Head CC notes

[James_Douglas]

I dug out my notes on the '47 Desoto engine rebuild from 10 years ago to check the head I am going to put on the '49 rebuild.

 

I thought I would post some of the data for folks that never saw the ancient posts.

 

I had a NOS head and took some measurements. I worked with Don Coatney and we came up with the following.  If anything here is amiss, I hope Don will chime in.

 

Stock Head is: 1.930 Inch

Stock Head has a 116 CC chamber.

 

Based on measurements from several heads...

 

I got a loss of ONE CC for every 0.0034 inch milled off.  To get a compression ratio of 7.7 to 1, the final CC needs to be 84cc.  This assumes a deck height of zero, the piston flat with the deck and a Fel-Pro Gasket with a CC of 19.

 

I hope this is helpful to someone.  I did the CC work with a set of sparkplugs in at sea level and room temp of about 60F. I used dyed water.

 

James.

 

 

[Niel Hoback]

Very interesting. Where on the head did you measure 1.93?" A head bolt boss, if so which one? Thank you for the information.

Edited December 11, 2015 by Niel Hoback

[Plymouthy Adams]

_{I think your figures are a bit off for the head volume...using water to measure direct to the chamber and pouring off or just adding by syringe etc will allow water to dome...and as you do the gasket opening and thickness again this will add to the amount of water and add that to the 218 piston top that is slightly below deck...compounding your errors....using liquid to cc direct is not good....using water in a graduated cylinder and modeling clay to check displacement is the better and more accurate measurement...and also the 218 piston reside below cylinder top compare to the 230 close to the top...I think you will find a head volume of 92cc more in the range for a 218 stock at 6.99 advertised CR}

Edited December 11, 2015 by Plymouthy Adams

[Don Coatney]

James. I forgot you had done this many years back. I do still have  the photos of head and head gasket measurements.

 

 

[James_Douglas]

I used a graduated cylinder with a CC plate. I use water as it tends to have a concave meniscus.  By filling the hole at the very edge of the cylinder head with that edge slightly tilted up, gravity helps to minimize the concave meniscus effect.

 

I am not saying that my notes a absolutely correct. But there are probably good to something like 2 or 3 CC's. Anyone who wants to take a 237-251-265 cylinder head and see if my results are close or not, by all means do so and post the results.

 

As to the thickness, I used one of the head bolt bosses.  Just like Don did.  They were all very close.

 

One must be careful however.  Some machinists, mine included, mill the head of each bolt hole to get them perfectly flat before they mill the head surface itself.   

 

Interestingly, if you take the data I posted and cross check it against the head milling chart I got for Don all those years ago, it basically tracks.

 

Close enough for something that is not going to the moon.

 

James

[55 Fargo]

1.930, and 116 cc combustion chamber, that does sound big. What is the compression ratio, with this? 5.5-6.5 :1?

Sounds like you could take a 100 thousandth  off that head and be safe.

[ashyers]

Thought I'd add this to the thread.

 

I just finished cc'ing a 230 cylinder head, P/N 1676337-1, I believe it's a '57-'59 head with an original compression ratio of 8:1. The chambers ranged from 68.1cc to 76.5cc. I believe my #'s are good within a cc. The thickness of the head at the corner bolt holes was 1.801", 1.800", 1.795", 1.793". The thinner side was on the valve's side of the head. There was some distortion/wear from the bolt bearing on the head's surface, so these #'s have some variability.

 

I'm very interested in what a stock M37 6.7:1 head's combustion chambers measure.

[timkingsbury]

Thought I'd add this to the thread.

 

I just finished cc'ing a 230 cylinder head, P/N 1676337-1, I believe it's a '57-'59 head with an original compression ratio of 8:1. The chambers ranged from 68.1cc to 76.5cc. I believe my #'s are good within a cc. The thickness of the head at the corner bolt holes was 1.801", 1.800", 1.795", 1.793". The thinner side was on the valve's side of the head. There was some distortion/wear from the bolt bearing on the head's surface, so these #'s have some variability.

 

I'm very interested in what a stock M37 6.7:1 head's combustion chambers measure.

The thickness of the head is a red-herring.  There were lots of different head thickness's with the same compression ratio and  some heads with the same thickness

with different compression ratio.   Big Block Dodge trucks are a classic example.  But the cc of the chambers is the relevant item.   Your range of close to 8.4 cc difference across chambers is unusual.  Not saying  your not accurate but I have never seen that much range across chambers and I have done a lot of heads personally.

[Dave72dt]

Interesting there was that much variation in cc.  Ideally they would be very little variation.

