I picked up this crank today. The owner, a very knowledgable early Ford guy, Chuck, claimed that it was a Mercury crank. He had a HUGE supply of parts and said that this crank was given to him in trade and was supposed to be a Merc crank. We mic'ed it and the journals seem good (never turned) but rusty. Both the Tex Smith and Frank Oddo books say to look at the oil plug on the snout end of the crank to see whether it might be a Merc 4" crank. Ford cranks typically had a 3/8" plug, but the Mercs had a bigger 5/8" plug. Well, we found that this crank has NO plug at all. (see pict). There is definitely NO plug or hole in this crank. I don't claim to know a lot about flatheads, but Chuck said he had never seen a crank without the oil plug. He was dumbfounded and then very curious to know more about it. I told him I could ask here. What do you make of this crank?
You could always take it to a machine shop with V blocks and have them measure the stroke. 4" is Merc. All of them I've ever owned had the big oil pasage plugs in them. The tiny plugs(pencil eraser size) are the 3.75" cranks. Brad
What's the Lincoln crank look like? Just guessing. Never seen a Ford or Merc flatty crank without a hole.
Are you sure that its ready to put into an engine?? Maybe all the machine work is not done? ie drilling of the missing holes. The front part look kind of long and funny, nothing ive seen mounted in any flathed. more like a mounting point for a lathe/grinding equipment.
The size of the oil cleanout plug is not a sure-fire indicator of crank stroke. While the tradtional indicators of 3/8 = 3-3/4-inch stroke--5/8 = 4-inch stroke is probably okay for American cranks, it does not always apply to Canadian cranks nor to the "new" crop of French cranks that have become available to us in recent years. Canadian Ford (3-3/4 inch) cranks have been manufacturered with 5/8-inch cleanout plugs, as have French cranks. Also, Canadian Mercury cranks have been manufactured with 3/8-inch cleanout plugs. I know this to be true because I'm presently lightening and polishing a 4-inch CM crank for Digger Dave that has 3/8-inch cleanouts While the size of the cleanout plug is usually a good indicator of crank stroke, it's not an infallible indicator. When in doubt, measure.
Thanks for all the advice. This crank does have journal oil holes, but no cleanout holes. I will check closer for any casting numbers. Failing any news, I'll probably take it to an engine shop to have the throw measured. It's likely that it is not a Merc crank, but it's certainly worth checking. I'll report back. Thanks, don
Haring, does it have ONE or TWO oil holes in the bearing surface of each rod throw? That looks like an early (pre '49), and if so would have one hole only in each throw and certainly wouldn't be a 4". The 1CM does ID a Merc crank, but only those made after 1950. There were two or possibly three versions. 1CM is a 1951 prefix. An edit: What I am getting at here is that pre-1949 cranks do not have cleanout plugs--their oil passages are just straight drillings from main to rod throw like most modern engines. The plugs, used only in the late cranks, cap an extra passage that serves as a sludge trap off of the feed passage. The early crank can be conclusively identified by the single feed hole for each rod journal--that is, one hole per two rods. Bruce
An almost "sure fire" way to tell the Ford and Merc cranks apart is; ..Measure the WIDTH of the LARGE counter weights. (on the flats at right angles to the axis of the crank) UNDER 6" = FORD, OVER 6" = MERC The sludge plug sizes are not always the best indicator. Canadian sludge plugs are usually THREADED. (both Ford and Merc)
[ QUOTE ] Are you sure that its ready to put into an engine?? Maybe all the machine work is not done? ie drilling of the missing holes. The front part look kind of long and funny, nothing ive seen mounted in any flathed. more like a mounting point for a lathe/grinding equipment. [/ QUOTE ] Looking more closely at the picture; I think you might be right. It could have been a "reject" crank that wasn't totally finished and someone pulled it from the scrap bin. There would normally be a clean out plug at the location indicated.
