Combustion chambers through the years...

[lahti35]

Did the flathead combustion chamber shape change much over the years? I've read that the later 50's heads had "the best" chamber shape... true of guff?  

 

I'm looking to pick up a 230 down the road and mildly build it up a bit... trying to figure out the best engine to start with in so I can be on the lookout...

[TodFitch]

I think the basic shape was pretty much the same but as gasoline got better (higher octane) they reduced the volume of the combustion chamber to raise the compression.

[Don Coatney]

Conventional combustion chambers have all been round for as long as I can remember. 

[Plymouthy Adams]

I read where there was a slight design change in the later years but I do not recall the site no do I remember them making any mention to the minute change specifics.  I have but one later production 230 and that is a 1958 model...but the head is on the engine and the engine purrs   so have had no need to remove inspect or compare....but I think the biggest part of the power was the mention of a cam change to also take advantage of the CR and better fuels..

Edited September 16, 2015 by Plymouthy Adams

[Andydodge]

Tim...that's interesting re the cam change.......I thought that the raised compression ratio up to 8:1 from 1957 to 1959 in the 230 would have gone a long way to raise the HP to the listed 132hp, but a different cam profile would also be of use to........I've never seen any list showing the stock cam specs thru the yrs which would be useful also.......andyd  

[Plymouthy Adams]

I have never seen the cam profile specs...I have never bothered to V-block one either..not sure I have one out of a block to check...profiling the cam with a degree wheel and dial indicator is not hard to do...BUT even at that I would need to do the same with a known late model cam also for comparison..last fall I V-blocked a unknown 440 cam that was given to me..and read the specs..crossed it to the exact part number from there...

[meadowbrook]

Wondered about that too. If my 50's engine were to be rebuilt, I would want it done to the late 50's spec as 30 extra HP sounds more fun.

And this raises another thought. I wonder what the real 'net' hp is on these engines. My engine was advertised as 103 Hp, and I am sure that is gross hp, so I am thinking the net rating would be more like in the low 90s or maybe less.

[SmokeyC3]

Took this picture a couple of years ago when I did a head swap. Top one came off my engine, block numbers indicate it was from a '47 Dodge One ton truck, at some point it was swapped into my '56. Bottom one I pulled from a '54 Plymouth That was at the local U-Pull-It, then had it shaved .060" . There are some differences in the chamber designs.

[Reg Evans]

Can anyone here identify the year of 25" Chrysler heads by their casting numbers ? 

I want to up the compression ratio on my '39 Chrysler 241 and have 3 spare heads here with the following numbers. 

869847-1 or 1120806-1 or 1313826-1. 

I am guessing by the numbers that the one beginning with 13 is the latest of the 3 and maybe has the best CR.

Maybe I don't have to have the existing head shaved and could just swap on one of these.

Anybody ?

[busycoupe]

The one with the highest compression ratio should have chambers with the smallest volume. Perhaps you could put an old plug in a chamber, turn the head upside down and measure how much water it takes to fill.

[Plymouthy Adams]

fill it with clay and then drop said clay in a graduated cylinder say of 500cc in volume with 300 cc of water already in place...then measure the displacement...less math as heads chambers are expressed in CC...

[Reg Evans]

That's a good idea Tim !

 

All 3 of my loose heads look like this one that I had .050 removed.  Guess it's time to remove the head off my 241 to compare.

 

 

[greg g]

The Edmunds head I have (no it is not any good, swiss cheese) has combustion chambers that feature just a flat surface over the piston.  The bulk of the machined area is above and around the valves. I believe this was supposed to be a 9 to 1 head when installed on a Dodge 230.  If I am not mistaken, the Dodge piston at TDC is flush with the deck, while the 218 leaves a bit of unfilled area at TDC.  The gasket would provide the clearance between piston and head when installed.  I did a paraffin template for a guy who said he was going to try to cast some heads, but nothing ever came of it.

[pyrodork]

Is it safe to assume a stock 218 head has a better CR than a stock 230 head? While working on my 230, I noticed a crack. I have a bad 218 with a good head. Figured I could swap them, but wanted to get advice before putting in the time.

[Niel Hoback]

I would not assume there was any difference at all in the heads. You can compare the shape of the combustion cambers to see if there has been any extreme shaving done.

[dpollo]

There is more to the "flathead" than meets the eye !  Chrysler's engines employed the Riccardo design with a squish chamber

above the piston to create a swirl or turbulence.  The chamber was revised for the 1952 model year.  These heads can be identified by the DPCD logo in a circle near #2 cylinder.  Other brands which used the valve in block design had many configurations, some of which worked better than others.    As you may have guessed, I am a long time supporter of the NAAFH.  (National Association for the Advancement of Flatheads)

 

The best way to raise compression is by substituting a head from a smaller displacement engine  .  Like a (USA) 218 head on a 230

 

or even better, a Canadian 218 head on a 251.   This way you do not lose volume around the valves.

 

If you are checking the volume of a chamber, use light oil rather than water, it is more accurate.  Also you can do the math  pi x r squared x height for cylinder volume for  say a 218 and a 230 which may have both started out with a 7-1 ratio. To maintain the 7-1 ratio the chamber in the head must be smaller for the 218.  A ratio of the bore sizes will tell you how much.( Include any overbore)

 

All heads can be identified by the part number and it pays to check especially if your engine has been through the rebuilders.

I had a 228 which came from Pacific Reman.  with a 265 head.  compression reduced to about 6.5 -1-- disappointing. 

[Cpt.Fred]

interesting information there.

do you have a picture that shows one of these encircled logos?

[dpollo]

I have not had much luck posting photos to this forum  but two features will help identify a head.

 

The extra water passage at the front  51 and up except Spitfire engine

The DPCD in a circle from 52 up

 

and also,,   56 up had a smaller threaded hole for the temperature sender.

[Dartgame]

To determine compression ratios you must measure the cyl head volume using a buret graduated in milliliters (cc's), you also need to take into account the cyl head gasket cc's and also the piston cc's at TDC and BDC. It then becomes a simple calculation. The stumbling block for most is getting a buret, not cheap.