Compression ratio vs. H.P. rating ?

[Reg Evans]

My 38 Dodge coupe with a transplanted 52 Dodge 230 and only 2K miles since a complete rebuild is my fastest old mopar in my collection including my 52 1/2 ton with a 251. I'm always amazed at it's power compared to the others.

I don't know if the head was shaved or not but,if not,the c.r. is suppose to be 7.0 and h.p.at 103.

In my junk pile I have a stoved up 59 Dodge 230 and it is rated at 8.0 c.r. with h.p. at 135.

Now, if I have that head cleaned up and milled a little can I expect to get at least 30 more horses out of the 52 engine?????

Can it really be that simple????? or were there other internal differences in the 52 vs. 59 engines.

Oh yeah,I'll also be adding cast iron headers and a 2 bbl carb. Should I add a drogue chute

[greg g]

Reg, check out the spec sheets for Dodge in the 50 at;

http://www.carnut.com/

you can see that compression ratio went up incrementaly through the 50's from 7 to 1 at 103 HP to 8 to 1 and 135 HP. Also interesting that the 1958 coronet 6 is runing 8 to 1 and is rated at 138 HP but the rating is a 4000 rpm instead of 3600. Interesting that the Plymouth HP was always rated lower. The 56 plymouth chart shows the 2bbl set up at 131 while the dodge with the same CR and a single put out the same 131. But the chart does show that HP went up with CR. I don't think there were any other internal changes.

According to my machine shop guy, my CR is just a bit over 8 to 1 (Cr is also affected by cylinder volume due to over bores. So my engine with the +.030 pistons, and .040 off between the head and block he calculated at about 8.1 to 8.3 to 1. I can tell you it has a lot more ummmph than the 218 ever had. from 40 to 70 seat of pants says it will pretty keep up with my modern vehicles.

[Reg Evans]

Hey thanks Greg for reminding me of that site. I went through and printed all the Dodge,Plymouth and Chrysler engine specs. for 1930-59. I'm gonna enlarge them and wall paper a wall in the garage with them.

[48mirage]

I looked at the carnut stuff also, on the difference between the '56 Plymouth single barrel and the 2 barrel carb. When you compare Plymouth to Plymouth they do show a 6 hp increase between the 2 engines. That would seem about right with a 2 barrel manifold the engine would breathe a little easier.

Jim