1986 D-350 Engine Ideas

[skeeterkiller]

Hey, so brand new to the forum and Dodge in general, I just picked up this 1986 D-350 2wd with the stock 360 and 4 speed. I was hoping to get opinions on options for the engine. The current motor is not too happy and smokes like a steam train. So after some research I hope I am on the right track, Option A: Rebuild this motor (found a guy who says he can do it for $675) but this price doesn't include nor does he plan to do any machining, doesn't seem like that will work out too well long term but then again all new to this. Option B: Pull a LA 318 or 360 from a junkyard. Nearest pull-a-part has a big variety and if I only get the block and heads I could probably be out for under $300. Option C: MAGNUM!! For real though do you think a 5.2 or 5.9 swap would be worth it? If I reuse most of my LA stuff it probably be only a couple hundred bucks difference.

From what I have compiled so far is that either way unless I find another 360 LA I am going to be buying a flywheel. And to my understanding all 318s LA or Mag flywheels interchange as they are internally balanced motors. The 360 on the other hand is external so it needs a properly weighted flywheel and front damper to not shake itself to pieces. Also the 360 Mag and LA flywheels are weighted differently so they do not interchange.

So ideally I would like one of the Mag options as from what I have heard they seem pretty stout and you are better off finding one of those in a wrecking yard that is useable without needing to be rebuilt. I plan to go carb either way simply as I already have most of the stuff for it. Including the Holley 4 barrel that came with the truck. I also plan to to retain the LA front dress and timing cover since I already have it and it seems to be in working order.

Basically I am trying to buy as little as possible (at the yard) since they don't sell complete engines, rather they still charge per main piece (block, head, intake, etc). I understand that I will need a new carbed intake for which I plan to use this one. ($189 no-name dual bolt pattern for LA/Mag). I haven't decided on electric vs mechanical pump as its only difference is the hughes cam adapter or using a electric edelbrock pump I already have. I am not really worried about the cost of the intake since the dual pattern means I could basically keep it in the truck forever no matter what engine is in it. Not really sure yet about distributor, I may just reuse the current one in the truck as it seems to work well. So to my understanding that just leaves the flywheel, to which I am very confused. Specifically on the 5.9, is there an OEM one I could find out in the wild or is it just bite the bullet and buy it new, and if thats the case is the extra money worth it to have a 5.9 when I could potentially get a 5.2 and find a used flywheel? Also I have read about the weights on the LA 360 flywheel, if I remove them could I use it as is on a 5.2 mag since then I suppose it would be neutral balanced? This is kinda where I am at and really looking for some insight on the subject.

Like I said this is my first Dodge so still learning, not afraid of the work though and I am up for the challenge. My dad will be assisting me as needed so I am not too worried about the assembly side. Oh also the trans is in perfect working order with a brand new clutch kit so ideally not wanting to mess with that. Thanks

 

[JJEH]

Welcome to the forum.

If it was me and I wouldn't need it, then I'd recommend rebuilding the. Take your time and go over every part with that guy (if you trust him) and then take it from there as to rebuilding or replacing. In the meantime, you can check chassis, axles, etc. Let it be a nice father & son project, no hassle, no sweat, just quality time and not overdoing it. Because if you overdo it, it can become frustrating really quick and then the fun is gone.

 

[skeeterkiller]

Welcome to the forum.

If it was me and I wouldn't need it, then I'd recommend rebuilding the. Take your time and go over every part with that guy (if you trust him) and then take it from there as to rebuilding or replacing. In the meantime, you can check chassis, axles, etc. Let it be a nice father & son project, no hassle, no sweat, just quality time and not overdoing it. Because if you overdo it, it can become frustrating really quick and then the fun is gone.

