Thread: main bearings and rod bearings: HELP PLEASE!!

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Hi,
i wana figure out if the main and rod journals on a forged 427 crank have been cut down or if they're standard. The upper main bearing has a symbol (attached), and next to the symbol it has the numbers 5203. The lower has the same symbol and the numbers 5202. and nothing else is stapmed on them.
The rod bearings have the same symbol and the numbers 5177 stamped on them...and nothing else.
Is my crank std., 10 under,20 under?
thanks for your help

if it was cut it would have how much stamped on the back of the bearing .010 or .020 sometimes it will have std. on it. sounds like its std.

Take the crank to an automotive machine shop. They will usually mike it for free.

i seen this i think it is vander built bearing. i think the spelling may not be rigth. the company was sold many times and they went down hill. they had a three pices rear main bearing that looked from the back side look like it was snap two gether. mich used the bearing make up and call it the v bearing much better bearing . you can measure the thickness of the bearings too this will tell you if they are stand ckeck in the milddle a lot of bearings have some to them eccentricity but when i bulid a engine i check the crank with a micrometer and the bore of the rod and the block with dial gage and put the bearings in with the crank out torque the bolts up to spec and set mic off the crank and setup the dial gage off the crank measurement and put dail gage back in the bore this will give you oil running clearances and do the rods the same way you should have a rod vise and you can plastigage to. but this is much better .if you know some one with mic s to set it all up this is the way i do it but there is a couple ways

plasti-gauge, now thats a word you don't hear to often anymore. not to long ago we did most of our motor overhauls in the car, you would get, if you was lucky about 80,000 to 100,000 miles on the new motor, then you would do a ring job and get another 60,000 to 75,000 out of the block before you pulled the motor out and had it bored and new pistons put in. we didn't have any mic.,(you couldn't get the mic.'s to the shaft in the car) so we used plasti-gauge to determine how much the crank was worn and you could buy .001, .002 and i think .003 oversized bearings to take up the slack. you could also use shim stock to shim the bearings out, if you couldnt get oversized bearings. if the block was worn to bad we would have the pistons knurled so the pistons wouldn't knock. sometimes you had no way to knurl the pistons, so you drove it with the piston knock.( now these was the good old days). this is a little write up about plasti-gauge .


http://www.plastigauge.co.uk/howitworks.htm

Ha, Pat! I was cleaning out a "junk" drawer in my rollaway a while back, and came across some old red and green Plastigage in the sleeves. I know it has been in there since the early eighties, and it just sort of fell apart when I took it out of the sleeve.

Originally posted by DennyW
So, Rambler, I guess you need some new stuff, or are we not using it any more ?

Mike, that was the best stuff to come about. Took a lot of time out of checking clearances, including tapered journels. Great stuff. Mine is still good.

couldn't go to work without it.

Originally posted by DennyW
So, is this link dead now ? Or, is mikekgvk going to let us know what's going on ? Waiting !!

you can wait, but i wouldn't hold my breath.

Plastiguage is great stuff. I never did real well with a mike, so untill digital calipers came out, I plastiguaged it. It was more of a go-no go situation. I remember back then, stuffing a 318 into a Dart in shop class. We got several engines donated, took them apart, swapped parts untill we got a good engine. New bearings, rings. We did the head work. It took all school year, but it eventually ran, and ran for some time.
The auto parts store down the street does not carry it. It has to be ordered.

Hi guys,
i cant use plastigauge cuase i have the crank out of the motor and threw out all but a few of the old bearings. i have the crank for sale on ebay. i'm gonna go get a mic gauge and put it on the journals to make sure what size they are.
thanks for your reply's everyone

Grandpa told me he did a lot of 'experiementing' with plastigauge, and in his opinion it wasn't worth a $hit. He said its accuracy varied with temperature, etc.

I seem to recall that plastiguage must be done with a dry assembly.. is that right?

Originally posted by firebird77clone
Grandpa told me he did a lot of 'experiementing' with plastigauge, and in his opinion it wasn't worth a $hit. He said its accuracy varied with temperature, etc.

I seem to recall that plastiguage must be done with a dry assembly.. is that right?

i dont understand that statement at all. what was he doing with it. its was the only way to check clearances in the car and still is far as i know. nobody said it was 100% acct. it put you in the ball park. what did he use, nothing?

Plastiguage will tell you what the oil film clearances are, but not the bearing undersize.

the first time i ever saw any Plastiguage my brother was laying under a bus, with the oil pan off checking the clearances on a crankshaft to see how much ware he had, so he would know what size bearings to go back with. his choices was .001, .002, or .003. if it was worn more than that then he would have pulled the motor and had the shaft turned to .010. i call that checking for bearing size.

Back before Plastigage, we would shim a bearing with shim stock and try to turn the crank (by hand, of course!). When it wouldn't turn easy, you got some idea of the clearances. Crude, and lots of room for error. And engine damage. Plastigage forever!