stock grand national turbo good match to a 225 slant?

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'99 T/A
plannin out a 64-66 turbo SL6 barracuda

It's a pretty good match, one of the few factory single turbo setups on an engine that size that's semi-obtainable. Certainly a better match than the K-car turbo I used to have, which could build double digit levels of boost at 1,500 RPM but run out of breath at just over 3,000.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Matt,

Was that the Mitsubishi or Garrett turbo that you used? Sounds like it would be a good match for an 1800 RPM slant 6 driven generator.

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Joshua

I use one with good luck. It starts building boost at about 2000 rpm. I shift around 4500. I run 20psi.

See:
http://www.slantsix.org/forum/viewtopic.php?t=24037

I used the '87 GN T4. It is sized nicely for the slant. Be sure to build a low compression engine. Een 7:1 might not be too low. But the 7.5:1 that many stock engines were in actuality would be very good. Mine is 8.5:1, and I have had to fight pre-ignition. I seem to be winning that basttle now, but I would chose a lower compression ratio if doing it again.

Sam

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A friend of mine is planning a /6 GN turbo build and I'm sure I'll have a hand in it. He's wondering how much boost he'll be able to put to it without an inter cooler? Sam, you think stock compression might be too much? Can you buy pistons that sit deeper in the hole? or how else would you drop compression without stacking head gaskets?

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There is a dished /6 piston for trucks, but I think a little combustion chamber polishing and a FelPro head gasket (thicker than the stock steel shim gasket) would get you where you want for compression. Don't turn the car into a slug when off boost by getting the CR too low. Stacking gaskets is just asking for a failure.

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Joshua

What about a blower off those 3.8 gm v6's ? Ain't no turbo lag with a belt driven blower.

The itsy-bitsy Mitsubishi. You're right, it might work on certain industrial applications. It's just not a good one for a performance street car or racing.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

with a proper intercooler, would 8.5 still be too high?

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'99 T/A
plannin out a 64-66 turbo SL6 barracuda

A "proper" intercooler would get you out of detonation most likely. But there is not much room in front of the engine for a big intercooler. I have a friend with an '87 turbo Porche, and his intercooler is about twice as thick as mine, and his engine is slightly smaller at about 3 litres. I think if my intercooler were sized like his, detonation would not be a problem. But then, the bigger the intercooler, the more turbo lag you experience. I experience almost none with the GN turbo. I think with the proper fooling around with AF ratio, coolant temp and plug heat range you can eventually figure a way to get out of detonation. I have not gone with a water injector set up yet, and that is a good fall back to kill detonation as well. However, I do think if my engine were 7.5:1 this would not be a problem for me. On the other hand, I think it runs better when NA at 8.5:1. EVerything is a compromise with this stuff.

Sam

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