janan5243 Posted July 10, 2014 Report Share Posted July 10, 2014 someone offered me a Chrysler spitfire head for a reasonable price. He has a 1939 Desoto coupe, Canadian. Says head is for a 25" block. would that head increase compression ratio over stock 49 head. Would it be worth having as a spare. He is asking $ 250.00 Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted July 10, 2014 Report Share Posted July 10, 2014 Spitfire head does nothing special except say Spitfire. A forum member gave me a Spitfire head several years ago. They are available in some boneyards for a lot less than two fifty. Quote Link to comment Share on other sites More sharing options...
Conroe Powdercoating Posted July 10, 2014 Report Share Posted July 10, 2014 for 250, go and get your head milled .080 and then spend the rest on beer, rubbers and hookers 1 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 10, 2014 Report Share Posted July 10, 2014 as the CR is based on squeeze..the bore and stroke is unchanged...then the only way to increase the CR is with milled head or a head combustion chamber redesign..in '39 the CR was naturally lower than the production year '49 based simply on comparing the potentcy of the fuel of both production years..stock '39 to stock '49 would be a possible reduction of .5 CR Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 11, 2014 Author Report Share Posted July 11, 2014 Thanks for the help & advice. Is an aluminum head a better idea? Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 11, 2014 Report Share Posted July 11, 2014 better choice for what? the cast iron head when milled to match the performace level of the engine has proven itself over the very course of time..the fact it still is performing on your engine all these years speaks volumes...aluminum head...all out race when shaving weight may be an advantage would the aluminum prevail...seems the porosity of some of the later made heads is a problem per some experienced related to me in seeking a fix for problems..so your call...oh and ah on the aluminum..or solid advantage of proven casting on a shaved cast iron head.. 1 Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 11, 2014 Author Report Share Posted July 11, 2014 point taken. Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 11, 2014 Author Report Share Posted July 11, 2014 I checked my compression before & it runs from 92 to 101 with 92 being center cylinders increasing to 101 at end cylinders. Is that strong enough to consider milling head? Quote Link to comment Share on other sites More sharing options...
Conroe Powdercoating Posted July 11, 2014 Report Share Posted July 11, 2014 (edited) I checked my compression before & it runs from 92 to 101 with 92 being center cylinders increasing to 101 at end cylinders. Is that strong enough to consider milling head? damn, dunno what happened, it wouldnt show the quote or post when I tried to reply. anyways, with compression readings like that, You need to freshen the engine up, I personally wouldnt aid in its well worn demise by adding more compression. Edited July 11, 2014 by Conroe Powdercoating Quote Link to comment Share on other sites More sharing options...
54Illinois Posted July 15, 2014 Report Share Posted July 15, 2014 I have a head off a 52 Desoto you could have for a lot less. Get it shaved, and see what happens, that way you would not ruin the original. Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 15, 2014 Report Share Posted July 15, 2014 things normally are considered as wearing together..point is, is you lower end up to a CR increase? 1 Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 15, 2014 Author Report Share Posted July 15, 2014 Don't know. Engine is original. runs good, is very quiet. No internal noises to scare me. Can it be reringed without honing? Methinks that is probably not advisable. How much for head? If engine is rebuilt without boring out but milling head & dual carbs how much horsepower gain? Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 15, 2014 Report Share Posted July 15, 2014 to me..the HP gain for the money and time spent is negligible..but if doing it to preserve the engine, rebuild, dress the valves, upgrade intake and exhaust along with a decent increase in cam lift and duration...you can get a healthy running engine with a noticeable kick..but then again..it is more for keeping the car looking like a carry over from the past than for actual all out performance..milling..your CR will be directly related to the grade fuel you wish to purchase.. Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 16, 2014 Author Report Share Posted July 16, 2014 I think that in my newness to the old car experience I am on the wrong track. My engine runs very good , considering it's age & mileage. Leaks oil but doesn't burn any. My concern, which I mentioned in another post, is the engine rpm's when pulling some steep hills. If I get a good running start, I make most of them in high gear. One hill in particular, that is on way home, I can't get running start. Car will make it in high gear but am down to 20 mph in parts. If I downshift, pulls easily but by 30mph rpms are up there. I would also like to be able to cruise at a lower rpm. Guess it just makes me nervous listening to engine. I probably should concentrate on a rear end ratio change. Probably easier & less expensive. I know there are a lot of posts about them but don't know how many are on Desoto. Am hoping that serious engine work is off in the future. Will do a total rebuild with modifications then. Thanks for all input & advice Quote Link to comment Share on other sites More sharing options...
