slant 6 question

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trudysduster

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I haven't been on here in several years due to building new house and garage. Hadnt had the time. Also the cars I had then were not slant 6 cars but I have picked up 3 more a body cars and now I am dealing with slant 6 issues. Question is are most of these slant 6 /904 interchangeable. I read somewhere about the 1966 being a stand alone year that the crank is different and it has to mate with a 1966 only. Also can you put a slant six from 1967 Dart down in a 1976 Dart Sport with no real problems. I believe I have either a cracked head or bad head gasket on the 76 Dart Sport and for now I plan on dropping a different motor in ( from a 67 Dart )and going through that engine. just wanted to know a little bit before I get into it.
 
I'm no expert but tranny was change in 1968 . The hub size on 67 and earlier crank motor doesn't mate to 68 and up. Hopefully someone with more knowledge will chip in.
 
65 and older 904 trans is a cable shifted trans and has a small input shaft/torque converter pilot, flanged output shaft.
66-67 904 trans has a "linkage" shifter, and a slip yoke output shaft. Still has the small spline input shaft and converter pilot.
68 up 904 went to the large spline input shaft and torque converter pilot.
Also I think the speedo cable connection changed somewhere around 65, 66, and 67
not sure of the year, but sometime in the '70's the 904 had a "lockup" converter, which has a different input shaft spline, and converter.

You can put a 68 and newer slant six engine, in front of any slant six 904. If using the 67 or older 904, you need an adapter bushing in the end of the crank.
If you want to use a combination of early (67 down) engine, and late (68 up) trans you need a special built torque converter (not many converter builders will do this any more), or use a later crankshaft, or have the hole in the end of the crank made larger.
Keep in mind if using a late 904 (68 up), and engine in a 65 down car there will also be linkage issues, and a different driveshaft.

Also can you put a slant six from 1967 Dart down in a 1976 Dart Sport with no real problems.
Not easily. engine has the small converter pocket, converter has the large pilot.
 
65 and older 904 trans is a cable shifted trans and has a small input shaft/torque converter pilot, flanged output shaft.
66-67 904 trans has a "linkage" shifter, and a slip yoke output shaft. Still has the small spline input shaft and converter pilot.
68 up 904 went to the large spline input shaft and torque converter pilot.
Also I think the speedo cable connection changed somewhere around 65, 66, and 67
not sure of the year, but sometime in the '70's the 904 had a "lockup" converter, which has a different input shaft spline, and converter.

You can put a 68 and newer slant six engine, in front of any slant six 904. If using the 67 or older 904, you need an adapter bushing in the end of the crank.
If you want to use a combination of early (67 down) engine, and late (68 up) trans you need a special built torque converter (not many converter builders will do this any more), or use a later crankshaft, or have the hole in the end of the crank made larger.
Keep in mind if using a late 904 (68 up), and engine in a 65 down car there will also be linkage issues, and a different driveshaft.


Not easily. engine has the small converter pocket, converter has the large pilot.
so if I have a 1976 I should stay as close to that year as possible. I also have a line on a 1974 low mileage engine and that should work better in the 76. This is what I needed. Thanks
 
I heard that the blocks around 1974 are best if building a stout racing engine. The side web is thicker or such. The early engines had 3 staggered core plugs and later ones 5 in a row. Sometime around 1980, the head changed to "peanut" style and lost the spark plug tubes. Slightly later (perhaps), they changed to hydraulic lifters (changes to oil flow from block). I would avoid the peanut heads because you can't remove the lifters without removing the head (same deal in my 2002 3.8L V-6), and you can't get a performance hydraulic camshaft (if so inclined).

There was a version of the 904 transmission, termed 999 maybe late 1980's. I think it has advantages like a lockup converter and perhaps 4th overdrive gear, both giving better mileage. Would be interesting if it bolts up to a 1968+ Dart. I doubt they changed the crankshaft hole or bellhousing bolt holes. Google on AllPar, SlantSix.org, and others.

Sounds like the 1967 engine can't bolt to your 1976 transmission (crank hole too small). I think you can even have fit issues between an engine for an automatic and stick-shift of the same year, like the crank hole needs to be deeper to fit the stick's throw-out bearing. You might do best to swap the 1967 head onto your block, after at least a "ring and bearing job", though might be smarter to overbore for larger pistons while "in there" if compression is low since new rings doesn't fix "out of round".
 
peanut heads started in 1975 still solid lifter, til 1980. and yeah, there are performance cams available all the way thru the run of /6s... many have taken to having their original cams sent out and reground, which is another option.
998/999 versions came out in late 70s advantage was wider gear spread in 1st and 2nd vs regular 904. There never was an OD automatic made to directly bolt to a slant block. people have used the old '60s smallblock to slant trans adapters used in trucks and vans of the day, before they made a 727 case specific to a slant.
Lou Madsen ("Dart 270" on the /6.org site, IDK if he comes here) somehow adapted a GM automatic OD (I think it was a 200R4) to a slant 6.
The wider gear spread of the 998/999 helped off the line acceleration and the lockup converter (if it works, Mopar had lots of issues with the early lock ups) can save fuel under cruise but won't make much difference if you mostly drive "in town" below ~40.
 
Lou Madsen ("Dart 270" on the /6.org site, IDK if he comes here) somehow adapted a GM automatic OD (I think it was a 200R4) to a slant 6.
.
Lou did use the 200R4 in his Dart. Car can run mid 12's in the 1/4 mile, and gets mid 20's mpg on the road. However it was not a inexpensive conversion.
 
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