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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Power Tryp
Joined: 16 Apr 2009 Posts: 434 Location: Calgary, Alberta
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Posted: Mon Aug 01, 2016 1:42 pm Post subject: |
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Why do that when you can run an easily replaceable MLS head gasket that will not require extra work and ham strings you into the oe style replacement? _________________ Melanie - 1980 931
NoName - 1980 931 (seeking rebuild)
Green tartan interior, you don't see that on a Civic. |
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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Posted: Tue Aug 02, 2016 12:20 am Post subject: |
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Power Tryp wrote: | Why do that when you can run an easily replaceable MLS head gasket that will not require extra work and ham strings you into the oe style replacement? |
For one the MLS may or may not require special block and head surfacing for its smoothness requirement that may have to be done in a machine shop.. I do not want to pull my block and mess with the bottom end as replacement rod bolts are ridiculous expensive..
2 I'm not sure what would result in the better finished product as in victor reinz with O-ring vs MLS..
3 I like doing work that I can do myself, I avoid someone else doing work on my cars like the plague..
4 I've never heard of this tool or the ability to DIY block O-rings before and find it very interesting and something that I would very much like to do.
5 teach a guy to fish..
Instead of buying a fish (MLS and finishing work) I could but the fishing pole (Groove-Matic) and be able to O-ring my next block for free after I eventually blow my current bottom end to smithereens.
6 The cost of this tool/an O-ring job, could be driven to bargain basement levels due to multiple uses, doing other engines, and could even be easily shipped around for others to do their 931s at say $40-$50 each it would pay for itself..
But then I forget sometimes how uninterested people around here are in progressive tuning..
This time around I'm probably just going to run a victor reinz with ARP studs and see if it blows up.. _________________ 80 Turbo - Slightly Modified |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Tue Aug 02, 2016 1:29 am Post subject: |
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I strongly urge you NOT to o-ring your block. If you do, your only choice will be to go with copper gasket from MLS which will still require proper surfacing of the head and block.
Ask me how I know. _________________ erstwhile owner of just about every 924 variant ever made |
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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Posted: Tue Aug 02, 2016 2:46 am Post subject: |
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That's why I post here.. I'll head your advice on this one Dan...
What method would you guys recommend to prep my head and block surfaces for an OEM gasket? _________________ 80 Turbo - Slightly Modified |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Tue Aug 02, 2016 3:14 am Post subject: |
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FWIW, during my own hair pulling over block prep for MLS gasket, I bought a RA "sample" piece to see what the various ratings actually looked and felt like. The spec specified by Cometic is not all that smooth (quite rough in comparison to the mirror finish found on some modern aluminum blocks). . .I'd put it about the roughness of a glossy business card, which I would say is attainable it situ and without machine work.
I use these things on an angle grinder for all surface prep. _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Tue Aug 02, 2016 3:22 am Post subject: |
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Rasta Monsta wrote: | FWIW, during my own hair pulling over block prep for MLS gasket, I bought a RA "sample" piece to see what the various ratings actually looked and felt like. The spec specified by Cometic is not all that smooth (quite rough in comparison to the mirror finish found on some modern aluminum blocks). . .I'd put it about the roughness of a glossy business card, which I would say is attainable it situ and without machine work.
I use these things on an angle grinder for all surface prep. |
I agree, the surface prep concern is highly over-rated. Cometic specifies it for somewhat obvious reasons having to do with liability. I would be more concerned about the true-ness of the head and block surfaces, which really can't be addressed with the block in the car.
Rasta, that tapered bristle disc, do you use that with an angle grinder? Speed? _________________ erstwhile owner of just about every 924 variant ever made |
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motormouth
Joined: 28 Feb 2010 Posts: 118 Location: Canton
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Posted: Tue Aug 02, 2016 3:32 am Post subject: |
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From what I have heard, cast iron is not actually supposed to be all that smooth. Talking to some old school engine builders here in Detroit, the opinion is that the block and heads (if the heads are iron as well) should be true (flat), but not mirror finish. It is only once you start to use aluminum that you need a perfectly smooth finish.
If I recall from heat transfer, aluminum is something like almost twice the thermal expansion coefficient of iron. Because of the material of the block and heads being different than the gasket, you actually want the aluminum to slip across the gasket.
So, not having built my engine yet, just from my research and what I remember from engineering classes, you would want the head to be a mirror finish, but the block to be not so smooth. That way the gasket will stay in place relative the block and the head will slip as it heats up and expands.
I am kind of curious how O-ringing would work. Then you would be dealing with a linear expansion in the o ring relative a surface expansion in the heads/block/gasket. I wonder if that would create a poor sealing environment as everything heats up and expands differently.
Last edited by motormouth on Tue Aug 02, 2016 4:15 am; edited 1 time in total |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Tue Aug 02, 2016 3:55 am Post subject: |
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ideola wrote: | Rasta, that tapered bristle disc, do you use that with an angle grinder? Speed? |
I run it on an underwhelming Craftsman angle grinder that came with my compressor, full blast.
One does need to be mindful about lingering too long or pressing too hard on a single spot, because those discs do remove material, albeit very slowly.
Great for prepping any gasket surface. . .manifolds, water pump, filter consoles, etc. _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Tue Aug 02, 2016 3:59 am Post subject: |
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Thanks, that is a really great tip. I have 3 engine builds queued up, and I always dread using the gasket scrapers! This ought to make it a snap. _________________ erstwhile owner of just about every 924 variant ever made |
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Power Tryp
Joined: 16 Apr 2009 Posts: 434 Location: Calgary, Alberta
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Posted: Wed Aug 03, 2016 2:26 am Post subject: |
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Sorry I didn't respond again to this before but between helping my friend with his '85 Mercedes and the difficulty with mobile posting... anyway.
All that is stated above is good advice and I really only have one more bit of evidence. When Olsberg MSE turned development of the Duratec 2.0L engine over to Mountune they switched from a gas filled o-ring prep to a five layer MLS gasket in order to increase reliability. More can be read at motoiq. Although You probably won't be putting 600 hp down I have my fingers crossed for you. _________________ Melanie - 1980 931
NoName - 1980 931 (seeking rebuild)
Green tartan interior, you don't see that on a Civic. |
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Mike9311
Joined: 14 Dec 2004 Posts: 1678 Location: Chicago-ish
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Posted: Thu Aug 04, 2016 10:47 pm Post subject: |
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Rasta/Dan
You guys are not concerned about rounding off edges with a tool like that? I assume it works since you posted it but I still want to ask (dislike assumption)??? _________________ 1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Posted: Fri Aug 05, 2016 12:13 am Post subject: |
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The performance shop that rebuilt and assembled the engine in my red 924 left the head suraface quite rough. Nowhere near the Ra specified by Cometic. It has been holding for years now. _________________ https://www.the924.com |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Fri Aug 05, 2016 1:02 am Post subject: |
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Mike9311 wrote: | You guys are not concerned about rounding off edges with a tool like that? |
Depends on the material. Like I said, the disc will remove metal, but verrrry slowly. White is the finest "grit," and would take forever to damage a cast iron block. _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Mike9311
Joined: 14 Dec 2004 Posts: 1678 Location: Chicago-ish
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Posted: Fri Aug 05, 2016 1:02 am Post subject: |
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Rasta Monsta wrote: | Mike9311 wrote: | You guys are not concerned about rounding off edges with a tool like that? |
Depends on the material. Like I said, the disc will remove metal, but verrrry slowly. White is the finest "grit," and would take forever to damage a cast iron block. |
Very cool. Thanks for the link _________________ 1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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