/6 or v8 swap?

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Penstarpurist

Penstarpurist

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Have really hit a decision making wall. I flip back and forth from thinking about doing a v8 swap into my wifes 75 valiant two door or putting in a /6. The car sits currently with no engine or transmission, so in that respect it is a blank slate. I've got at least half a dozen 318's and 360's sitting around, as well as several /6's. Transmissions to match. Two of the /6 engines and transmissions are 1975's. As is one of the 318's, so I could go back fairly original with year date correct. Not that it's all that important in overall to be date specific but would be a bonus I guess. I've gone as far as buying a Schumacher v8 conversion kit, but can shelf it for another project. Performance is not super important, definitely second place to how good it looks. Summer cruiser, car shows maybe. I think the /6 would be the easiest way to go. Any thoughts?
 
If.its a 6 car originally ...yeah easier

But for cruisin and negligable worse mileage id 318 it. I like my 6. But id rather the 318 for the sound, and extra highway power.
 
Lol, I'm not sure going for worse milage would be ideal for this situation. 10 years ago I wanted to big block swap my tired small block manual suburban. It obviously got poor milage with the small block, I told her that the big block would be better cause it would have less effort to get the truck motivated with the bigger motor.......well I installed a big block, dual 40 series flowmaster, 2.5 pipe, aluminium intake and edelbrock carb. It definitely motivated the rig far more, sounded mean, 36" tires, 4" lift, big winch bumper, etc. But when she realized it didn't better the fuel economy she was not happy. Now, it could be driving habits that killed that possibility. And while she was not happy with milage, she grinned ear to ear everytime she drove it, which was often. Wouldn't even turn the radio on, said she liked the sound of the cam rumbling through the 40 series. That said, she still has not forgotten about it, and throws it out there every time I start talking about engine swaps and upgrades......dang. Haha.
 
cdnEHbody said:
Id rather take the mileage hit...slight...and have the extra torque
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I can't argue that. I tell my son all the time to build his car to enjoy driving it. That it should be smiles per gallon over mpg. When I ask my wife she says "do not build it like its your car." And bad milage is out of the question. I say if it's just a summer cruiser who cares about milage. And I think to myself that I have never put much emphasis on a /6 and it might be a fun project. But, then hp is important too. What to do? Decisions.
 
/6 with one of those 4 barrel fuel injection which ever you like, or do the same to a 318. Be good for cruising and mpg, or slap a little turbo on the /6 and have both fuel and little extra hp.
 
I got better mpg when I switched to a 318. Better power, better cold weather starts, I can’t think of any reason to not put a v-8 in there. I liked the slant six just fine, but the 318 was an improvement
 
The only way I would run a slant six is with a manual transmission.

I have a daily driver 68 dart and it started with an auto. Felt like it was hamster powered. I switched to an od 833 and what a difference!

Exhaust is the single most effective way to wake up a six. People usually put bigger carbs but that is useless if it can't expel the extra volume because an engine is an air pump.

A six will cost more to make a good runner unless you already have parts like headers or a improved exhaust manifold like one from a super six.

A 318 is reliable but everyone has one. A six can be made to go. I usually do 2700 RPMs at 85 mph on the highway with decent throttle response, even better throttle response a gear down in 1 to 1.

Throttle response seemed to lag more with an auto, so I really do believe the transmission is the key to a slant.

A 318 will run better with an auto. IMO although I have had 318/4 speeds before......fun !!!

If your wife is short like me then a piece of wood 2x4 duct taped to the clutch pedal will help. Definitely get a 3 finger clutch, it's worth an extra effort on the knee to get a better, harder shift.
 
I have thought heavily about a turbo. Whether it's on a /6 or 318. Plus, with a/6, I wouldn't be able to leave well enough alone and I would have to push the envelope to see how much power i could get out of it. At least a turbo is really somewhat of a no sacrifice power adder. And if I am going to put all the money and effort into it just to get the power I would from a mild v8. And like was said, efi and theres some milage.
 
My wife is short, so the 2x4 is a great idea. Paint it black, a little chunk of rubber mounted on it for grip. Perfect idea, thanks. But no I don't have any performance parts saved up for a 6. So it would be more money out, and as much fun as a manual transmission would add I dont want to start down that road with it. Her daily driver is a manual, so the automatic will be a nice break in her fun cruiser. Which I have to keep reminding myself of. I have to get back to the mindset of economic red shiny cruiser. Fat tires out back, bucket seats and Hurst shifter, vinyl top delete, a/c, flat black hood with dual scoops, black tail stripe. She wants the look, but will never race it. Said when she wants to go fast she will run the big block duster. As its getting wrapped up before her car gets started on. Honestly the bone stock /6 might be all she needs. Maybe a mild cam. Then for once a motor installation can be straight forward, all the wires where they should be. I might be getting lazy in my old age, but its sounding better by the minute.
 
Easy upgrades. Compression increase..the rv-10 cam grind. 2.25 exhaust. Tbi or a 2 barrel. Also, slants like advanced timing. Can probably sneak 5* or a bit more with stock distributor. Limit your overall, and run more. Some guys recurve . I havent yet. I limited it wirh an different governor and run 11*

Tbi is looking better and better these days!
 
