Anatomy of a Flame Arrestor

Hi all,

I have for the past several years had my flame arrestor's position on the valve cover blocked off with a pipe plug. I probably did this because I had misplaced the unit. I don't drive the vehicle much but would like to have this part of the PCV system working. Can I just install a straight NPT adapter for a 3/8" hose into this hole and plumb it into the air cleaner or is there more to the internals of the IH flame arrestor that I should split for a replacement unit?

 

The purpose and design of a flame arrestor, using fine metal mesh, steel wool, or something similar, is to cool any gasses enough that a flame front can't pass through it and into the crankcase. It works the same as putting wire gauze around the flame of a lantern, making a "safety" lamp safe to use in the possibly combustible atmosphere of a mine.

 

Oddly I was cursing several IH part suppliers tonight looking for a few items when I ran across a spark arrester which is probably the gismo you are looking for.

 

That's close but looks more like the PCV valve in the rear of the engine behind the carb in a grommet set into the valley cover. It doesn't have the threaded part. True to ScoutParts.com standard operating procedure it is also incredibly overpriced.

 

Or, make one by threading two close nipples into a female connector after putting a wad of coarse stainless steel wool into the connector. Get fancy and use brass pipe fittings, or turn parts on a lathe and ..... Yes, use some Yankee Ingenuity, but be sure it functions correctly as an arrestor.

 

The one from Scout Parts is the type that connects in-line with a hose on either side.
Super Scout in Springfield sells the thread-in style for the valve cover.
http://www.superscoutspecialists.co...ster-scout-800-scout-ii-pickup-travelall.aspx

 

I have always used a small screwdriver and poked out the old mesh. Then would put course steel wool back inside.
It catches the oil from the air before it goes into the carb.

I have tried those cheap Mr. Gasket vents. But unless you have it mounted to about a 4" tube. They will spray oil out from it.
If you don't want to run a hose to the air cleaner. Clean the spark arrestor and mount the filter to the hose end.

 

I don't currently have an OEM flame arrestor available. That's why it's plugged off. I've been messing around with this and think I have a good solution but may need to have some fittings ordered to the local Fastenal. The head scratchiest part is that the bung on the valve cover seems to be a 1/4" NPT. However, any standard 1/4" NPT I try to thread in there binds up on the first couple threads. The plug is an internal flare type and goes right in. And I had a spare 1/4" external flare type which works fine as well (but doesn't suit my design). Seriously - Are flare NPT fittings different from not flare with regards to diameter and thread spacing?

 

If you have a thread pitch gauge, it is easy to determine if the bung hole is threaded 1/4" x 18 or something else. Most fittings for connecting tubing or hoses use standard screw threads (e.g. 1/4 x 20), not those of the NPT system. Your bung hole may have one of them, in which case you can try screwing in a bolt to see how it fits. Here is a table giving thread size for a variety of common hydraulic fittings:

https://www.discounthydraulichose.com/v/vspfiles/downloadables/thread_guide.pdf​

That's not to say there aren't fittings with one end being NPT and the other having a different form.

 

Dana Strong, that article is a keeper. I'm off work next few days I'll track down the right fitting tomorrow. I was looking at ways to plumb the arrestor into my air cleaner and came across this doodad from K&N. It's for marine applications and they call it an Air Filter Vent kit.


Goes between the upper and lower plates. It's about $15. The other option I had thought up was using a couple of NPT adapters attached to each other through a hole I'd drill in the lower plate. The latter would hide the hose better. I'll make the game-time decision once I get there.

 

A nylon (brass if you wanna splurge!) elbow nipple (about $2) from the hardware store going through the bottom plate will be more like oem and make pulling the air filter off a lot easier--I know I check my carb/choke often...

 

This is what I did to the 68. The filler cap/breather was in a Help aisle and then picked a grommet and elbow. The hose connects to a factory fitting on the air cleaner. This will keep it a stock closed PCV system. If you want OEM, the one listed from Super Scouts is the way to go.

 

Greg, that's purdy neat!

Here's what I did:

Fittings:
5/16" JIC x 1/8" Male NPT
1/8" x 3/8" Reducer
3/8" Male NPT to 3/8" Hose Barb Fitting
Cost: ~10-12 bucks.

Inside the Reducer/Barb fitting threads I place some clean steel wool. Air flow isn't horrendously restricted (I could blow threw it). The steel wool is split up because I stuffed some into the barb fitting cavity and another piece in the reducer cavity so it wouldn't interfere w/ the threads while assembling.

 

Just noticed in my FSM CGES-160 Page 55 that Item 65 states: "Install flame arrestor and hose to left cylinder head cover. Note: V-392 engine uses one flame arrestor in each cylinder head cover." My valve cover w/ the flame arrestor bung is on the passenger side which is the right side viewed from the rear. It was like that when I bought the vehicle in 2003 so I put the valve covers back on that way when I rebuilt the engine. Is there something wrong w/ that?

 

mine is on the passenger side ... someone asked me if I switched them at a work day the other day .... no one could offer a reason that it was a bad thing ... in fact for me it puts the oil fill on that side towards the front ... seems like a betters spot than in the back on the drivers side

 

hmm... I was just researching this today because when I got my Scout there was nothing attached to it. I was boggled why I couldn’t find a new one anywhere, and apparently they are hard to come by. I thought it was a bad PCV valve because I pulled it out and it didn’t rattle. Now I have to look to see if that mesh is there.
Also mine is on the driver side (345)

 

SSS has them listed on their site. I wouldn't throw it away though, seems like it's easily serviceable. Plus they are harder to come by.
I found a shot I took in 2010 of my heads, and I don't see any differences between the two. I think the Flame Arrestor on either side is probably fine. Which is good - cuz I'm not swapping VC's

 

Other half of my DIY flame arrestor - the connection to the air cleaner.

2x - 3/8" to 3/8" adapters
1x - 3/8" to 3/8" 90 degree female adapter
1x - 3/8" to 3/8" hose barb fitting
1x - 5/8" grommet.

Installing the grommet required a 3/4" drill bit and some dremmel work to clean up. Ball peen hammer to straighten the flange before installing. Does form a tight seal - had to lube fittings to get them through w/o bending the pan.
I believe my total cost was probably $15 for this part. Unavoidable either way because I would have had to install it even if I had just bought a used arrestor from SSS. I do need to investigate finding a 3/8" hose fitting w/ fewer barbs on it or shave some of them down because I can't pull off the hose after installing haha. I'm not even using a clamp.