\6 swap question

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Vali68

Vali68

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I found 2 possible candidates to replace my slant 6 that has the cracked block. The first one is a free \6 from a 66 Valiant. Will this one mount on my 68 Valiant with no issues? I heard some where that the earlier model \6 had a different arrangement or something with the tranny.
Or I found a newer 5 freeze plug engine that came out of a vehicle that was running propane before. The numbers on this motor are 4343 730. The numbers on my block are 2463430-13. Can I use this one? I heard the 5 freeze plug motors are newer and better built.

I also have a third choice for 250 as well. The numbers on this block are 2806830-3. 5 freeze plug on manifold side.Will this one work?
 
Old engine with a newer post 1968 tranny is a bit of a problem...you will need an old transmission to match, or you can get a modified torque converter that will mate the two of them together. I just got the TC from Hughes Performance; it was $220 plus shipping. It has the small snout on the front to match the smaller crank pilot hole that is in the old engine's crank, and it has the right number of splines to fit the input shaft on the later tranny. Or, you could pull the crank out of the early engine and get it drilled to match the larger snout of the late TC. One thing you can't do, though, is turn down the snout diameter on the later TC to fit the smaller crank hole. Not enough metal on the snout.
 
If I'm not mistaken, the industrial slants were a little more beefy. But it seems like your going to have to pay for the free one in any case, unless you get the tranny with it.
 
DustyRoads said:
Old engine with a newer post 1968 tranny is a bit of a problem...you will need an old transmission to match, or you can get a modified torque converter that will mate the two of them together. I just got the TC from Hughes Performance; it was $220 plus shipping. It has the small snout on the front to match the smaller crank pilot hole that is in the old engine's crank, and it has the right number of splines to fit the input shaft on the later tranny. Or, you could pull the crank out of the early engine and get it drilled to match the larger snout of the late TC. One thing you can't do, though, is turn down the snout diameter on the later TC to fit the smaller crank hole. Not enough metal on the snout.
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This is all really good info and advice.:glasses7: Nice to see a no B.S. posting like this.
 
I've got a bit of the same situation with a '67 motor I'm picking up to rebuild, and this is really helpful. Thanks, everybody!
 
The nice thing about dealing with Hughes was they knew what I wanted. I didn't have to explain it in super-detail; the guy (Pete) said, "We have those", and gave me four different stock numbers for four different stall speeds. When I dropped the order, I got it in three days. Nice folks.
 
DustyRoads said:
The nice thing about dealing with Hughes was they knew what I wanted. I didn't have to explain it in super-detail; the guy (Pete) said, "We have those", and gave me four different stock numbers for four different stall speeds. When I dropped the order, I got it in three days. Nice folks.
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I needed the same thing; early (small) pilot hole, forged crank/late 904 (1968.)

Only differece was, mine (also from Hughes) was $500.00....:angry7:

But, it stalls to 3,000 rpm, no problem...:blob:
 
One other option, I think you can change the input shaft in the later transmission to an early one to use the early torque converter, if you can find the parts, but they are cheap to ship. Smart to rebuild the tranny first anyway. It isn't hard if you get the ATSG manual and good snap-ring pliers, but don't quote me since I never did this.
 
Makes sense that you can swap the input shaft, but I'd question the economics. I just rebuilt a 904 and it was over $100 for the kit and another $30 for a front band, $25 for the book, and a bunch more for the cleaning supplies, snap ring pliers, etc. If you can get away with just swapping the converter, I'd go that way. It's not overly difficult, but complex and time-consuming. But the forum is all about options, and you brought up one that certainly would work!
 
I am running a 1965 170 small crank engine, 1964 pushbutton trans, with the 1968 up front pump and input section with the V-8 four disc clutch pack. Converter is a 9.5 inch with the small snote and the large splines. This is in my 66 Cuda.
PS: It is NOT possible to install the low ratio later gear set into the 65 and older case, without major mods.
 
According to the Mopar 6 cylinder manual, the only engine affected by the crankshaft flange change was the 170 CID. They say all 198 & 225 used the larger flange.

The best heavy duty crankshaft (same source) comes from the truck. The forged crank was phased out at the end of the 76 model run. The two cranks are not interchangeable (balance issues). In the stamping on the block look for 225E for a cast crank engine.

IMHO, having a cast crank engine may not be such a bad thing. It depends on how the car is to be used and what kind of power do you expect to get from the engine. Though the forged crank is the stronger of the two types, its mass works against it when the engine revs up. The cast crank should rev up quicker than the forged crank, all else being equal.
 
...another option. use the 66 engine with a newer crankshaft for the larger counterbore......
 
2 Darts said:
According to the Mopar 6 cylinder manual, the only engine affected by the crankshaft flange change was the 170 CID. They say all 198 & 225 used the larger flange.
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That is incorrect. the 170 and 225 both had the crankshaft flange/pocket change between 1967 and 1968, same as the small block. The 198 engine was not even in production at tha time, so yes, it only came with the large crank flange/pocket.
The best heavy duty crankshaft (same source) comes from the truck. The forged crank was phased out at the end of the 76 model run. The two cranks are not interchangeable (balance issues). In the stamping on the block look for 225E for a cast crank engine.
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This is sort of correct. It was not all truck crankshafts. just the 225-3 truck engine, which had a shot peened crank, according to chrysler, but not many have ever seen one. Also the cast crank has different size main and rod journals, then the forged crank. so it is not just a balance issue.
IMHO, having a cast crank engine may not be such a bad thing. It depends on how the car is to be used and what kind of power do you expect to get from the engine. Though the forged crank is the stronger of the two types, its mass works against it when the engine revs up. The cast crank should rev up quicker than the forged crank, all else being equal.
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This is totally correct, if I remember correctly, the first slant door slammer in the 10's had a cast crank.

The Mopar slant six manual has a lot of good stuf in it, but there are also some mistakes.
 
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