I'm building a 73 Dart Swinger. With a boosted slant six.
Here are my plans.
rebuilt /6 punched .020 over
port and polished head
Electronic Ignition
JY TBI system w/ Megasquirt setup.
Custom grind Solid cam. 225*/225* @ .050" .480"/.480" lift.
340 valve springs and retainers. Solid lifters and custom pushrods.
Ported exhaust manifold
rebuilt /6 727 tranny out of 80's truck or van.
2500K stall
66/67 B body 8 3/4 sure grip. 3;55 or 3;23 gears. (this car will see highway use often)
Spring perches relocated to fit.
Cooling mist water injection kit.
two stage boost control. 10 psi for cruising, and 15 psi for burnouts/racing/fun/when I feel like it...etc
HY35 Holset Turbo
Custom Pulse header
3" exhaust w/ Bullet style Race muffler.

My question to you is, if I am always going to be shifting below 6000 RPM's, will I be alright with stock cast pistons? I want to run 8;1 compression. This car will LIVE on pump gas, and be 100% street driven. I'm wanting to net 320 RWHP so that means around 400HP at the crank. This setup should run low 12's if traction is "caught". Any other advice you could offer would be great. Saving $550 on pistons would really be a money saver, and help cutdown on the overall budget of the car. Thanks.

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"Women are to be loved, not understanded."

You would need to use one or the other, ported exhaust manifold, or header, not both.
Maybe cast pistons would work at 10 PSI, if everthing was right on, as far as the tune up. At 15 PSI, don't think cast will hold up.
Custon pushrods will not be neccessary.
I suggest you use a 904 trans, not the 727.
Don't know any thing about that turbo, so can't comment on that.
Would also suggest PFI, instead of TBI.
You will need to do some "beefing" inside the motor, to allow 400 HP.
Shift point around 5,000 rpm is more reasonable.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Read this good thread re turbos and cast pistons. Ray is the owner and founder of MoparMarket in Australia, and has a tuff 225 turbo. He posts here as well.

MoparMarket in Australia

If you have the holset, you should try it!
I have a feeling it would work nicely
Does it have the wastegate built into the turbo, or is it external?
You may want to port the wg if it is in the turbo, as they are a bit small.

I am a bit worried about the tbi thing... Can you get injectors big enough for the power, when they operate under the higher air pressure(and fuel pressure inside)?

Ah yes, I can get big enough injectors for the TBI. I've already talked to a Tech at Megasquirt and he says that using the Megasquirt setup with the TBI should be no problem.

Sorry, I meant the custom pulse header. I copied and pasted this combo that I posted on another site to hear. I want all the imput I can get and I forgot to remove the exhaust manifold part.

I believe the Holset is an external wastegate turbo.

On the custom pushrods, I know Chrysler wasn't exactly steller on their measurement tollerances and I've heard that with an aftermarket cam and lifters, that pushrod length needs to me measured and pushrods ordered accordingly.

Michael

_________________
"Women are to be loved, not understanded."

Only three reasons to run custom pushrods on a slant.

1) Milling the head and/or block over about .80-.100, pushrods would be too long. Since you want About 8-1 compression, not an issue.

2) Using a "reground" cam with a very small base circle, pushrods could be too short. Not likely, with the cam specs you list. Most slant cams are on new cores.

3) Using a very very radical cam profile, with very high pressure valve springs. Pushrods might not be strong enough and bend. In this case you would want a 3/8 dia pushrod. Again, not needed, with the cam numbers you list.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Okay, so with a custom cam that won't go over .500" lift I don't need custom pushrods. Something that I like as it will lower the cost just that much. Thanks.

Any other opinions or tips on the build? I'm thinking of just running cast pistons until they blow as I will have another shortblock that I am going to build when I have more money.

Also, why the 904 and not a 727? Wouldn't it be cheaper to pickup a good 80's slant six 727 instead of build a 904?

Michael

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"Women are to be loved, not understanded."

I know you can get big injectors for tbi, but how do they react to the higher pressure needed when you are under boost?
Or are you doing a draw thru?
If you are, the Holset don´t have the right seals...

Why are you building a great car and not put the forged pistons in. I would recomend forged pistons git er done. Also Charlie is right the 904 is better behind a slant. Hell the one in my car is three years old and have no problems other than flex plate bolts comming loose but that just happenend at Hamilton. And all it gets is wide open every pass. Thanks Ron Parker








Hell Hath No Wrath Than A Possum Scorned

Everything else being equal, a 904 will run about .2 sec, and 2 mph better in the 1/4 mile, then a 727. The 904 is lighter, and has less rotating mass then a 727. Either trans should be at least "freshened up." The cost of this is very close to the same for either trans. A 904 has the torque capacity to handle a slant or a small block V-8. I don't know of any slant six race car, running a 727.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Going w/ forged pistons all depends on how much $$$ is available at the time. Okay, so the a904 it is. What all would you suggest for the tranny being freshened up? Thanks.

Michael

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"Women are to be loved, not understanded."

I am lucky because i have a transmision builder that goes back and knows MOPAR trans. My trans is a racing trans and he built it for that doint know the details I told him what i wanted and he built it. But it gets real hard racing action ask Charlie and he will tell you the second person you want to know is the transmision builder . The first for me is the engine builder. Thanks Ron Parker







Hell Hath No Wrath Than A Possum Scorned

Okay, since the stock kickdown linkage is "carb specific" What is to be done when I go to the TBI MS system? Thanks.

Michael

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"Women are to be loved, not understanded."

Use a cable kick down. Either a Lokar, or homemade from a motorcycle/bicycle cable.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

How exactly does a cable kickdown work? Thanks.

Michael

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"Women are to be loved, not understanded."