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Twin Turbo 4.3 Chevy


Z-TARD

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Has anyone done one of these yet? I'm pretty much commited to the SBC swap for now, but I've been kicking this idea around for a future project maybe. I can't really think of many disadvantages to using this engine. It's based on the SBC, so a T56 tranny would bolt up without too many issues. The aftermarket is there for it, maybe not as abundant as the SBC but still more selection and cheaper than a lot of imports. With twin turbos, I'm pretty confident that some disgusting horespower levels could be reached. After picking up this hood over the weekend, I just can't get this idea out of my head......

Hood.jpg

 

Mike

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Pretty cheap really, I saw a pair of aluminum heads go for $800 complete.

 

I considered going with a built 4.3, but after doing alot of research, I found that it would cost BIG BUCKS!

 

If you do decide to go with a 4.3, you want a aluminum four bolt main block or a aftermarket block. A pre-balanced shaft factory OEM block could be used, but will require major machine work and four bolt caps.

You also want a forged ODD-FIRE crankshaft that doesn't have the shared offset rod journals of the even-fire factory cranks.

 

Mark

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I considered going with a built 4.3' date=' but after doing alot of research, I found that it would cost BIG BUCKS!

 

If you do decide to go with a 4.3, you want a aluminum four bolt main block or a aftermarket block. A pre-balanced shaft factory OEM block could be used, but will require major machine work and four bolt caps.

You also want a forged ODD-FIRE crankshaft that doesn't have the shared offset rod journals of the even-fire factory cranks.

 

Mark[/quote']

All true, depending on how much hp you intend to make. I was walking the 2 bolt mains once I got up tp 14 psi, choked heads,85 block. Later blocks were somewhat better. Callies used to make a nice odd fire forged crank.

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Not sure what your idea of "disgusting power level" is, but 600rwhp from a huffing big-inch V6 will get your attention (and the track owners) in a hurry. Remember, my 2750# GNZ was "only" pushing 520rwhp, calculated with a 1/4-mile formula, which probably means ~540 peak on a dyno or 650 at the crank with a 17% drivetrain loss. Got your attention? So why not a Buick V6? For whatever reason, they hold up better under high boost. My current engine is a pedestrian vintage 4.1L shortblock found in generic early-80s GM grocery getters. Those engines have the same crank and rods as the 3.8L turbo. I am still running the stock pieces with ARP rod bolts and a girdle. The pistons are SpeedPro hypers with the coated skirts (oh sacre bleu!), OEM timing gear set and a mild cam. Heads are ported stockers with ARP head studs and a port-matched intake, stock headers and a T-66/P-trim turbo. Top that off with a good I/C, DP/WG/exhaust, TEC and she is purring at almost 27psi on pump gas and alky injection. Real exotic and expensive stuff, huh?

 

BTW, it sounds like you want to build a TT engine just because you have that hood.

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I think scottie is right, the buick has inherit advantages since it was turbocharged from the onset in some models, so parts are available. The 4.3 platform is a one off, so not that it hasn't been done before, but you'll be forging new territory in the z world.

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Hmmmmm... I was under the apparently mistaken impression that the SBC internal parts such as rods, pistons and splayed main caps would work in the 4.3 since it's basically an SBC minus two cylinders. Correct me if I'm wrong, but I seem to remember the buick V6 having a different bellhousing pattern than the SBC as well, which would make the adaptation of the T56 a little more complicated than with the 4.3.

 

At this point though it's all academic, as my current project is getting the status quo SBC swap. I figure at the rate this project is progressing, I'll have time for another one sometime in April of 2043..... Getting the hood is definitely what started this idea, it just looks like everything would line up perfectly under there. I figured the 4.3 would make a good cantidate because it retains a lot of the advantages of the SBC while being a smaller, lighter package that would bias even more weight percentage towards the rear of the car than the V8 it was based on. Thanks for all the info guys, keep it coming!

 

Mike

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Your correct the buick has a different bolt pattern. The 4.3 is as condusive to boosting as is the sbc, basically the same engine minus 2 cylinders. The even fire crank and the odd fire crank both work fine. They make an even fire steel aftermarket crank, I think it's LA enterprises. The odd fire is cheaper in steel. You can install or at least I've seen 4 bolt caps installed on the 4.3 block, don't know how it worked though. Pistons are the same, rods are basiclly the same, just narrower by .050 or so, easy for a competent machine shop to narrow properly. If you go with the money is no object theme, they manufacture rods for that application.

 

I'd like to see it work.

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My reference to the reliability of the 4.3L on boost is limited to what I hear and know about them as used in the Sy/Tys. All that goes out the window when you start talking bowtie blocks, custom internals and shop specials. Still do not know what your idea of big HP is, but keep this is mind. When you get these little V-6s wound up on boost and pushing 600-700hp, you are talking mega, tranny-breaking torque, enough to break a T56. I am not talking about hopped-up smallblock torque, but bigblock-on-steroids torque, like 650-700lb/ft. The T56 can probably live but it depends on how you intend to use the car.