If you do go with the /6 @Rainy Day Auto hit it well in her post, I did the exhaust upgrade and the re-curved distributor I had a member do here, it woke it up a bunch, then I added a fresh air breather system that I feel the /6 loved as well.
A breather from a Jeep and an old carp hat to a 390 cfm, it was a much better driving car.
I would go 318 if it was me, I thing the high way and fun driving will be more enjoyed with the 318

Here is what I did, in pictures you will see a slant six manifold that was split with 305 chevy exhaust flanges welded to them, and ran 2" pipe to a single 2 1/2 pipe to the back bumper with a muffler.

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But doing everything was costly , just add it up and you can see why I am going 360 now after driving her for 6 years that way, I am now doing a 360 and have got all the disk brakes up front and a 8 1/4 rear with tall high way gear (sure grip) I wish I would have dun this a long time ago

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Just remember the old saying "When Mama's happy,,Everybody's happy !!"
 
I wasn't aware of all the upgrades that can be done to wake up the old slants. I saw theres a new manual coming out in February next year on how to rebuild and modify slants. Like $25 on Amazon and they are taking preorders on it. I am going to preorder mine today, even if I end up putting in a 318 just to keep costs down I still want to learn more about the /6. I am intrigued by them after hearing all the potential these engines posses. Memike, thanks for the pictures and information, it has definitely given me lots to think about for this upcoming project. Who knows how this will work out when it's time to powerplant the valiant. Shoot, I've been looking for a 340 for a demon project I dont even have yet. If I find one before I find a demon, maybe it will end up in the wifes car. Who knows, maybe she will come around to the idea that smiles per gallon beat mpg everytime. Haha.
 
abodyjoe said:
No way I’d waste my time with a 6. I’d go minimum the 318.
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Yeah, my kids say the same thing. If I keep the freeway flyers and go basic 4 bbl, mild can, dual exhaust I could probably get a sbm ro lay down decent mileage and be peppy with alot less cash into a/6 just to get it to the same performance as the 318. I may have to sit down with the wife and explain to her the /6 is a great choice for milage, but will lack any performance without having to go all out to get it motivated then milage will suffer anyways. Lol, its a tough sell for a v8 or built anything as she daily drives a 4cyl kia soul. I would think that alone would make her crave more performance in her cruiser. After all she used to drive a 71 cuda daily for years.
 
If you have a decent slant and trans laying around it shouldn't cost much to throw it in the car to make it driveable. Then she could drive it around to see if it's bearable.

If she decides a little more power would be nice, it could be hotted up a bit with minimal cost. If she wants a lot more power, then the 318 could be swapped in.

Don't forget cooling, brakes, rear end, etc.

If she likes attention, talking to strangers at stop lights and car cruises, the slant will give her more than the 318 will.
 
I have a magnum 5.2, bone stock with a carb intake and thermo quad, in a 71 dart, and 3:23 gears, it gets 21 MPG, which is better than the slant it replaced, with 3 times the power.
 
I have had everythng from the slants to 426 hemis, maxie wedges, and small blocks in between. I love driving my slants bone stock, but yep slugs. I just lke to cruise down the road in them. A good teener an get just agood mileage. I have had 833 OD slants get 25. Best by far. But a stock SB has never interested me much except the 4 speed AAR's I had. Prefer the torque of a good geared 383 over them all really.
I really have a feeling your wife and you will prefer a good sounding, running SB with a gear that keeps it interesting.
The turbo would wake up the slant and costs some $$$$ too! Good luck!
 
I do have a few slant six engines laying around. But all of them came out of cars that have sat for 20 years or more. Same with a few of the SB engines. So none of them are drop in ready and will at least need opened up to give them a look over and at least a regasket. She's not much on chatting with anyone about anything, at least not random strangers. She and my kids are not really into that, they make me call parts houses, vendors, appointments, etc as I had a very sociable job for many years and can talk about anything with anyone at any time. But a car like this may bring her out of the shell. My oldest son is learning this with his 71 valiant as every car guy that sees it in a parking lot approaches him about it. And he does like to see people interested in it.
 
I never take cars to shows but I do like to attend and see and visit with non ego folks. The slant will get more conversation anywhere, show, gas station, anywhere, and the /6 to v8 has been done 5 million times! I have driven 5-6 slant cars bone stock, I have 2 super sixes right now, I have swapped out several slants for 318 and 360's. I like it all.
If you go slant, the engine can gain some omp with milled heads and right cam. OR, NOT to mention the turbo. Eye candy would be the dual single carb setup although NO benefit over a good 2 bbl no doubt.
 
Just a FYI, I spent 20 grand on a Drag race Slant Six to run a best of 12.93 in a 67 Dart. Was it worth it ? Well to me it was because I've had just about all the Mopar engines in many different cars over the years. I will tell you it was fun spankin' allot of cars and drivers that made fun of me. But your situation is different.
 
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