Need to know compression ratio for a '78 Dodge motorhome w/ 440

Question

we failed our smog test and I wan to go through the motor and test everything to see where I'm sitting, but I don't have a manual, never owned a dodge or motorhome, and don't know the specs for the motor.

Answer 1

all the ones i have seen on the motor homes including the 78 that i own have a 9;1 ratio on them,mine has the 440 4 barrel carb on it,with air,and yes its a gas hog,about 12 miles to the gallon or less,but they was good engines,good luck

Answer 2

The only advertised ratio I've ever seen for 440 motor homes was 8.7 to 1 and I've never seen a two barrel 440 of any kind, not saying  they weren't made, just saying I haven't seen one. The later model 440's compression ratios were sometimes as low as 8.0 - 8.1 from the factory when actually measured by your local machine shop, I personally saw this three times at two different machine shops and was surprised. The 1978 Chrysler with the 440 four barrel engine had an advertised compression ratio of 8.2 -1.

Don't know why you need the info and it makes no difference but if you're doing a rebuild remember the higher the compression ratio, the higher the octane needed to prevent spark knock.

Answer 3

8.7 to 9.1 depending on 2 or 4 bbl and the type of heads you have, use 9.1 if you have '904 casting heads jet 2 point richer for a 4 bbl carb