Supercharger OR Turbo

[thachevythang]

Well I'm kinda torn between the two. I like the the sound of a turbo and the looks you can get with some on a classic, then, I like the looks of a hot rod under the hood! I'm looking for which ever is going to be a more street friendly build and one that will be driven! Not daily driver type. I just don't believe in a trailer queen! An every Sunday cruiser and maybe the occasional road trip once a year.

Ease of install has to be the supercharger. A Turbo set up is out of my skill level to build but I wouldn't mind paying a little extra for install etc.

Turbos I'm still reading on and like the rear mount idea. I would have to switch to efi or get a blow through carb and run some serious piping for it all. It doesn't look PURDY how I like but the powers there.

Here's the end all be all question for me: Which one requires more mods to the engine block itself? I've read about blower motors with just a stock block and small amount of boost and there you go! Horsepower out of the box! I'd like to run it on a stock block first (if possible) to get familiar with the install, parts, build, etc. then build one specifically for whichever application.

I've got a 305 I would like to put out of its misery. Maybe not a good canidate but it's just to get familiar with the build. I'm wanting to build a 383 for the specific set up over time.

[Irish_Alley]

I had a 04 impala with 3.8 supercharged that thing would hall. No lag it was right there if you wanted more boost you just change the pulley. With a turbo I wouldn’t run it on a stock engine unless you kept the boost down but that’s like having a stingray and never taking her past 60 what’s the point except just to say yeah I got one of those

[K20Wulf]

Centrifugal supercharger all the way http://www.procharger.com/tech.shtml

[thachevythang]

I thought it would be a more heated debate, but were talking about an american classic truck not imports so not really suprised.

Reading here and there I've read that with a blower motor you want to have a lower compression. I was also suprised to read that 305's are popular with hot rodders for that reason. That aside the 305 is just for the purpose of getting it built and me getting familiar with the set up before I build the 383. I'm still learning the trade. I've done 4 rebuilds and by no means an expert. I still have some questions of course.

I found kits for 383's and really didn't know there were so many different combos with the rods, crank, etc. I just thought it was a bored over 350 and call it a day!

Whats the preferred method to build a blown 383?

What about the heads? I like the vortec heads but I'm sure even they will be restricting. Curious because I've seen the Blower kits with vortec style intakes.

The 4-7 and 2-3 cam swaps, will they really make for a smoother running engine and prolong the life of the crank?

Any help appreciated, OR maybe a good book reference!!!

 

[Captkaos]

As far as building motors for a Blower vs Turbo, there is not difference.  Both provide added piston volumes (boost) above normally aspirated.  For that matter, motors built for use with Nitrous would be the same.
The difference between them are HOW the provide the boost.  Blowers run off the crankshaft and power is associated with rpm directly, boost is increased linearly.  Turbo's run off the exhaust so it is related to exhaust flow (indirectly associated with rpm), it can go from 0 boost to 15 in a matter of seconds and since the turbo is feeding the engine more air, more air feeds the turbo.
An 8lb boost pulley on a Blown motor is set to 8lbs as the max given RPM, 8lbs of boost on a turbo is just were the limit is set before boost is bled off before going to the engine.
So, if you want more boost out of a blower you have to change pulleys, if you want more out of a turbo you flip a switch.

Building an engine for supercharger applications require a strong bottomend (crank, rods and pistons) due to the extra forces added to the combustion chamber.  It doesn't matter if you use a 150 ci 4 cylinder or a 500ci top fuel dragster, the engine must be built handle these pressures, for a SBC you are talking forged crank, pistons and a good set of rods.  

If you don't intend to go over 5-7lbs, you can pretty much drop one on a stock bottom end if you can control your foot, but the problem is you won't be able to, and stuff will break quickly with boost.  In addition to all of this, you are going to have to upgrade your fuel delivery system as more air (a lot more) is going to require more fuel.  If you are running a carb, it needs to be setup to handle the boost (Haulin is doing it this way)  If you are running EFI, you need bigger injectors and abiblity to tune the ECM for optimum fuel/air ratio...  etc etc...

With that building an engine isn't done by picking parts you think are good and mashing up an engine.  You need to define with yourself what the end result is going to produce and design accordingly and all part needs to meet this design.  The cam design (valvetrain for that matter), piston design (compression) etc is specific.  What works fine on a NA motor won't work on a boosted motor...

BTW there is no way I would waste time on boosting a 305, unless it was something I was just playing with.  In general, 305's have MORE compression than a comparable 350..... unless you put open chamber heads on it.

[1979C20]

Turbo chargers are FREE ENERGY. It reuses the exhaust gas to perform boost, and takes no added energy to operate. Blowers use crank rotation, putting more strain on the engine and require a lit of  power to operate. lowering mpg. I say go with turbos, but thats because ive been thinking about turboing my truck since I bought it.

Also, turbos are less common on older muscle vehicles. Everyone has a blower. Why not make it your own?

[thachevythang]

I'm looking into one of the weiand mini blowers. I think the only difference between the two are ones a little slimmer for hood clearance. I don't want to go an all out dragster and it suck to cruise in, or use nitrous and have to get a refill! I know if I go big I'm going to get myself in trouble. Had to get rid of 2 bikes for that reason.

