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A quick search suggests that there are strongly-held feelings on the subject.  My basic question is which grit I should choose if getting a silicon carbide Flex-Hone (ball hone) for glaze-breaking in the course of a rebuild.  So I'd at least like that question answered, but don't have a problem with informed opinions wading in as to the relative merits of doing it.

 

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There is no merit to doing this and ESPECIALLY not with a flex-hone. If you are going to do it, it needs done on a power hone machine with diamond hones and it needs to be a two-step plateau hone with an extremely fine finish. 

DO NOT TOUCH the cylinder walls. Got that? 

Your fears of ring seating issues are unfounded and based on 1970's era ring and cylinder technology. Which these engines are NOT. 

What is this "glaze" you speak of? What is it composed of and how did it get there? And what are you attempting to accomplish with roughing up the cylinder walls at random with gravel glued to wire spun up in a drill perfectly suited for mixing drywall mud?

GD 

Edited by GeneralDisorder
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As I indicated, I noted your frequent strongly-expressed opinions on the subject.

My understanding is that the "glaze" isn't a deposit (as you suggest), rather the mirror finish resulting from hundreds of thousands of miles' worth of wear against the old rings, and that new rings (that still carry microscopic surface roughness) need a similarly slightly-roughened cylinder wall to wear against in order to bring the two into conformance with each other during break-in.  The foundation of this notion is that a new, rough ring will not seat in properly against the cylinder wall previously "mated to" the old ring.

If this understanding is incorrect, I'd welcome a more thorough explanation of the present case (without the gravel, drywall mud, etc., hyperbole).  I'd also like to hear dissenting opinions, should any be present.  Just looking to get at the truth, not for a dustup.

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The rings are lapped perfectly cylindrical and smooth in a tool steel tube at the time of manufacture. They virtually do not require any seating. What little "break in" takes place is kept to an absolute minimum by ensuring the rings are smooth and the walls have a finished plateau surface devoid of any raised wear points. The top ring is a steel nitrided ring and virtually requires no "seating". Secondary compression/oil control is cast iron and these will seat easily with no honing at all. Indeed the Subaru rings are so thin that honing the cylinder is likely to overheat the rings and cause them to lose their spring tension resulting in WORSE compression. Also the wear materials and impregnated honing grit will tear up your bearings and shorten engine life as they mix with the oil and end up through the whole engine. 

Show me a mirror finish in a used Subaru bore and I'll show you a block that needs to be bored oversized due to excessive wear. 

There are NO cases where a flex hone is a suitable answer. If the bores have so much wear that all the cross hatching (which are the valley's of the plateau finish) is gone, the bore is SHOT and no amount of honing will bring it back. It would require a rebore to the next piston oversize, and the last step in that process is a proper diamond finish plateau hone. 

I can produce references from the 80's that were already stating not to hone cylinders on a rebuild unless absolutely necessary if you want to achieve quickest seating and highest ultimate compression. Piston ring manufacturing, and engine manufacturing tolerances eliminated the need for honing on rebuilds back in the 1980's. Things have only got better since then. 

The reality is - if the bore isn't good enough to run - you need to bore it out to the next piston size. 

And more important than the cylinders BY FAR, is the line hone. After 100k the line hone takes on all the shape and appeal of an elderly bag lady. With the #2/3/4 main's having sometimes three times the allowable oil clearance. 

And the best reason of all - I build Subaru engines FOR A LIVING. I do this every day and we build everything from stock to engines making well over 600 crank horsepower. I haven't honed a cylinder wall in 15 years and not a single engine uses oil or has failed to properly seat the rings. And they seat FAST. It has been (wisely) said that on the first revolution of the engine the rings are wearing in - on the second they are wearing out. I will typically do a 100 mile break-in and then we go full-throttle. My engines always exhibit perfect, uniform compression, and the oil changes show no wear materials. The first oil change at 500 miles ALWAYS shows ZERO oil consumption. 

Oh yeah - and it isn't opinion. It's FACT. Once you have done this as many times as I have - it's not an opinion anymore. I speak from VAST experience. 

