Head just resurfaced, is this good enough ?

[serviceguy]

Yesterday I picked up my head back from the machine shop. I don't believe that I specifically required the head to be milled when I dropped it there, I can't remember. Anyway, I was in a hurry and did not inspect it with the machinist right there, which was in hindsight a bad idea since it was the first time that I used this machine shop. I wouldn't be able to anyway because I forgot to bring my reading glasses and without them I can't see a thing from up close (I am that old).

When I finally made it home and found my reading glasses I noticed that the tool marks on the surface are straight and crosshatched rather than showing a radius like you would expect from a mill tool. It doesn't look like a sand belt job, but it feels a little rougher than I expected (using as a reference my memories of other heads I had resurfaced before), and even though I am going to use an OEM composite HG it got me a little concerned.

It appears as it could be a stone ground job and the machinist said he only shaved 3/1000". Would this be something I have to worry about or I can install the head back on an forget about it? I would hate to go back and argue with the shop over nothing (the shop was recommended by a number of members both in here and a DSM board local to me so I would not expect a fast one being pulled on their side).

I would appreciate any clarifying comment.

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[Marchev]

It's kind of hard to judge the finish by a picture, but it doesn't look bad. I don't see any deep gouges from the tools. You can ask the machinist what kind of finish they usually get, and if you have an access to a profilometer check it yourself. If I remember right finish should be in the 40-50RA

 

[97gsxIA]

For a composite headgasket, this is perfectly fine.

If you were going MLS, you'd need to check the RA to make sure.

 

[hotrodssnova]

I would do the oil port mod before clamping it down.

 

[serviceguy]

Thanks for chiming in. I would be interested in an opinion from a machinist/builder on what type of process seems to have been used for the resurfacing of this head.

 

[donniekak]

Looks like it was belt sanded. Lots of times it is sanded at an angle, then flipped around to try to keep the head level.

 

[serviceguy]

Definitely not belt sanded, never thought it was. There's no way it would come out like that. I actually spoke to the guy that did it and it was done with a CNC cutter, he assured it would be fine with a MLS HG (not that I am going to use it anyway). I know that he could have just said that, but this is a very reputable shop and it also looks like one, they do a lot of work both domestic and imports only specifically automotive.

I guess I over reacted, Ive got a lot on my plate these days.

Thanks for the input. Issue solved.

 

[94awdcoupe]

sorry but that head was on a table sander. thats not a cnc finish. not even close. there are sand lines going three directions. cnc is one direction and the lines follow an arc as the cutter head is rotating in a circle and head is passed under neath. sanded heads are never very flat. I would stay away from that machine shop. they flat lied to you. belt sander takes five minutes. cnc can take an hour.

there are actully three ways to surface head. CNC, table sander, and surface grinder.

cnc is best and gives smoothest finish. surface grinder can be good if the stone used is fine enough to produce smooth finish. belt sanders suck as its impossible to get even cut on the head. leading edge cuts way faster than trailing edge. I have had cylinder heads ruined on belt sanders they were cut so crooked.

 

[darknezz7]

I agree that it looks sanded. Theres 2 machine shops in my town, one they come back like that and worse (blemishes and low spots...)

the other is always MIRROR shiny with an ra of around 5-10

Sorry crappy pic but you can see the smooth shine

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cleaned up the valves myself there btw

I do think yours will be fine for composite though.

 

[serviceguy]

The pic actually looks a lot worse than in person. If I look at it from the same angle as the one in your pic it does looks as shiny and the finish looks extremely flat and regular. I am aware of the markings angles (even though I can only see 2 angles) and that is what worried me but they are exactly symmetrical longitudinally. What bothers me is why would he assure me that it could be used with a MLS knowing it was belt sanded, if that was the case it would be easily disputable in case of sealing failure.

Edit: I just e-mailed the shop asking for further details on the type of process used for that job. I would expect the BS (if any) to stop once it has to be put on paper (electronically speaking that is). If I don't get a reply I guess I'll have to go there again. Really not looking forward to it.

 

[serviceguy]

Wow, I feel like an idiot...the shop replied to my e-mail saying that they only use a specific machine for heads and blocks and that it leaves a recognizable semicircular pattern on the head surface...so I sent him the same picture I posted above that shows straight / crosshatched markings across the head...awaiting a reply.

 

[serviceguy]

Last update, I'm sick of this thing!

Stopped by the machine shop and pointed out the markings to the shop manager who had to agree it did not look like it was milled. He was even more puzzled by the look of that head because apparently they don't have a belt sander in the shop. Turns out they scotch brite the heads after being shaved on their Rottler SF1400, according to the machinist in order for the aluminum head to be used with a MLS HG.

