390 cfm carb,
headers, low end cam, dual exhaust, mallory ign, It got 14-15 MPG. When it was stock it only got 17-18 highway. Which is aprox the milage I get in my 350 TBI Blazer on the highway. But to be fair my k5 is injected with OD. The bronco was carbed with a non Od C4 trans. Both have 33" tires Bronco had 3.40 gears. k5 has 3.73.
 
I'm planning on a 292 swap into my 81 K5 here in a few years. With a longer stroke then a 454, it has lots-o-potential for torque. I want to adapt a vortec system off of a 4.3l V6 to make it run. I figure with the FI on there, and a 5 speed OD tranny, I should get above 20 mpg's on the highway. Heck, my Yukon get's about 18-19 on the highway, and it weighs a lot more then my 81.

The straight six is definately lighter then the V8. I made the mistake of swapping the 250 origianally in my 81 with a 350, and have been disappointed. The six was lighter, made much more torque, and was unstoppable. I have a grocery list of ways I tried to kill it. The front end of my Jimmy sits about a half inch lower with the V8 in it. That old six was a reliable motor, this 350 has been nothing but trouble.

Besides, I want to do something different. Last I recall, no one has a Chevy Blazer with a FI 292 with A/C running a 5 speed tranny and a soft top. But that's just me.
 
Thunder said:
A 292 will make a lot more torque down low than a 305. But I doubt if it will match it in fuel economy. They are known as notorious gas hogs. I had one in and old work truck with a utillity bed. Even with the stock 1 barrel carb it only got 14 MPG if you drove it easy.
Click to expand...

Yeah, but smaller isn't always better. That 1bbl carb goes from gas-saving to gas-guzzling when the motor stops breathing. The carb isn't the only thing. That head is also a restriction.

292's also came in 3/4 trucks which are usually work trucks, often with utility bodies (heavier).

I'm looking at it this way: If the 292 has less displacement and yet makes more torque at the given RPM, then it's either A) burning way more fuel, or B) making much more efficient use of it's displacement.

I think it's both, although more of "B". It can definitely be made more efficient through better fuel management (EFI) and a better intake design (see my earlier comment about the new aluminum head coming out).
 
I've actually been doing research on this exact thing. I'd like to swap out my 6.2 diesel for an inline 6. I'm kinda torn on which to get though, the 250 or 292. I'm leaning toward the 250 since it seems to get better mpg and with some small upgrades can be as torquey as the 292.

My main reasoning for this is the unavailablility of diesel in my area and the price of it. I paid $4.49 a gal the other day.

I'm looking into converting it to tbi using the system from an s10 and should get about the same mileage as with the diesel with my od trans.
 
So what are the numbers for the 305 and the I6? I'd compare 350 as well because by all accounts, 305's and 350's end up getting the same mileage in these trucks. We already know the 6's don't do as well as you'd expect in mileage based on their displacement, which means they AREN'T efficient. I suspect you'll be pretty surprised at the 305 low end torque. Not sure if all were, I suspect yes, but the truck 305's were all 9.2:1 compression ratio, so if looking at another vehicle 305 just for comparison, make sure compression is the same.

I see the mention of the AL head, but looking at Clifford, their rebuilt head is over $1000. You can do a V8 with Vortecs for less than that! On that note, the cylinder heads appear to have the same problem Oldsmobile does...outdated chamber design that doesn't perform as well as modern stuff, and that will ALWAYS be a hindrance to the motor. If whoever is making it is smart, the new head will have updated combustion chamber design, but when Edelbrock made their Oldsmobile stuff, they ignored technology in favor of the cool factor of aluminum.

In any case, if a rebuilt stock cast iron 6 cylinder head is over $1000, I can't imagine a new, aftermarket AL head is going to be cheaper.

There is something to be said about doing things differently, but unless it's a show truck, being different doesn't mean it makes sense, at least to me. If you could get V8 torque down low (heck, V8 all around power) with mid 20's mileage, I'd be all about it, but that's just not the case.
 
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