Year to year /6 compatibility

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brandongjohnson

brandongjohnson

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Aug 3, 2015
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Boston, MA
Hi there,

I've been a browser/occasional poster for a while now. I actually have an '84 D100 with a /6 and was directed here a few years back when I had a lot of questions about the slant 6 that's in my truck; so far this has been an incredible resource for me. It's a 4 speed A833 truck, and ideally I'd love to keep the slant. About 9 months after I got it, the truck started smoking quite a bit. After a valve adjustment/new seals and no decrease in smoke I decided to run a compression test (probably should have done this first) to find only 25psi on cylinder #5. I tried many different cheap "fixes" (longer freeway trips, marvel mystery in the cylinder, etc) to no avail.

I was planning on possibly just putting in a new set of rings on cylinder #5 but decided to try to do this right and actually do a proper rebuild. The only problem I have is finding a place to work/ability to have the engine out of the truck for more than a few weeks (it is currently still drive-able, although I avoid longer trips). I'm looking to put together a slant from another vehicle and then just swap it in a weekend or two. Since I'm going through the trouble, ideally I'd like to go with a "best" or "better" year(s) of the motor. Any suggestions for years to look for or avoid? Compatibility into my truck would be a little bit of a concern too, although from what I've read, most, if not all of these motors should bolt right in and up to the transmission as well. The motor/truck would just be kept mostly stock with the exception of the electronic ignition and Holley 1920 that I have on it now.

Thanks in advance for any help you guys can provide.

-Brandon
 
Been driving Valiants and other Mopars with slants in them since the 60's.I like the pre 1967 motors but that's just me.The 70's motors are good as long as you lose all the pollution control stuff and put on an early carb. That wakes them right up.Any year will fit in your truck especially seeing that it's a standard shift vehicle.I wouldn't use anything later than a 78
 
valiantwagonguy said:
Been driving Valiants and other Mopars with slants in them since the 60's.I like the pre 1967 motors but that's just me.The 70's motors are good as long as you lose all the pollution control stuff and put on an early carb. That wakes them right up.Any year will fit in your truck especially seeing that it's a standard shift vehicle.I wouldn't use anything later than a 78
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Do not use a pre 67 motor. The crank flange and flywheel mounting are different. Also whatever engine you use make sure the pilot bearing hole is finished. Some cranks for automatics are just drilled, and not reamed to size. Also a pre 81 engine will have a solid lifter adjustable valve train, not hydraulics like your engine. Nothing wrong with that, and can be converted if you wish. Just be aware of the difference.
 
The 68 and new have a 'better' combustion chamber than the old ones and the said bushing diameter of the pre 68 motors. Then there is the peanut plug and the drool tube heads. And the much later hydro lifter motors. all good.
 
I always thought the later model heads without the "drool tubes" to be an improvement.
 
Thanks for all the info guys. I'll keep an eye out for a post 1968 motor, otherwise it sounds like everything will bolt up. I have my fair share of projects, so I'm mostly just looking to keep this truck as reliable as possible. I'll probably transfer my 1920 Holley over for the time being and look into a 2 barrel in the future. The extra power is always a bonus, I'll see if I can find the sweet spot with a 1969-early 70s motor and try to avoid the low compression/emissions hassle.
 
jas0162 said:
I always thought the later model heads without the "drool tubes" to be an improvement.
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Pros and cons. No oil leak concerns, though seals for the spark plug tubes are cheap and easy to get. Peanut heads use a different spark plug (smaller hex), though probably good choices there. Biggest disadvantage is that you can't change lifters in the peanut heads without removing the head. My 2002 3.8L Chrysler is also like that.
 
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