Happy to be here! Lots of interesting topics and discussions going on. You might be on to something here, I don't have any reason to rush the process and I want to do it right. We actually restored a 80s Yamaha together and it was a lot of fun and I wouldn't trade the bike for the world. Our biggest worry with the cheapo rebuild guy is that if there is something wrong with the block and it doesn't get taken care of properly we may be back in this place in a year or two and trying to find a LA 360 block. The motor is the truck's original with 143k miles. But it was also on a farm and it has a gooseneck so I imagine they weren't easy. I spoke with a machine shop and to clean it up properly will be about $500-600 as long as the block and heads prove good, plus the $675 for shade tree rebuilder ($1200+ and no warranty on assembly). I suppose we could attempt the rebuild ourselves (rebuild kit shade tree guy is using is about $375) but we have never attempted a full rebuild. Our draw to the Magnum engines is it would basically be bolt and go accounting for minor things like intake, flywheel, dist, etc. Then if it died in a year or two we would just throw another junkyard motor in it. Both are work for sure but I like the thought of being able to find good 5.9s for the next couple of years without much hassle. Still though, we haven't settled on anything yet and are eager to hear about the pros and cons for each option.

 

[Travelin Ram]

What is the planned use? Daily driver? How many miles do you expect to put on it? Could be that something as simple as valve stem seals could get you another 100k miles.

I’d think about doing a wet/dry compression test and getting some idea of the overall condition before firing the parts cannon.

I have also extended the life of some old tired smokers just by getting stuck rings freed up. It’s not unusual in old vehicles for operators to get careless about oil changes and gum up the rings.

 

[skeeterkiller]

What is the planned use? Daily driver? How many miles do you expect to put on it? Could be that something as simple as valve stem seals could get you another 100k miles.

It would be mainly just a fun weekend kind of thing, but I would need it to actually do some work from time to time. I also want it to be able to comfortably drive 3+ hours at a time without me having to worry about it.(Craigslist/FB marketplace pickups) Probably not many miles anytime soon but I have no plans on getting rid of the truck, although I don't have a ton of money to spend on it I'd like to think I have enough to make it a very reliable and fun truck. (I'd like to stay under $2000 but its not a deal breaker to go over). You make a great point of freeing up the rings and the comp test, how do you go about freeing stuck rings? Would it be an engine out kind of job or is there some process or additive? Also the additional power of a carbed 5.9 is another draw, 250hp would be more than enough and if I don't have to throw a big cam in or anything to get it I'd be happy.

 

[Travelin Ram]

Diagnosis can be done easily in place. Let’s start with a quick and easy observation to assess ring blow-by. When it runs, we're looking to see if the crankcase has negative pressure (as it should if the PCV system is working and the rings are not terrible). I do a quick and dirty check by opening the oil fill cap -carefully with a rag over the area- and see if it's pulling air in, or blowing vapors or oil mist out of the engine. @Sherman Bird is a smarter guy than me, he attaches a vacuum gauge to the dipstick tube and looks for 2" of vacuum.

The outcome of this test; if it's pulling air in then the rings are likely not horrible and the PCV is working. If OTOH it's blowing vapor out the crankcase, next step is check the PCV system. Make sure the hose(s) are all intact and the valve works. It's a check valve, air should pass from the crankcase to the intake manifold, not in the reverse direction. Replace the PCV valve if in doubt and reassess.

A leaking or clogged PCV will lead to a pressurized crankcase which means more oil consumption, likely oil leaks, and buildup of sludge and crap in the block, which can contribute to stuck rings. So sort this first.

 

[Travelin Ram]

Now as to the rings: If you're getting a lot of blow by, and the PCV is working, clearly the rings are leaking. This assumes the engine is running on all 8 of course, and does not have a gross failure like a hole in a piston.

But let's pass that on for the moment, because you'll have to pull the plugs to check compression, and that's the next diagnostic step. Remove them all, keep track of where they came from, and give them a close look. There's pictures and videos all over the web of how to assess plugs, so I won't repeat that here. You will get a lot of good feedback here if you post pictures of the plugs and ask for input.

Plugs will likely tell you something about the relative health of the cylinders; are they all evenly contributing or are some oil fouled and others are clean?

 

[Travelin Ram]

Plugs out and inspected, now it's time for a compression test. Dry compression followed by wet will tell you a lot about the health of the block. Post up the results.

Uneven pressures will point you to some cylinders being more problematic than others.

