Re-surface tops of heads?

[Jonny042]

I'm finding that my heads have a very small amount of warpage (less than .001") and that will easily be flattened during surfacing the sealing area but I never hear of anyone resurfacing the tops of the heads where they meet the cam towers?

It's a very small amount, skimming a couple thou off would do it, is it worth the trouble?

Pics of my head fixture and of me measuring sealing surface. Shaped like a potato chip..... not entirely sure if the tops of the heads have the same issue. If they do it's less that I can detect with a good straightedge.

[Jonny042]

Well I decided to go ahead with this. At least go to the trouble of removing the 8mm dowels from the head and checking for flat and taking a thou or two off. Bought this tool and it worked great:





Will check in with the results after I'm done.

[nocarrier]

Just curious.......After you surfaced the head to cylinder sealing surface. Did you remove the head from your fixture and check the cam tower side to see if it is flat and parallel to the head side? I checked a set recently and they were pretty good. I want to say they were in at about .0005.

I checked them on my surface plate using a surface gauge with a test indicator in it.

[Jonny042]

Originally Posted by nocarrier

Just curious.......After you surfaced the head to cylinder sealing surface. Did you remove the head from your fixture and check the cam tower side to see if it is flat and parallel to the head side? I checked a set recently and they were pretty good. I want to say they were in at about .0005.

I checked them on my surface plate using a surface gauge with a test indicator in it.

That's the surface I am referring to, yes. I'm guessing by the lack of responses that it's not commonly done, so not required. I, however, could not leave well enough alone. It was just as easy to run it over the surface plate with some wet-or-dry to flattent them out. I couldn't really get a repeatable measurement on the warpage but it wasn't much. Maybe .001 at the most. It felt good to do it even if it wasn't 100% required. But now I KNOW I've got a nice flat surface as a starting point for the cylinder sealing surface since my surfacing fixture references off this surface

[Neil Harvey]

Should always be done and is when we recon heads. How else can you measure the head heights accurately? The tricky part is, which end do you machine first as both faces have to be parallel.

Typically the back side will have the least amount of taper, is lapped and the chamber side cut first. Then the head is flipped around and the backside skimmed using the new chamber face as the finished surface. Its good you have given this this level of attention. a lot don't.

Your fixture looks ok, but do you ever see any change in out of round tolerance with it set in a 3 jaw?

[Jonny042]

Originally Posted by Neil Harvey

Should always be done and is when we recon heads. How else can you measure the head heights accurately? The tricky part is, which end do you machine first as both faces have to be parallel.

Typically the back side will have the least amount of taper, is lapped and the chamber side cut first. Then the head is flipped around and the backside skimmed using the new chamber face as the finished surface. Its good you have given this this level of attention. a lot don't.

Your fixture looks ok, but do you ever see any change in out of round tolerance with it set in a 3 jaw?

Hi Neil, Thanks for checking in! I indexed the fixture (made a mark for jaw #1 which is marked on the chuck) and machined the fixture making sure the pieces always go back in the same orientation. From what I can tell so far with my fiddling, I am getting repeatable results if I take the fixture out and put it back in place. I'm double checking with the dial/test indicator and plan B is to re-face the fixture immediately before machining all 6 heads one after the other if I cant get it to dial in. Plan C, of course, is the 4 jaw chuck.

My main concern is that the head are all the same height and parallel and I am confident I have a handle on that. But......

One thing I haven't fully chased down yet is the radial runout (ie, is the combustion chamber exactly centered). It seems to be off from head to head by up to .005". I'm not feeling like it's a hugely critical thing as the cylinders fit pretty loose in the heads, maybe up to .030" play? Not to mention we are talking about Carrera cylinders in SC heads, overbored to 98mm......

PS/Edit - because I didn't have the heads 100% cleaned up I was having trouble getting consistent readings around the outer diameter of the sealing surface so I wouldn't say I'm at my wits end with it just yet.

[Neil Harvey]

Originally Posted by Jonny042

Hi Neil, Thanks for checking in! I indexed the fixture (made a mark for jaw #1 which is marked on the chuck) and machined the fixture making sure the pieces always go back in the same orientation. From what I can tell so far with my fiddling, I am getting repeatable results if I take the fixture out and put it back in place. I'm double checking with the dial/test indicator and plan B is to re-face the fixture immediately before machining all 6 heads one after the other if I cant get it to dial in. Plan C, of course, is the 4 jaw chuck.

My main concern is that the head are all the same height and parallel and I am confident I have a handle on that. But......

One thing I haven't fully chased down yet is the radial runout (ie, is the combustion chamber exactly centered). It seems to be off from head to head by up to .005". I'm not feeling like it's a hugely critical thing as the cylinders fit pretty loose in the heads, maybe up to .030" play? Not to mention we are talking about Carrera cylinders in SC heads, overbored to 98mm......

PS/Edit - because I didn't have the heads 100% cleaned up I was having trouble getting consistent readings around the outer diameter of the sealing surface so I wouldn't say I'm at my wits end with it just yet.

This was my concern. One reason to consider doing this in a 4 jaw, so you can indicate the heads the same run out. All heads are not the same. It doesn't really matter as the heads overlap the cylinders typically, but if you are doing this, why not do them all the same. That's called pride in your workmanship.

[Jonny042]

Originally Posted by Neil Harvey

This was my concern. One reason to consider doing this in a 4 jaw, so you can indicate the heads the same run out. All heads are not the same. It doesn't really matter as the heads overlap the cylinders typically, but if you are doing this, why not do them all the same. That's called pride in your workmanship.

But all heads for the same motor should be the same, and if not, machined such that they are, correct?

[Neil Harvey]

Absolutely.

Remember, "the devils in the """"".