hi looking for some help on my 21 stud flathead I recently spun a con rod bearing but luckily didnt do any damage to to the crankshaft so I located a full set (4) new bearings and decided to replace all of them, after changing all of them I torqued 3 of them down and when i come to torque the 4th set down I cannot spin the engine over if I back it off till it just nips up I can spin it although a little tight i got a figure off 35-40 ft-lb torque on the cap bolts is this correct? After taking off one side(cap) it will spin but as soon as I put the other cap on it locks up again anybody got any suggestions or am I being a bit heavy with the torque settings they didn't seem that tight when I originally undid them It almost seems as though when I've tightened it down the shell expands and grips the sides of the crank I have tried other good bearings and it still does it, does the bearing spin on the crank? and the con rods spin on the bearing,should there be side to side movement (thrust) or not trying to get my head around it, any help would be appreciated, thanks
I had the same problem with a 99A motor. get some scotch brite, bearing blue, and work out where the tight spot is, and rub down that area. Sometimes it will be right near the parting line, in this case I carefully rubbed down the flats where the halves meet with 600 grit. Its very slow and tedious work, but you do learn a lot about crush and clearances. floating bearings cant actually be expected to float perfectly between the crank and rod when turning the engine during assembly..they always drag a little..frustrating as that is. you develop a feel for how much drag there should be once torqued up. the rods wont quite drop under their own weight, but close as you can get to that is good. As to thrust, yes the bearing should have side clearance, and the rods should have side clearance in the throw too, the specs are out there in the googleweb. PM me if any of this doesnt make sense. I think Im strange, as I love clearancing these bloody things..I have two early motors to build next month..Fun!!
Sounds like you have to do some measuring. Check the thickness of the bearings to be sure one set wasn't mispackaged. Also need to measure the spread of the bearing shell. Will the bearings from one of the good set work on the set in question? Torque is generally 45 ft. lb., so you are OK.
With the full floating rod bearings, you need to measure the distance from one side to the other at the parting line. I can't remember the dimension, but it is in the ford hop up books. If the bearing is too "wide" you hit it gently with a small hammer to move the sides together. If it is too "narrow" then you set the bearing back side up on a board, and gently hit the bearing to spread it out. I'm no expert and when I first saw this in a book I thought it was pretty wild stuff. I just looked it up in Tex Smith's "The Complete Ford Flatheard V8 Engine Manual" by Ron Ceridono. The dimension to shoot for is 2.217" to 2.227" If you have the book, it's on page 118, right-hand column.
Also check to see if the bearing is positioned away from the radius of the journal. Just a silly question but have you numbered the rods and rod caps? If you have mismatched the rods and caps, this will also bind the shaft. You need to make sure that the caps are fitted in the correct direction on the rod too. A
I'll soon be assembling a 99A with floating rod bearings and am gathering info. Just curious, but how does an engine with floating rod bearings "spin a bearing"? Aren't the floating bearing supposed to turn free in the rod? What happened? Bob
Good points everyone! Yeh the hammer on a block of wood method scares me a little, after all the curvature could get all uneven very easily.. If they are decent bearings, and your crank and rods have been machined freshly, and measure up correctly, it should only be a very minor adjustment. I guess eliminating other problems first is the go. measure everything thrice.
There was no mention of the rods being resized nor the shaft machined. My rule of thumb is that if a bearing has spun you resize even if it looks ok. Heat can distort ID and OD. It’s peace of mind. Also, you should go on a fact finding mission and find the cause. Oil pressure is normally the culprit for bearing failures in a good running engine. Pressure problems can come from Low oil levels Pressure relief valve problems Oil pump problems The oil it’s self The filter Or my personal favorite....PEBSWaT......(problem exists between steering wheel and throttle)....... i.e. the person driving the hell out of the engine A
Lowsquire, Flatjack, JonF ,AFL and,bobscogin first let me thank you for your replies, are you saying that I should be able to "spin " the bearing when its in position and torqued up? I had taken them off in sequence and cable tied them up to a piece off card so they are not "mixed" up I will check the "thrust"when I get home from work later. Thanks again Guys
Yes. I'm unclear as to what you mean "spun a rod bearing". That's a term that's generally used to describe a malfunction in an engine with fixed rod bearings wherein the bearing shell is fixed to the rod with tangs and does not rotate. It gets "spun" when the rod bearing, for some reason, seizes to the crank, shears the locating tangs, and turns in the rod instead of the journal. The floating flathead bearings aren't fixed to the rod. They should have clearance between the bearing and rod journal, and the bearing and rod end. This allows them to "float". I was curious as to how your bearing malfunctioned. Could you elaborate? Bob
A buddy of mine paid a cousin of his to replace a singe piston in a 305 Chev because he blew a hole in it with a leaky head gasket. My buddy asked me to pick up a starter for him because after they got the car put together it wouldn't turn over. I stopped by the place to check things out and found the box for the new rod bearing -- 0.010 ?! I asked why to the cousin and he said he thought there might be that much wear on the crank !? All it takes is one. That said, bobbooth, is the flathead American or of British descent? I have read here on the HAMB that some of the British ones had fixed rod bearings and not the floaters. Let me see if I can find one of these threads so that I don't mislead -- because I am just going off memory.
