Topic: Guessing I need to resurface??

[Brady]

Soooo. got my cylinder head bead blasted last week to clean up all the carbon. long story short. they blasted the mating surface w/ glass and it looks like this now.   am i right that this is going to need to be resurfaced?

[70CB750]

How is the surface quality?

[Bankerdanny]

You're not the first person to experience this.

I would think that an experienced shop would (a) know not to blast the gasket mating surface or (b) ASK, "is there any place that you don't want blasted?"

[Brady]

You're not the first person to experience this.

I would think that an experienced shop would (a) know not to blast the gasket mating surface or (b) ASK, "is there any place that you don't want blasted?"

yeah, they do engine work too. i asked before to make sure as well. he said it wouldn't be an issue....shoulda told him to boil it.

@70cb750  it's smooth still...no where near as prior but smooth. what are you thinking?

[iron_worker]

I would get it surfaced. The head gasket requires a certain surface finish to seal properly and I think if you had it tested you would see it's way off due to all the tiny "dimples" in the surface now.

It's either that or risk blowing a head gasket down the road.

IW

[70CB750]

I would check it for flatness - steel ruler and bright light helps - and use it without resurfacing if it is flat.

The surface would have to be pretty "hilly" to cause a leak by itself.

[nancy]

Not just the gasket mating that is threatened is it? Wouldn't the valve seats be possibly compromised as well?

[iron_worker]

Yes, valves will have to be lapped for sure.

IW

[RAFster122s]

Yes, the valve seats will have to be lapped smooth or valves cut to restore their sealing surface. They screwed up your head, caused a lot more work.  Who was the shop, so others can avoid them. Definitely wouldn't give them any more business and would share the experience with others to "help" their business given it appears they are looking to line their pockets with additional service charges.

[iron_worker]

I watch this series of videos off of youtube:

Mercedes Benz 6-Cylinder Head Resurface

The guy measures the surface finish "Ra" at the end. You can see it needs to be very smooth.

IW

[754]

I think the blasting would if anything , improve the head biting into the gasket.. ..

[iron_worker]

From what I understand that is an old school methodology or way of thinking. Any modern type gaskets require the surface to be as smooth as possible.

IW

[754]

Works great for base gaskets.. On big bores it helps..

[Brady]

hmmm. well what to do.

i was planning to relap valves and seats anyway so no biggie there....i have a lead on a cylinder head w/ springs and valves in really nice shape for about the same it would cost to resurface....i may just do that anyway.

on the bright side i snagged a 650 cam to drop into my 550 today.


what am i out if i try to make this head work?  $$ for a new head gasket and  time/energy to replace it?  what's the consequences of just trying it out? just leaks or low compression yea? not going to blow the engine right?

[70CB750]

Do more research on it. Opinions are like aholes, everybody got one

I would like to know more on it too.

[thirsty 1]

You say they used glass beads?  I wouldn't glass bead the mating surface myself but I wouldn't have a problem putting it together either.  Glass beads break and don't take material like sand. They will take material if the nozzle sits in one place for say 10-15 seconds but if they just went over the surface then no biggie. I know I'm new to this board but I use a glass bead machine at work all the time. I'd check the surface for dips and high spots. If its ok then run it. I also use copper coat but that's just me. Rubb it down with a red scotch brite pad and check for trueness. You might be surprised.

[thirsty 1]

One thing I would do is run a tap in ALL of the holes. There is bound to be debris left over and putting bolts in holes with left over glass beads will not work. Chase out those threaded holes. Check the thread in my sig. You'll see a complete engine glass beaded.

[Brady]

Do more research on it. Opinions are like aholes, everybody got one

I would like to know more on it too.

yea i found a lot of threads saying it would need to be resurfaced but nobody that had actually tried a head in this condition and whether it worked or not....i may still just get that other head i have a lead on b/c my valves were so cruddy i was considering getting new ones anyway...i also have one slightly sticking in a guide so the head isn't in the best condition to begin w/.....bike was running prior to disassembly w/ a spun crankrod bearing on #4.....


if i use this thing i'm going to pressure wash the bejesus out of it to make sure it's clean.

