225 swap to 318?
#2230330
01/08/17 08:30 PM
01/08/17 08:30 PM
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Joined: Jan 2017
Posts: 1 Nuevo León, MX
EduardoIbarra
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OP
member
Joined: Jan 2017
Posts: 1
Nuevo León, MX
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Hello guys, I'm new here, my name is Eduardo, from the north of Mexico. I have a Dodge Dart 1973 with a slant 6 225 engine. I filled my tank and did a 3hour long road trip this morning and surprisingly, I ran out of gas. I thought the gas was leaking somewhere but it wasn't. Then I checked its fuel economy and found out that it gives 16mpg, which is too low on my perspective for a slant 6.
Anyway, I did some more research and it seems that the 318 has better fuel economy than the 225 with 22mpg. My question is, is the swap as easy as taking away the 225 and putting the 318 engine? or my stock transmission, alternator, etc. are not compatible with the 318?
Thanks!
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2230412
01/08/17 10:03 PM
01/08/17 10:03 PM
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Joined: Nov 2003
Posts: 12,494 Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
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Western Colorado High Desert
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Welcome. Would need to change the tranny, starter, radiator. Change or modify the wiring harness. Change the K-frame to a V-8 one or use conversion motor mounts. I would change the torsion bars to bigger ones for better handling with the heaver V-8. Probably some minor things that I'm missing.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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Re: 225 swap to 318?
[Re: moparmarks]
#2230472
01/08/17 11:23 PM
01/08/17 11:23 PM
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Joined: Jan 2003
Posts: 43,575 Round Lake Beach, Illinoisy
Rhinodart
Rhinotruck
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Rhinotruck
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Posts: 43,575
Round Lake Beach, Illinoisy
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Possibly the driveshaft.
Last edited by Rhinodart; 01/08/17 11:24 PM.
The funny thing about science is that if you change one miniscule parameter you change the entire outcome to the way you want it.
JB Rhinehart, Realist
A-Body's RULE!
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2230790
01/09/17 02:11 PM
01/09/17 02:11 PM
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Joined: Jul 2011
Posts: 959 Chicago
PurpleBeeper
super stock
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super stock
Joined: Jul 2011
Posts: 959
Chicago
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I "think" the transmission might be the same....A904 I believe. In general, the 225 six cylinder should get better mileage than a 318 eight cylinder. Maybe just rebuild the 225 if mileage is your main concern?
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
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Re: 225 swap to 318?
[Re: moparmarks]
#2230909
01/09/17 05:16 PM
01/09/17 05:16 PM
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Joined: Jan 2003
Posts: 4,998 North Pole,New York
formula_s
master
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master
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Posts: 4,998
North Pole,New York
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Welcome. Would need to change the tranny, starter, radiator. Change or modify the wiring harness. Change the K-frame to a V-8 one or use conversion motor mounts. I would change the torsion bars to bigger ones for better handling with the heaver V-8. Probably some minor things that I'm missing. Too many chefs here spoiling the soup but no need to change the starter.
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2230961
01/09/17 06:15 PM
01/09/17 06:15 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
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Having swapped a small block in place of a slant six in a 72 Dart I can tell you this.
It's not a simple swap if you don't know what you are doing and don't have all the parts on hand. I did the swap in one day, about 9 hours, but I had everything on hand.
You will need a complete engine and transmission, your slant six transmission will not bolt up to the 318.
You will need the proper three piece kick down linkage from a small block. The slant six linkage will not work, one piece kick down linkage will hit the firewall and not work.
You will need conversion motor mounts or a new K frame, when I did this swap there were no conversion mounts and I had to replace the K frame with a V8 one. Go conversion mount if you can.
If you have power steering you will need the V8 mounting brackets to put your pump on the V8. If you V8 donor has power steering you can probably use it's pump instead.
If you have AC you will need the V8 mounting brackets to put your AC compressor on the V8 and probably the V8 AC hoses too. My donor was an AC car and it's hoses fit my Dart.