[ashyers]

Variation aside, anyone have #'s for some of the different castings out there? I plan on cleaning up the chambers a bit and would like to have a ballpark  idea of what the CR of this engine will be if I'm working w/ a 76.5cc chamber on a std. bore 230. Thanks.

 

Andy

[DJ194950]

Variation aside, anyone have #'s for some of the different castings out there? I plan on cleaning up the chambers a bit and would like to have a ballpark  idea of what the CR of this engine will be if I'm working w/ a 76.5cc chamber on a std. bore 230. Thanks.

 

Andy

 

Some head casting #'s with motor size and years get some info but not all you are  looking for attached:

 

DJ

 

[meadowbrook]

What is the effect of cylinder to cylinder cc variation on how the engine runs?

[JBNeal]

Different volumes in combustion chambers will have different compression ratios, which will cause an imbalance of power being generated which leads to a rougher running engine...not as bad as having a miss, but vibration issues can lead to premature internal wear and a buzzing sensation throughout the undamped portions of the vehicle

[knuckleharley]

1.930, and 116 cc combustion chamber, that does sound big. What is the compression ratio, with this? 5.5-6.5 :1?

Sounds like you could take a 100 thousandth  off that head and be safe.

Guys,I think you can assume it is safe to take .125 off any head from the early 50's back. I just had the warped head on my 39 IHC pu milled a couple of months ago. It was so warped oil actually leaked out from under the head and ran down the block,and it would also foul some of the plugs.

 

The machinist had to take .125 off just to get it flat.

 

It almost seems to be supercharged now to the power it had before. I could run 55-60 MPH with it all day before,but it took a long time to get up to that speed. Now it's almost like driving a 60's 6 cylinder pu.

[55 Fargo]

Guys,I think you can assume it is safe to take .125 off any head from the early 50's back. I just had the warped head on my 39 IHC pu milled a couple of months ago. It was so warped oil actually leaked out from under the head and ran down the block,and it would also foul some of the plugs.

 

The machinist had to take .125 off just to get it flat.

 

It almost seems to be supercharged now to the power it had before. I could run 55-60 MPH with it all day before,but it took a long time to get up to that speed. Now it's almost like driving a 60's 6 cylinder pu.

Yes well a 51 dodge 230, compared to a 58 dodge 230, could be upwards of 30 hp, because of the compression increase. It sounds like a beautiful thing....LOL

I figure my engine, could benefit from this also, getting to 65 mph quicker would be nice....

 

Now .125 on any un-planed head, dunno, each situation would dictate what or how much material should or can be removed before head gaskets and other things like detonation could be an issue...

38 International green diamond engine, say about 65-80 hp, compression ratio 6 : 1, shave .125, get it to 7.25:1, and add about 10-12 hp no doubt...

Edited March 9, 2016 by Fargos-Go-Far

[knuckleharley]

Guys,I think you can assume it is safe to take .125 off any head from the early 50's back. I just had the warped head on my 39 IHC pu milled a couple of months ago. It was so warped oil actually leaked out from under the head and ran down the block,and it would also foul some of the plugs.

 

The machinist had to take .125 off just to get it flat.

 

It almost seems to be supercharged now to the power it had before. I could run 55-60 MPH with it all day before,but it took a long time to get up to that speed. Now it's almost like driving a 60's 6 cylinder pu.

Well,I did state EARLY 50's back. I have no doubt you could safely take that much off a 58 230 Dodge head,too. You might have to change pistons if you did,though.

 

I have even heard of machinists creating thick copper head gaskets to make up the difference for heads that had to be milled too much to make them flat. I THINK it was even possible back in the 50's buy special order head gaskets thicker than normal,but I might be remembering that one wrong.

[knuckleharley]

Yes well a 51 dodge 230, compared to a 58 dodge 230, could be upwards of 30 hp, because of the compression increase. It sounds like a beautiful thing....LOL

I figure my engine, could benefit from this also, getting to 65 mph quicker would be nice....

 

Now .125 on any un-planed head, dunno, each situation would dictate what or how much material should or can be removed before head gaskets and other things like detonation could be an issue...

38 International green diamond engine, say about 65-80 hp, compression ratio 6 : 1, shave .125, get it to 7.25:1, and add about 10-12 hp no doubt...

Most likely 25 or more effective horsepower because now the plugs aren't getting fouled and each cylinder is hitting hard. Like I wrote before,it took a really long time to get up to cruising speed before,and it's more like driving a 50's or 60's 6 cyl pu now. The difference in acceleration was really surprising,and so was the smoothness.