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G T A 04-21-2002 05:09 PM

Line Boring
 
When is it necassary? I have a good 4 bolt main 350 block that I would like to build up but is has rusted from sitting. I'm planning on honing the lifter bores to remove rust and having the cyls bored .30. Question is, should I have the crank journals line bored or just honed? Should I be concerned about the rust? The block wil be going for cleaning and boring but I will have to ship it away for the line boring and I don't want to do that.

4 Jaw Chuck 04-21-2002 06:06 PM

Generally I prefer not to align hone an engine, most times it is not necessary. To check, invert the block take your crank and install the bearings in the block, lubricate and then check for crank runout with no main saddles installed or seals. There should be less than 0.002" runout, if not regrind the crank. Next install the main saddle caps and torque, be sure to lubricate copiously. Next rotate the crank and see how easily it rotates, there should be no binding at any point if the crank is straight. In doing this procedure you have just checked your mains alignment and once you remove the main caps you can check for clearance with plastigage etc.

Even if the block has a lot of corrosion a wire brush can remove the heavy stuff and then you can see how much pitting is on the mains surfaces. Scotchbrite works good for this. I wouldn't hone unless the crank was binding or the corrosion was so bad that the surface area contacting the bearings is compromised with pitting. If you end up align honing the block (hardly anyone bores them anymore) have the machinist put in a couple of "tenths" (0.0001") more crush on the main bearings, won't hurt anything. Make sure you install the bearing shells dry, any oil on the backsides will hold the shells off the surface and reduce your clearance.

Most shops only align bore to restore the cam to crank relationship if the engine needs a lot of align honing (pretty rare). Remember anytime you align hone the crank gets closer to the cam which will make your cam chain slacker, there are special short chains for this if you need them. I would spend the money I would spend on align honing and have the engine blocked and decked including the trans face, this way you know the deck heights will be the same and the crank will be square with the trans. All these things are unnecessary if the block is straight to begin with. All the more reason to find a good machinist who takes pride in his work.

bullheimer 05-09-2002 01:39 PM

my machine shop wont aline hone, they only line bore, says honing doesn't cut it. same price. i had mine honed by someone else and he ragged on it. was already assembled so i left it. mic it and see if they're out. remove rust with whatever, take to car wash and wash, dry in sunshine, spray with wd40, stick in big plastic bag till ready to serve.

F-1Rodder 05-09-2002 05:03 PM

Another point of view on this. Its a little like dating, you never know where she's been. An align hone will clear up that question. But if you are building a motor for power, I would do as much as possible to insure perfect alignment. You may not have thought of this, but you may want to consider "decking" the motor to insure all cylinders are equal volume and to insure you know what compression you will end up with. This is also a machine shop operation, but I consider it an absolute for high perfomance and to assure a proper cylinder head quench.

reddwarf 05-09-2002 09:12 PM

Align honing must also be done when a main cap is replaced


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