Engine venting (1 Viewer)

[akwheeler]

I have a old SB350 in my 40. I'n an attempt to make it as water resistant as possible I ran only 1 crank case vent from the PVC valve to the PVC valve vent on the carb. Is this enough crankcase ventalation or am I causing pressureization problems.

THanks for your help

 

[nailbender]

If you mean you hooked up the original PVC setup then your OK. More inportant is no water goes down the intake. A littel water in the oil won't kill your engine immediately but down the intake is a real fast death!

 

[Brian in Oregon]

Many military vehicles have long been set up for deep fording. I have a 1951 Dodge M37 that was set up this way. In fact, you could submerge the truck completely under water with only the fording intake snorkle and exhaust stack out of the water, and it would run for hours.

The trick is simple. These trucks were among the first to have PCV. The PCV intake was taken from the air cleaner, which could be hooked up to a snorkle. There was no other venting on the engine. When fording, you pulled out a handle on the dash, which was connected by a cable to a valve setup that basically shut off the PCV. This had the effect of pressurizing the engine. No matter how well sealed, there was a chance water could get in when the engine had a vacuum applied to it. But when pressurized, the water was positively kept out.

It was more complex than that, because the system was also set up to vent or pressurize the fuel tank as needed.

Axle are another issue. Often a hot axle hitting water is cooled, dropping the temperature inside. If the axle is hot enough, and the water is cold enough, it is possible to create a vacuum and suck some water in. These trucks only had atmospheric vents on the axles and transfer case, but some later trucks had vent or pressure lines run to them.

The transmission was also sealed, and had a drain plug that was installed on the bottom of the bellhousing to seal it up when fording. The bellhousing and transmission were open to each other.

It is possible to plumb the PCV on any vehicle to emulate what the M37 and other military trucks had. It might not be the easiest job of actually sealing the engine up.

As for the axles, tranny and transfer, in my opinion it would be best to simply run an air tank and a low pressure regulator, and have a vent setup that could be pressurized as needed. It wouldn't take a lot of air or rpressure to do this. In fact, you don't want much pressure because you risk blowing seals out. Two or three PSI is probably all that is needed.

My M37 has been upgraded to a Dodge 318 V-8. I have done things like drill and tap the bellhousing for such pressure lines, and was working on plumbing the axles and transfer for vent/pressure lines. The project went into limbo about four years ago due to a serious illnes, and I haven't gotten back into it to finish it yet. It will not be able to ford as deep as the original flathead six, but I think I can at least get it to ford up to the tops of the fenders. The biggest problem area is the ignotion system. Military systems are sealed. Completely. I'm hoping to find a surplus sealed distributer setup from some applications that ran 318 or 360 engines, but they are like hen's teeth. Otherwise it's a matter of trying to shield the distributer as much as possible and make sure the ignition wires are well sealed. Filling the ends with non-hardening silicon sealant helps a lot.

The electrical system is another issue. The M37 had a totally sealed generator and wiring harness. Unless you can find milspec generators or alternators, this is a problem, especially with salt water or water with heavy minerals. One way around this is to mount the alternator as high as possible on the engine. There are bracket kits to do just this for hot rods. Jegs carries them. The idea is to get the alternator above the water as muich as possible.

Another overlooked problem is the fan blades. You better believe that some fans are flexible enough that when they hit water they can literally pull themselves forward into the radiator. An electric fan can be turned off manually. Or you can run a fan with stiff blades and hope they don't bend. Or put a round guard between the radiator and fan so the blades will rub on it and not the radiator. On some WWII vehicles a small lever was set up so when disengaged it would loosen the fan belt to the point where the fan would not run. Obviously this was for very short distances, as the water pump did not work either.

BTW, don't forget to seal the starter.

 

[Mark W]

I have a old SB350 in my 40. I'n an attempt to make it as water resistant as possible I ran only 1 crank case vent from the PVC valve to the PVC valve vent on the carb. Is this enough crankcase ventalation or am I causing pressureization problems.

THanks for your help

If your engine does not have excessive blowby, then this will be fine.


Mark...