GD

Edited by GeneralDisorder
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I want to get to see GD's shop some day.  Heck, I'd even be free help for a week.

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GD:

Thank you - I appreciate the detail of your reply and will follow your advice.

A question, though:  This approach (and your description of the ring manufacturing in particular) is predicated on the cylinder not wearing out of round over time.  If true, that's very impressive.  I'm curious what the tolerance spec for out-of-round wear is, and what your experience is in this regard, i.e. how many miles will a block typically have to see before going out of round far enough to need reboring?

 

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They don't ever go out of round that I have seen - not enough to worry about. I have seen as many as 470k on a block and it still had the cross-hatching visible - threw a rod bearing because the main line was so hour-glassed that there wasn't enough oil pressure to the rods. They do eventually get tapered a little bit but not so much that it seems to affect the ability of the new rings to seal or their longevity. The unfortunate reality is that the block is a limited life-span part. They can only be line-honed one time because of the way that process works, oil pump fitment, and moving the crank center-line with respect to the cylinder deck..... and typically the engines don't make it past 300-350k without a bottom end failure due to the hour-glassing effect and the consequences to the rod bearing oil pressure. The more power the engine makes in stock form or in modified form, the less time this process takes - it is the primary reason that engines making 500+ crank HP are usually limited to 30-40k miles of lifespan. Maybe less depending on how much track use they get. 

Regardless, the only way to know is to measure it is with a (very) accurate bore gauge and mic set, and if it's found to be outside of acceptable tolerances (I have yet to see this on an engine with "normal" wear - excepting things like valve or piston catastrophic failure and the obvious consequences) , then the only solution would be to bore it to the next oversize and accept the unfortunate consequences of having to put a diamond finished plateau hone on it and dealing with the additional break in materials in the oil. It does take a machine shop with a bore plate and a very good understanding of the proper cylinder wall finish to get it "just right" - that is aggressive enough to run in and properly seat, but also fine enough to not overheat and damage the ring tension. 

In any case no useful work can be performed with a dingle-ball hone. It will not correct out of round or taper conditions because it is not a rigid machine hone, and the surface finish isn't a problem unless one or both of those conditions is also present. And if that's the case.... boring oversized, line honing, decking, cleaning, etc is approaching the cost of new case halves from Subaru. Which are less than $900 wholesale. So if it's all jacked up and needs all that work - you just get a nice shiny new one and don't worry about potential machine shop mistakes, and turn-around times. Not to mention drop-off and pick-up, fuel costs, etc. 

AND, if you are even considering a new set of case halves.... that makes no good sense either for an N/A engine (we buy them for custom turbo short block builds only), because Subaru of America sells reman short blocks complete with pumps, pan/pickup, and all block plugs, seperator plate, main seals, etc - ready for heads. These are about $2300 and come with a 3 year / 36k warranty when installed professionally. They are BY FAR the best deal going when you consider the warranty, and our success rate using them has been 100%. The cost for these is far lower than I could do one in-house for when you consider all the included parts. As such we virtually never build N/A engines unless we are doing custom high compression. etc. 

GD 

Edited by GeneralDisorder

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An OT but related question, if I may.  What's your preference for sealing the block halves?  I think the TSM calls for an anaerobic flange sealant, but I've seen some speak favourably of Ultra Grey in this application.  I've long had nothing but fear of and loathing for silicone RTVs in general, but the specialized gasket variants tend to be a better breed.

 

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I have tried the anaerobic flange sealants but the success rate isn't 100% and the cleanup if you have to take it apart in the future is HORRENDOUS. 

The RTV sealants really are the best for this job, but not all are created equal. We use and reccomend the Three Bond products used by Subaru. The current flavor that supersedes all previous variants is 1217H. 

The Ultra Grey products are ok, but are a little softer when set. 

Application to the case halves for assembly is extremely delicate. I use the smallest tip I can get on my tube of 1217H to apply it around the bolt holes closest to the mains and then a razor blade to spread and scrape it back from critical lubrication passages. VERY thin application so as to minimize squeeze out. It can be a frustrating race against the clock if it's hot in the shop. The thin application wants to dry on you. I chose my rod/main assembly lube based on being able to apply it before I start the RTV application and not have it run or creep on me. Lubriplate Engine Assembly lube is the answer in that regard. 

