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Old 03-31-2020, 03:41 AM   #1
VB242
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Default Crank scraper install

I'm installing an Ishihara-Johnson crank scraper, the install instructions call for .040" clearance but reading about some of his other customers installs they get them much closer all the way down to ,
.010". Has anyone gone tighter on the tolerance? Does the crank grow that much once it gets hot? I assume it works better the tighter you get it .
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Old 03-31-2020, 06:32 AM   #2
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What kind of RPM are you turning? Never got around to installing one on a sbc but I would follow the instructions. Others may get away with less clearance but what about if there is drag that you never know about until that next tear down. Who know what is going on at 7500 or more. I was looking at a D stroked LS 427 that that they shift at 8200 rpm. That give me a hard on!!
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Old 03-31-2020, 06:35 AM   #3
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What kind of RPM are you turning? Never got around to installing one on a sbc but I would follow the instructions. Others may get away with less clearance but what about if there is drag that you never know about until that next tear down. Who know what is going on at 7500 or more. I was looking at a D stroked LS 427 that that they shift at 8200 rpm. That give me a hard on!!
It's got all brand new bearings, I wouldnt imagine there's enough play at any rpm to move more than .002-.003 or if there is I wouldn't have any oil pressure.
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Old 03-31-2020, 07:31 AM   #4
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It's got all brand new bearings, I wouldnt imagine there's enough play at any rpm to move more than .002-.003 or if there is I wouldn't have any oil pressure.
You are right on that but I would still like the margin. There are some incredibly smart people on here. Let’s see what they say but it’s still your time and coin. Can you guess how much windage you are giving up by going with instructions?
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Old 03-31-2020, 09:45 AM   #5
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So...his pics of the redblock scraper are actually from my build. Keep in mind you've got a limit of .010" on crank end play assuming nothing fails. On top of that plan for a little expansion as well. I went for around .030" and had no issues, at least until the thrust bearing went south, which wreaked havoc, destroyed the scraper as well, stress fractures all over it.
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Old 03-31-2020, 11:27 AM   #6
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My machinist (R&L Engines in Dover NH) once told me it's 0.030" clearance on internal moving parts, minimum.
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Old 03-31-2020, 11:49 AM   #7
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The I/J scraper I had, came with a Teflon edge that was sort of sacrificial.
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Old 03-31-2020, 11:59 AM   #8
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I used to build a lot of pontiacs and some various other v8s, and plenty of people CLAIMED to run them touching (cheap home-made sheet steel).
I run about .020"-.030", the last one I did was on a corolla. Have not done a red block volvo.
It can be pretty far away and still work. You aren't scraping oil, you are making an air dam.
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Old 03-31-2020, 12:54 PM   #9
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Looks like .030 is the number to shoot for
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Old 03-31-2020, 07:06 PM   #10
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Set close to .030

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Old 04-01-2020, 10:28 AM   #11
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I gotta get one of these
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Old 04-01-2020, 10:40 AM   #12
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As the pressurized oil from the main and rod bearings is slung from the crank, the scraper reduces the parasitic loss, by reducing the amount of spray that the counter weights, etc. must rotate through?
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Old 04-01-2020, 11:42 AM   #13
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That's the idea, reduces the oil mist entrained in the air in the crank case
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Old 04-01-2020, 02:09 PM   #14
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Sounds like a win. Especially at high revs.
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Old 04-01-2020, 02:53 PM   #15
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On the B18/20 up to B230s that have not been fitted with squirters, has anybody given consideration to how the scrapers are going to affect cylinder wall lubrication which relies on oil being flung off the crank? I don't recall lubricating jets / notches on the B20 con rod or off the top of the main bearing supports so cylinder lubricating oil would appear to be what originates from the con rod big end bearing sides and gets thrown upwards by crank rotation. The I-J scrapers seem to work on just the outside edges of the counterweights with lots of clearance to the webs and big-end so perhaps does not affect the majority of the oil supply to the cylinder walls? Is the loss of lubrication from oil being flung off the bottom and outside of the counter weights immaterial - in which case is the reduction in suspended oil from using the scrapers immaterial?