As stated, in your engine the bearing has clearance between the rod journal and the bearing ID AND the bearing OD and the ID of the rod. This lets the bearing "float" on a film of oil at both of these interface areas being physically attached to neither the rod or the crank. The rod bearing has a spec for both the ID and OD so the clearance is correct for both. If one of these is out of spec then you have the possibility of interference when the rod bolts are tightenend down and thus grabbing the crank. It's best to have someone seasoned in flatheads to assemble the bottom end of these as it's real easy to screw up the clearances. Frank
"USA uses one set of bearings per 2 rods, full floating...cuts total friction, almost eliminates rod problems at high load or rpm, costs more, requires careful fitting...some British engines used 2 versions of odd bearings that lock to rods. At least one of these can take USA/Canadian bearings...get a repro Pilot manual." Bruce Lancaster http://jalopyjournal.com/forum/showthread.php?t=276307&highlight=flathead+rod+bearings But after re-reading your original post I realize you said you bought a complete set of 4 rod bearings -- that means that you have full floating bearings, with one bearing for 2 rods. Here is some other good info on the floaters that has been shared: http://www.btc-bci.com/~billben/bearing.htm
I see what you mean I used the term wrongly i suppose basically I was using the car and was just about to pull of the highway into a gas station and i heard the rattle start and coasted in i then got the car recovered home. after dropping the oil pan it was pretty obvious what had gone as i could move the connecting rod up and down about 25 thou i then . The engine is a British military unit (based on a 37 motor that was rebuilt in dec of 1945 with 0.10 grind on the crank across the board. I measured it and confirmed that it was indeed 0.10 ( 1.899) under the standard 1.999 so I ordered the bearings to suit while i waited for the bearings to arrive I thought I would check the oil pump which is a early one (like a teapot) as I had some later truck pumps I tried one in the sump and it was only then that I realised what had gone wrong with the motor and why it had let go on the bearing, the oil dipstick is the wrong one in fact i dont know what it is off which meant that the pick up tube was at full just barely above the oil level never had a flatty before so didn,t realise it was different. So basically I have fitted the bearings but when you come to torque up the last set it is impossible to turn over by hand granted I am lying on my back on the garage floor. I was also told that you could go up to 60 ft lb of resistance so i tried to turn the engine by the crankshaft nut on the end with everything torqued up but even at 70 ft lb i still could not budge it, the moment I just slacken off it will move quite freely. Anybody know what (thrust float if any) I should have? It almost feels like the area that where the 2 conrods fit is to small as though when you apply the correct torque it tries to spread the "lips" at the edges therefore binding up ,hope this makes sense Again thanks for your replies been some good reading/info given
If it is the same rods that had the bearing problem in the first instance, it would pay to remove the rods completely from the engine and have them resized. Its a pain but will be worth it. It's good that you found out why the problem happened in the first place. A
Yes very happy I got to find out what caused it,so you reckon they have gone out of shape? do you know what side-to-side movement if any i should have? Anyone a definite on the torque settings for the "caps" on a 21 stud using castleated nuts/split pins?
Did you put the rod caps on backwards? this happens sometimes and the rod locks up and tears the shit out of the bearing.............
Thrust clearance rule of thumb for conrods is .030" to .058" for most V8 engines. You could also measure the remaining 3 journals as a guide. Hope this all helps to get you back on the road. A
Thanks for that I knew I read that somewhere I think your right, must of got hot in there real quick though I know what you mean but not in this case as everything is stamped in order and then cable tied to a thick piece of card in order Now that is interesting as I dont have any at all,like I said earlier it feels as though when you torque them up the cap starts to bind and want to force the "lips" of the bearing apart. Right i'm going to have to do some more probing/measuring around on sat morning,better not do any today as its my wedding anniversary and I don't think my good lady would appreciate that Thanks Guys
Hi,look the bearings wore to excessive clearence,when that happens the crank and power from the piston beats up the bearing and rod.when the rod gets beat up it gets wider,like as if you hammered a piece of metal.you still have not found the cause!!!possible causesil starvation from pickup or worn oil pump,improper installion of rod and bearing,by a back yard mechanic like you installing a out of round and sized rod with a new bearing.you must remove and inspect all other bearings and rods,if copper is showing through bearing surface they all should be replaced and rods should be resized and bushed by a machine shop.thats the deal from someone with 40 years of motor rebuilding.joe
I think i get the message, thanks for your input i will have to have a word with the british military about there shoddy back yard mechanics, see earlier posts.
How did you go "bobbooth" with remeasuring? Just a question that come out of Joe's post, have you looked at all the bigend bearings and measured the other journals? Also, could you post a photo or two of the shaft and rod? Might help by some of us having a look. Cheers AFL
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