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Large baffle leak

vernon smith

Well Known Member
The picture below is the baffle at the rear of the engine with the top motor mount protruding through it. I'm looking for an easy effective way to plug up/cover this huge pressure leak.



Carl.jpg
 
You can mold or buy a fiberglass cup which mounts to the baffles and covers the hole. Alternately, you can take a piece of baffle fabric and make a baffle to seal the opening.
 
I just made some nice looking fiberglass covers for mine using 8 oz disposable food containers as plugs. The kind you get at the deli for stuff. Someone does make and sell them though.
 
I made my own out of fiberglass. Use a greek yogurt single serve container and clay to make the form.
 
Engine Mount Covers

I hammered a pair of covers out of some 3003 half-hard sheet. Annealed twice during the work if I remember.

i-9d59Vcq-M.jpg
 
ok, now if you go to the left of that mount, see that big opening with the screen over it, that is your heat for the floor. I have one also, I always have high cyl3 heat in the summer. guess what happens when you close off the heat in cabin, it gets dumped into the wind so to speak. so in the summer you have a total leak of cooling air off that no3 cylinder. I would be more concerned with blocking off that in the summer.
 
ok, now if you go to the left of that mount, see that big opening with the screen over it, that is your heat for the floor. I have one also, I always have high cyl3 heat in the summer. guess what happens when you close off the heat in cabin, it gets dumped into the wind so to speak. so in the summer you have a total leak of cooling air off that no3 cylinder. I would be more concerned with blocking off that in the summer.

Yes, that goes to one of the heat muffs.

Something that has help many. Throw a couple washers on the bolt holding that rear baffle between the baffle and engine. That should help those last two cylinders a bit.

If the middle cylinder is significantly higher than the rear, that won't help.

You can also look at the castings between the fins on that cylinder. Sometimes there is quite a bit of waste material blocking airflow. Get a small file and remove anything that doesn't look like a fin. It will be obvious.
 
ok, now if you go to the left of that mount, see that big opening with the screen over it, that is your heat for the floor. I have one also, I always have high cyl3 heat in the summer. guess what happens when you close off the heat in cabin, it gets dumped into the wind so to speak. so in the summer you have a total leak of cooling air off that no3 cylinder. I would be more concerned with blocking off that in the summer.

Not exactly correct. In winter the air goes to the heat muff and then to the cabin. In summer the air still goes to the heat muff but gets dumped to the bottom cowl, not the cabin. This dumped heated air into the bottom of the cowl also reduces the pressure across the engine, slightly reducing engine cooling.

The point - you will alway be taking air from the top of the engine unless you block this outlet.

A compromise - install an orifice in the SCAT hose flange, perhaps an inch in diameter. You will still have boatload of heat for the cabin, just a little slower but hotter. Make the orifice out of 0.032? aluminum, cut it into a disc, drill the 1? hole and use aluminum tape to hold it in place. The SCAT hose goes over it.

Carl
 
You don't want to completely block the flow of air to the heat muff, just reduce the flow. The heat exchanger needs some air flow. No flow will seriously shorten the life of the muffler and heat exchanger.
 
Yes, that goes to one of the heat muffs.

Something that has help many. Throw a couple washers on the bolt holding that rear baffle between the baffle and engine. That should help those last two cylinders a bit.

If the middle cylinder is significantly higher than the rear, that won't help.

You can also look at the castings between the fins on that cylinder. Sometimes there is quite a bit of waste material blocking airflow. Get a small file and remove anything that doesn't look like a fin. It will be obvious.
I've done that. you are not getting my point. I will do this when summer comes. I'm going to block off this hole, it robs cooling air from no. 3, my problem cylinder. it makes perfect sense. sure I have put the washer in that spot, sure I opened up the area for the fins, still gets hotter on no.3 than any other cylinder. so why not cut off the air leaving right there to the heater valve, which in the summer when closed goes out no nowhere, not cooling the jug on no.3, it's a no brainer to stop the exit air. so that's my goal this summer. :)
 
You don't want to completely block the flow of air to the heat muff, just reduce the flow. The heat exchanger needs some air flow. No flow will seriously shorten the life of the muffler and heat exchanger.

thought of that very thing also. I was also thinking of rerouting that hose to the very front of no.1, where the air comes in. I have two heaters on my RV, left and right. I have the left taken at the very front on the left side, that goes to the left exhaust and goes into my panel, heat at the panel is very nice. this right side comes off the back at no. 3 jug. my no4 jug does not get hot even though there is the oil cooler there, strange, but that 3 does. So, maybe I'll just block that rear right side and put it up front like the left side. I do see blocking the heat muff from air flow could cause it to fail, don't want that. :)
 
I've done that. you are not getting my point. I will do this when summer comes. I'm going to block off this hole, it robs cooling air from no. 3, my problem cylinder. it makes perfect sense. sure I have put the washer in that spot, sure I opened up the area for the fins, still gets hotter on no.3 than any other cylinder. so why not cut off the air leaving right there to the heater valve, which in the summer when closed goes out no nowhere, not cooling the jug on no.3, it's a no brainer to stop the exit air. so that's my goal this summer. :)

You need to allow some flow through the heat muff. Otherwise the heat muff insulates the exhaust pipes and the pipes get/stay too hot. Reducing the hole to 1" might be a fine compromise.
 
I completely closed the hole off on the back baffle. I then inserted a "Y" in the scat coming from the front air supply. Still more heat than I need and helped reduce CHT on number 5
 
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