I'm new to the game of trying to build up a leaning tower of power, but here's what I'll be dealing with. I've got a 73 Swinger six/auto that runs good, but it's getting tired. I know that up until 71 the slant six put 145 ponies, then it got choked down by the pollution garbage. I plan on going through the engine, with the goal of regaining the original output plus 20 percent, if I can. What I need is lots of advise, and information as to what parts I need and where to get them. One item that I have on hand is a nicely machined stock intake that been converted over to accept a Carter 2 barrel carb from a 318. This intake has been set up with a dual plane insert, so it should provide good fuel atomization. However it remains to be seen if it is used in the process of gaining the performance I'm looking for. I appreciate any help you can provide, and I thank you in advance for any help you can give. Dick trickydick20@juno.com

There wasn't a significant power drop in 1972 when the 225's rating went from 145 to 115. The significant difference was in the rating system, which changed from SAE Gross Brake Horsepower (engine minus alternator, exhaust system, air cleaner, and other power-using accessories) to the more realistic SAE Net Horsepower (engine as installed in the car).

my dad was a slant six fanatic.He sometimes ran the dyno at the local army tank designing plant. He put a stomberg 97 from a ford flathead v8 on an adapter and picked up about 8 horsepwer once back in the early 70's.
kev

Dan's stated that the system for rating horse power was changed in the early 70's. I can accept that, although I'm still curious why when I changed
out the tired six in a 71 Duster with one from a totaled 72, it didn't have near the same snort that the tired 71 engine did. I don't know if it has to do with the timing, or the Cam configuration or what, but there was a big difference in overall engine performance. This is why I'm looking for answers to building a six that can perform and still be a decent driver. Dick

There was some variable at play there. The '71 and '72 engine are the same. Both years (in fact, all years) had 8.4 to 1 (advertised) compression, the same cam shaft (starting in '71, a higher lift cam sourced from Chrysler Marine Division), points ignition, carb, etc. Perhaps the '72 had a different jet in the carburetor, timing different, etc. Which brings up another question. Why are the gross ratings the same for the early engines with the weaker cam as for the later engines with the higher lift cam?

Q) Why was the "Hemi" rated at 425 hp? A) The factories, could use any number they wanted.
This was common, with all makes, not just Chrysler. If you look at the engine build specs, (head cc, deck hight, comp distance, carb, etc) for different years, you will see changes, but no change in power, listed. The reverse is also true. There might be a power difference between years, but no change in engine specs.

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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

Yeah, factory HP ratings are like watts are to stereo systems (even more so way back then). More of a marketing tool than actual scientific data. That's how all those factory shivvy "turbo-jets" put out so much HP. You ever meet a shivvy guy, by the way, that didn't claim that his particular small block puts out at least 400hp?

"Well, the factory rated it at 350, then I stuck in a cam that give it 75hp, then the big dominator holley carburetor gimme about another 60, and them there gold roller rockers picked me up about another 20, etc etc."

- Notice how shivvy guys add up every potential advertised hp increase to their already grossly overstated factory rating. You'll be looking at yet another 350 with a big cam and a holley and blue silicone oozing out of every crevice and blue smoke wafting out the tailpipe, yet it's a "600 hp" motor!

The '72 slant 6 in my Kermit (Valiant) is the best running, "fastest" most powerful bone-stock /6 I ever sat my ass in. Don't know about factory ratings, but that's my seat-of-the-pants rating.

D/W

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If it ain't broke, fix it!

A lot depends on what you want to do with your car.

My car is a daily driver.

I wanted to be able to drive it anywhere, park it anywhere, and not have to worry about needless complexities.

I also wanted to make it a little retro.

So the motor has an Offenhauser two carburator intake that uses two of the stock Carter "BBS" carbs. It's got a mild cam with fairly short duration, but fairly high lift. The head's been milled a tenth of an inch to bring the compression up to about 10:1. The head's also been ported & polished. The block's been bored .060 over.

I have "6 into 2" Clifford headers (1 and 7/8 inch primaries), but those are probably overkill, and I would consider Dutra Duals next time. The headers run through 2 inch pipes out to a couple of Flowmaster 40's.

Ignition is handled by a nifty product called Pertronix, which is a "drop in" electronic ignition kit.

This set up has proven to be very reliable, and surprisingly powerful. Yesterday, for example I was driving through a parking lot and saw a puddle of water. Just for kicks, I punch it as I was driving through it.

I almost got REALLY sideways, so don't do this at home. The point is that this motor's got ton's of torque, and has real good power up to about 4800 RPMs or so.

The idle is pretty smooth, and the car is not super loud (I would suggest NOT getting dual exausts). It starts up like a charm and runs at just the right temp.

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1963 Dodge Dart, motor by Doug Dutra, Offenhauser two carb intake, Pertronix, Clifford 6x2, Flowmaster 40's, Erson RV15/295 RDP, head work. Addco anti-sway bar, urethane suspension bushings, KYB's, racing leafs, SSBC discs. Need ZDDP? Get STP.