I am looking for the specs on a 78 440 pulled from a motorhome.

I know its a low compression motor, but how low? Is there a difference between truck engines and the RV counterpart in the compression range? Are the RV heads different cc? Years ago I had a 78 D250 with a 440, and the heads on it used a tapered seat sparkplug rather than the compression washer style.

I have 906 heads I can use, but if thats not going to change the compression I'll probably just use what it has.

This is going to be a low budget spruce up using a whiplash cam, and other parts I have on the shelf. Just looking for a choppy idle grocery getter that makes people wonder if its fast.

Mopar made two different 440 truck and motorhome motors, the regular 440 and the 440-3 H.D. motor. Which had extra cooling passages in the block and heads for cooling the exhaust seats on the motor mount side of the blocks, those 8 holes are around .200 diameter in the blocks and heads and steel shim head gaskets
As far as the compression ratio I'm thinking they may have had the same compression ratio in both motors, I'm not sure of that in 1978 though

I believe the 440-3 motors are the ones that use the tapered seat plugs.

I and a buddy both had over heating problems using those blocks without the properly matched heads. You need the 452 with the tapered seats and holes to match the blocks. My truck and his Cuda would hit 230 plus easily. We were both using 906 heads. I gave up on my truck motor and put the 400 back in to sell it. He changed out his block with a 70 before it fixed it. I remember people having problems in motor homes after a rebuild if they used a head gaskets without the extra holes as well. Now I think all head gaskets have extra holes. We live in Texas and it is hotter than most parts of the country.

However, someone is going to say they ran the MH block and 906, etc heads and had no problems. Well, mopar designed it with holes in the block and holes in the heads to match for a reason. It was to cool the heads better.

I have a 78 440 from a motor home in my 77 pickup. They are 8 to 1 compression. I would use the heads that are on it. Mine has an rv cam of unknown specs that was in it when I bought the engine. It's definitely not a high horsepower engine, but it's got plenty of torque.

my 78 440-3 from a MH runs just fine in my 88 d100 even uses the d100 318 rad/shroud.

it has the #452 small "peanut" plug heads or did have. I changed them out 20,000 miles ago when I installed a set of the car #452 regular plug heads along with the whiplash 440 flat tappet cam/springs.

180* t-stat and holds around 190*- 210 in slow traffic/dog days of summer here in FL. drops right back to the 180*-190* when moving along.

I did a home pocket port clean up/guides/back cut valves/3-angle VJ on the peanut heads and have them on the shelf.

I had more trouble with it running hot before I curved the dist. with my retard timing it would heat right up. locked dist full mech advance-dialed it right in on 32* runs like a beast and fine in traffic.

my understanding the "EXTRA" water ports are around the tapered plug seat to cool it and not to be confused with the steam holes in the heads which can get blocked with incorrect gasket.

I was cautioned about porting in the chambers and pockets as it is easy to find the added water passages with a grinder in these heads. the block port that feeds around the plug seat gets blocked even though the gasket has the hole. on the standard car #452 heads this hole/port is not drilled.

this is what I concluded rebuilding my 78 440-3 from a 1-1/4 ton 10 lug chassis MH for my 88d100. and have both sets of heads on the bench picking gaskets.

machine shop said it would be fine as it is basically the same head casting.

if you go with a whiplash 440 it is as described... idles like a funny car and cuzes in daily traffic no problems runs like a beast on the street.

my speed shop said those cam specs would not work with out comp/pistons/3500 TC/gears ect. ect…

stock truck 727 turning 2.76 gears with a 29/15/15 M/T sounds like a funny car coming thru town 3rd gear idling along 25 mph choppin away.

got the 833 4 speed and 3.91sg going together next.

good luck and you will like the whiplash line of cams. works great for lopo street engines.

hey peeps - finally joining Moparts! Figured I'd chime in with my recent experiences with "RV-440-3" engines to help clarify some things, particularly with the water pump housings and thermostats. Some of this will be repetitive and some not. I think it's pretty close to accurate but welcome any clarifications.

Background. My truck is a 2002 Dakota quad cab; 78 "RV" 440 from a 79 Winnebago Motorcoach, 46RH trans w/SMR adapter, Atlas 4, D60/14B, 40" Toyo's on Hutchinson beadlocks - the truck is built for rock crawling and hard core overlanding - I call it my 'Rocklander'. Lots of strong hardware and modern touches including Holley Sniper EFI and a CVF Racing serpentine kit.

