Inside Diameter between main bearing cap and corresponding block bearing recess "F" engine (1 Viewer)

[Stevepipeman]

I found a loose main bearing shim after crankshaft removal, one of about a half dozen installed by the Factory in several locations on this 1971 "F" block. Does anyone have the factory specs for the inside diameter between the main caps and the corresponding bearing recesses? My experience with shimmed caps is nonexistent. If I chew up any bearings in this rebuild I'll need to jump in the river with it chained to my leg.

 

[MoCoNative]

I'm not sure on the ID of the cavity with the cap back on. Typically you want to put the shims back exactly where they came from. They account for the material removed when the caps were cut free from the block casting on the old blocks.

The shims will match the shape of the caps, so the front and rear are unique shaped. I would also assume that each leg of the cap would be shimmed essentially the same per cap. If you have one cap that is shy a shim on one side I would assume that is where it went.

In the end, the gap/journal size is confirmed using plastigage and the shims are used to get that measurement correct. That may be the only way to find its location. Don't loose any of them. I don't know if you can get them any longer, last crank I did, we bought a set, probably through Specter. Shim material can be sourced however from a good parts store, they probably don't have to be perfect die cut to work.

I know all to well what happens with poor shimming, or none at all, (engine builder never really fessed up to what he had done.) Seized the engine solid after 45 minute run in period.

 

[Stevepipeman]

Thanks for the good info. Spector sells shim sets, but I have all of them. I wired the bolts to the caps to hold the shims in place as I pulled the caps and bearings, but one got past me and wound up on the floor so I'm a little freaked out about it. I will be plasti-gauging all the bearings before final assembly. Cam and lifters replaced, crank ground .010, cylinders bored .020, block & head decked, new valves seats. Too much for an old "F" motor, but rig is a perfect 2 owner Arizona truck w/ 178k miles. Spinning a main bearing is not an option.
Thanks for your help.

 

[MoCoNative]

I can see how one can be lost. Is it one for the middle caps or ends? That will help narrow it down. The holes have to be round, you don't shim the caps with different thicknesses from one side to the other, so whatever stack of shims is missing one, that is where it goes. In other words, if a cap has a .010 and .020 stacked on one bolt, there should be matching shims for the other bolt of that cap, as an example. The factory shims had the thickness printed on them.

Are you using the FSM, the old manuals are really quite good for the engine section I thought. Really a thorough step by step. Some tips, put some locktite sealant on the rear of block cam plug. If it leaks it makes a hell of a mess, appears as a rear pan or main kind of leak. I used blue RTV on all the cork gaskets, coat each side. Use good gray RTV, we always used a Ford product, on the corners of the oil pan where the little square cork chunks over the caps transition to the flat wider cork. This square corner can leak if you don't get some goop there.

Don't forget the oil squirter for the cam gears. The new allenheaded screws for the front timing plate are nice if yours are dinged up. I RTVed that baby on with a good gasket. The front timing cover needs RTV on the cork, with the front oil seal installed, and then slip it over the crank nose. Then install the front pulley temporarily to align the front seal before tightening any of the retaining bolts. There is enough slop in those holes that the seal can be off center to the crank. Also put some locktite thread sealer on the lower two big bolts of that cover that go in the front bearing cap??, either way they can leak past the threads as they penetrate the crank case area. Same for the water pump bolts, thread sealant on those, or they will weep as they penetrate the water jacket. Flywheel bolts also penetrate into the crank case through the end of the crank, they can leak oil.

 

[Stevepipeman]

I'm going to head to the machine shop and look at my main caps. I don't know if oil was holding some of the shims tight to the caps and I just didn't notice them because I'd have bet the shims were not stacked evenly between one side of the cap and the other, but I wouldn't doubt your knowledge for a minute. The shims I looked at closely where all OEM Toyota and marked with the thickness of each. I'm glad to know they are placed symmetrically, which will make determining the placement of the odd shim a lot easier. Thanks for your experience in covering the easily neglected areas where leaks tend to occur. There's nothing worse than a new engine that needs a new maxi-pad and a quart of oil every 300 miles. Thanks again for your valuable experience and the time you took to lend it.