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Old 04-25-2016, 09:12 PM   #1
Wyo_sti08
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Default Resistance when turning over engine without heads (video)

I just bought the bumped up closed deck shortblock from off the line performance( machined and assembled by iAG) and when I turn the engine over by hand without the heads on it moves freely for the first 180 degrees then it gets harder to turn for the other 180 degrees then easy again. Is this normal?
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Old 04-25-2016, 10:50 PM   #2
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When rotating a Subie engine (no heads) there is more resistance to rotating when the pistons are at the midway point of the bore. There is a minimal amount of resistance when the pistons are at TDC/BDC.

That being said, it does not take much effort to spin a bare block Subie engine.
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Old 04-25-2016, 10:59 PM   #3
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But it would vary depending on where its at in its rotation? Because it's not that it's hard to rotate it's that the resistance changes midway through a rotation and that's what worries me.
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Old 04-26-2016, 06:23 AM   #4
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Quote:
Originally Posted by 2milehi View Post
When rotating a Subie engine (no heads) there is more resistance to rotating when the pistons are at the midway point of the bore.
Really? Why?
And this is for "subie" engines? Not all piston engines?

anyway, rotating anything with that many bearing surfaces by hand is tough, it's always going to feel notchy, you can't apply constant torque by hand. Once you stop or slow down it will get tight, you have no oil pressure.
Going that slow adds to that 'feeling'
go faster and try not to stop every 90 degrees, it reciprocates after all, maintaining rotation keeps it smooth

IMO that looks normal but obviously over the internet nobody can feel it
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Old 04-26-2016, 07:55 AM   #5
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Hard to tell but do the Pistons come out of the block?
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Old 04-26-2016, 08:30 AM   #6
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Put a crank pulley on it, if you cant turn it by hand with the pulley on it something is wrong IMO.
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Old 04-26-2016, 06:34 PM   #7
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Quote:
Originally Posted by rtv900 View Post
Really? Why?
And this is for "subie" engines? Not all piston engines?
With just about all 4 cylinder engines, the crankshaft is flat. When the pistons are at TDC/BDC there is little movement from the piston and that is less friction (piston rings against the cylinder wall) that needs to be pushed through.

When the pistons are mid way in the bore, there is a lot of movement from the pistons and there is more friction that needs to be pushed through.

With V6 an V8 engines some pistons are at TDC/BDC while other pistons are mid way through the bore.
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Old 04-26-2016, 08:38 PM   #8
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What rods? What bearings? Clearance? What assembly line?
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Old 04-26-2016, 08:51 PM   #9
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Quote:
Originally Posted by Delphi View Post
Put a crank pulley on it, if you cant turn it by hand with the pulley on it something is wrong IMO.

He's using a big breaker bar lol
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Old 04-26-2016, 11:57 PM   #10
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It's not that it's hard to turn its just the change in resistance I was worried about. I spoke to iag and off the line and they both said it was normal being that the engines not broken in yet and that it has no oil in it.
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Old 04-27-2016, 12:20 AM   #11
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spiiiin, little sticky, spiiiin, little sticky... is that what you're seeing?
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Old 04-27-2016, 12:42 AM   #12
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Yes exactly
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Old 04-27-2016, 02:54 PM   #13
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I spoke to iag and off the line and they both said it was normal due to there being no oil in the engine and that it hasn't been broken in yet
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Old 04-27-2016, 04:15 PM   #14
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It's probably been assembled using a very thick assembly lube also something like Lucas. It's like Syrup that alone will give you some resistance. Now if you have a binding that's an issue usually do to an egg shaped rod journal. Are they new rods? I've also herd that something like this can happen if factory rods are installed with the bearing tangs facing the wrong direction. Is it getting stuck (binding) when a piston is at bdc? Could just be the added resistance between the cross hatches and rod angle
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Old 04-27-2016, 05:10 PM   #15
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It's a brand new closed deck shortblock from off the line built by iag
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Old 04-27-2016, 07:32 PM   #16
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Quote:
Originally Posted by Wyo_sti08 View Post
I spoke to iag and off the line and they both said it was normal due to there being no oil in the engine and that it hasn't been broken in yet
Was this before or after you posted?
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Old 04-28-2016, 12:59 AM   #17
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After
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Old 04-28-2016, 03:22 PM   #18
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Quote:
Originally Posted by Wyo_sti08 View Post
Yes exactly
you're good then.
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Old 04-28-2016, 05:21 PM   #19
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Alright cool thanks
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