My particular 440 is date coded 1978, 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 I think the car/truck 440s were 440-1. The major differences were mostly related to cooling, meaning as mentioned above two additional cooling ports at the outer edges of the cylinder walls, with (or in my case without) heads with the matching additional cooling ports, and, the big distinctive difference, the RV heads had 5/8-socket spark plugs with a non-crush-washer seal. The heads that were on my 440 are the typical 452s with the normal 13/16-socket 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, and here's the kicker specifically regarding cooling - 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, AND...a specific/matching 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 has a lower 'skirt' which when opened lowers down into the recess below it which blocks off the bypass port in the water pump housing, sending the majority of the coolant through the radiator...and without which (with a typical non-skirted thermostat) will not block the bypass port, which will not send the majority of the coolant to the radiator - it will just continually 'bypass/circulate' most of the coolant 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. My intel indicates the Mr. Gasket 'stats are of marginal quality but the Milodon ones are good. Pics of the Milodon (silver top) and Mr.G skirted thermostats -





...compared to a non-skirted 'regular/non-RV' thermostat -



But wait - there's more. The RV water pump housing has a recess just below the top which fits the thermostat perfectly, but the non-RV pump housings do not. And, 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. 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...in the RV applications...is supposed to be placed in the pump housing itself, and not in the upper thermostat housing. I don't think the thermostat is supposed to go in the upper housing, because 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 cast iron upper 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 do the proper cast iron welding to 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.

Here is my upper thermostat housing 'filled in' -



...and sanded flat -



...and Permatex 27036 'max torque' ultra grey to seal it all up -



Results: In the 2 hours or so of having my engine alive it had the standard non-skirted thermostat in it, and its been running between 210-225 the whole time. But after installing the skirted 'stat it got to 180* and tossed the anchor - never going a degree higher .

Anyway, hope this helps anyone else out there who has the RV hardware, especially in the cooling department.

Cheers,
- Sam

Welcome to the board! That's great information. Talk about over engineering. Thanks for researching that out and congratulations on the results!

That's some nice detective work, and I learned a thing or two today

Hmm. That’s quite some detective work. Leave it to Mopar to do some odd like that. I don’t know what housings either of the motors I had used but they would both go to 225 on a hot day in Texas in a heartbeat. The thermostat may have been the problem. I know my block was a NOS shortblock so I probably had a regular housing. I’ve still got the block but have not used it again.

sure thing - happy to help. I figured there were likely others like me banging their heads trying to figure out why their otherwise 'perfectly assembled' cooling system just isn't doing the j.o.b., so I googled it and found this thread, and just wanted to pass on what I'd found and experienced. I've had mine running twice now since swapping in the skirted 'stat and my 440 is running cool as a cucumber - just perfectly. I also have a double-thick Wizard radiator, but now I'm pretty certain the thermostat will be doing very little 'work' trying to cool the engine - I'm instead hoping that the thermostat will...like a Cummins...have to partially close itself to keep the engine at 180* - that would be eeeexcellent

The 440-3 and 413-3 were designed for extra heavy duty cooling purposes as many were used running continuously under load for marine, water and oil pumps, and generator applications. Both had anemic compression ratios down at a measured 7 to 1 or less.

413 uses a skirted themrostat as well, and as you noted will run hot with the regular non skirted variety- no matter what the little guy at autozone and his computer tell you. The 413 variety is radically different with a high mounted water pump housing that bolts directly to the heads, and the
heads have closed chambers that measure about 90cc and use sodium filled exhaust valves. Both the 440-3 and 413-3 heads have the peanut plugs located in the center of the chamber like a small block Chrysler. This helps alleviate detonation, along with the extra plug cooling passages.

I am working on a frankenmotor 440 rv block with the 413 small valve heads. Between the heads getting cooling first due to water pump design, the quench I will have with a zero deck piston and the closed chamber, and the cooling effect of the sodium exhaust valves, I should be able to run 9 to 1 compression on 87 octane swill. Motor will be all done at 4500 rpm which is fine for my motorhome or any towing application. Plan to run a 518 overdrive as well to keep the revs down with a 4.56 gear and 32 inch tall tire.

For those working with these that want a nice stump pulling torque cam for towing or RV get in touch with Mike Jones he will fix you up with his special grind for these engines. Sligthly higher duration with way more lift and area under the curve.