jeffsunzeri Posted July 16, 2014 Report Share Posted July 16, 2014 Changing the head is easiest and least expensive way to get a good increase in power on your engine. In 1949, high octane fuel was 88 octane, and your engine was designed to easily run on 77 octane. An increased compression ratio (within reason) from shaving the head does not add a lot of stress to a relatively healthy engine, so I'd say go for it. You should see and feel your hill climbing and cruise speeds change significantly. The whole job of changing the head is much less than an 8 hour day, especially if you are swapping one head for another. I'd say you are on the right track with a head swap. The choice is whether you buy another head and have it milled, and do a swap, or remove your head, send it out for milling, and replace it. To get full benefit you will want to adjust your timing a bit to take advantage of the new compression ratio and possibly run a high octane fuel. Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 16, 2014 Author Report Share Posted July 16, 2014 do you think my engine, with the posted compression would hold up to a higher compression ratio? 54Illinois: what do you want for head? Quote Link to comment Share on other sites More sharing options...
jeffsunzeri Posted July 16, 2014 Report Share Posted July 16, 2014 Yes. I don't think you'll be getting any failure due to the increased CR or power. A good move would be to replace the head bolts with studs to help prevent a possible blown head gasket. Just promise to never use your increased power for evil deeds! 1 Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 16, 2014 Author Report Share Posted July 16, 2014 where would I get the proper studs? Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 16, 2014 Report Share Posted July 16, 2014 jeffsunzeri, on 16 Jul 2014 - 12:50 PM, said:Yes. I don't think you'll be getting any failure due to the increased CR or power. A good move would be to replace the head bolts with studs to help prevent a possible blown head gasket. Just promise to never use your increased power for evil deeds! have you actually installed these ARP studs as most here suggest?...me...I am not impressed with them...in any aspect of the application.....goodly sum of money for what I see is not added gain 1 Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 17, 2014 Author Report Share Posted July 17, 2014 Plymouthly: are you referring to the whole head mill & stud project or just the studs? Quote Link to comment Share on other sites More sharing options...
janan5243 Posted July 17, 2014 Author Report Share Posted July 17, 2014 Don: what is your opinion? I realize that this is only advice. You seem to have done a lot of work on these engines. Quote Link to comment Share on other sites More sharing options...
jeffsunzeri Posted July 17, 2014 Report Share Posted July 17, 2014 Vintage Power Wagons offers a kit (vintagepowerwagons.com) and you can measure the length of your head bolts and order the individual studs and nuts from a number of sources such as NAPA, Summit Racing, Fastenal and others. I have actually installed the studs on 2 of the 4 mopar flathead sixes I currently operate, as well as a few more for customers. In at least one case, I replaced studs that were already there, and in the others the cost was about the same as replacing all the old, corroded head bolts. It's difficult to justify re-using 60 and 70 year old head bolts considering the overall cost of a failed head bolt or damaged thread. When I look at the wear and tear on the threads in the block due to the usage of head bolts, I am glad I have used the studs. Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 17, 2014 Report Share Posted July 17, 2014 I do not care for the studs...they are not the correct length in my book, class of fit is so poor it borders on ridiculous..I wwould never use them on any of my engines....I would go with aftermarket bolts first..your call however...some folks just like a flash in the pants idea.. Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted July 17, 2014 Report Share Posted July 17, 2014 Use caution on using just any bolt or stud as the correct ones must be undercut on the shank. If they are not undercut then they will rust fast to the head and with studs make head removal very difficult and with bolts make them prone to breakage. If using an aluminum head studs may offer better clamping force as the torque specifications differ between the course thread of bolts and the fine threads of studs. But the choice is yours. Pictured is a head bolt and a stud showing the undercut. Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted July 17, 2014 Report Share Posted July 17, 2014 not pictured in Don's picture is the associated tempered washer that should be part of the stud install..critical if using aluminum head Quote Link to comment Share on other sites More sharing options...
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