218/230 head

[claybill]

are these heads the same? compression-wise? I know they fit.

any advantage of a 218 on a 230? vice-versa.?

bill

[Plymouthy Adams]

Based up ont fact that Ihave seen the same casting number on both the 218 and the 230 and throw in the very wierd factor that the CR ratio for the same given years is identical between the 218 and the 230..head volume is definitely the changing factor...for example

the 218 has a cylinder volume of 36.29 and a CR of 7.0 thus the head has a volume of 85 CC's

the 230 has a cylinder volume of 38.36 and a CR of 7.0 thus the head has a volume of 89.8 CC's

so if you slap the 218 head on the 230 theoritcally you have a CR increase of .39 (.4 advertised)

the above is based straight on the values given out of my motors manual for year 1949 where both engines had a 7.0 CR...and the intent in them days was the CR based on octane of fuel being produced for that era..

So unless you just happen to know the exact year application..know if it is stock..or know just what has been milled over the years...the head must be CC'd...also bare in mind any block cut and overbore will have to be factored into the equation as these will increase CR..but stock year for year..the 218 head when placed on the 230 will give you a CR increase...

In 1956 the CR was 7.4 and yes the stock bore and stroke remained constant therefore to get to that CR the head would have to be 85 CC ie you are now back to the 218 stock head of 1949 on the 1956 230 engine...

[greg g]

Hey Tim don't forget the stroke part of the CR equation. I noticed that with my 230 the piston to top of block clearence is nearly nill, on the 218, it is nearly 1/8 inch. So the 230 has considerably more squeeze than the 218. so if the machined area in the 218 head is smaller, a 218 head on a 230 would yield more squeeze still.

I think some one mentioned that the 42 218 head had the smallest chamber.

Be interesting is some one could cc a punch of heads to see "the rest of the story" On the various spec charts areoun looks like each .5 addition to the CR yields about 5 HP, so it would be good info.

[claybill]

i c.c.'d a fenton head last spring and it came to about 72-75cc's

and the stock 218 was 85. amatuer job but informative.

bill

[HalfdollarMayflower]

Hey Tim don't forget the stroke part of the CR equation. I noticed that with my 230 the piston to top of block clearence is nearly nill, on the 218, it is nearly 1/8 inch. So the 230 has considerably more squeeze than the 218. so if the machined area in the 218 head is smaller, a 218 head on a 230 would yield more squeeze still.

I think some one mentioned that the 42 218 head had the smallest chamber.

Be interesting is some one could cc a punch of heads to see "the rest of the story" On the various spec charts areoun looks like each .5 addition to the CR yields about 5 HP, so it would be good info.

Somewhere I heard that a '57 or '58 head has a better shaped combustion chamber which unshrouds the valves a little more. This is 2nd hand though so take it with a grain of salt.

[Plymouthy Adams]

58 runs 7.6 CR and the 59 was maxed at 8.0...

[HalfdollarMayflower]

Great information here!

Tim, can you give us a run-down on cyl head cc's or compression ratio thru the years?

Also, is there a list somewhere that gives casting #'s for the various years?

[Plymouthy Adams]

wish I could but I have these engines assembled and not able to do a CC of the heads. I think I may be able to get my hands on a couple more and do some testing but that will not be an immediate undertaking..trust me..I do plan an in depth study here

[Jim Saraceno]

I can tell you one difference between the newer heads and the older heads is the hole for the temperature sensor is different. I found that our when I bought and rebuilt another engine for my car. I ended up using my old head because of that.

So I still have the newer head sitting in my basement. You guys want me to measure something on it?

[HalfdollarMayflower]

Hey Tim don't forget the stroke part of the CR equation. I noticed that with my 230 the piston to top of block clearence is nearly nill, on the 218, it is nearly 1/8 inch. So the 230 has considerably more squeeze than the 218. so if the machined area in the 218 head is smaller, a 218 head on a 230 would yield more squeeze still.

I think some one mentioned that the 42 218 head had the smallest chamber.

Be interesting is some one could cc a punch of heads to see "the rest of the story" On the various spec charts areoun looks like each .5 addition to the CR yields about 5 HP, so it would be good info.

Does anyone know if there was a change in piston design thru the years that might also account for the CR increase?

Also, can someone verify that the '42 head has the smallest Combustion chamber?

[greg g]

I believe the pistons are all flat top. 4 ring aluminum oval ground.