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Turbo six on a budget
https://slantsix.org/forum/viewtopic.php?f=30&t=66070
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Author:  Jack Ormson [ Mon Jul 05, 2021 8:54 pm ]
Post subject:  Turbo six on a budget

I have a 72 dart swinger with a 225 auto in it. I am desiring more hp and decide to turbo the slant. I am only 15 so i dont have a huge pile of cash and am trying to do this build on a budget of 1500. My end goal was ~350 hp at the crank in a engine that can be a daily drive.
My plan was to run a
1: original bottom end with just a rebuild and larger gaped rings
2: original valve train
3: light clean up on the head (no major porting just cleaning up the casting slag)
4: stock exhaust manifold with a turbo flange mounted to it
5: 4bbl intake and carb with hanger 18 mods
6; The turbo kit T3/T4 turbo kit running 10~15lbs of boost.
My main question is this a viable way to get 350 hp reliably with out blowing up my engine.

Author:  ProCycle [ Tue Jul 06, 2021 8:36 am ]
Post subject:  Re: Turbo six on a budget

On a 'blow through the carb' setup there's little need to run a 4 barrel. The turbo can push enough air to make 350 HP through a one barrel and having the smaller throttle plate will give you much better control of the power delivery. It will also be easier to set up and to tune.

Author:  MadScientistMatt [ Thu Jul 08, 2021 6:57 am ]
Post subject:  Re: Turbo six on a budget

Jack Ormson wrote:
I have a 72 dart swinger with a 225 auto in it. I am desiring more hp and decide to turbo the slant. I am only 15 so i dont have a huge pile of cash and am trying to do this build on a budget of 1500. My end goal was ~350 hp at the crank in a engine that can be a daily drive.
My plan was to run a
1: original bottom end with just a rebuild and larger gaped rings


Sounds reasonable. Check the condition of the bores; you may just be able to put in some fresh rings with more gap and avoid a lot of expense.

Quote:
2: original valve train


Milling the valve guides for to allow a larger cam may be out of the budget, but you can get some flow improvements from back-cutting the valves, even the "chuck it in a drill press and use a file" method.

Quote:
3: light clean up on the head (no major porting just cleaning up the casting slag)


There's a pretty rough transition between the port and valve seat that I'd also recommend cleaning up. This is a pretty easy area for improvement; you don't need to be Larry Widmer to pick up gains here.

Quote:
4: stock exhaust manifold with a turbo flange mounted to it


Be careful with welded on flanges; welds in cast iron often crack, particularly if you're dealing with a well-used manifold.

Quote:
5: 4bbl intake and carb with hanger 18 mods


My own view is that for a street car, there's no carburetor like no carburetor, but EFI is likely to be out of you budget range. Hopefully people who are better than me at carb tuning will chime in.

Quote:
6; The turbo kit T3/T4 turbo kit running 10~15lbs of boost.


Do you have any more details on this particular turbo?

One other detail: Don't forget a good way to tune your spark advance so you can have timing retard under boost.

Author:  SpaceFrank [ Fri Oct 22, 2021 1:58 pm ]
Post subject:  Re: Turbo six on a budget

For a budget build, I think a J-pipe of appropriate size (say 2.25" or 2.5") from the stock manifold outlet to a turbo flange is your best bet. Definitely wouldn't recommend welding cast iron unless you seriously know what you're doing. Maybe use a die grinder to smooth out/slightly enlarge the manifold outlet to match your J-pipe ID.

When cleaning up the port to valve seat transitions, don't remove much material from between the inlet and exhaust valve (toward the center of the cylinder). The walls are very thin there, so just smooth out whatever ridge is left from cutting the valve seats and be done with it. You'll probably want to spend more time on the bottom/short side, i.e. the inside corner that the air has to take from the runner to the port.

Agreed with Matt, ignition timing is very important under boost if you want the engine to live long. One way to cheese it for minimal dollars is to use a locked-out distributor with no mechanical advance, then set your initial timing to 15 degrees or so BTDC. Your pre-boost performance may suffer, but you can theoretically continue to use vacuum advance as long as you clamp down your vacuum advance line so it doesn't fly off under boost. If you convert to HEI ignition, a forum user named SSGPohlman has a write-up in here about how he used a special 5-pin HEI module (from certain Oldsmobiles, I think) that had a built-in function to retard timing 5 degrees whenever the fifth pin is grounded. You can then wire that pin to a simple pressure switch in the intake that closes whenever it sees positive pressure.

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