'71 Demon Ebay turbo kit

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Three60Demon

Three60Demon

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Hey all, I have a 1971 Demon with a mild 360 (cast '74 bottom end std. bore, ported cast heads, Torker II, 650 Brawler, Comp XE cam) Last summer I bought an Ebay twin turbo kit and before installing it, I'd like to know if anyone has experience with these kits in particular. I've seen some big single turbos in A bodies but never twins. I have a series of questions that I hope can be answered here.

- Am I building a timebomb?
- Intercooler or no intercooler? Air-Air or Air-water?
- how much boost on stock internals?
- Carburetor mods or replacement?
- For low boost, would I need water/meth inj.?

I'm certain there will be more questions to follow once I dig into it, but this is a good start. Thank you in advance for the replies and advice.
 
water meth eliminates the need for an intercooler.. 8 psi on some good headgaskets and arp studs will do. I would say go Holley efi as it would be easier to manage things... Some will tell you buy this and buy that.. Not needed... 8 psi is safe all day....
 
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Get a blow through carb and run < 6 psi. Send it!

That's engine #1. When you detonate that one or as a revision before it detonates get yourself some closed chamber heads (cast production or Speedmaster cheapies), Eagle SIR rods, some forged flat top pistons. Try to find a cheap single plane like a TM5 Edelbrock and run a water methanol kit. All these options are the lower cost options and keep you from spending stupid big money on the "proper" parts but are good enough to do the job and have satisfactory reliability and performance.

Bottom line? Your current engine isn't right for boost. The reason for my recommendations is it allows you to wade into the waters while learning. You can go big if you have a big budget AND knowledge. With knowledge you can perform just under those big builds without having to spend as much.

You want closed chambered heads and flat tops for the quench which staves off detonation. You could probably buy a set of Speedmasters for the cost of building a set of closed chambered Late LA heads. A cast crank isn't the best option but it would be good enough for a mild turbo build. The stock rods have zero place in a forced induction build. You will want a single plane. Throw the whole single/dual plane debate out with forced induction. Single plane is always the answer but with all that forced air in 360 inches and a cast crank you will do good with just a BASIC single plane (lower cost too). TM5's are almost free nowadays.

Fuel and spark are the most integral parts of a FI build. Timing retard, rich/lean conditions, fuel supply .... This paragraph may represent the biggest investment and definately the area that you need to get right whichever (carb or EFI) fuel system you go with. If you cheap out anywhere don't let it be on your ignition timing. I would recommend a cheap FiTech FI ready EFI for timing control if you use a basic distributor (locked out of course). If you use a blow-through carb you will want to step up to an MSD-6 Programmable along with O2 and MAP sensors. You can tie all that into your water-methanol signal to control when it sprays. Costs will be about the same. You will want to run an EFI pump or surge tank with either and just use the appropriate regulator.

This is a distributor I was going to look more into on my revamping of my Procharged 408" blowthrough engine.
Progression Ignition Might be a better route than MSD's Programmable.
 
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There was a couple guys on here had twins, I THINK (maybe mistaken) "maddart?"
 
What kit did you buy? What do the headers look like? What turbos came with it?
 
There are more singles then twins, but youll have to search for them, few builds with twin are running aftermarket blocks and efi. Cost wise like above, blow through and 6 psi will be a fun ride, can go meth injection and a air/air intercooler, can have the meth on a micro switch then only comes on at wide open and use it to boost octane and cooling, and have the intercooler for around town cooling. Mine and turbodart68 both have aftermarket blocks, slowfab has a nascar block and heads.
 
Somebody else on here has tried those headers before and as I recall they won’t clear the fender wells on an A body.
 
subcom said:
Somebody else on here has tried those headers before and as I recall they won’t clear the fender wells on an A body.
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I had my suspicions about that just by looking at the headers out of the box. They look like they'll mate up to the heads just fine, but I assumed I would have to make some dents in the headers. They'll be wrapped to contain heat as well as hide said dents.
 
If you don’t add ring gap, then yes you’re building a time bomb. Even at 8 psi. Disassemble it, gap the rings, add head studs, add mls gaskets, and you’ll have a bottom end that will live a while on boost. I can’t imagine why anyone would build any turbo set up without some form of intercooling, it’s free horsepower. For a street car an air to air is as simple as it gets. Consider this engine a sacrificial lamb while you learn to tune a boosted set up.
 
TT5.9mag said:
If you don’t add ring gap, then yes you’re building a time bomb. Even at 8 psi. Disassemble it, gap the rings, add head studs, add mls gaskets, and you’ll have a bottom end that will live a while on boost. I can’t imagine why anyone would build any turbo set up without some form of intercooling, it’s free horsepower. For a street car an air to air is as simple as it gets. Consider this engine a sacrificial lamb while you learn to tune a boosted set up.
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Definitely add ring gap. There’s no such thing as free horsepower, there’s always a cost whether it’s time, money or reliability. They can add significant power but Intercoolers are expensive and add significant cost and complexity in packaging. For 8psi, I’d run a blow through carb and a cheap water meth kit. I’m 1200+ whp and still running nothing but water/meth.
 
Hemirunner said:
Definitely add ring gap. There’s no such thing as free horsepower, there’s always a cost whether it’s time, money or reliability. They can add significant power but Intercoolers are expensive and add significant cost and complexity in packaging. For 8psi, I’d run a blow through carb and a cheap water meth kit. I’m 1200+ whp and still running nothing but water/meth.
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I don’t disagree with you, water meth does work. But a decent kit is more expensive than an air to air, and you have to keep filling it with something (more $). An air to air is stupid proof (read: simple). I like the blow through carb, Ive made a bunch of power with one and they’re a form of intercooling by themselves. On my big block the temp delta across the carb was 115 degrees at 9psi.
 
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