Good pressure dry and wet close to the same indicates a cylinder with good rings.
Low pressure dry and significant increase wet indicates worn or stuck rings. (more later on how to find out which)
Good dry pressures all around indicate the oil isn't bypassing the rings which meaning more likely valve stem seals are the source of the smoke. Not necessarily 100% because oil rings and compression rings are different, but likely.

 

[Travelin Ram]

So by now, you'll have a pretty good idea of what's happening. Chances are you have identified a few cylinders that are the worst contributors to oil burning. Now to figure out of the rings are worn out, or just stuck. The only way to do that assembled, is assume they are stuck and try to free them. If oil loss improves, you're on the right track. If there's not improvement, then it's ring or cylinder bore wear, and you're out a little time and very little money. But you know what you have.

To free stuck rings, the process is inject the magic juice of your choice into the cylinders, a few ounces in each, and let it marinate overnight. Turn the engine over by hand, and repeat. Sometimes once will get it done, or it may take a number of repetitions. I'd do a couple of reps to start and then assess to see if the engine is getting better. Less smoke / less oil consumption. Oil consumption over miles driven is a better indicator, but slow.

Of course there's the question of what magic juice? There are a number of commercial products such as Berryman's. Some people like Marvel Mystery Oil, or homebrews like ATF/acetone mixes. I've had good results with diesel fuel. IMO any petroleum solvent works, and I've not seen any definitive science on what juice is fastest. No doubt some will dissolve deposits more quickly than others. But speed just isn't important if you're doing this in a situation where you have plenty of time.

After your ring freeing juice has had time to do it's work, turn the engine over by hand a final 2 complete revolutions, just to make sure there's not enough left in any cylinder to hydrolock it. Very unlikely, by now all that juice has seeped past the rings, hopefully taking gum and varnish with it, and landed in the crankcase.

Drain the oil and put fresh oil in the engine. New filter would be a good idea too, the juice may loosen up old crud in the oil pan too. At this point I'd spin it over with the starter (plugs still out) to expel any remaining solvent or loosened carbon out the plug holes.

Replace the plugs and fire it up. It will smoke like a chimney in the beginning, until the remnants of solvent and loosened deposits are burned up or blown out the exhaust.

After it warms up to temperature it's time to drive and assess. Hopefully the blue smoke is diminished, or maybe completely gone.

 

[Travelin Ram]

As long as you're in there, I'd say spend a few buck to get a borescope and take a look. Something like this:

https://www.amazon.com/gp/product/B01MYTHWK4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

That's a good tool for visual inspection to see what's happening inside the cylinders. Looking for carbon buildup indicative of oil burning as well as the cylinder walls to see if they are scarred, worn, or if the crosshatching remains.

 

[Sherman Bird]

Diagnosis can be done easily in place. Let’s start with a quick and easy observation to assess ring blow-by. When it runs, we're looking to see if the crankcase has negative pressure (as it should if the PCV system is working and the rings are not terrible). I do a quick and dirty check by opening the oil fill cap -carefully with a rag over the area- and see if it's pulling air in, or blowing vapors or oil mist out of the engine. @Sherman Bird is a smarter guy than me, he attaches a vacuum gauge to the dipstick tube and looks for 2" of vacuum.

The outcome of this test; if it's pulling air in then the rings are likely not horrible and the PCV is working. If OTOH it's blowing vapor out the crankcase, next step is check the PCV system. Make sure the hose(s) are all intact and the valve works. It's a check valve, air should pass from the crankcase to the intake manifold, not in the reverse direction. Replace the PCV valve if in doubt and reassess.

A leaking or clogged PCV will lead to a pressurized crankcase which means more oil consumption, likely oil leaks, and buildup of sludge and crap in the block, which can contribute to stuck rings. So sort this first.

