Turbocharging a 250

[Anonymous]

Would it be possible to turbocharge a 250 with the intake log head? Im thinking maybe adapting a 4 bbl carb if possible or a 2 bbl carb if it is not possible. Custom make a header. Get a garret TO4B turbo, a wastegate, an intercooler and custom make all the piping as well. The stock compression ratio would work i believe. Would bigger valves need to be adapted to the head? Do you think this is possible to achieve or not? How would gas mileage and driveability be affected? A stock C4 and 2.78 rear gears would be used.

 

[CobraSix]

Anything is possible...just matters how much money it takes.

it is possible to adapt a turbo to a log head. Personally, I would consider a EFI system to work with the Turbo, else you have a lot of carb tuning to do.

Not sure how drivability on the Log will be effected, but generally, Turbo cars are just as fuel efficient as non turbo cars, so long as you stay off the gas and drive the car like it is non-turbo. Turbos are good for that, since they don't have parasitic drag like a Supercharger. Case and point, my Volvo is a 5 cylinder turbo, 250 HP. The same car came with a non-turbo, 160HP version with the same engine. If you compare the numbers, the mileage is exactly the same.

Slade

 

[Anonymous]

It is very easy to turbocharge a 250 log head engine. That is exactly what I am doing to the 250 in my '66 coupe, using a turbo setup from a late 70's turbocharged Buick 231 engine. The block is in the shop right now, but tonight I can post pics of my turbo setup, and show you how to tie it into the stock cast iron exhaust manifold.

The GM unit uses a 4-bbl quadrajet in a draw-thru mode, is completely devoid of electronics (you can even use your original ignition system), and is pretuned and prejetted for a similar sized engine. These units are very cheap - I paid $45 for the complete setup, as the GM turbo guys all migrated to EFI to make big hp numbers. I'll get you some websites, too.

Any turbo likes to be torque loaded, so your trans and rear gears are a good starting point. OTOH, I wouldn't claim that your fuel mileage will go up with such a setup, but if you stay out of the loud pedal, it won't go down much, either.

To start with, I wouldn't change a thing on a runnning engine. If it is tore down for rebuild then bigger valves will give you a bit more power potential, but I urge first-timers to stick with stock engine internals until their system is running and fully sorted out. THEN is the time to start experimenting.

 

[Anonymous]

Stan,

What do you mean by "torque loaded"?

db

 

[XFlow_Fairlane]

I am with stan....build a solid bottom end (rod bolts and forged pistons) after that you can always swap heads and whatnot.

nick

 

[Anonymous]

Please post the pic's I'd love to see what the setup looks like with the stock exhaust(less money to spend on the setup). Those websites would s ure help cause my grandma has a chevy 250 which i could turbocharge as well in the future i mean when i have more money.
Let me see if i got you right. You said I shouldnt change a thing internally as long as the engine is working fine. So there's no need to reinforce the bottom end or is there?

Thanks for all the feedback.

 

[Anonymous]

What do you mean by "torque loaded"?

Technically, "torque loaded" means that the boost is growing faster than RPM is increasing as an engine accelerates. That's a good thing. If on the other hand you run out of gear before reaching max boost, then your turbo can't ever run as efficiently as it should be able to.

Overgearing is a common problem with guys new to turbocharging. They come from a normally aspirated racing background, where steep gearing to get an engine to accelerate as quickly as possible is a key to success. In tatao's case, a C4 with 2.73 gears will allow the turbo to stay on full boost and highly reactive to throttle position throughout the RPM range.

Hope this helps...

 

[66Sprint6]

Ok,
Im doin a blow through on a 66 six banger with a Holley 2300 perched high atop it. What should I do as far a fuel sending. I am NOT going to do draw through and am holding out on efi till I can get some more $$$$$. Should I build a pressurized enclosure for the carb, or just go for a bonnet. Also, what about fuel sending unit etc. I need to know guys!
Matt

 

[Anonymous]

what about a centrifugal turbo/blower ?

 

[Anonymous]

Okay, here are the photos I had in mind. This first one shows a Ford 223 I-6 with a turbocharger. The photo is reversed so that it looks like a 200 or 250, but the idea is the same. Hook a "J-Pipe" between the exhaust manifold and the turbo, and you are in business.

These next photos show some of Ak Miller's Ford 200 and 300 engines with blow-thru and draw-thru turbos. I don't have detailed instructions about how to build this, but any reasoanably clever mechanic should be able to work out the details.

<img height="387" src="http://home.earthlink.net/~rps1976/Images/Turbo/Ak-Blow-Through-2.jpg" width="623" border="0">

And finally, here is a photo of the Buick 231 Turbo I am using.

Hope this helps!
The first website I had in mind is http://www.hotrod.com/techarticles/42798/
Be sure to read through it for its many subtle clues to what really works for turbocharged engines. There are more, but that should get you started.

