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Posted By Discussion Topic: Mercury Crank -- page: 1 2     johnmyron 11-28-2010 @ 6:56 PM reply profile send p.m. Member Posts: 97 Joined: Oct 2009 In process of complete restoration of 53 convertible. Considering hopping up flathead a bit as want to drive this car more than my 47 sedan. At this vintage, does a merc crank still have more stroke? Can it be added without other modification? Also considering adding better heads, polishing ports, etc. Will likely ad 3/4 cam for better breathing. Comments on what works please. Thanks, john wells supereal 11-29-2010 @ 7:52 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 John: There are Merc 4 inch cranks around, but often are pricey and need work. We ground one a while back for a customer in Illinois. You need the rods and pistons to complete the switch. Using a mild street cam and other modifications really won't provide much increase in power under normal driving, and seldom justifies the expense. The crank does provide some extra displacement, to 255, and more displacement equals more horsepower. There are some very good aftermarket finned aluminum heads available that will give you most of the boost without changing the block. Stroker 11-29-2010 @ 7:52 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 John: Yes, a 49-53 Mercury crank will provide a 4-inch stroke in any flathead engine. You will want to use the Mercury rods, unless you plan on buying special pistons, as the eye-to-eye length is shorter to allow for the extra stroke. Alternatively, you can run 21A rods, which will allow you to run the early style full-floating bearings, and still have the correct eye-to-eye rod length. If you opt to run your stock 53 Ford rods, just make sure your piston supplier is aware of the combination, so that they can provide the correct location for the wrist pin hole. Pauls39 11-29-2010 @ 10:02 AM reply profile send p.m. Member Posts: 81 Joined: Oct 2009 49-53 merc cranks had a 4 inch stroke giving you 255 cu.in. The stock cranks are available but pricey. All flatheads rods are 7 inches. Mercury pistons have the pin hight set 1/8" higher to compensate for the added stroke, otherwise the piston would stick out of the bore. Early rods, 21A can be used if the 4" Merc crank is offset ground 1/8" giving you about 263 cu.in. You must use full floating bearings which are getting real expensive and special pistons. I doubt it would be worthwhile in a street engine. Speedway Motors sells new cranks with up to 4 1/4" strokes. Bore the engine to 3 3/8" gets you 304 cu. in. Complete rotating assembly $1699.00. How fast can you afford to go? Stroker 11-29-2010 @ 10:33 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 John: I must have had a "senior moment". Paul is correct regarding the 7" eye-to-eye rod length, and both Super and Paul are correct regarding the scarcity of good 4 inch cranks. I'm also showing my age for favoring full-floaters, which of course your 8BA never came with. Ah, the "golden years". Long gone are the days like in 1957 when I walked into a Ford-Merc dealership and bought a new Merc crank for $125. If you go the Merc crank route, you will need the pistons with the .125" higher pin hole however. proxie35 11-29-2010 @ 2:06 PM reply profile send p.m. Member Posts: 74 Joined: Jun 2010 John, If you will go to my post (My 50 Coupe) You can see a picture of my engine. It has a Merc crank, 3/4 cam, finned heads, 4 bl carb & Air. I have One small problem with the engine. I've had several flathead experts ride in my car & they all say the problem is the cam. Stroker 11-29-2010 @ 3:44 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Proxie: I see you are running a 50's vintage Rochester (Cadillac?) 4-bbl. What problems are you having, and why do you believe it is related to your "3/4 race" cam. What cam do you have? John: My reference to 21A rods and full-floating bearings are probably not valid suggestions today. I used 21A rods, because I stroked the stock Merc crank another 1/8 inch., and the smaller "big-ends" of the early rods meant that I could use stock bearings, and didn't have to weld-up, or metal-spray my cherry crank to match my now smaller offset journals. After 53 years, you'd think that the guy that uses the handle "stroker" would remember what he did. My flathead with a serious bore job, ended up at 296 cu. in., and I started out with a Weber 3/4 (F-1) grind, and decided that wasn't quite enough, so went to an Isky 404 along with 3-97's and Edelbrock heads. The 404 would probably be a bit much in a heavy car, but it jerked my 32 pickup along quite nicely. Let me add that increases in stroke do not affect the displacement as dramatically as increases in bore. Having said that, unless you want to pop for one of the "French military flatheads", or one of Don Fergueson's alloy blocks, you are probably better off just doing a clean-up bore, and concentrating on a good induction system; perhaps 2-97's or better yet one 4-bbl, some decent aluminum aftermarket heads, and a cam that allows you some decent mid-range torque plus a good set of headers, and free-flowing straight-through glasspack mufflers. Given the changes in carbs., you also might consider a Mallory or other after market ignition, as the original Ford only works well with a stock carb set-up. Paul: Thank's for setting the record straight! alanwoodieman 11-29-2010 @ 3:48 PM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 engine builders around here by the complete rotating assemble from Speedway to get the 4" crank, piston, rods, etc. If you really want a 4" merc crank, I have one that I will sell, I beleive there is also a complete set of 8BA rods, but no pistons. alan48@charter.net proxie35 11-29-2010 @ 4:44 PM reply profile send p.m. Member Posts: 74 Joined: Jun 2010 Stroker, My engine preforms Great. I could never explain my problem here, in type. Please email me your ph# & I'll give you a call & discuss my problem. fordpontiacman@msn.com Pauls39 11-29-2010 @ 10:26 PM reply profile send p.m. Member Posts: 81 Joined: Oct 2009 Proxie, It would be interesting to hear what problem you are having with this combination. I am building a Merc 60 over with an Isky Max-1 cam and Holley 4bbl to run in a plastic 34 coupe. Stroker, I know the senior moment thing, BTDT.

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