Hey all, I am new to the group and have a 74 Charger 225 in a 28 Rat Rod. Currently supporting a 904 looking to go manual. My dad is a retired Chrysler mechanic and turned me on to Mopars at a young age. This is my first slant 6 and I am wanting to improve on HP. Like the looks and reputation of the old slant. I have been on here searching and reading. Great info by the way. I am currently statione in Iraq and still in the design stage. Just wanted to hear what you guys have to say on the easiest way to get about 225HP out of this thing.

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Kenny P
28 Rat Rod Slant 6

Step 1 -- Increase compression ratio

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Part of Tyrde-Browne Racing

Cam and Compression

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Cam and Compression. Got it. Any particular cam and size in mind? And should I go solid or hydraulic. Is the best way to improve compression milling the head or piston swap? Like I said, I am new to the slant but I think I am really going to enjoy building this one. Unless you guys kick me off this forum due to too many questions.

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Kenny P
28 Rat Rod Slant 6

Oh heck no, questions are a good thing!

Compression would be first, cam next...but depending on cam that can slide into porting and bigger valves...(lots of power to be had by opening up the ports...but you'll need to pick the right cam and compression ratio to make it all right.)

FYI, I left a set of white dry erase boards behind in storage at F-3 Camp Slayer that had the calcs for a 11.5:1 long rod slant six on them...KBR probably has them covered in doodles on how to reduce the cost of paper plates at the DEFAC by now...

-D.Idiot

Thanks, I may get back to Slayer soon. If I come across your dry erase I'll send that out to you. Untill then, I wouldn't mind having those numbers if you still have them. I am seriousely considering going a little radical. Why not go out in the deep waters the first time. Wouldn't mind seeing up around the 250hp range. Fuel injection and turbo is not out of the question either. I am currently sitting around stock. Small cam, 2bbl, and 2.5 in. exhaust. It's in a 28 roadster, so I have almost no room restrictions.

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Kenny P
28 Rat Rod Slant 6

I took notes and pics before I left, so they are not needed, but the "gibberish" might still be there...LOL...

Keep your head down and stay safe!

-D.idiot

Some (smart people) say to cut down the block to increase the compression, but I forget what the reasoning was. Cylinder head porting and polishing is helpful as well as electronic ignition.

I dunno why, but Iraq brings out the most creative slant six thoughts for people. Me, at the old embassy in 2004, I figured out most of my suspension and brake bits and pieces for the cuda. It is where I also made the money to actually do all the work I wanted.

G

I'll look into cutting down the block and surfacing the heads and see which is more beneficial. definitely going to electronic ignition. I would like to know what a good cam, carb or fuel injection system set up for around 10.5 to 11.1 cr would be. Any thoughts?

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Kenny P
28 Rat Rod Slant 6

keep in mind that your compression ratio right now would be good for a big turbo setup :p

think long term and how much $$ it will take to get to you goal properly. you sound like you know enough to plan a some builds

Aaron

It's a subtle detail until you wrap your brain around it, then it becomes an "ah-ha!".

The higher your compression, the more important is your quench ("squish") area, to promote more complete burn and to live with lower octane fuel, not to mention get decent fuel economy. The shape of the available volume when the piston is at TDC is amazingly important in determining how the flame front will behave. Shaving the head but leaving the pistons down in the hole yields a different result than shaving the block.

Here's a nicely informative article:
http://kb-silvolite.com/article.php?action=read&A_id=35

Since you've got time on your hands, you might enjoy researching closed-chamber vs. open-chamber heads, too. And swirl port heads. Don't forget to look at the slantsix.org articles section... Doc has written some good stuff about heads and combustion chambers.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

OK, explain to me how reducing the height of the block improves the combustion chamber shape over reducing the depth of a round, open combustion chamber.

The combustion chamber shape stays nearly the same you just move the head gasket and deck surface in relation to the cylinder which is defined by the cylinders in the block and vertical walls of the head's combustion chamber.

Closed chamber heads are another story and one in which quench may come into play. 225s just have the head and piston so far apart at TDC that it matters not from a chamber shape perspective if the material removed comes from the head or block.

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Joshua

Joshua, the only real benefit that I can see is that the older style pistons have the rings lower on the piston. So by shaving the deck, you would get the rings closer to the top of the cylinder and less fuel loss down the side of the top of the piston. With the use of a newer style piston there would be little or no distance. I have noticed that the 170, 198, and 225's all share the same bore. So, maybe some stroker combos would help in some HP.

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Kenny P
28 Rat Rod Slant 6

Like I said, I am new to the slant 6. Also. new to this Forum. I may have started tis conversation under the wrong agenda. Probably should try to move to Racing Q & A. Sorry, didn't mean to start up so slanted.

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Kenny P
28 Rat Rod Slant 6