im swiching out pistons in a rebuilt 37 ford flathead. i thought it whould go back together easyer. rods are kinda tight. plastigague reads about .0015. motor turned over fine before, im stumped.
Also, the Ford overhaul manual is online now somewhere--who has a link? I'll try to bring in a copy tomorrow and post official lingo on this. Since bearing is a floater, plastiguage just pushes it over against the other side of ita clearances. No can use.
Also, a tech tip on the bilben site: anytime you see a tip posted by "JWL", you can be assured you are getting the right stuff. Those things contain collected posts from a number of people, and so of course contain contradictions and sometimes scary misinformation. JWL good.
A full reprint of the old 38-48 Ford engine overhaul manual is on the Ford Flathead V8 Engine website (www.flatheadv8.com). Here is a link to the main webpage. You want the Chapter 3....Assembly link. There are 5 pages which you must click thru. The specific section on the rod bearings leaves a bit to be desired. I guess they expect you to mic the rod end ID and the crank journal OD. Then mic the bearing thickness. TOTAL difference is supposed to be between .0015" and .0035". They allow a maximum tolerance of .005" for a motor's existing rod bearing wear. Keep in mind.....this was printed in 1948 I believe and the techniques were those commonly in use at the time. No mention of "plastigage" at all. http://www.vanpeltsales.com/FH_web/FH_37-48engine-rebuilding/v8_overhaul-forwrd-contents.htm Fitting the floater bearings is apparently a bit of a trial and error process to get them to "float" properly. Careful double-checking of measurements is important. Ron Holleran's book on Ford flathead motors covers this process in detail. With pics too. I don't know if Ron is on the HAMB but he does check in on the Fordbarn Early V8 forum frequently. Hope this helps anwer that question............... Mac VP
JWL does a better job on the adjustment process than the manual, so consider that done. I just found the Canadian version of the Ford overhaul manual under my desk. Here's the measuring part of the job: Original connecting rod bore: 2.2195-2.2200 on little crank, 2.3595-2.3600 big journal. Bearing thickness is measured by using a known diameter cylindrical plug on inside of curve to allow micrometer to fit, then subtracting the spacer. Standard bearing --discard if less than .1085. Add 1/2 of oversize plus 1/2 of undersize to that for thickness permissable for non-standard. Measure crank pin and rod bore. Total allowable clearance, which would be difference of these measurements minus bearing thickness, is .0015-.0035 on new, max of .005 on used assemblies. Hope I typed all those blasted numbers right. If this all hurts your head--it does mine--remember you want total measured clearance within limits, then you want a reasonable split of that clearance between inside and outside--that's all, don't fuss too much. Advantage of full float is slight reduction of friction losses and greatly diminished chance of rod failure under abuse, as rod failure generally is started by bearing pinch at parting line under high revs. In early OHV days, some engines were converted to early Ford bearings to combat rod failure at the strip as people began to figure out how to get the new engines to rev. Aftermarket rods, welded and aluminum, stiffened the rods and ended the need for this mod.
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