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Old 11-16-2010, 05:27 PM   #1
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Default fitting new m-tuned rods

I only plan to fit m-rods to my 1.8 not planning a full overhaul as the engine appears to be in good condition 5% leakdown.
What I was wondering is should I use the original bearings from my old rods or should I fit new bearings in..........If i fit new bearings is it necessary to run it in on mineral oil or will it be ok on synthetic..
any help much appreciated thanks.
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Old 11-16-2010, 05:34 PM   #2
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If they look flawless/brand new with no wear/scuffing/etc on em there's no reason you can't reuse.
As for break in, there are tons of different opinions, IMO I'd use regular for the 1st couple hundred miles.
my .02
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Old 11-16-2010, 07:42 PM   #3
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are you installing new rings?
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Old 11-16-2010, 08:00 PM   #4
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If you're going to the trouble and expense to put in better rods, don't cheap out on the bearings. If I had an engine that far apart it would get new main and rod bearings.

As for break in oil, what 90R said... are you using new rings?

If you've honed the cylinders and installed new rings don't use synthetic. Despite the 5% leakdown numbers I'd probably do a hone/rings just due to having disturbed everything during the disassembly/reassembly process.
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Old 11-16-2010, 10:32 PM   #5
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If they look flawless/brand new with no wear/scuffing/etc on em there's no reason you can't reuse.
And since they're used bearings, they won't look brand new, and you should replace them.
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Old 11-16-2010, 10:38 PM   #6
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And since they're used bearings, they won't look brand new, and you should replace them.
I wouldn"t condemn then before a round of plastigauge. I'd be more concerned about the ring seal after reassembly.
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Old 11-16-2010, 11:38 PM   #7
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I once ran my 323gtx w/o oil. The new bearings were looser than the oldass "worn" bearigns accordign to the plastigauge. I put oil in it and the knock went away. I still have that package of bearings somewhere in my attic.
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Old 11-17-2010, 12:47 AM   #8
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atleast get rod bearings you will not be removing the crank so there is no need for main bearings if the originals are in good shape.
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Old 11-17-2010, 03:44 AM   #9
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Get the small end measured as well. I had to hone mine a touch to fit FM Wisecos.
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Old 11-17-2010, 11:31 AM   #10
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atleast get rod bearings you will not be removing the crank so there is no need for main bearings if the originals are in good shape.
You generally don't need to remove the crank to replace mains... just one main cap at a time.

Plastigauge is for *******... use real measuring tools.
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Old 11-17-2010, 12:31 PM   #11
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You generally don't need to remove the crank to replace mains... just one main cap at a time.

Plastigauge is for *******... use real measuring tools.
and why the hell would you do that if there is no problem and, you dont have the chance of contaminating it ie dissasemble and, reasemble it. it is 50 dollars wasted and time wasted as well.
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Old 11-17-2010, 12:51 PM   #12
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are you installing new rings?
Iam keeping original pistons and rings.no honing.
How do you hone the small end to get it to fit. Just use fine grade emery? or a small fan buff wheel in a drill?
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Old 11-17-2010, 01:13 PM   #13
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If you remove the pistons from the bore you must use new rings and hone it. Just a bottle brush hone will do the trick, but you have to do it. You will never.. EVER get the rings lined up in the bore exactly as they were before you removed them. That will cause sealing issues, bad compression etc. If you can manage to keep the pistons in the bore while installing new rods, more power to you... but don't pull them out and put them back as they are.
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Old 11-17-2010, 01:14 PM   #14
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/\ I agree
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Old 11-17-2010, 01:24 PM   #15
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Awww **** now this makes me think getting new pistons and rings might be better idea.
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Old 11-17-2010, 02:59 PM   #16
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and why the hell would you do that if there is no problem and, you dont have the chance of contaminating it ie dissasemble and, reasemble it. it is 50 dollars wasted and time wasted as well.
Sorry, what is this "contamination" you speak of when building engines?

I have a phrase that Rennkafer told me when we were building my first motor - "Cleanliness before Godliness"
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Old 11-17-2010, 03:06 PM   #17
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i implied a possible not an imperative.
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Old 11-17-2010, 03:08 PM   #18
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Grow a sack,get new forged pistons AND rings and balance that **** as well,crank,rods and pistons.

Balanced motor sound and smoothness = better than college sex
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Old 11-17-2010, 06:14 PM   #19
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Originally Posted by magnamx-5 View Post
and why the hell would you do that if there is no problem and, you dont have the chance of contaminating it ie dissasemble and, reasemble it. it is 50 dollars wasted and time wasted as well.
He will already have the oil pan and head off to change out rods, pulling main caps isn't going to cause contamination worse than those two operations. The reason you'd do it is when you've taken the time, effort, and expense to take the engine apart that far you may as well do main bearings. This way you know for absolute fact you have good ones in place. Leaving the old ones in damn near guarantees someone didn't change the oil regularly in the past and the bearings look like *****.

Maybe I'm just a distrustful bastard... I've seen inside too many "professionally" built engines at work to trust anything I didn't do myself.
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Old 11-17-2010, 06:19 PM   #20
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if i remove pistons rods and crank is there much more to remove so that i can take block for a rebore?
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