Later model vehicles also have heated PCV's my 2004 Ranger 3.0L has an electrically heated one... I've a customer with a 2002 Ranger 3.0L whose PCV is heated via coolant. The purpose is to negate freeze up/ condensation due to the delta effect of orificed air's tendency to drop below freezing and form sludge at the valve, thus form sludge throughout the engine. (hot, oil vapor laden humid air is suddenly super cooled as it is crammed into a tiny orifice of the PCV valve, and that tends to emulsify the oil and force mixture with oil making a thick, soupy concoction which quickly becomes sludge.)

 

[pacofortacos]

Chances of finding a 5.9 magnum in the junk yard that doesn't have cracked heads would be slim. Better chance of finding a 5.2 without cracks - but the oem head is the weak link (mainly the exhaust valve seats).

However, there are aftermarket magnum heads - which are far superior to the LA heads as far as chamber design and flow.

Magnum vs. LA. Side By Side Comparison

The Magnum was Chrysler's final evolution of the true inline wedge engine. Here is a quick rundown of the differences and similarities between the 273 throug...

www.youtube.com

 

[PaPitt]

I'VE BEEN READING ALONG JUST Because I too have a 1988 D250 FLATBED / Automatic in mine . 143000. miles also .. & Mine also has the 5.2 318.
I'd sure like to have a 360 just for more power. As i'm retired now & I still have a big Farm. So the 5.9l motor would sure pull much better. & I do understand neither motor will get any fuel mileage. SO AGAIN the 360 sure catches my eye. I'm read all the post to you as to gain information for what I may want to do. .. But my vote is to find the 360 .. But I'm wanting to know what all I'll have to change .
A. Around the Flywheel & Convertor area.
B. What do i need for the intake / throttle body items. ''I DON'T WANT TO SWAP TO A CARB ON MINE''.
c. What about the computer , can it use my 318 computer or does it too need to be changed along with the 360 items.
I hope my comments help you think of all the question you need.

 

[Sherman Bird]

I'VE BEEN READING ALONG JUST Because I too have a 1988 D250 FLATBED / Automatic in mine . 143000. miles also .. & Mine also has the 5.2 318.
I'd sure like to have a 360 just for more power. As i'm retired now & I still have a big Farm. So the 5.9l motor would sure pull much better. & I do understand neither motor will get any fuel mileage. SO AGAIN the 360 sure catches my eye. I'm read all the post to you as to gain information for what I may want to do. .. But my vote is to find the 360 .. But I'm wanting to know what all I'll have to change .
A. Around the Flywheel & Convertor area.
B. What do i need for the intake / throttle body items. ''I DON'T WANT TO SWAP TO A CARB ON MINE''.
c. What about the computer , can it use my 318 computer or does it too need to be changed along with the 360 items.
I hope my comments help you think of all the question you need.

The 360 will bolt in to replace the 318. As for all the particular hoses, belts, wiring, I'd think they would be similar enough to work. I also think the torque converters MAY differ in that the 360 is externally balanced and the 318 is internally balanced, or vice-versa.
All the Mopar people I've ever known have all had good things to say about the 360. It'd be worth your while to check into it. Good luck, and Peace!

 

[u2slow]

@PaPitt I really think you need to correct (factory) pcm and throttle body to make the 360 swap viable. There's a bolt-on balance plate you can add from QuickTime.

Most people I know that are more gas-dodge savvy are of the opinion the 318 is noticeably better on fuel. This is more a 'half-ton/commuting' opinion though.

If this is for farm use, you may want to consider deeper axle gearing (say 4.10 or 4.56) for more grunt.

 

[PaPitt]

Yes Years ago I had a 92 or 93 half ton it as a nice truck. & While I GOT maybe 15+ with it. But it couldn't haul a trash trailer.
& Yes mine today is a farm truck .. I don't think my flat bed has 4:11's . I'm afraid if it did have 4:11's . it'd not get 4 miles per gallon. Because with what ever I have now It just get maybe 7 most of the time. But man I like this truck.
.... & Yes I've came to the CONCLUSION that I'd need the 360 computer also & I just believe That the only way to swap to the 360. WOULD BE FINE ANOTHER OLD Truck with a 360 & but the complete truck . So there's no wrecking yard trip adding to your cost.
SO i GUESS i'M IN THAT HURRY UP & WAIT.