[ QUOTE ] Haring, does it have ONE or TWO oil holes in the bearing surface of each rod throw? That looks like an early (pre '49), and if so would have one hole only in each throw and certainly wouldn't be a 4". [/ QUOTE ] Ah ha, missed that question. If it only has ONE oil hole in EACH throw; that would make it a FULL FLOATING BEARINGS crank. And your right, THEY didn't have "sludge" plugs. MERC engines began in 1939, (with insert bearings and two oil holes per journal) which is also the same year "Full floating bearings - rod" were discontinued and went to "insert bearings." So if it only has ONE HOLE PER JOURNAL; then it can't be a MERC. [ QUOTE ] So..it isn't a MERC but an early Ford. The 1CM does ID a Merc crank, but only those made after 1950. There were two or possibly three versions. 1CM is a 1951 prefix. An edit: What I am getting at here is that pre-1949 cranks do not have cleanout plugs--their oil passages are just straight drillings from main to rod throw like most modern engines. The plugs, used only in the late cranks, cap an extra passage that serves as a sludge trap off of the feed passage. The early crank can be conclusively identified by the single feed hole for each rod journal--that is, one hole per two rods. Bruce [/ QUOTE ] Correct me if I'm wrong Bruce, but aren't we refering to PRE 1939? True they are PRE '49, but might as well keep from confusing the troops! Dave Just a little side bar; early engine builders would often use a "late" Merc crank with "full floating" bearings with the early rods. Was supposed to be the "HOT" setup.
Digger dave thats when you offset grind the 4" crank to get a longer stroke. the journal ends up the size of the early journals so you use the full floating bearings and the earlier rods. Dont mean to hijack the post, but something has been puzzling me about those oil cleanout holes. I was always under the assumption that there was a hole through these cleanout holes into the crank, but my merc crank does not. Is the only purpose of these holes to pick up sludge from the oil as the crank rotates through the oil in the pan?
[ QUOTE ] Just a little side bar; early engine builders would often use a "late" Merc crank with "full floating" bearings with the early rods. Was supposed to be the "HOT" setup. [/ QUOTE ] I beleive that was done by offset grinding the 4" crank 1/8" and down to the earlier full floating journal size making the 3/8 stroker crank. Bore it .125" and you have a 296cid flattie Brad
This crank only has one oil hole in the journals, so that would make it an early full-floating bearing crank, right? Not even close to a Merc crank, but I appreciate all the input. I learned a lot. Chuck builds A and B engines, so understandibly might not be as well-versed in the V8 parts.
Single hole is all pre-49 (48 truck), Ford and Merc--all had 3 3/4 stroke. Merc cranks of the 49-up type could be offset ground to the smaller prewar Ford size for full float 4 1/8, or used as is with the big journal (prewar Merc, all postwar early engines) full float rods. Full float rods drastically cut bearing speeds and theoretically offer a small horsepower benefit due to lowered drag. They also offer (in my opinion, based on my reading of Yunick's publications on rod failure) a good deal of protection against rod failure/thrown rods at high RPM. Engine builders for a while in the early fifties converted OHV V8's to full floating in an attempt to prevent rod failures as the racers began to hit high revs. I think these efforts stopped as serious racers switched to aluminum and other special rods. The main disadvantage of floaters is now expense, because the early bearings are getting scarce. Two hole cranks can use either full float or late rods. One hole cranks (all originally would have been 3.75 stroke. Early strokers of several types and early type aftermarket cranks do exist) can only be used with the early rods.
[ QUOTE ] Digger dave thats when you offset grind the 4" crank to get a longer stroke. the journal ends up the size of the early journals so you use the full floating bearings and the earlier rods. [/ QUOTE ] Forgot to add that part! Your right, the last flathead engine I had was done that way; gave a 4 3/8" stroke. [ QUOTE ] Dont mean to hijack the post, but something has been puzzling me about those oil cleanout holes. I was always under the assumption that there was a hole through these cleanout holes into the crank, but my merc crank does not. [/ QUOTE ] If you have plugs (on the outside) and it appears NOT to have a hole behind it, use a sharp tool (ice pick) and do some digging. The crank that I sent to av8 had so much HARD PACKED CRUD behind the plugs, that I wound up having to drill the stuff out. FoMoCo was never known for being consistant. So who knows; you might just have a Merc crank without clean out plugs. [ QUOTE ] Is the only purpose of these holes to pick up sludge from the oil as the crank rotates through the oil in the pan? [/ QUOTE ] Ford and Merc flatheads never had "full flow" oil filtering. (only a small amount of oil is actually filtered) As a result "crap" would circulate through the engine. When the oil "passed" through the crank, centrifical force would "trap" the crud in the sludge traps. Flathead engines when being rebuilt, MUST have those plugs removed and the traps cleaned out, or your just going to invite early bearing failure.
naw the crank has the 5/8 holes, but they do not run all they way into the rod journal. so if I put a plug in the hole it would be sealed off and no oil would get into it from either side
[ QUOTE ] naw the crank has the 5/8 holes, but they do not run all they way into the rod journal. so if I put a plug in the hole it would be sealed off and no oil would get into it from either side [/ QUOTE ] If the crank has plugs (4) they are shallow, it should have a "sludge traps." Take a piece of coathanger and push it down each of the holes on the crank journals. (plugs out) You should be able to see the end of the coathanger wire inside the traps. Some were smaller diameter than the plugs. Each oil passage on the crank connects to one of the traps. (insert bearing cranks) The connecting rod bearings are all fed oil by the traps. If they are PLUGGED; NO oil!!
ok I believe the plugs are still in it after looking at it again. how do I get the damn things out? any special technique?