 

[Anonymous]

Im thinking of a blow through setup like the one in the second picture. Which is better, blow thorough or suck through? How big of a difference does it make to have an intercooler in a blow thorough setup? Wouldn't the stock exhaust manifold be too restrictive and slow down the exhaust gasses too much?

 

[sefus]

a gn set up wont really work because it had no electronics. ie: special mechanical fuel pump.

you dont need to intercool although it boosts performance, but you will run plenty cool without it. a good carb bonnet is the best idea as you eill need to tune quite a bit and tuning in an inclosure is a biotch.

 

[66Sprint6]

awesome, I can do the carb bonnet, but the enclosure would suuuuuck.
Matt

 

[Anonymous]

What is a carb bonnet?

 

[Anonymous]

Tatao,

Before I proceed much further, I wish to emphasize to you that a log head engine is not an ideal candidate for turbocharging, for reasons enumerated here and elsewhere. I am turbocharging mine to create a unique and fun car to drive -- that's all. I'll share what I know, have read, and am guessing at with the proviso that any persons modifying these engines from stock are doing so at their own risk and are completely responsible for what happens.

That having been said, let me get to your questions. From what you ask, I am guessing that you are new to turbocharging. If that is so, I can not over-emphasize the need to educate yourself somewhat before proceeding, especially if this car is your daily driver. You need to get and read Corky Bell's book Maximum Boost. There are other turbocharging books out there, but Bell's book is aimed particularly at the DIY, budget minded shade tree mechanic working on old technology engines.

I think that a draw-thru system (suck through) is the way to go for one of these old engines. With a draw-thru system you don't have any electronics to worry about, no fuel pump issues, no hats, bonets, or carby enclosures to design, fabricate and troubleshoot. No return lines to the fuel tank. No expensive specialty carbs to buy. No intercooler to buy and install. A draw-thru also gives a nearly perfect fuel air distribution to each cylinder, because the compressor blades are mixing the fuel and air together at 60,000 to 100,000 revolutions per minute. Think of it as the ultimate blender...

You just have to provide oil to it (usually from a "T" at the oil pressure sender) and an oil drain-back line to the sump (see my top photo above). Rig your fuel line and throttle linkage, along with an air intake system and exhaust and you are nearly ready to go.

Now, it is true that we have restrictive intake and exhaust logs. But they are probably good for half a bar of boost. My aim is a 50% increase in power and torque from my system, and I think that's totally feasible.

Here's another website for you (http://www.flash.net/~rjgeorge/tnotes.htm) This guy is the guru of these old pre-electronics GM turbo units, and between his website and the many links he offers, you can get a pretty good education on first-generation turbo systems.

Cheers!

 

[Anonymous]

I had never thought about the suck-through setup that way, but it does make perfect sense. A question I have is, in a blow through the compressed air( more than 14.7 psi) gets to the carb where it provides the necessary amount of fuel for a good mixture.
Correct me if I'm wrong but in a suck through the air going into the carb and turbo is at standard atmospheric pressure along with the mixture for such air (14 .7 psi)so the fuel mixed into the air would be less than the one mixed into compressed air or not?
If that is true wouldn't the mixture end up being lean after the air is compressed? Or would it be a good mixture since air is constantly being sucked into the turbo before it gets compressed so the ratio would end up being the same eventhough the air has been compressed? Sounds kind of confusing, hope you understand what I'm saying.

 

[Anonymous]

BTW, a carb hat and a carb bonnet are the same thing. See the thing that sits on top of the carb in my second photo above? That's a hat/bonnet.

A blow-thru setup can achieve proper mixing of the fuel and air, but it generally takes more effort, unless you start with a carb designed for the application. These are available, but are fairly rare and are usually quite expensive. Tuning them is also generally considered more challenging than it is with draw-thru's.

You are correct that a draw-thru provides a consistent a/f mixture across the RPM range, just as they do in a normally aspirated application. It is normal to jet their secondary circuits a couple of jet sizes richer, though, to preclude top end lean-out. This ease of tuning is another factor that makes them attractive for older engines.

 

[Anonymous]

I found this site:
http://www.grapeaperacing.com/GrapeApeR ... bocams.cfm

It's got information about turbocharging. I did all the math for a 250 with a 5500 redline, assuming 80°F outside air temp. and 10 psi of boost. The result was a 37% increase. How would you go about getting a 50% increase. Another question I have is if it is dangerous no to cool down the compressed air or can these engines take the hot air. You can see the outlet temp. doing the math and tell me if the engine can handle air going in at those temperatures. How much of a difference percentage-wise would a intercooled setup have over a non-intercooled setup. Would water injection help cool things down?

 

[61Futura]

http://cgi.ebay.com/ebaymotors/ws/eBayI ... egory=6137

Here's a nice donor car for the turbo

 

[addo]

Huh?

Because we sell our cars at wholesale prices and we do not charge a dealer service fee, all sales will be charged $150.00 for fees that are incurred for expenses to complete the sale. This fee is necessary so that we can continue to sell wholesale to you.

Donor schmonor! It's a nice enough "relic" as is...