ok - just about everything is back together, and in the process I discovered a couple things.
First off, more 440 "RV" tech info. My particular 440 is date coded 1978 and was originally in a 79 Winnebago Motorcoach, and because it was intended for an RV is actually has a few minor but important differences between it and a standard car or truck 440. First, the RV 440s were designated at a 440-3, whereas the car/truck 440s were 440-1. The major differences were mostly related to cooling, meaning two additional cooling ports at the outer edges of the cylinder walls, with (or in my case without) respective matching heads with the additional cooling ports, and, the big distinctive difference, the RV heads had 5/8 spark plugs with a non-crush-washer seal (my heads are the typical 440-1 452s with the normal 13/16 plugs and crush washers, so either my 440 just didn't get 'em...or more likely the owner of the RV had the heads swapped out for non-RV heads - my engine did have Fel-Pro head gaskets on it, which was not original, so a head swap was most likely). Also, the RV 440s also received a specific
water pump housing, pn# 3751216, easily distinguished by either the CB on the front inlet or the additional bypass port under the thermostat, which I discovered is kinda important.
RV water pump housing (note the two cast recesses for the thermostat and bypass port) -
Also, I discovered that a "skirted" thermostat
must be used in conjunction with the RV water pump housing - at least it does if you want it to be cooled properly. The 440-3 thermostat (I opted for the Milodon 180* unit, #16406) has a lower 'skirt' which when opened blocks off the bypass port in the water pump housing, but without which (with a typical thermostat from the parts stores) will not block the bypass port, which will
not send the majority of the coolant to the radiator - it will just continually 'bypass' both within the block/heads (the intent being to warm up the engine rapidly) and some will go through the radiator, but not all, which I believe is why my 440 wasn't cooling well (it was cooling so-so, but not great) - and yep I had a standard 440-1 thermostat in there. Pics of the skirted thermostat are below -
To recap, here is my RV water pump housing -
But wait - there's more. All of the upper thermostat housings I've found have a recess in them too, which according to the books is to center the thermostat in the 440-1 non-RV applications. The strange part is my 440-3 water pump housing
also has a recess for...I think...the thermostat. Now, because the thermostat lower skirt is supposed to extend down into the lower recess and block the bypass coolant flow I chose to presume the thermostat is supposed to be placed in the pump housing itself, and not in the upper thermostat housing. Should the thermostat go in the upper housing? - don't know, but if it did then there would be the chance of it not aligning with the lower recess, so I went with the lower/below-the-gasket placement. Then, UltraGrey RTV, gasket, more RTV, and upper "thermostat" housing went on, bolted to 18 lb/ft. I'm pretty sure my thermostat housing is not for an RV application and is simply for all the 440-1 applications. I have not yet found a genuine 440-3 thermostat housing, but if I did I'd wager there is no recess in it for the thermostat.
But still, my thermostat housing had that recess in it...or at least it used to ;) . To try to get maximum clamping and sealing potential from it I went ahead and had a local welding shop fill in the recess, and I machined it flat - actually I machined it to perfectly match the pump housing with just the slightest detectable amount of center 'rise' to get that much more clamping on the gasket. So, just posting my process and pics for it all... :)
Upper thermostat housing 'filled in' -
...machined flat -
I got the Milodon thermostat, skirted/RV design (silver), compared to the less reputable Mr. Gasket version -
and Permatex 27036 ultragrey to seal it all up -
Now I only recently became aware of all this 440-3 "RV" info and I'm really glad I did. But while I was getting smart on the RV info I was in the meantime trying to find a better way to seal a big block thermostat housing. I was trying to find a way to use a more modern thermostat with the rubber seal around the outer edge, one which would not require using a gasket at all - just bolt the top housing down and 'done'. I did find a thermostat which I think would have worked great...at least for those with a non-RV water pump housing, NAPA pn# 375-180, which I think is from a 2nd Gen Cummins -
If I'm not mistaken, that thermostat (180* in this case) would simply sit on top of the standard water pump housing, and it would be capped off with the thermostat housing of your choice with the recess in it, and...I think...you'd never need a gasket. Anyone want to test my theory? :)
But, I have a RV pump housing, so, naturally, I can't use it :( - noooo I have to use the RV stuff....unless I swap in a non-RV housing...which I wasn't ready to do. Nope I'm gonna do the RV thermostat thing first and see how awesome my cooling system now will be. It's all back together and I'll be pouring in coolant tomorrow morning.
Interesting stuff I continue to learn in this Hot Rod life of mine. And, with all of this extra work done, I'm now inclined to think that...if I had originally assembled the system with the correct skirted thermostat the stock radiator may just have cooled my 440 just fine. If that were the case, then I am now inclined to think that with the correct 'stat in there now plus the Wizard radiator and max-duty fan and clutch...well I may just have inadvertently achieved a max-overkill cooling system for the truck which...I'm hoping...may just keep my 440 at 180* all day long...which is what I was hoping for to begin with 👍 . Time will soon tell...