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View Full Version : First timers mistake our not. (cam bearings)



Falkon
05-06-2011, 02:06 PM
A few weeks ago I took my engine in to get it cleaned up, bearings replaced, new pistons and just about everything else.
Got my engine back about a week and a half later and started to resemble it. As i was starting I noticed that two of the new cam bearings had a little nick in them on the outer edge. I didn't think this was such a big deal, ya it needed to be fixed but that was something i could easily do. But my dad insisted that i got ripped off by the machine shop and that i take it back and have them put new ones in that did not have any nicks.

Well i just got back and yes they said they would put new ones in, but the main guy said that that happens to cam bearings all the time, and that its just a mater of filing them down smooth so that the cam shaft will fit properly. Then my dad countered with saying, "If you polish, file, or refinish them it warps the bearing making it useless".

So my questions is.
1. Did having a small nick in the outer edge of the cam bearing really make that big of difference? My thought, yes but easily fixed and not a big deal

2. For those of you who have replaced cam bearings, either by yourself of by someone else. Are small nicks common?

3.Does refinishing, polishing, or filing nicks really warp the cam bearing?

4. Did i make a small mistake by not worrying about a small nick? I know that if it was a crankshaft it would make a difference. But does a small little, easily fixable nick really make that much of a difference.

:thankyousign:
Sorry I forgot to take picture of it, but the best way i can describe it, is a small protruding nick in the metal about the size of a grain of sand or 2-3 salt crystals. Not that big.

Scott_Hower
05-06-2011, 02:46 PM
Doubt the bearing will "warp" from a nick. Never heard of that before; they're circular.
Cant remember, but I seem to recall them having a chamfered oval in them to line up with the oil feed holes. Probably depends on the size of the nick.

If the right tool is used to pull them into place, you shouldn't have any nicks. More likely to warp/damage them by not using the appropriate tool to get them square to the bore. My shop doesn't like to install cam bearings without also having the cam, so they can size them. Never watched them do it; guessing they just polish the bearing it the cam is too tight.

What's a head bearing?

Falkon
05-06-2011, 02:52 PM
Don't know why i typed head bearing, must have been thinking of something else.

DrEntropy
05-07-2011, 07:13 AM
The bearing-to-block interface is an "interference fit", requires a press tool to do properly. Whacking them in "by eye" with a drift, etc. can in fact warp or deform them. As for the cam journal to babbet clearance, it is toleranced. Can't recall off the top what that clearance is but if the shop didn't have, or ask for the cam to check/fit it, something's fishy.

And the bearings can be nicked or gouged if the cam is installed/removed without paying attention to position of the lobes in the process.

dklawson
05-07-2011, 07:28 AM
I agree with the Dr. The shop should have asked for the cam prior to installing the bearings. That allows the shop to size the installed bearings after installation.

Falkon
05-07-2011, 09:01 AM
Yes they did ask for the cam both times. I did get the engine back later last night. The cam fits properly now, last time it was hard to get it in our out. It appears they fixed the nicks and also possibly polished them.

Now i can finally start putting things back together. Any tips or tricks for reassembling the engine?

DrEntropy
05-07-2011, 09:19 AM
Prelube EVERYTHING well, mic and measure everything to double-check clearances (PlastiGauge!), stick to the torque table. If something "feels funny" stop and investigate. You only wanna do this once. :wink:

Falkon
05-07-2011, 12:09 PM
Ya I have the book that tells me what all I need to do. The only part that's confusing me a bit is the order in which the pistons go in. I lost my peace of paper that tells me so.
Is it front to back 1 2 3 4. Or back to front 1 2 3 4

Hap Waldrop
05-07-2011, 02:30 PM
A series engine also have offest rods, so there is certain direction on they go in in the manauals.

smaceng
05-07-2011, 02:33 PM
I'm a little worried that the numbering of the cylinders is your big worry in putting it back together. Numbering starts in the front and goes to the back. Do you have someone who can help you during the rebuild? It could not hurt to have a shadow person to help you, otherwise ask away and we will try to help!
Scott in CA

Falkon
05-07-2011, 03:57 PM
This is my third engine rebuild that ill be doing just in the past 6 months, so not meaning to be cocky or anything, but i do have a very good idea of what im doing and yes my dad is helping me, and I especially know what can go wrong if you put things in the wrong way. I asked about the order cause i lost my piece of paper that had everything written down on it, like the order and direction of the rods, etc. I think i will start a new thread post for the engine rebuild. Right now we are just getting the basics in; cam, pistons, crank shaft, etc. There are a few more small parts we still have to order.
You can almost bet that i will have many more questions. Thanks for the help so far.

jlaird
05-07-2011, 10:34 PM
Front to back, front is number 1, etc.