Need info on 251 engine

[Michel D]

No i just need to no if y can have parts for them.

The only one that is damadge is in the M152
The guy was using it to push snow and sand!!!

Now i have a bad oil pressure it start cold at 40 psi and drops wen it
warms up!
But the thing is that the oil pressure is fluctuating

[Wpns 421]

I had the engine in my M37 rebuilt in Hull at a small garage that rebuilds engines. I have all the pistons etc. If you need parts the best place to call is Vintage Power Wagons in the US they have absolutly everything for the Dodges. Yesterday I called them and ordered new spark plugs for the M47 and M43.
In my M series vehicle I use a special oil sold by Stinson Fuels, it is a 15W40 oil designed for older type trucks it is design for older type engines to compensate for higher RPMs while having the viscosity and durability of newer diesel engines. My salesman sold told me this, so I bought a couple cases and use them exclusively on the M37, M43 and especially the Iltis.
Michel j'ai beaucoup de pieces pour ton camion. appel moi si tu as besoin de quelque chose. 819 827 4361 Gilles

[Michel D]

Ok dose some one no what could make the oil pressure on my engine fluctuate 10 to 15 psi!
I no that my gage is ok.
it is not the oil filter.
The oil pressure starts at 45 psi cold and start fluctuating between 35-45 psi. and more the engine warms up the pressure goes down and down!

May be the oil strainer is taking some air!

[Alex Blair (RIP)]

Originally Posted by Michel D

Ok dose some one no what could make the oil pressure on my engine fluctuate 10 to 15 psi!
I no that my gage is ok.
it is not the oil filter.
The oil pressure starts at 45 psi cold and start fluctuating between 35-45 psi. and more the engine warms up the pressure goes down and down!

May be the oil strainer is taking some air!

Micheal..This is normal for the oil pressure to drop back after warming up..
and it will go down after warming up and will fluctuate with changes in RPM..
My old flat heads would start out cold at 40-50 PSI and drop to zero pressure at an idle warm..If it bothers you..put a piece of tape over the gage ..so you can't see it ..Sounds normal to me..

[Michel D]

The problem is the 2 other engine that i have starts up at 45 psi and stays at 40 psi HOT!

[Alex Blair (RIP)]

Originally Posted by Alex Blair

Micheal..This is normal for the oil pressure to drop back after warming up..
and it will go down after warming up and will fluctuate with changes in RPM..
My old flat heads would start out cold at 40-50 PSI and drop to zero pressure at an idle warm..If it bothers you..put a piece of tape over the gage ..so you can't see it ..Sounds normal to me..

Mike..
If you start at 45 PSI cold and you drop off 15 PSI..even 20-25 PSI..that would still be lots of oil pressure..hot..15-25 Psi HOT IS OK..YOUR OTHER TWO ENGINES MUST HAVE BEEN REBUILT AT SOME POINT..

You may want to change your oil over to straight 40 Weight..non detergent oil..That was the summer weight oil that it was designed to use..Multi grade detergent oils were not even invented when that engine was designed..
It wasn't until 1968 that Castrol came out with it's Castrol GTX 20-50Weight multi grade that multigrades came into play..
And then they cut back on the zinc and phosphorous as anti wear additives when the catalytic converters came in so there are a lot of changes in motor oils since the 251CI came into being..Go back to the oil that was designed to run in it and enjoy it..

That is if you drive it only in the summer..you could drive it when it was cold but may have to plug it in to warm the oil before starting..Even with 40 weight ,non detergent oil in it you will see some drop in pressure..
That would quiet your engine,not drop as far on the oil Gage and work OK ..But the engine may be getting a little tired and a new set on main bearings and a regrind on the crank ,if it needs it ..but I wouldn't worry about it and drive it like it was until you decide to rebuild it..
Enjoy it and don't worry about it..
BUT..if it still bothers you..change the oil guage..It is probably worn out and will flicker and vibrate and do all sorts of tricks..it would be my first step ,if it was mine..

[Michel D]

thanks for your help i found out that the oiling system is not the same on this one!

[Bob Carriere]

Bonjour Michel

All oil is thicker when cold and the oil pressure will be high. Once the oil gets hot and thinner and water like it will leak from every bearing on the crank and on the camshaft. You may have just one or two worn bearing but it is enough to drop the oil pressure...... some sludge circulating in the oil system could explain the fluctuation or you have a worn bearing that may be moving...spinning on the lower end of a rod and drip more and somethimes less.

Old M37 would run well on 20 to 25 pounds warm..... below that I would get scared of doing damage.......

If you care about saving the engine before you get real bad damage..... don't drive it..... tear it down before you need a major regrind or score a cylinder wall...... if everything is worn loose you will never find oil thick enough to bring the pressure up......

Parts are readily available check out......www.vintagepowerwagons.com make sure you look at the Canadian 251 engine parts

Another excellent source of information is.....http://www.dodgepowerwagon.com

Like Gilles offered I may also have parts also....... you might be able to get away with just flipping the engine over and doing crank main and rod bearings
....... I even polished cranks by hand with progressively finer emery paper.... not a good job but the darn thing ran good..... they are fairly forgiving compared to modern thight clearance engine.....

Do you have a Dodge military shop manual for the engine..? Dodge flat heads are not hard to work on...... except you have to take the whole darn block to the machine shop to get a valve grind job.

Boob