I get the windage tray and in fact Volvo R-sport sold a modified B18/20 oil pan incorporating their version of a windage tray. The scrapers I am not so sold on as to whether they are a good idea.
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Old 04-01-2020, 04:40 PM   #16
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Interesting. My HS shop instructor told us that motor oil: "cooled, cleaned, sealed and lubricated." Important functions.

So, on the squirters, I always thought that the function of the added oil volume was to cool the pistons to reduce detonation. Not to improve lubrication.
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Old 04-01-2020, 04:48 PM   #17
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Quote:
Originally Posted by LC4CARL View Post
Interesting. My HS shop instructor told us that motor oil: "cooled, cleaned, sealed and lubricated." Important functions.

So, on the squirters, I always thought that the function of the added oil volume was to cool the pistons to reduce detonation. Not to improve lubrication.
Why not both?
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Old 04-01-2020, 07:21 PM   #18
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Quote:
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Interesting. My HS shop instructor told us that motor oil: "cooled, cleaned, sealed and lubricated." Important functions.

So, on the squirters, I always thought that the function of the added oil volume was to cool the pistons to reduce detonation. Not to improve lubrication.
I am sure that there are lots of explanations for the 1993 (or whenever ) fit of squirters on the B230. I note that Volvo had OHC turbo motors for a number of years without detonation issues. I had an '87 745 turbo with turbo + that ran just fine on 87 pump gas. So, I am not sure what would have changed around 1993 that would have created a detonation problem motivating Volvo to cool the piston crowns. However, after Volvo introduced its low friction version of the engine with the shorter piston skirts they developed a problem with piston slap that would emerge about 3 - 4 years into ownership. Around 2000 a Volvo tech I knew said that just about all the '87 and later B230 FTs developed some level of slap (typically starting first on the #4 cylinder) as time ran on and his explanation was that Volvo added the squirters to help address piston wear.

Take it for what it is worth. If you retrofit squirters to your B230 and aim them up directly under the crown of the piston your objective is definitely more into cooling since splash onto the walls is secondary. I don't know how they are aimed when the are installed by Volvo. I do know that Honda B engines and I believe my C engine have jets / orifices to squirt oil on the cylinder wall thrust face and those engines are NA so any piston cooling is probably secondary.

My primary interest was whether the retrofit of scrapers on a B20 would result in a material reduction in lubrication to the cylinder walls.
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Old 04-01-2020, 09:44 PM   #19
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Plenty of oil is being flung from the sides of the mains and rods.
Scrapers and windage trays reduce the ability of the crank to whip up spray from the bottom. Think whitecaps and waterspouts on a bay.
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Old 04-01-2020, 10:19 PM   #20
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Great stuff.
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Old 04-01-2020, 10:38 PM   #21
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Interesting - so the redblock version doesn't come with the teflon scrapers? The I/J kit I used on my whiteblock years back had those as mentioned by another poster.

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Old 04-02-2020, 12:09 AM   #22
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Depends which version you buy. The cheap one doesn't, the nicer one does.
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Old 04-13-2020, 02:18 AM   #23
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James on here once asked me if I had a scraper when he noticed how much piston knock my car had when cold. I do, but I can't guarantee it would be different if I didn't have a scraper... I don't have the teflon add-ons, so they aren't THAT close. These engines get sloppy even without them.

That being said, I haven't seen the oil pressure light come on while on the race track(in my street car with the I/J scraper) and I've been running it for over 100k miles, I think.
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Old 04-13-2020, 12:56 PM   #24
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On the FP SCCA [1275cc] race car that I maintained for 20 Years for a friend, we ran a scraper for a while with .010 clearance. The engine lived most of it's life on the track at 6800+rpm, red line was 8800 rpm if the driver was paying attention, one time at Daytona he looked down at the tach and saw 9400 rpm. We used every thing that the rules allowed. 20 years of racing and 18 division championships. It all depends on what you are going for.
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