Okay, here's what I'm trying to do. I have a '69 Chevy C-10 1/2 ton short wheel base that I'm sort of hotrodding/restoring. I have a 454 hi-perf block that I got out of a '73 suburban with big oval port heads. I haven't researched to find out the valve/combustion chamber sizes. I will most likely use the OE castings because I just want good low end torque.

I want to use something like the Edelbrock Pro-Flo injection system with a towing type camshaft. I would also like to turbo this engine. That's where my question comes in. I konw to use ~8:1-8.5:1 compression, and forged internals. I would expect to run around 15psi boost to about double the hp output of the engine N/A.

I want this to be as reliable as a hot rod can be, meaning pump gas, daily driving "friendly", and longevity. What kinds of things would I expect to run into doing this project? I can't decide single or twin turbo, obviously single would be cheaper. Not sure on size either. An intercooler would be a must, for this, should I just get a custom fabbed one in front of the radiator? Something like the Banks intercoolers for their Cummins/Powerstroke upgrades? This won't be an actual daily driver, but I would like for it to be capable, the end idea is to have the truck tow my other show truck (383 powered S10). Maybe my goal is too farfetched and I'd be just as well off using the 454 by itself, but I just want that turbo! Guess it's because it's one of those hot things these days to have on any vehicle, but I just don't see many going on big blocks that aren't for the strip. Anyways, any help is appreciated.

Matt

rad, you can get good horsepower and driveablity from your combination. The key will be the fuel injection. Besides forged internals it would be very wise to upgrade the valves. It isn't necessary to increase valve sizes. If you have to enlarge a valve, make it the exhaust valve. You would be better off running twins. Two T4OB turbos would work very well for your engine size. An A/R of around .68 to .78 would yield a very drivable yet powerful street engine that could be used for towing. At 15 psi inter-cooling is a must. I don't know if a Cummins inter-cooler will work. I use Turbonetics or Precision inter-coolers for my turbo builds. I am working with a customer on a 632 twin turbo engine for a pro touring car. I have great expectations for this engine.

Thanks, I wasn't really saying I'd use that particular intercooler, just trying to throw an idear out there about what I was talking about with location. I know that the A/R has to do with the actual housing size of the compressor/turbine, but I really have not idea as to what is good/bad. Also, is a T04B what people commonly call a "Garrett T4" turbo? The only thing I've ever really known about sizing turbos is the Mitsubishi sizes (my girlfriend has a hopped up GS-T) and sizing used by HP Turbos (60mm, 66mm, 76mm and so on). The metric sized ones are based on the compressor wheel's diameter I believe. I just can't seem to find any articles that give good starting points for the turbo size to cubic inch ratio. Based on what I have heard, would something like two 47mm turbos be what you're talking about? I too would like the twins, but more for looks than performance .

454 are prone to detonate. 8.5:1 cr is good for a mild cam and pump gas without a turbo. You need to get the compression down to 7.0:1 if you plan on a turbo for a BBC.

I run the factory compression ratio (7.4:1) on my turbo Z car and use 13 to 15 psi of boost and use 93 octane.

FYI, 15 psi of turbo boost will double an engines output. A mild 350 hp/450 ftlb 454 engine would make 700hp/900 ftlb at 15 psi of boost with an intercooler and the correct air/fuel ratio.

You might want to look into a remote turbo system like the one from Squires (www.ststurbo.com). Remote systems work on slightly different principles than those mounted close to the manifold. Close to the manifold replies on port velocity and are more efficient as far as peak power is concerned. Remote mounts rely more on the pressure built up in the exhaust system and won't produce as much power. But if you only need 7-10 psi they are much easier to plumb. The STS site says they start at only 5 psi, but with "additional tuning and turbo upgrade" can make near 20 psi. They generally don't require an intercooler as the long compressed air tract cools the charge some, which isn't as hot in the first place. The only thing I don't like about them is the air filter under the vehicle. I'd make a metal shield to keep most dirt/trash out of direct contact if possible. A pair of small turbos on dual exhaust would easily supply 5-7 psi. Not doublt the HP, but a good kick in the pants nonetheless.

One of the best basic intro's to turbocharging can be found at http://en.wikipedia.org/wiki/Turbocharger. It's not a "how-to", just explains how/why everything works.

Don't think remote turbos are something new. Visit any USAF museum and take a good look at the WWII fighters and bombers. A B-17 used remote turbos. The outboard engines had about a 4' run of pipe to the turbos, the inboard runs around 10'. That's 6" ID pipe coming from a nine cylinder 1823 cubic inch radial. Of course it red-lined at around 3,500 rpm and "only" produced 1,200 hp @ 3,000 rpm even with the turbo (575-1000 w/o turbo, depending on model). I've never seen torque ratings on these monsters, but radials produce GOBS of torque at low rpm, so don't need to turn like a V or in-line engine. I've never seen any specs for how much boost these things used, but it can't be much -- likely around 5 psi. Main use forthe turbo wasn't to gain power per-se but to keep from losing it at high altitudes. P-38s also used turbo chargers, though most other planes using the Allison V-1710 used a single stage supercharger. But I'm digressing way to much...

