Crank Grind - Is a reblance necessary?
#1203301
03/25/12 07:16 PM
03/25/12 07:16 PM
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Joined: Jun 2006
Posts: 5,159
CT
GTX MATT
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OP
master
Joined: Jun 2006
Posts: 5,159
CT
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Would it be necessary to rebalance the rotating assembly after grinding the crank .010 on the rod and main journals? I would think mains would absolutely not matter and I would think the weight difference on the rod journals would be minimal.
And from what I understand the factory balance jobs aren't too close to begin with.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Crank Grind - Is a reblance necessary?
[Re: GTX MATT]
#1203302
03/25/12 08:19 PM
03/25/12 08:19 PM
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Joined: Apr 2007
Posts: 905
SD
zrxkawboy
super stock
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super stock
Joined: Apr 2007
Posts: 905
SD
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I agree w/ your opinion on all points.
It's Swifty! Swifty, you toad sucker!
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Re: Crank Grind - Is a reblance necessary?
[Re: zrxkawboy]
#1203303
03/25/12 08:22 PM
03/25/12 08:22 PM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Marysville, O-H-I-O
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how much metal is .010" cut on the journals? we're talking about .005" per side of the journal here. that's the thickness of a sheet of notebook paper.
so you're looking at a difference of grams, at which point, when you enter in the debate of how much oil to account for on the parts when calculating the balance numbers...I think you're well within the safe margin of error
**Photobucket sucks**
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Re: Crank Grind - Is a reblance necessary?
[Re: 70Cuda383]
#1203305
03/25/12 10:01 PM
03/25/12 10:01 PM
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Joined: Jan 2003
Posts: 1,602
westerly, ri. usa
440lebaron
top fuel
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top fuel
Joined: Jan 2003
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westerly, ri. usa
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bearing thicker/crank thiner. should even out
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Re: Crank Grind - Is a reblance necessary?
[Re: GTX MATT]
#1203306
03/25/12 11:47 PM
03/25/12 11:47 PM
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Joined: Aug 2003
Posts: 775
Eastern WA
ProStock1320
super stock
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super stock
Joined: Aug 2003
Posts: 775
Eastern WA
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Quote:
And from what I understand the factory balance jobs aren't too close to begin with.
So, has the engine ever been apart before? Is this grinding the first on the crank or was it balanced when you put the engine together last? If you're pulling it for the first time and are going to grind on it, I would think you'd want it balanced just for your stated point above. If it was previously balanced, I'd agree with others that you're within tolerances - especially for street use.
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Re: Crank Grind - Is a reblance necessary?
[Re: ProStock1320]
#1203307
03/26/12 02:18 AM
03/26/12 02:18 AM
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Joined: Jun 2006
Posts: 5,159
CT
GTX MATT
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This is the first time its been apart, it was torn down because of low oil pressure with a valve train rattle at higher rpm and an intermittent complete loss of oil pressure. It looks like the complete loss of oil pressure was being caused by crap trapped against the screen on the pickup. The low oil pressure looks to have been a combo of bad cam bearings, and worn rod and main bearings. The crank looks ok, nothing inbeded and no deep gouges. However, it has a strange imperfection on some of the rod journals where it has a sort of ridge protruding upward, and the rod bearings were worn through to the copper where these ridges were.
Anyway, the car had like 20 lbs of pressure at hot idle and around 45 at 1000 rpm and up. The ridge wasn't bad at all, I'd gather it had about 100k on the clock. Its about $150 to grind a crank where I am so I figure I may as well go for it. This engine is going to be basically a stock HP street engine for daily driver type use, so nothing really fancy is required.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Crank Grind - Is a reblance necessary?
[Re: GTX MATT]
#1203308
03/26/12 03:42 AM
03/26/12 03:42 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
Striving for excellence
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Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
Anyway, the car had like 20 lbs of pressure at hot idle and around 45 at 1000 rpm and up.
This in itself isn't terrible depending on the weight of oil that you had in there. 5w30 with those numbers isn't bad. 20w50? Uhhh, time for some work.
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Re: Crank Grind - Is a reblance necessary?
[Re: GTX MATT]
#1203309
03/26/12 10:04 AM
03/26/12 10:04 AM
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Joined: Jan 2003
Posts: 74,937
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 74,937
U.S.S.A.
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Quote:
This is the first time its been apart, it was torn down because of low oil pressure with a valve train rattle at higher rpm and an intermittent complete loss of oil pressure. It looks like the complete loss of oil pressure was being caused by crap trapped against the screen on the pickup. The low oil pressure looks to have been a combo of bad cam bearings, and worn rod and main bearings. The crank looks ok, nothing inbeded and no deep gouges. However, it has a strange imperfection on some of the rod journals where it has a sort of ridge protruding upward, and the rod bearings were worn through to the copper where these ridges were.
Anyway, the car had like 20 lbs of pressure at hot idle and around 45 at 1000 rpm and up. The ridge wasn't bad at all, I'd gather it had about 100k on the clock. Its about $150 to grind a crank where I am so I figure I may as well go for it. This engine is going to be basically a stock HP street engine for daily driver type use, so nothing really fancy is required.
It sounds like you are just going to do a rebearing rebuild on an engine with 100k miles on it ?
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Re: Crank Grind - Is a reblance necessary?
[Re: JohnRR]
#1203310
03/26/12 10:38 AM
03/26/12 10:38 AM
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Joined: Mar 2007
Posts: 12,008
Finally a HUSKER again
Moparnut426
I Live Here
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I Live Here
Joined: Mar 2007
Posts: 12,008
Finally a HUSKER again
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Quote:
Quote:
This is the first time its been apart, it was torn down because of low oil pressure with a valve train rattle at higher rpm and an intermittent complete loss of oil pressure. It looks like the complete loss of oil pressure was being caused by crap trapped against the screen on the pickup. The low oil pressure looks to have been a combo of bad cam bearings, and worn rod and main bearings. The crank looks ok, nothing inbeded and no deep gouges. However, it has a strange imperfection on some of the rod journals where it has a sort of ridge protruding upward, and the rod bearings were worn through to the copper where these ridges were.
Anyway, the car had like 20 lbs of pressure at hot idle and around 45 at 1000 rpm and up. The ridge wasn't bad at all, I'd gather it had about 100k on the clock. Its about $150 to grind a crank where I am so I figure I may as well go for it. This engine is going to be basically a stock HP street engine for daily driver type use, so nothing really fancy is required.
It sounds like you are just going to do a rebearing rebuild on an engine with 100k miles on it ?
The factory engines werent "balanced", they just were "matched" when put together. Ive seen shade tree shop engines come appart with 3 different pistons, and a few with different brand bearings and other stuff miss matched and they hung together on the street, But a true balance is far more in depth than the factory.
I would think what your doing is fine for a Hone, bearing, rebuild.
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