Cylinder head milled Your thoughts?

[Boyd12]

this cylinder head was milled by PPG in Florida. I noticed that it appears they began a process so smoothing out the roughness and quit most of the way through. I any suggestions as to why they would stop?

 

[etemplet]

Looks like they didn't have a cutter large enough to machine the surface in one pass. Pretty common and the end result looks pretty good to me . I'd stone it but then I stone all those surfaces. Looks like it needs some deburring as well. You could probably mount it as is and not give it another thought. Good Luck !!

 

[Boyd12]

I have a stupid question; could they have made two passes to get the other part? Is this considered good work?

 

[etemplet]

If the cutter isn't perfectly square and you move over without adjusting the tool height you'll get marks like that. IF the offset is too much it will leave a larger ridge and sealing problems will result. If you can feel it.... its not good.

 

[mikidymac]

I will warn you that I would not recommend a performance or high compression head on a DI ski. If they just cleaned up a damaged head that is one thing but you don't want to add performance parts to a DI.

 

[racerxxx]

Looks like they cut the domes as well to keep the compression stock I'd assume. Nothing looks out of the ordinary to me. I see those machining lines all day long at work.

 

[Boyd12]

Perry Performance Group works on these for a LIVING! when I asked why it looked like this, they refused to answer the question.
I spent a number of years as a service director and never once did I see machine shop work like this. If i sent it to someone that worked on lawn mower engines, I would not be surprised. PS they didnt charge me the half a$$ price for the work!

 

[etemplet]

I really don't see much wrong with that finish unless you can feel the ridge with your fingernail. Even so, gaskets are quite efficient in sealing imperfections. Not a whole lot in life needs to be absolutely perfect to work. I always stone gasket surfaces to make sure there are no high spots and also shows me how bad the low spots are.

One of the first things you learn is always debur your work. That wasn't done and needs to be.

 

[Boyd12]

Both cylinders are like this. Is this head gasket leaking?

 

[mikidymac]

Really can’t see what you’re showing.

 

[Boyd12]

It appears there is fluid running down the cylinder wall from where the head bolts to the cylinder.

 

[Boyd12]

Glen at Perry Performance Group said I need to re-torque the head. I checked SD manual and on the Di, it is never needed. Should I re-torque the head?

 

[jhjesse]

Looks like they cut the domes as well to keep the compression stock I'd assume. Nothing looks out of the ordinary to me. I see those machining lines all day long at work.

As a 30 plus year machinist I concur with racerxxx. If you are concerned flip the head over and use a precision straight/knife edge and check it with an 0.02mm feeler gauge for flatness.

 

[jhjesse]

Glen at Perry Performance Group said I need to re-torque the head. I checked SD manual and on the Di, it is never needed. Should I re-torque the head?

I would and I do on my engines. Can’t hurt.

 

[jhjesse]

I’m with mikidymac. I don’t understand what you are showing. The only thing I am seeing is a empty spark plug hole, fuel rail with no air injector but some kind of spacer in its place.

 

[Boyd12]

As a 30 plus year machinist I concur with racerxxx. If you are concerned flip the head over and use a precision straight/knife edge and check it with an 0.02mm feeler gauge for flatness.

Since you have many years as a machinist, I have a question. PPG began the process of making the head SMOOTH. Then QUIT before finishing the process. Why would anyone do that?

 

[Boyd12]

I’m with mikidymac. I don’t understand what you are showing. The only thing I am seeing is a empty spark plug hole, fuel rail with no air injector but some kind of spacer in its place.

I enlarged the image. It looks clear enough to me, but I dont know if you are seeing the same image as I am.
The red rectangle is around the spark plug hole. inside the hole is a horizontal line, which appears to be where the head bolts to the cylinder. there is fluid running down from that point on both cylinders. the question is whether or not the head gasket/head is leaking. I had some moisture on the RAVE valves when I pulled them out 3 minutes after I shut the engine off so I removed the plugs and found this.

 

[etemplet]

Since you have many years as a machinist, I have a question. PPG began the process of making the head SMOOTH. Then QUIT before finishing the process. Why would anyone do that?

Can you show a picture if the markings/evidence of smoothing the head? I see a few marks, some are tool marks. Bad machinists are often "skilled" in the art of camouflage.

 

[etemplet]

RE- torquing doesn't hurt anything. I always give the bolts time to relax and check them again. Some people Re-Torque after the engine's first warm up and cool down.

 

[Boyd12]

Can you show a picture if the markings/evidence of smoothing the head? I see a few marks, some are tool marks. Bad machinists are often "skilled" in the art of camouflage.

The bottom area is very smooth, the top is rough (arrow pointing up) (from the resurfacing table?) There is a RIDGE you can feel that steps up from the smooth area to the rough.

 

[CreekerMike]

I enlarged the image. It looks clear enough to me, but I dont know if you are seeing the same image as I am.
The red rectangle is around the spark plug hole. inside the hole is a horizontal line, which appears to be where the head bolts to the cylinder. there is fluid running down from that point on both cylinders. the question is whether or not the head gasket/head is leaking. I had some moisture on the RAVE valves when I pulled them out 3 minutes after I shut the engine off so I removed the plugs and found this.
View attachment 48157

If you can visually identify a milky white fluid running down the cylinder wall then chances are your headgasket is leaking. Usually the result of an improper torque sequence. Ide pull the head off and reinstall with some copper coat as added protection.

 

[jhjesse]

Since you have many years as a machinist, I have a question. PPG began the process of making the head SMOOTH. Then QUIT before finishing the process. Why would anyone do that?

I don’t know the answer to that as the head is not in front of me and I was not there, but I think you have to take it a step further and QC the surface using a precision straight edge with an 0.02mm feeler gauge to determine if the head is in fact flat, or if it has high/low spots. If it does, is it within acceptable criteria. I personally would not machine half a head if that is in fact what was done, but again from you picture it is hard for me to tell if it is half machined or just a machining mark from making two passes with a smaller cutter. The dome machining is obvious to me.
Also anytime you machine the sealing surface from a DI head you need to machine the domes deeper as to not reduce the squish of the cylinders too much.
The main thing I am trying to convey to you is flatness. It can be the prettiest machining in the world, but if it is not flat it is useless.

 

[Boyd12]

I don’t know the answer to that as the head is not in front of me and I was not there, but I think you have to take it a step further and QC the surface using a precision straight edge with an 0.02mm feeler gauge to determine if the head is in fact flat, or if it has high/low spots. If it does, is it within acceptable criteria. I personally would not machine half a head if that is in fact what was done, but again from you picture it is hard for me to tell if it is half machined or just a machining mark from making two passes with a smaller cutter. The dome machining is obvious to me.
Also anytime you machine the sealing surface from a DI head you need to machine the domes deeper as to not reduce the squish of the cylinders too much.
The main thing I am trying to convey to you is flatness. It can be the prettiest machining in the world, but if it is not flat it is useless.

Thank you for your input! which side of the ridge do I put the straight edge on?

 

[etemplet]

Th cutting tool was not square when they set it up. I"d try to blend the ridge on a nice gradual taper to eliminate any step. To me that is your best shot and the gasket will likely do its job. Hopefully. Good Luck.

 

[Boyd12]

Th cutting tool was not square when they set it up. I"d try to blend the ridge on a nice gradual taper to eliminate any step. To me that is your best shot and the gasket will likely do its job. Hopefully. Good Luck.

Thank you!!! PPG quality control tech!