I can have what's left of a Flathead motor and there's a very good chance that it came from a 53 Merc. The body is nearby- no motor. Either that or the entire motor was transplanted to an F-2 truck. The owner passed away. Is there a way to identify the mercury motor from the exterior- just in case it's in the truck? Or some casting numbers to check on the loose motor? I don't remember there being heads on that block. Either way, is the crank worth saving alone? Thanks, Dan
One more site with TONS of info..... http://www.flatheadv8.org/rumblest/intro.htm Chris Nelson Kansas
[ QUOTE ] merc crank has a dimmple on the front of the front wieght. easy way to i.d. ray [/ QUOTE ] Ray, you need to add the words, A "CANADIAN" in front of "MERC crank!" USA made MERC cranks didn't have the "dimple." ONLY IN CANADA Y EH A.
[ QUOTE ] ok I believe the plugs are still in it after looking at it again. how do I get the damn things out? any special technique? [/ QUOTE ] USA Merc cranks (almost all) used "Welch* plugs" (*lots of other names) that were driven into the openings for the sludge traps. To remove (and you better have the crank out of the engine for this "trick") you will need a slide hammer that you can hold a sheet metal screw in the end. (you can rent them) You drill a small hole in the center of the plug, screw the slide hammer in and GENTLY start sliding the weight on the hammer so it "pulls" on the plug. If all goes well they will pull out. If you happen to have a Canadian Merc crank; they have THREADED plugs. If your lucky they can just be turned out with a big screw driver. If your not so lucky (like me; using a screw driver) then break out the drill with a couple of extended length drill bits, (I used 10" long) and start drilling. Start with a 3/16" drill bit and try an EZ-OUT.
Unless I missed it, how difficult would it be to measure the stroke? You don't need a machine shop to do it. One relatively simple way to do it would be to knock out a couple of V blocks from wood, screw em to a piece of plywood and lay the crank within. Roll the crank over so the rod journal is to the right as far as it will go. Make a pencil mark on the plywood straight down from the outer edge of the journal. Precise is nice, but not necessary, we're dealing with a quarter inch here and not thousandths. Roll the crank 180 degrees, make a mark on the inner edge of the journal. Making marks at the outer edge of the journal on one side and the inner edge on the other approximates very accurately the center to center distance. Measure the distance between marks and that will tell you whether you have the 3 3/4" or 4" crank. If the crank is in a free turning engine, measure the travel of the piston at the top and then at the bottom. That will also give you your answer. No reason you can't measure with a tape and the Mark 1 eyeball the distance between main journal center and rod journal center and come up with a measurement that's half of what the stroke is. IE: 2" = 4" crank. 1 7/8" = 3 3/4" crank. Once you've done a few of them with a tape measure and eyeballing it, finding a 4" crank in the field is no big deal....
[ QUOTE ] Unless I missed it, how difficult would it be to measure the stroke? You don't need a machine shop to do it....... Once you've done a few of them with a tape measure and eyeballing it, finding a 4" crank in the field is no big deal.... [/ QUOTE ] C9, I mentioned earlier that the fast way to determine if you have a Ford or Merc crank; is to measure the width across the flats of the large counter weights. (right angles to the center line of the crank) Mike Davidson (the Aussi flathead guru) discovered that if the width of the large weights is UNDER 6" it is a Ford 3.75 crank. If the width is OVER 6", it's a MERC 4" stroke crank. This "trick" is still working for me after checking about 30 cranks.
[ QUOTE ] C9, I mentioned earlier that the fast way to determine if you have a Ford or Merc crank; is to measure the width across the flats of the large counter weights. (right angles to the center line of the crank) [/ QUOTE ] Saw that and it looks like you guys have done enough of them to prove the point. Thought I'd toss the stroke measurement bit in there for other engines as well. I see a lot of confusion about stroke with some of my SBC running friends. Most interesting one is the guy whose gonna stroke his SBC with longer rods. I gave up arguing with him about that one....
The Jalopy Journal