The T04B is not a bad choice for a tow vehicle like you are building. You just have to be careful because the those turbos vary greatly in size. Some are as small as the large T03 on the compressor side. You can get a matched pair of those off of ebay for about $500 and be done with it. I also like the HX35 Holsets off of the 5.9 Dodge cummins. Those are widely available for about the same cash and they have built in wastegates which is a big plus. You want to make sure and get a matching set of turbines and not get an HY35 from the Automatic trucks. There are a couple of different turbine sizes out there on those turbos so just watch for it. There should be numbers cast in the turbine housing.

The cummins intercooler would work pretty well for what you are doing. It is large and would likely fit perfectly in front of your radiator.....perfectly being a relative term.

I also want to caution you that 15 psi WILL NOT double the power of the engine. You have to keep in mind that in the sweet spot the compressor is only going to be about 75-80% effcient. This means you can count on a little less than that for power increase.

I would also stay away from the edelbrock unless you are planning a new ECU. They dont understand boost talk

Chris

As long as the air temps remain close to ambient (good intercooler and well matched turbo) and if the fuel/ratio stays correct then 15psi will just about double the hp.

My engine pretty much doubled its output at 15 psi. 135hp non-turbo then 270hp with 15 psi. I measured the before and after hp figures with a G-tech meter and with actual 1/4 mile trap speeds from the local drag strip so I'm sure I'm not off that much. In any case, 15 psi is a bunch and tuning becomes very critical at high boost levels.

An old inliner Z engine is much less prone to detonate than a BBC, and I have all that I can handle with 7.4:1 cr, 15 psi of boost, and pump gas with this engine. That is why I think a 7.0:1 cr bbc would be a good idea for a 15 psi turbo application. Maybe 8:1 cr for 7 psi of boost.

From what I've read it would have to be a pretty amazing setup to be able to take the air back down to ambient (or even close) after passing through the turbo system. That would be almost 100% efficiency. Also keep in mind that generally, intercoolers that remove MORE heat have a size affect of less flow. This will all depend on the entrance and exit sizes/angles, and the design and size of the rows themselves.

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1997 BMW M3 - 3.2litre Inline 6 cylinder

About the only way to do it is with a chilled water intercooler. It can be brought down below ambient that way. However, that is a drag race only setup. You are still not going to be hard pressed to double the HP.


Chris

I just began reading about that type of intercooler. And as you said it is possible to run them at more than 100% efficiency but they are for serious race/marine use only.

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1997 BMW M3 - 3.2litre Inline 6 cylinder

Yep. If I ever get my truck back on the road I am planning to have one made for it. I have a guy that offered to make the intercooler for the price of parts and I already have the intercooler core.

Chris

I have never measured my inlet temps, but a friend of mine has an identical setup and can data log with his Haltec efi. And the temperatures on boost are very close to ambient on his car, within 5 or 10 degrees. In fact, the air temp drops when the boost comes up! Of course this is for only short time periods, one pull in 4th gear from 3000 to 6000rpm. We are both using IC's which are most likely too big for our little 168 cid engines which could have something to do with it.

I am a bit confused as to how that would be possible. Wouldn't something cooling as pressure builds refute the laws of thermodynamics. Not trying to be nit picky but I just want to make sure my lessons/info are solid lol.

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1997 BMW M3 - 3.2litre Inline 6 cylinder

Yeah, I am having difficulty as well. The only way I can see it being possible is that with increased speed the turbo gets cooler air with less underhood heated air. The intercooler also gets more air the faster you go so it gets more effcient. You can guarantee that the air coming off the compressor is hotter with more boost. I am having a hard time with a 5-10 degrees of ambient reading as well. That puts intercooler effciency way up there. There is no way that boost alone is making the temps drop. Physics will not allow.

Chris

Sure, simple physic would not allow that! But there are a lot of other things going on under a hood to make it possible.

While driving at a constant speed, driving down the highway. Air is moving pretty slow in the intake tubes which heats the air from high engine compartment temps. Plus the air isn't going through intercooler during high manifold vacuum due to the bypass valve. So, once boost starts to build, the bypass valve closes and runs a bunch of air through the intercooler that has been sitting right up front in the wind getting "cool soaked" to ambient temps. So, the inlet temps drop when the air passes through a cool intercooler. I'm not making it up. The data logger doesn't lie. That is just what the data says.

On a 90 degree day while driving down the highway, inlet temps would climb to 120 or 130 in the manifold. Hit the throttle, boost pressure kicks in, BOV closes and the air inlet temp drops to 100. Believe it or not, it happens all the time.