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250 l6 potential

I'm going to aim for 200+ HP, if possible, with Vortec EFI and all. But with the right parts, I don't see why not, the 4.3 V6 makes what, 230 now? I know my brothers 93 Rodeo with the 3.2 V6 made over 220, stock(-ish) with an exhaust and intake. I think I can make it powerful and driveable and efficient at the same time. At any rate, the 81 will become my do it all vehicle when that day comes.
 
What about turbo's? Manufacturers are putting them on more and more cars nowadays, at least in Europe they are, but how about a turbo'd 250 six with 5-speed manual? THAT'S unique.
 
original balzer said:
Factory horsepower numbers are useless in this discussion. These guys are taking about "building" one, I doubt any of these guys would rebuild it stock.
Another thing to consiter is the years they where used where NOT a good era for HP or efficiancy. I dont have a book handy but I do know my 79 gmc with a 400 small block was only rated at something low like 140HP. My point is they wasnt even trying to make decent power in the 70's and 80's. At least not until the last of the 80's. Not to mention the sales of differnt engines would determine how much R&D a family of engines got. Im sure V8 powered trucks FAR out sold I6 powered trucks.
That brings me to a question about the thinking of the people who packaged trucks. "Why do they offer striped down no frills work trucks with LOWER power engines?"
wouldnt it make more sence to give the "work" trucks more power?

Simply put the market didnt demand improvments to these engines. I think if someone was willing to take the time to do it right the rewards would be just what he or she expected. I personally wouldnt bother with a 250 might as well start with the big boy and build a 292. One built correctly should make exellent torque. Torque would help a vehicle maintain speed, the easier it is for the engine to do that the less fuel it should burn, in theory. Real world results as we all know will tell a differnt story.

Here is how I would build a 292, bore it to a 305, 12:1 pistons a custom ground cam to support LPG, a custom long tube intake with close to equil lenth runners, and I would have to do some research on heads or head work. And finally a good header. I would run this engine on LPG only rather than any sort of dual fuel set up.
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Thank you! :bow:

3 on the tree said:
Personally, I like the 250 better. It will rev, unlike the 92.

In my 70 K5, the 250 goes up a 12K foot pass in high gear, even if its only 35-40 mph.

A pretty good source for mild hop up parts is Mercury Marine. They used the 250 in quite a few inboard applications, and rated them around 165 HP.
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Yeah, but rev to what? My truck rarely saw more than 3500rpm. A 292 will do that and more. And again, in stock form it's choked by a 1bbl carb. Read Leo Santucci's book. His 292s rev and then some...but that's totally useless in a truck.

noJeepshere said:
What about turbo's? Manufacturers are putting them on more and more cars nowadays, at least in Europe they are, but how about a turbo'd 250 six with 5-speed manual? THAT'S unique.
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I'm 1 step ahead of you. I found a guy selling Chevy L6 turbo exhaust manifolds on eBay several months back. I'm deciding whether to stay 700R4 or 5sp if/when I do the 292 swap.
 
Yea :mad: now throw a turbo at me butt wad. With the LPG and a turbo it would be simply amazing. Unfortunaltly I dont know much about turbos or forced induction period. I do know austrailia has force fed LPG engines down, and make crazy HP and MPG figures. I think it takes even more calculations to force feed a engine built to run on LPG. Basic LPG systems are pretty simple and makes it just like fuel injection. LPG also likes higher compression and doent need the octane that a simularly built gasoline engine would.
 
Factory numbers are not useless.

You've got to figure that the stripped down engines of the time were built to the max possible *at the time*, for the purpose. That means that an 8 or a 6 would be encumbered by the same restrictions outside of the physical characteristics of the engine. If you don't start with a common baseline (such as being stock) then you are being unrealistic in your finished product. Heck, build one that makes 50HP and call it an improvement if you want, only person that needs to be happy is you.

Lack of investment in development I believe. If they were still carbed in '88, it was already planned to be going away.