Your alternator will work, if you use the V8 mounting brackets.
Wiring, you can use the slant six wiring with minimal mods. Basically, the wires to the oil sending unit, distributor and coil will be longer than needed, you can coil them up. The wires to the alternator and coolant temp sensor work as is.
Radiators are different, you might be able to use the slant six radiator with some creative upper hose routing, especially if you do not have AC.
Exhaust will not work as it, but you should be able to get/make a Y pipe to connect the small block to the slant six exhaust.
Assuming you have a 904 style transmission behind the slant six right now and your v8 donor also uses a 904 style transmission you can keep your current driveshaft.
I believe the accelerator cable will work so no need to swap that one out.
Not sure if the slant six fan shroud will work with a V8, I can't remember since I did my swap in 1994 it's been a few decades now.
I had a complete donor for my swap, 79 Cordoba, so a lot of the stuff you will need I had with the donor. Some of it I had to buy.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: 225 swap to 318?
[Re: Sixpak]
#2231036
01/09/17 07:58 PM
01/09/17 07:58 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Posts: 36,041
Lincoln Nebraska
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^this^ The '73 model year was reportedly the worst as far as discombobulated tune up specs with Ma & everyone else trying to stay ahead of the gov't emission and economy regs of the time. initial was TDC on a 198 or a 225 with an automatic & 2&1/2 BTDC if a 225 cube & a stick!. bump the timing up to 15. get the FBO $22 plate to limit the total to 32. play with the jets (hopefully it is a Holley). toss the heavy dist spring & replace it with a mr gasket #925B or MP light spring in its place. Maybe advance the cam 4 deg. If so tune the dist last. If you are under the pinging point at any time you are OK.
live every 24 hour block of time like it's your last day on earth
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2231043
01/09/17 08:04 PM
01/09/17 08:04 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
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up yours
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I would not bet on a Mexican market Dart having anything close to US spec's in 73. I know for a fact that points were still used in the Mexican market GM's until at least the 80's.
Assuming it is a Mexican market Dart and not a US spec one.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: 225 swap to 318?
[Re: RapidRobert]
#2231223
01/09/17 11:50 PM
01/09/17 11:50 PM
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Joined: Jan 2003
Posts: 43,575 Round Lake Beach, Illinoisy
Rhinodart
Rhinotruck
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Rhinotruck
Joined: Jan 2003
Posts: 43,575
Round Lake Beach, Illinoisy
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I just sold a 72 Mexican Dart with a slant six that was originally a 3-speed on the column but changed to a 904 and all the parts were the same for a US Dart. It had points distributor too.
The funny thing about science is that if you change one miniscule parameter you change the entire outcome to the way you want it.
JB Rhinehart, Realist
A-Body's RULE!
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2231232
01/09/17 11:57 PM
01/09/17 11:57 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
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Posts: 14,889
up yours
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Yeah, but 73 is when a bunch of stuff changed.
Electronic ignition, bigger bumpers, smog stuff
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2231256
01/10/17 12:24 AM
01/10/17 12:24 AM
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Joined: Jan 2003
Posts: 20,183 Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
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Park Forest, IL
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As said before, something is wrong. Try fixing it first. I'd bet if you're disappointed with Slant mileage, 318 will cause you to frown too.
I just did a 340 install in a '73 Slant Duster. A good tune-up on your Slant will be much easier and cheaper.
"Everybody funny, now you funny too."
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Re: 225 swap to 318?
[Re: EduardoIbarra]
#2231282
01/10/17 12:53 AM
01/10/17 12:53 AM
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Joined: Nov 2003
Posts: 12,494 Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
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Really? My friend drives his 70 340 Cuda all over the country and gets 20 mpg all day long. I got 23 mpg in a 73 D100 318 no problem. My 79 B200 318 w/ 833OD got a steady 26 mpg. Over 20 mpg for a 318 A-body should not be hard to do. Like stated before, maybe see what all is wrong with the /6.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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