[Jerry Rxman Griffin aka MuthaF'er]

If I used it I would be tempted to use an old style or graphite gasket that would seem to conform more to that surface than a MLS gasket.

[750IV]

I would run a wet stone over it with WD40 or even water and you will be amazed on how smooth it ends up. The better stones have a smooth and a rough side. Use the smooth side.
750IV

[754]

 Put a straightedge on it..if its bowed..the blasting is a non issue..

[lucky]

I think the blasting would if anything , improve the head biting into the gasket.. ..

Exactly.  Not a problem.

If the valve seats were blasted I doubt it would even effect that very hardened steel at all.

[iron_worker]

If you're going to run it as is I would use the old school fiber type head gasket as they were designed to take up some surface imperfections of common machining practices of the day.

Since machining has improved more and more they have gone to more MLS and copper head gaskets which need a very smooth and flat surface but are ultimately stronger if the surfaces are prepared as they should be.

IW

[crazypj]

I would skim it 0.010", but, I would skim it even if it hadn't been blasted 
Slight bump in compression won't hurt anything 

[Brady]

i'm probably just going to snag this other one w/ springs and valves. looks to be in better condition all around than mine.

[Reganator]

I'd be interested to see if it works out.

I'd be inclined to think it would be fine, but I can understand your apprehension in running an experiment. 

I'd also point out that the Mercedes head in that video is a tad different.  It's a bit more complicated with the cooling jackets and all, and they were in part resurfacing to remove a warped area of the head, which is more about making it level than smooth, but I'm sure they were going for both.

Compare that to your head up top with those big meaty mating surfaces.  Hard call to make, but if I had to put money on it I'd bet that it would work out just fine as is.  If I were doing it myself though... I don't know, it would be hard not to take it to a shop and have a couple thousandths of an inch taken off for as cheap as I can get that done around here.

In short, I think you should run it as is for science.

[70CB750]

I would skim it 0.010", but, I would skim it even if it hadn't been blasted 
Slight bump in compression won't hurt anything 

I think even less than that would smooth it out - the surface profile wouldn't be 0.2mm.

[trueblue]

The bead blasting won't hurt the sealing ability of your head gasket if you are using a standard composite gasket.  That merc head that was being "straightened" by machining is leaving the cams prone to failure.  When a head bows not only is the head surface warped so are the cam tunnels.  The correct procedure to straighten such a head is to first remove the cams and use the cam bearings as your reference point then with careful application of heat pull the head back into shape.  Once it is straight then run the head surfacer across it to ensure it is flat, you shouldn't have to take anymore than a couple of thou off to achieve this.  But back to the OP, your head will be fine, I would be more worried about the cam bearings having been hit with the bead blaster.  FWIW I have run heads that have had the gasket surface bead blasted on watercooled engines without an issue .

[754]

Keep in mind the other head may need as much or more work.

[Brady]

The bead blasting won't hurt the sealing ability of your head gasket if you are using a standard composite gasket.  That merc head that was being "straightened" by machining is leaving the cams prone to failure.  When a head bows not only is the head surface warped so are the cam tunnels.  The correct procedure to straighten such a head is to first remove the cams and use the cam bearings as your reference point then with careful application of heat pull the head back into shape.  Once it is straight then run the head surfacer across it to ensure it is flat, you shouldn't have to take anymore than a couple of thou off to achieve this.  But back to the OP, your head will be fine, I would be more worried about the cam bearings having been hit with the bead blaster.  FWIW I have run heads that have had the gasket surface bead blasted on watercooled engines without an issue .

Thanks for the note....no worries on the bearing surfaces as they only blasted the bottom side and ports... so topside is untouched.

[Duanob]

If you're really worried about the surface mating use some copper gasket spray. I use it anyway. haven't had a leak of any kind yet. Not even the oil passages that are prone to leaking.