I like my Oldsmobile, but if I was smart I'd dump the Olds motor and put a Chev in there, since they are cheaper and have better aftermarket support. But for some reason I'm going to stick with the Olds motor. Same thing with building an L6 I suppose, if you want to, do it. Just be realistic about the potential.
 
3 on the tree,

I think comparing automotive or, SAE net HP, to a marine product's horsepower is "apples to oranges".

In the early seventies auto manufacturers started rating their engines at the flywheel, with all accessories operating and with stock intake and exhaust systems.

In the mid eighties outboard manufacturers started rating their engines at the propeller shaft instead of the flywheel.

How does the Mercruiser division of Mercury Marine rate the horsepower on the sterndrives?
 
As far as MPG's a 292 will out do a 350 anyday. My grandpa bought a new K20 in 74 and another one in 76 {it was a 73} both were 292/4spds with 4.56's and they were easier on fuel as farm trucks than the K20 with 350's he had that had 4.10's. So IMO for trail used they would also be easier on fuel.
 
I have to argue. In no way shape or form, was factory engines built to the max possible. At least not in the 70's and 80's. I belive they was trying to get the HP as low as possible. Take the change in how they rated HP from the rear tires early on to the flywheel later. small blocks putting out 330hp at the wheels compaired to 140hp at the flywheel? Thats a$$ backwards! plain and simple. They where shooting for low power numbers to make cars use more gas and raise the gas prices.

I dont know what the "stock" rated HP was for the 1960 chevy c10 with a 327 thats sitting in my yard. What I can tell you is it is stock and original. AND that big ole heavy truck will flat out smoke any (stock) 70's or 80's truck i have owned, hell im not too sure my 97 would out run it in a drag race. The point is that 1960 had WAY more power than a 70's or 80's truck regaurdless of how you measure it. The 70's and 80's where cripled from the factory.

On the other hand I understand what your saying by using stock numbers as a baseline, but do you know anyone that uses a flywheel dyno? Are you talking about a 1960 something 350 v8 or a 1980 something 350 v8? Because tthose 2 engines are going to have totaly differnt HP both stock rated, and actual output.

If you want a baseline you need to find a bone stock zero mile engine and put it in a simular vehicle as your project and run it on a dyno. Then build your engine the way you want and dyno it the same way.

However a chevy 350 small block for example has been built a million times and its fairly easy to estimate the power output based on the modifications you do to it.

I still say stock numbers are useless in this discussion.
Even modern stock numbers are less than their potential. Just a few minor mods to basicaly any stock engine will net you HP gains.
 
Wasatch K5 said:
3 on the tree,

I think comparing automotive or, SAE net HP, to a marine product's horsepower is "apples to oranges".

In the early seventies auto manufacturers started rating their engines at the flywheel, with all accessories operating and with stock intake and exhaust systems.

In the mid eighties outboard manufacturers started rating their engines at the propeller shaft instead of the flywheel.

How does the Mercruiser division of Mercury Marine rate the horsepower on the sterndrives?
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I don't know how Mecr Marine rates their engines. I guarantee that their 165 horse 250 is more powerful than my 140 horse 250. Back in the EARLY 70's, the big three kinda cheated on their horsepower ratings. NO accessories, jacked up timing, and sometimes even a vacuum hooked to the exhaust to help scavenging.
 
I don't really have much to add... except that our '05 Trailblazer with the 4.2 gets the exact same gas mileage as my '98 S10 blazer with the 4.3...:dunno:
 
My big question now, with the inline 6, is what ratio would be best suited to a SWB truck with 33's or 35's along with a 250, 465, 208 setup. I'd think more of using 4.10's to get the best mileage out of that setup.

Keep in mind, this is what I'd like to have in a SWB, as I'd like to have the best of both worlds in fuel economy and an '81 to '87 SWB truck.

So what ratio? 3.73, 4.10 or 4.56? I'd like to see something that can get over 20 mpg. with the 250 stock motor.
 