 

In case it is not clear to most, GM trannies have 2 different bolt patterns referred to the Chevy and the BOP (Buick-Olds-Pontiac). Obviously the T56 would bolt right up to the cylinder-challenged SBC :D :D and the Buick V6 would need an adaptor like the one in the pic.

EngineTrans2_thumb.JPG

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Guest ImportMuscleZ

read this post, its on s10planet

http://www.s10planet.com/forum/showthread.php?t=1892&page=12&pp=10&highlight=turbonoma

 

I was into S-10's before i got into z's. Stuff for the 4.3 is there, and you can make over 500 rwhp, but its so damn expensive. Better to go with a 305 than a 262. trust me. Or, get a motor out of a regal t-type. SOO much easier

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Better yet look at this.

http://www.syty.net/forums/timeslips.php?

Look at some of the weights of these lead bricks, then imagine that power in a lightweight Z. Sure you can go fast with a 4.3. If your wallet is dictating the build, the advice is sound from the other members. Buick is the way to go and having a member with experience like Scottie is priceless. If your heart is set on a Chevy then don't give a rat's *** what everyone says and go that way.

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I remember a while back Hot Rod magazine or was it Car Craft? Anyway, they did a mild build on a 4.3 and got 300 to 325 horsies out of it, something like that anyway. Even 300 h.p. is like double the h.p. of a stock Z depending on year, etc. Then add turbo, and hold on! I am a SBC fan, but I would love to see a turbo 4.3, I'd say go for it.

Good Luck on whatever you decide.

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This type of engine has fascinated me from the beginning. I'm talking the racing V6s, specifically the Buick Stage 2 and the ex- NASCAR Bowtie version. Ford even had a V6 in this hunt that was competitive.

 

They are all characterized by massive bottom ends - 4-bolt splayed and crossbolted mains, Carillo/Oliver rods, and billet cranks with large journals. Most builders preferred the odd-fire cranks for ultimate strength, although some even-fire versions were used. The valve trains have mechanical roller lifters and Jesel/T&D rockers. They made 650 hp in Busch Grand National carbureted 14:1 CR form, pushing a NASCAR brick to over 200mph on the superspeedways. The turbocharged Buick Indy application made 1300hp on alcohol and still holds the lap record there. Turbocharged horsepower numbers in the 4-digit range are fairly easy with gasoline.

 

Heads on these things are capable of massive airflow numbers. 2.15" intake valves, 1.85" exhausts. Big block-sized ports. Intake cfms in the 350+ range at .600 lift are common.

 

They provide an ideal start point for a monster turbo engine due to the strength of the bottom end. Being a short V6, there will be lots of room up front/top for big turbos, not to mention giving good weight distribution in a Z. Probably would weigh close to as much as an SBC due to the extra iron in the block, but concentrated further back. An RPM range well into the 8K area makes for good roadrace flexibility, and the big torque is there if you can hook it up for drag racing. Careful drivetrain selection required here!

 

Now for the down side - $$$$$. The components and custom machine work are damned expensive. Ask me how I know. :rolleyesg Converting a "compression" motor to turbo trim involves custom pistons, valves, and camshaft, among other tweaks. Smart shopping on the used racecar parts market will pay off, but this is hit or miss - and some things you just need to buy new.

 

Looking at Scottie's power level and what he did to get it probably will give a good idea of the limits of the stock-type V6, whether It be a Buick or a properly built Chevy V6. I would think that head flow is what would limit horsepower in the stock block turbo motor, although you could reach the limits of bottom end strength with lots of boost. Probably there are more available turbo specific parts and knowhow for the Buick than the Chevy.

 

Still, It all comes down to the same things required to build big horsepower by any route - bottom end strength, sufficient breathing, and good fuel management, along with meticulous attention to detail in the design/assembly/setup of the engine.

 

So anyway, I'm a V6 turbo proponent if you haven't guessed. Some day maybe my 274 ci twin turbo odd-fire Buick will be out of machine shop jail and into the Z.

 

Do it I say - It's a cool way to go - that hood would work nicely with twin turbos - but doing it right isn't the simplest (or cheapest) route you could choose.

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The engine builder doing my 383 machine work does a lot of the nascar chevy V6 blocks for the Baja truck guys around here. Does enough work on them in fact that it has taken him two years now to get my block finished (Actually, still not finished....) Seeing these things in various stages of completion around his shop is one of the things that got me thinking about the 4.3 motor.

 

I realize that the Buick motor would be a better starting point for a turbo build, and Sottie's advice is not taken lightly. If he says it's a better motor, I don't doubt that at all. The mildly retarded part of me that doesn't play well with others still leans towards the 4.3 though, mostly because it seems that against all odds, it actually hasn't been done yet in a Z (At least not a turbo version).

 

Even with twin turbos, I probably wouldn't build it for huge amounts of boost. I'm thinking that 600 HP is probably about the most you'd want in a street driven car, and is probably well beyond what I am capapble of driving. I'll see how I feel about it after driving my 240 around with about 450HP for a while.

 

Mike

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