I had the BS meter on high but to be honest you can see a very faint round trace underneath the scotch brite scuffing. The head is going back on soon, I am not entirely sure this explanation makes sense (I would really love to hear from Bogus, unfortunately he's been off the site for a while) but I can't really go back and forth much longer, this thing needs to run!

 

[Diamond Star Werks]

There would be no reason to use scotch brite on a cnc surface for use with a mls or composite gasket. I have two machine shops that I use here and they both return heads with mirror like surfaces and do not scotch brite them after milling. That makes no sense unless they count on you using copper spray on the gasket to fill in the imperfections they made with scotch brite pads.

 

[serviceguy]

I know, it didn't make sense to me but they were doing it right there when I stop at the shop to ask them. They had a bunch of heads just finished like that, and they guy said he did it to the head because he assumed I was going to use a MLS (which I am not). Sure enough, if it doesn't hurt the sealing properties of the head it makes it look like it was belt sanded which can't be good. If you look at the right angle you can see the radius of the CNC tool, looks like a lot of work for nothing.

 

[bryanwheat]

I know, it didn't make sense to me but they were doing it right there when I stop at the shop to ask them. They had a bunch of heads just finished like that, and they guy said he did it to the head because he assumed I was going to use a MLS (which I am not). Sure enough, if it doesn't hurt the sealing properties of the head it makes it look like it was belt sanded which can't be good. If you look at the right angle you can see the radius of the CNC tool, looks like a lot of work for nothing.

I could see maybe wet sanding with 1500 or 2000 grit on a block with very light pressure, but a roll lock on aluminum is a good way to make it not seal with a mls gasket.

 

[serviceguy]

They just roll the pad on a straight stick and give it a few light passes diagonally.

 

[Bmxr152]

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My head was cnc machined and came out like a mirror. That head was on a sander, you can tell by the cross directional scratches. Looks just like my 302 heads I had done

 

[darknezz7]

as far as I know that is the OPPOSITE of what you want for a MLS. I have heard of a head being too smooth for composite gaskets but for mls it should be mirror.

odd anyway

I pick the project 4g head up today fro my machinist.

 

[92awddsm]

It was belt sanded the the cross hatch was put on it by wrapping sandpaper around a file and sanding cross then flipping it 90* and doing the same. I've worked in several machine shops and seen it hundreds of times. The radius you see if from the original milling of the head. They were feeding you bs

 

[serviceguy]

I am not familiar with the belt sanding process, but from what I read it would completely remove all of the previous finishing (10 years ago the head has been resurfaced and back then it was properly finished to a mirror shine) so i wouldn't be able to see the previous resurfacing finish under the new 'scratched'. If anything i believe they may have not resurfaced the head but just scotch-brited the old gasket residue away. I don't feel there's anything to do about it other than prove the head surface is not straight, and I should have done that yesterday.

I guess I am on the hunt for another machine shop anyway, anybody can point me in the right direction to a reputable one in the Northern NJ area? I believe none of the known DSM friendly ones around here are any longer available.

 

[92awddsm]

The amount of material removed all depends on how much pressure is put on the head while on the sander. It's basically a table belt and the head is held in place by hand. The true sign of the belt sander is the sanding scratches seen in the pic, end to end of the head. The cross marks are done to remove the roughness made by the belt. And Scotch bright isn't aggressive enough to leave a finish like that. Only sandpaper and a belt sander would leave an aggressive finish like that

 

[serviceguy]

Maybe, scotch-brite comes in multiple grades though and it only takes a very light amount of pressure to dull the mirror like finish of the CNC machine that still shows underneath. The finish is not as aggressive as it looks in the picture either, nor is consistent through the width or the length of the head, if you look at it from straight up you cannot see the marks, what looks like some deep scoring it's a combination of the picture angle and the camera flash, there isn't any other marking other than the light cross hatching. You do have a point, as you would think that scuffing the surface made sense only if you wanted to hide an improper resurfacing of the head and not a perfectly machine mirror like finish...

 

[darknezz7]

not to beat a dead horse

buut

cnc machined head, small world auto in eugene always does a great job.

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[serviceguy]

I said myself that I can't be sure that my head was CNC machined other than the shop assuring me it has been, and it actually looks like it was belt sanded, which bothers me to great extent. You're going to have alittle bit of a problem with that oil port mod though, I think whoever did it went a little overboard, hopefully not past the sealing ring of the gasket. Did you match it to the HG yet? Also, you sure you're within servicing limit? That rib next to the oil galley should be beyond the reach of the tool, while yours has been cut quite a lot.

 

[darknezz7]

I felt they he went a bit too far on the oil port too, I said to just go to the inner teardrop shape and only hollow it out a bit, gave him examples too. It is not outside the gasket but I feel its pretty deep, hopefully it will be ok. I have seen worse ones in the oil port thread.


I thought that small dot with the circle around it on the second pic middle left was the servoce limit marker.
See plenty of examples of the head being cut that far.

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