Fellas,

I'm pretty new to the CK5 forums and it's generally not good form for a newbie to pi** everybody off.

As such, I humbly suggest you Google something like "SAE horsepower rating".

SAE for Frat boys stands for "Sigma Alpha Epsilon", but in this context SAE stands for "Society of Automotive Engineers". They're the body that sets the standards by which horsepower is measured.

You can learn about SAE "Gross" horsepower which was pre 1972, SAE "Net" horsepower which was the change they adopted for the 1972 model year, as well as more recent changes.

3 on the tree, I don't necessarily disagree. A number of years ago I had a Mercruiser "454 Magnum" engine. It was rated at 365 HP. The standard 454 was called the "7.4" and was rated at 330 HP. The Magnum was an expensive option...a little over $3,000.00 but was indeed a High Performance engine with all the "goodies": four bolt mains, forged crank, forged pistons, more aggressive cam,
better heads, etc. The 7.4 was a more "vanilla" engine.

It ran well. It sounded great, it was a fun boat. But I don't know how they rate their horsepower.

I can say that I did many "speed tests" in that boat with the engine at full throttle for extended periods of time and adjusting the outdrive's trim to get the maximum speed. I have never held a car's accelerator pedal to the floor for anywhere close to as long. My gut tells me that a marine cam is for higher RPM use than a typical automotive cam, or especially an RV cam.
 
thatK30guy said:
My big question now, with the inline 6, is what ratio would be best suited to a SWB truck with 33's or 35's along with a 250, 465, 208 setup. I'd think more of using 4.10's to get the best mileage out of that setup.

Keep in mind, this is what I'd like to have in a SWB, as I'd like to have the best of both worlds in fuel economy and an '81 to '87 SWB truck.

So what ratio? 3.73, 4.10 or 4.56? I'd like to see something that can get over 20 mpg. with the 250 stock motor.
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x2...

I'm like you, I'm seeing the whole truck as a system, so I want the engine (including stuff like the cam) to match my gearing and tire size.

Horsepower is irrelevant. Just a number determined by torque and RPM. I want the truck to pull well on the road without lugging along, with a little in reserve for passing. Beyond that, the 85mph speedo is fine, since I don't plan to exceed that.
 
The more I think about getting a truck like this, the more I think about running propane and fuel injection.

Man! Such a setup should see at least 25 mpg., if not better, you would think.
 
original balzer said:
I have to argue. In no way shape or form, was factory engines built to the max possible. At least not in the 70's and 80's. I belive they was trying to get the HP as low as possible. Take the change in how they rated HP from the rear tires early on to the flywheel later. small blocks putting out 330hp at the wheels compaired to 140hp at the flywheel? Thats a$$ backwards! plain and simple. They where shooting for low power numbers to make cars use more gas and raise the gas prices.
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That sounds like paranoia grounded in a misunderstanding of how things were rated. Gross vs. net HP/TQ is easy...no accessories vs accessories, more inline with what you actually get when it's installed in the car. Confusing that they changed it, but moreso because regulations forced reduction in output at roughly the same time, making it LOOK like the engines lost a lot. It had nothing to do with intentionally using more gas. The impressive thing is that manufacturers are now exceeding the old gross numbers on smaller displacement engines!

As I said, factory numbers were the best possible FOR THE TIME. That means any engine built was handicapped to the same extent, and in actuality the smaller engines were probably less handicapped based on their (typically) lighter duty applications, such as heavy duty emissions trucks. I understand smaller engines were used as well of course.

If you can't call dyno tested factory numbers baselines, I'm not sure what you would call them.

The real problem is that almost no one (manufacturers or others AFAIK) dyno's engines under 2000RPM for the most part, so good luck trying to compare low end torque.
 
jonrpick said:
x2...

I'm like you, I'm seeing the whole truck as a system, so I want the engine (including stuff like the cam) to match my gearing and tire size.

