James_Douglas Posted December 11, 2015 Report Share Posted December 11, 2015 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. 4 Quote Link to comment Share on other sites More sharing options...
Niel Hoback Posted December 11, 2015 Report Share Posted December 11, 2015 (edited) 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 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted December 11, 2015 Report Share Posted December 11, 2015 (edited) 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 Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted December 11, 2015 Report Share Posted December 11, 2015 James. I forgot you had done this many years back. I do still have the photos of head and head gasket measurements. 1 Quote Link to comment Share on other sites More sharing options...
James_Douglas Posted December 11, 2015 Author Report Share Posted December 11, 2015 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 Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted December 13, 2015 Report Share Posted December 13, 2015 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. Quote Link to comment Share on other sites More sharing options...
ashyers Posted December 31, 2015 Report Share Posted December 31, 2015 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. 1 Quote Link to comment Share on other sites More sharing options...
timkingsbury Posted December 31, 2015 Report Share Posted December 31, 2015 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. Quote Link to comment Share on other sites More sharing options...
Dave72dt Posted December 31, 2015 Report Share Posted December 31, 2015 Interesting there was that much variation in cc. Ideally they would be very little variation. Quote Link to comment Share on other sites More sharing options...
ashyers Posted December 31, 2015 Report Share Posted December 31, 2015 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 Quote Link to comment Share on other sites More sharing options...
DJ194950 Posted December 31, 2015 Report Share Posted December 31, 2015 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 Quote Link to comment Share on other sites More sharing options...
meadowbrook Posted January 2, 2016 Report Share Posted January 2, 2016 What is the effect of cylinder to cylinder cc variation on how the engine runs? Quote Link to comment Share on other sites More sharing options...
JBNeal Posted January 2, 2016 Report Share Posted January 2, 2016 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 2 Quote Link to comment Share on other sites More sharing options...
knuckleharley Posted March 9, 2016 Report Share Posted March 9, 2016 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. 2 Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted March 9, 2016 Report Share Posted March 9, 2016 (edited) 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 Quote Link to comment Share on other sites More sharing options...
knuckleharley Posted March 10, 2016 Report Share Posted March 10, 2016 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. Quote Link to comment Share on other sites More sharing options...
knuckleharley Posted March 15, 2016 Report Share Posted March 15, 2016 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. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.