Thoughts on early vs. late Slants.

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kevin charles

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Hi folks,

I plan on putting an A833OD into my ’66 Dart (225, A903, 3:23). The original engine is fine, but I also have a 1981 225 in a parts van I picked up.

My research has told me the main differences (crank, head, lifters, etc), but I don’t actually have any experience with the later engines.

Part of me wants to keep the original engine in the car (either one would get Super-Sixed), but another part of me thinks it might be nice to have a lighter engine that I don’t have to adjust tappets on, and that I won’t need a bushing to mate the trans to it. The original engine is a known good runner, and the ’81 is unknown. The latter would be more expensive, as I would tear into it and freshen it up, but that doesn’t worry me.

I’ve read all the accounts of folks saying the later engines aren’t as strong due to the crank, but that’s not an issue, because my only mods with be carb and exhaust, so still well under 160HP, which is nothing for these beasts.

I’m curious what folks that have experience running both might have to offer. Please feel free to tell me which you would run if this were your car and why.

Thanks in advance.
 
I'm confused. What bushing would you need to adapt the O/D trans to your original slant? For the later flywheel? You can't use the original 66 flywheel?
 
I'd stick with the solid lifter engine. The slant 6 was not designed as a hydraulic lifter engine and it makes a poor one, IMO.
 
kevin charles said:
Different pilot size, I thought?
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OK, if you're using the later flywheel with the early engine, I believe you're right.

However, and I've not tried this with the O/D trans, but I used my original 65 170 3-speed flywheel with an early 70s slant six and a 65 4-speed bellhousing and trans. All I had to do was machine the center opening in the 65 flywheel to fit the later crank's register.

If you can keep your original 66 flywheel, it of course won't need to be machined for a 66 engine. But I don't know if your O/D trans bellhousing takes the same size clutch as what you already have.

Apologize for editing this a couple of times.
 
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kevin charles said:
Different pilot size, I thought?
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No sir. The pilot bushing is the same. The difference is the crankshaft register where the flywheel/flexplate mounts. I believe the split is 68 and up is the larger crank register and 67 and prior is the smaller. So you have to use the matching flywheel/flexplate/torque converter for the given crankshaft register size.
 
Agree, the pilot bushing is the same. I was thinking of the crankshaft register surrounding the pilot hole. Which of course is not the same thing.
 
RustyRatRod said:
No sir. The pilot bushing is the same. The difference is the crankshaft register where the flywheel/flexplate mounts. I believe the split is 68 and up is the larger crank register and 67 and prior is the smaller. So you have to use the matching flywheel/flexplate/torque converter for the given crankshaft register size.
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Thank you for clarifying that. I have the right bell, the trans, and all the right clutch stuff, so looks like I’ll just need a Z-bar (and the 300 other things I don’t know I need yet).
 
Something to watch out for: A lot of slant six engines did not have the pilot bushing hole in the crank finish reamed to the correct size, if the engine was getting an automatic trans. The hole is drilled, but not finished. The pilot bushing will not fit these cranks. NAPA used to sell an reduced OD sized adapter bushing but these were discontinued many years ago. Therre are a couple of "fixes" if you run into this problem.
1) take a stock pilot bushing to a machine shop on have the OD turned down smaller
2) have the hole in the crank reamed to the proper size.
3) use a late model pilot bearing (if using a 1968 or newer crank) More Information for NATIONAL FC69907
 
Yes, the more I process all this, the more I’m thinking the exact same thing.

Some day I’ll do something with that engine. I do have a little bit of a Slant fetish, and they’re still cheap to pick up.
 
Use your original engine.
You know it's good, so why open up a bag of snakes for little to no reward?
The only thing that I like about the newer engines is that they don't have the drool tubes and have hardened valve seats.
Not a big deal...
 
People argue with me about it, but the simple fact is, the slant 6 was not designed as a hydraulic lifter engine. The lifters don't have pressurized oil. There's no oil passage through the lifter bores. They changed nothing when they went to hydraulic lifters. This means the hydraulic lifters are the last thing to get oil, so they don't really pump up too well. The hydraulic engines oil the lifters "backwards". Through the block, through the head, through the rocker shaft, through the rockers and finally they get oil from down the pushrods. It doesn't take a college education to imagine the pressure loss. It's just a terrible design as a hydraulic lifter engine.
 
RustyRatRod said:
People argue with me about it, but the simple fact is, the slant 6 was not designed as a hydraulic lifter engine. The lifters don't have pressurized oil. There's no oil passage through the lifter bores. They changed nothing when they went to hydraulic lifters. This means the hydraulic lifters are the last thing to get oil, so they don't really pump up too well. The hydraulic engines oil the lifters "backwards". Through the block, through the head, through the rocker shaft, through the rockers and finally they get oil from down the pushrods. It doesn't take a college education to imagine the pressure loss. It's just a terrible design as a hydraulic lifter engine.
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I never knew that.
Thanks Rob, I learned something new today!
 
Dartnut said:
I never knew that.
Thanks Rob, I learned something new today!
Click to expand...
That's why if you're old enough, and remember the cars when they were new, you remember that some of the cars and trucks that had hydraulic lifter slants were noisy on startup and some even did it off and on while hot. They just didn't make a very good hydraulic lifter engine.
 
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