Horsepower is irrelevant. Just a number determined by torque and RPM. I want the truck to pull well on the road without lugging along, with a little in reserve for passing. Beyond that, the 85mph speedo is fine, since I don't plan to exceed that.
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I think that turbo'd under propane with 10-1 compression you should want about 2250 rpm in high at 65 mph. Or maybe a little more rpm say 2500. That should be the sweet spot for fuel economy. Use a well ported iron head and this setup should be easy to build and bulletproof when done.
 
smalltruckbigcid said:
I think that turbo'd under propane with 10-1 compression you should want about 2250 rpm in high at 65 mph. Or maybe a little more rpm say 2500. That should be the sweet spot for fuel economy. Use a well ported iron head and this setup should be easy to build and bulletproof when done.
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I'm not planning to use propane, as this would go in my DD. LPG would have to be cheap enough compared to gas to go the same mileage for less money to make it worthwhile to me.

I know that according to most RPM calculators, the more cylinders you have, the lower an RPM you can run at a given speed. But AFAIK, no consideration is given for the power output at a specific RPM.

I'm shooting for more like 2000rpm at 65. In order to turn 2500rpm at 65mph, I'd have to run *very* low gears with my 31" tires. 4.88's would still only put me at 2407rpm.

This is of course, in OD (.7 ratio).

It would pull like crazy though! :haha:
 
Build it torquey and gear it like a V8, you should pull some pretty good mpg's with that, just expect to go slow if you tow anything. Heck, a Blazer was never intended as a tow rig, though, right?
 
Call it whatever you like. When Im building an engine I dont realy care about stock power numbers. Plain and simple. You want to dig up 15-20 year old data more power to you. But as I said before These engines where neglected and didnt get much in the form of RESEARCH AND DEVELOPMENT. The 250 I6 was basicaly the same from 1950's through to the 80's No matter what they rated the power at.

Now lets stop argueing about stock numbers and distracting this threads original purpose, witch is the POTENTIAL of 250 I6, NOT outdated power ratings for them stock.

As with any engine the max potential is not as important as the potential you need in your intended purpose.
What I mean is your not going to build a top fuel drag racing engine for your daily driver. You need to target your prefered RPM range and build to the max possible power within that range.

NOW our trucks are usually large heavy 4x4's so keeping the power down low in the RPM's is what you should be shooting for. For instance 500 HP is not going to do you any good if it comes at 5000 RPMs and you never get over 3500 RPMs. Shooting for a specific power isnt feasable either. You need to focus on the max power at the RPM range you use most.

NOW heres where it gets complicated. The GEARING in the rest of your drivetrain can change the RPM range you use.
For example take a toyota with dual x-case's with low gear sets and low gears in the diffs. Lets just put out a crazy crawl ratio of 400 to 1. To go at a walking speed you now have to run the engine at higher rpm. If thats the speed and RPM you prefer then sure build it to make the most power at 5000+ RPM.
BUT since we are also talking about fuel milage when you drive that on the street your going to be out of the engines prefered RPM range, so it makes sence to build the engine for the RPM range you USE the most.

High RPM engines are going to struggle at low RPMs, think of it as lugging your engine. Economy does not mean low power, it comes from moving your truck at the rate you want (speed) in the RPM range of the engine that is easiest for that engine to do. ALL this time I been using horse power numbers, but torque is the number you want to look for. The more torque you have in the RPM range you use the most is going to be the key.
 
did not read the hole 6 pages but skimed,
There is a guy at our local mud hole with a k20 I6 dont know how built not much i dont think and that thig is an animal buzzes the **** out of it and runs the mud all day never has a problem makes you think twice about a big or a small block espically when they are the ones with hoods up.
just for ****s i got a 67 firebird sprint overhead cam I6 preaty rare but it was a factoy hipo car and made 215 hp stock came with a 4 barrel quadrajet and split exhaust manifold, I street raced it and beet alot of stock small blocks.And i still have it first car i ever owned
 
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