91 CRX MLS Head Gasket - Does this look smooth enough? - Fuelly Forums

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Old 05-20-2008, 08:41 PM   #1
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91 CRX MLS Head Gasket - Does this look smooth enough?

I just got the head back from the machine shop and this is what it looks like. You can see where there was some corrosion.

When I run my finger across the machined surface you can feel tiny hills and valleys. I did my best to capture it in photos.

The machine shop said that they machined it to spec and that "The head actually has to be rougher than you would think to help hold the gasket in place."

I've been working on getting all of the old composite type gasket (OEM Gasket) off of the block and the block feels MUCH, MUCH smoother than the head now feels :

Am I wrong to assume that the head and the block should have the same finish to them?

Does this surface look OK for a MLS (all metal) head gasket?

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Old 05-20-2008, 09:06 PM   #2
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did you ask the machine shop what surface finish they ground it to? They should know.
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Old 05-20-2008, 09:59 PM   #3
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I'm actually thinking that the machine shop may have screwed me on this head re-surfacing.

I went to pick it up and was looking at it. I noticed a lot of visible lines on it so I ran my finger over it and it felt quite rough, lots of hills and valleys. I told the guy that I was using a MLS (multi layer steel ) gasket. He said that he did it to spec and that "The surface has to be rougher than you would think to hold the gasket." I took his word as he works in a machine shop and paid the guy. I almost walked out without a receipt (I paid cash) so at the last minute I asked him for one. He handed me a piece of paper and without looking at it I folded it and put it in my pocket. Upon getting home I went online again and searched about using MLS gaskets in engines and found some unsettling points repeated on different sites.

They all said that the smoothness, measured as an RA value (meaning arithmetic average) have to be very low, indicating a very smooth surface. MLS gaskets and aluminum heads and blocks require a very low RA value meaning a very, very smooth surface.

From what I have read the block and head have to be returned to a near factory smoothness. As of now the block that I have been scraping gasket off of is very very, smooth and I can feel nothing when I run my finger over it. By comparison the head that I just got done feels like running my finger over sandpaper compared to the block that is still in the car.

When I got home I also looked at the receipt. All that it has written on it is "Surface Head" and "paid cash". I was expecting to see how much they shaved off, how warped it was, and also what surface finish (RA Value) they ground it to. There was nothing.

This link though a bit of a read states everything that I have read around on the net about surface finishes and the newer style MLS gaskets.

http://www.enginebuildermag.com/Arti...he_finish.aspx
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Old 05-21-2008, 07:34 AM   #4
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Considering it is a metal to metal seal, it is easy to imagine the surface has to be smooth since the steel HG is only going to deform so much. My company makes pressure vessels sealed with metal to metal seals that are tin (alot more ductile) and the surface finish is very smooth. The guy telling you it needs to hold the gasket? Like it's going to squirt out of there?

When I got my GSR's and CRX's heads back you had to look hard to see the machining marks, and you couldn't feel them running your fingers over the surface.

Unfortunately, I would try to find another machine shop and show it to them. If they didn't get the surface finish right, who knows how flat it is.
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Old 05-21-2008, 09:11 AM   #5
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with the pics, it's very difficult to tell

if you can feel the imperfections with your finger and light shows thru gaps using a straight edge, it's no good.

all this trouble is not worth the effort. guys on honda-tech literally give away lower mileage d-series engines. get a used one that has been maintained reasonably well and you'll be far better off.
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Old 05-25-2008, 06:52 AM   #6
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In Pic 3 are those depression between the cooling ports????? after maching If they are that head shouldn't be used. I would not put that head back on a customers car.


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Old 05-25-2008, 08:17 AM   #7
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You can see the same pits in pic 1 as well, but since these are 1/2" away from the combustion chamber, might they be OK?

I'm not an expert, I am just asking because I might put it back on my car if it was mine.
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Old 05-25-2008, 09:59 AM   #8
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for a MLS gasket you should not be able to feel/see any significant machining marks or texturing. if you can't get them to fix it, take a palm sander with some 400 grit and lightly touch it up.
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Old 05-25-2008, 06:04 PM   #9
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Did the old gasket fail in the area where the cooling ports are pitted? Like I said if it were a customers car that head would not go back on. But if its your own have at it.

John
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