Thanks for all the points Capt. Don't worry the 305 is only for mock assembly and getting the major components before building the block for the specifics as you pointed out.

1979C20: I've got a buddy that has turbos on his cutlass. You can't tell he has them until he gets on it and then he gets crazy looks. He built it with the cheap ebay turbos for mock up, then rebuilt them with a quality name brand kit and its been about 4yrs without any problems. Either way you always have exhaust and always have rotation of the crank. I just think the blower looks better under the hood unless you have one of those sweet looking nelson engines. I'd be setting turbos up rear mount style to save on parts up front. Though turbos on a rat rod style truck would be 1 in a billion!

[BLOWN BB]

Go with blower !!

[thachevythang]

Just found a used 142 set up today for 1000!!! Going to see it running and if it's worth it!

[klaussk]

I was always raised in the notion that superchargers are ten times better. So I'm a little bias here. Ill give a nice twin turbo setups props but id never build one outside of a high boost drag only car. For a daily driver I vote supercharger.

[thachevythang]

Well it wasn't the mini blower! It was a dual carb set-up on a big block. Got the word through somebody elses hearsay. He's just getting rid of the supercharger to give the car to his son. A pretty nice chevelle with a 502 but TOO big for what I'm looking for. Lucky kid!!!

[REVINKEVIN]

I have also been reading up on this. I really like the STS rear mount turbos. These kits sound real cool. They also put the extra weight of the power adder in the rear instead of more on the nose. You will see better fuel economy with this kit as well.   The air intake temp will also be lower.   Are you going to convert to EFI or go with a blower carb setup?  All this gets real expensive very quick. The truth is there is only so much power these trucks can put to the ground. The cheapest way to go would be is build a stout 355 bottom end, 180+cc aluminum heads, and the roots blower. Look at the Edelbrock supercharged crate motor for ideas. It makes like 507hp or so. In one of these trucks, that is a good street "fun" motor. My truck has an AFR headed 406 that should be around those numbers. It has no problem smoking my 315/35/20's. I have started collecting the data for my EFI rear mount turbo motor that I am starting this year. It is going to cost me around $11,000 in just parts. With the combo I am planning, 650rwhp should be achievable. 2 days ago I rode in my friends 754rwhp 2003 Cobra. Wheel spin was crazy with drag radials, but so much fun!  it is not really a good idea to start with the 305. Save your money for a little bit and get a good 350 block and go from there. You can pick a good one up for a few hundred dollars and start collecting on your forged lower end. Good heads go a long way in making power. Spend your money wisely here. My 1970 Z28 has a 408 with 210 AFR heads and my 1986 Silverado has a 406 with AFR 195's. These heads are built well from the start and I don't think you will be disappointed. Good luck and have some fun with your life. Horsepower is the true meaning of life my son.

[ehjorten]

I say small roots type blower on your 305 is the way to start based on your lack of experience and fabrication skills.  You basically get yourself a bolt-on kit with low-boost without much needed in the way of engine mods.  From everything that you have said in this thread I think a turbo setup is out of your league for now.  A turbo is going to be more efficient due to it using some of the wasted heat energy that is exiting the exhaust ports, but a crank-driven supercharger has more or less instantaneous boost.

Without trying to sound arrogant or anything like that...anybody that thinks installing a turbo at the very back of their exhaust system and then piping it all the way back to the engine just doesn't understand how a turbo works!  Will it make boost?  Sure, but be prepared for massive turbo lag and any weight distribution you might get from the turbo in the back is going to be offset by the extra weight you add in to pipe it all back to the front.  Also...poor flowing heads aren't as big of a deal on forced induction as they are on a N/A engine.  The increased pressure is there to help force more air through the ports.

I think your 305 would be just fine to start tinkering and playing with to learn more about forced induction.  I would start with the blower because it is going to cost you less and takes way less fabrication than a turbo setup, which is basically a custom fab situation for your rig.

[1979C20]

If the pipe coming off the turbo is air tight, you wont see much lag. The only advantage to running a rear mount turbo system is so you dont need an intercooler. To each their own.

[ehjorten]

The fact of the matter is that the real advantage of the STS turbo installation is that it is a quicker install with less fabrication time and expense.  Turbo's are designed to utilize the heat energy of the exhaust gas, and that energy makes up about 38% of the energy released by the IC engine.  The ideal available energy which can be used to drive the turbocharger comes from the blow-down engery transfer which takes place when the exhaust valve opens and the gas expands down to atmospheric pressure.  As the hot exhaust gases cool down they start to lose energy and volume.  It is true that lag due to length of air intake piping is minimal, but lag from length of exhaust pipe from the ports to the turbine inlet is real!  It can be minimized by reducing the polar moment of interia of the turbine wheel and/or reducing the mass.  The most effective method is by reducing the diameter of the turbine.  Small changes in diameter will considerably reduce the polar moment of inertia, thus increasing the acceleration.  Using two small turbochargers instead of one large one for a V-banked engine for example goes someway towards reducing turbo lag.

I have built a few turbocharged engines in my life and lots of N/A engines.  600-700 RWHP aren't a lie, but you don't need to turbocharge to get there.  That level of HP needs to be compared to the displacement of the engine.  It isn't that impressive if it is a BBC, but is very impressive if it is a small displacement 4-cylinder for example.