Edelbrock offers what they refer to as HighLift/Large Chamber head versus the older conventional design. I found this post from 2010 with lots of CR and head gasket calculations that leads me to believe the newer models with the larger combustion chamber might be easier to dial in the CR for today's gas: http://www.jalopyjournal.com/forum/showthread.php?t=482189 Info from the Edelbrock web site: Ford Flathead The original Edelbrock script logo design for Fords and Mercurys Rugged, ribbed internally and externally, with a large water capacity and excellent breathing characteristics Cast at the Edelbrock Foundry in the USA of T-6 tempered A356 aluminum 65cc heads support 8.0:1 compression ratio on blocks with a 3/16" base relief (stock bore and stroke), compression ratio increase is approximately 3/10 of a percent with each 1/8" stroke High Lift/Large Chamber versions feature a new "raised roof" combustion chamber design that is CNC machined for high lift cams and is perfect for reducing compression in supercharger applications or on low octane fuel High Lift heads have increased valve clearance and increased flow capacity Description Pair of Heads 1949-53 Ford-Mercury 24-stud (65cc) 1115 1938-48 Ford-Mercury 24-stud (65cc) 1125 High Lift/Large Chamber 1949-53 Ford-Mercury 24-stud (74cc) 1116 High Lift/Large Chamber 1938-48 Ford-Mercury 24-stud (74cc) 1127 For a fresh mild performance rebuild with a stock or mild cam, is it recommended to buy the newer model heads because of the e****gas (Ethanol) we have to put up with these days? Looks like there is quite a bit of difference in the combustion chamber size(74 versus 65). Don't want to buy one set only to find out I should have bought the other. Yes, I know CR is also dependent on bore, piston type, deck height, etc etc etc. thanks
What are you building the engine for? Street cruiser ? Street/ strip? I run the 1116 heads with a blown 289 ci combo so in my case I needed the CR drop and the valve clearance with a custom cam. The heads will lower your CR and provide extra valve to head clearance, but what is your application? Rat
Just a street cruiser with a little more power with a facelift. A 1946 59A is the core and the target build includes aluminum heads, dual 97s, headers, etc. Got a chance to pick up a set of 1125 heads real cheap and don't have a lot of time to build one on paper just to figure out A is better than B or vice versus and I thought there would be a wealth of knowledge on this forum. I found some info in this book but it appears to be a bit dated: How to Build Ford Flathead V-8 Horsepower By George McNichol As a bit of knowledge sharing, "than" is spelled with an "a" and used for comparisons: http://www.elearnenglishlanguage.com/difficulties/thanthen.html
Its a tough call on whether to buy the used heads or the new ones. Check the used ones out thoroughly and make sure they aren't a mismatched set, which is a common thing for an item such as this that could be close to 60 years old. Also check them out for water p***age corrosion(very common), stripped bolt threads and cracks and just overall condition. Also ask yourself, why are they "real" cheap.
one thing to think about is the gas back in the early '50s was only 80 octane--or somewhere in that neighborhood. at my local station, the e10 is 87,89 or 93. my big problem with "new" gas is its short shelf life and how it eats up the soft parts in your fuel system. i hear it's bad for automotive paint, too.
The Jalopy Journal