GD

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10 hours ago, el_freddo said:

@GeneralDisorder - what’s this “hour glassing effect” of the main line about?

Ive not come across this before. 

Cheers 

Bennie

The main journals in the block get compressed due to crankshaft flex from rod pressure exerted by the the force of combustion in the cylinders. This flex compresses the aluminium of the block such that in the thrust direction the main bearing oil clearances are opened up over time. The stock bearing clearance spec is .0004" to .0012" - I have seen engines with as much as .0035" on the #3 main. Excessive clearance on the main journals leads to insufficient oil supply to the rod bearings. 

Remember - aluminium has very similar density to oak - and the same feeds and speeds for machining are used for both. All the combustion pressure on the Subaru crank - which although being forged has some areas that are VERY thin in cross-section - causes deflection. This pounds the main line into an hour-glassed shape where the front and rear mains are usually close to spec, but 2, 3, and 4 are hogged out and it's like a hotdog down a hallway in there. 

It is for this reason that I WILL NOT rebuild a used engine without doing a main-line hone. Which involves surfacing the case on the smooth side, and honing the mains back to spec. It can only be done once. 

GD

Edited by GeneralDisorder
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On 11/7/2018 at 8:18 PM, GeneralDisorder said:
Quote

I have tried the anaerobic flange sealants but the success rate isn't 100% and the cleanup if you have to take it apart in the future is HORRENDOUS. 

On the other hand, you can lay down a bead, break for lunch, and then assemble the halves, since it won't start curing until mated.

Quote

The RTV sealants really are the best for this job, but not all are created equal. We use and reccomend the Three Bond products used by Subaru. The current flavor that supersedes all previous variants is 1217H. 

I don't know that stuff - will look into it (always nice to find a local disty).

Quote

The Ultra Grey products are ok, but are a little softer when set. 

Application to the case halves for assembly is extremely delicate. I use the smallest tip I can get on my tube of 1217H to apply it around the bolt holes closest to the mains and then a razor blade to spread and scrape it back from critical lubrication passages. VERY thin application so as to minimize squeeze out. It can be a frustrating race against the clock if it's hot in the shop. The thin application wants to dry on you. I chose my rod/main assembly lube based on being able to apply it before I start the RTV application and not have it run or creep on me. Lubriplate Engine Assembly lube is the answer in that regard.

Gotcha.  I normally only use assembly lube where the stickiness is really need to keep things from dropping, but get your point.  Would a suitably viscous oil (e.g. 20W50) not work as well?

And now that we're on the subject of lubes, I've seen mentions of using ARP Fastener Assembly Lube on the rod bolts in order to get more accurate torquing.  What's your take on that vs. using regular engine oil (e.g. 10W30)?

 

 

Edited by jonathan909
correcting messed-up quoting
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Yes I use the ARP lube for case bolts, rod bolts, etc. 

The Lubriplate is an off-white paste. It doesn't flow at all. Any weight of oil or "assembly lube" will creep and flow out of the bearings after assembly but before you get it started. I use assembly lube (Amsoil) for other applications like lifter buckets, and we use it for stock Subaru head bolts. 

GD

 

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I used straight up CRC engine assembly lube on the OEM Subaru head bolts (after a thorough cleaning of the threads and three lubed passes) and had zero problems with torqueing the heads.  I don't think the brand of assembly lube matters too much (for bolts at least) as long as its chock full of moly and graphite.

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The Amsoil assembly lube we use has no moly or graphite. But the ARP assembly lube does. I'm sure you could use either. Motor oil just doesn't cut it. 

GD

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The Subaru Factory Service Manual (2002 Forester) has a section dealing with reinstalling the Cylinder Head Bolts.

It reads:  'Apply a coat of engine oil to washers and bolt threads'

I have always followed that, and never had any problem.

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Anecdotal. How many have you done? I've done an average of 1-2 per week for about 9 years now..... 

Motor oil, more often than not, results in creaking of one or more bolts. Assembly lube does not. 

GD

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