The stroke on a 100 HP FH was 3.75” but on the Merc it was 4” but the 3.75 ” crank could be 4” if offset grinding to 2” journals by use lose bearings and the older rods. I guess this was done before 1950. But at 49 Merc had the 4” crank so at 1950 did anyone used the 4” cranks and go to 4.125” stroke ? Or did this came later on, or custom cranks ? But if someone did use a 4.125” crank back then how about the pistons ? Was it custom forged out cast on the market that had a shorter compression height ? Or was the std piston that headthick to cut off 0.125” ? Just qurious how they did it. One cool thig was Navarro used a 180 degree crank 1948 ( see pic ) but I has not read on his stroke and bore he used. Does anyone know ? This 180 cranks get light and create bad vibration and they give no HP, but must has sounded real nasty.
It was done the same way on typical flathead builds as with any "stroker" build. The compression height of the piston is changed (the pin is moved). All the major manufacturers - Jahns, J&E, Egge, Forgedture, etc. (back in the day) made pistons with various compression heights. You could order them right out of the catalog . . . and for the companies that supply performance flathead pistons today, same deal. The same holds true today - I use mostly Ross forged pistons and I can get them in standard "stocking" compression heights, or get custom ones. Typically, I measure the actual compression height with the crank in the block, a set of bearings, a rod and a piston pin. This way, when I supply a CH number to Ross, I know I'll get a piston that is exactly where I want it - with the correct squish into the head. Also, sometimes I move the ring pack down a bit - due to having a deeper relief in a racing style block and/or due to the extra heat generated by boost.
Ah, that was intresting information even back then they had C-H change for sale, so that mean in 1950 it was possible stroke a 4” crank to 4.125” and use the std 7” rods. I guess no one alive now know what Navarros 180 crank was on stroke or bore at and how it sounded... ;- )
I can't tell you the exact year that 4 1/8" stroke pistons were commonly made (stocking items), though I'm sure you could get custom pin heights even back then (if you knew the right folks). The average guy didn't have the money for all this fancy stuff - though everything was "bolt on" if you knew the right parts combinations and could get the pistons and crank work done. The rods that were used were the 221 Ford Rods - either 91A or 21A rods with 2.00" full-floater bearings. Now days for a higher horsepower build one can buy H-beam rods off the shelf for the smaller crank journals. I see no real reason to have a billet 180 degree crank made - as you also have to have a billet 180 degree cam made to go with it. Lots of money to spend - only to have the fillings of your teeth get shaken out! LOL
I have a set of 4 1/8 stroke x 3 3/8 going in a 59a block. I could use help finding a supplier for piston rings. they are elgin pistons. I may have found a set of rings in the pile of parts that the engine and pistons came in but there are no oil rings in the set. Is it possible to buy only the bottom rings?
Cannot offset grind a 3 3/4" Stroke crank to 4" using 2" journals, the go to before the Merc 4" crank was 3 7/8" stroke. Shops like CT Strokers, Speedomotive etc. were selling 4 1/8" stroker kits in 49. Navarro used a 3" stroke crank with a 3 1/16" Bore (Small Cube Motor)
Johns Rod & Custom, Yes if use a std 3.75 crank its hard to offset it to 4” and go std 2 pin but maybe at a undercut ? -But how did the stroker companys get a 4.1/8 crank 1949, did they used a Merc 4” crank or used weldings ? So Navarro used the 85 HP block std bore and used a destroked from stock stroke to a custom 3” 180 degree crank ? With a 7” rods the pistons must had a more C-H 0.375” extra over std ? Or did he also made longer custom rods 1949 ? Cool to know historic info. He had a blower, so was this for cl*** at B-ville by use a only 177 cu in engine ?
You probably know way more than I do and I have no experience with it at all. But my dad had a friend who’d been around the block a few times, was probably 10/15 years older than he was. I recall him telling us how they used to offset grind cranks. I ***ume they had a shop do it, not sure. But the journals were welded thicker, then offset ground. Have you heard of that before? Always wondered about it.
Navarro actually de-stroked his cranks to run in a specific cl***. I forget what cubic inch his motors wound up being, but it was in the high 190's or low 200's c.i. range. He made up for the loss of power of the smaller cubic inches by using a GMC blower and other tricks like oxygen injection. For period-correctness sake, I wouldn't get hung up on this. I'm in the camp of running as big as you can using quality parts that are available today. My motor is a 292 cubic inch with a lot of work done to it and an aluminum flywheel. It is snaps with a blimp of the throttle, has great torque and equally great top end. This winter, I'm going to install a quick change center section which will even give me more options when going on longer trips. I'm starting to plan to do a 304 c.i. (+/-) motor with a 99A block I have.
It wasn't long before guys were having "welded strokers" made to increase the stroke to 4 1/4", 4 3/8" and even some wild combinations at 4 1/2". Guys like CT and Reath were well known for this. I'm sure there weren't many places making billet cranks - but there had to be a few (just don't know who).
I’m Ok with a Merc 4” crank, just like to hear the history. Welding cranks is not new even if I dont know about the 40’s but when strokerkits came cheap it was with the Chinese parts. I talked to a Swede today with huge experiance ( his father worked on this allready on the 50’s and he took over business ) and he said its no gain ( only pain ) light a 4” crank out.
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