How do I measure cylinder to see how much has been milled off???
I think that this is the best way to measure. It is what "the engine sees" as best that we can measure in a garage.
You can also use the cover plate that I have in my compression write up to help measure. Don't bolt it down, and rest it on the head face and measure through the fill hole. Use the cover plate as a floating reference from the head/block face of the head.
You have to measure what you have, and not depend on "what they usually are". There are casting tolerances and production tolerances. There is no way for us to know "where they were running" for these dimensions from day to day. They vary. It's part of manufacturing/machining.
The foundry could have variation on their datums and locating pads from time to time. Then there are machine tolerances that also depend on where the machines were running the day that they machined your heads.
They also batch run heads to be milled in the engine plant for recycled heads. If the block sealing surface of the head gets scratched/gouged on an engine that has been built, found to have a problem, then stripped down and the parts recycled, they will batch run the heads through the machine line and mill some off the face to clean up any marks or scratches on the face.
They batch run these as they have to set the machines to mill deeper than the regular production heads, and then reset the machine back to run the first time through production heads. They tend to set the head face milling operation not to cut too much off of the face (run them "fat") so there is enough material left in case they have to be resurfaced if they get any damage in handling at the engine plants.
Basically, it's difficult to tell if they have been milled or not. To measure that accurately would require a special built gauge to measure from the machine datum to the head face or put them on a CMM (Coordinate Measuring Machine), both of which is way too expensive for us hobbyist to have in our garages. The best way for us to get an indication is measure the block face of the deck to the combustion chamber depth of the head, or cc the heads. But even then, it's not for sure.
Measure from the deck to the quench pad on the intake side of the chamber with a depth mic or a depth attachment for a calipers. Should be roughly .095" from the ones I have checked.
The area at the lower portion of the chamber in this picture.
The rocker rails are cast so poorly its not a good reference point.
I think that this is the best way to measure. It is what "the engine sees" as best that we can measure in a garage.
You can also use the cover plate that I have in my compression write up to help measure. Don't bolt it down, and rest it on the head face and measure through the fill hole. Use the cover plate as a floating reference from the head/block face of the head.
You have to measure what you have, and not depend on "what they usually are". There are casting tolerances and production tolerances. There is no way for us to know "where they were running" for these dimensions from day to day. They vary. It's part of manufacturing/machining.
The foundry could have variation on their datums and locating pads from time to time. Then there are machine tolerances that also depend on where the machines were running the day that they machined your heads.
They also batch run heads to be milled in the engine plant for recycled heads. If the block sealing surface of the head gets scratched/gouged on an engine that has been built, found to have a problem, then stripped down and the parts recycled, they will batch run the heads through the machine line and mill some off the face to clean up any marks or scratches on the face.
They batch run these as they have to set the machines to mill deeper than the regular production heads, and then reset the machine back to run the first time through production heads. They tend to set the head face milling operation not to cut too much off of the face (run them "fat") so there is enough material left in case they have to be resurfaced if they get any damage in handling at the engine plants.
Basically, it's difficult to tell if they have been milled or not. To measure that accurately would require a special built gauge to measure from the machine datum to the head face or put them on a CMM (Coordinate Measuring Machine), both of which is way too expensive for us hobbyist to have in our garages. The best way for us to get an indication is measure the block face of the deck to the combustion chamber depth of the head, or cc the heads. But even then, it's not for sure.
