6.9 rebuilding tips

[nelstomlinson]

There is also an International manual which covers the engine and the injection pump.

 

[Mailbox]

After grinding the seats, all my valves are sitting too low in the head. The valve head recession relative to the head surface is from 0.055" to 0.072". My book says it should be 0.043" to 0.055". I know I can't get less than the minimum, but what happens if I exceed the maximum? For now I am planning on installing new seats. Does anyone have any tips on removing the old seats? There is no lip that I can grab ahold of. Everything was finished really smooth. I can't even tell for sure where the seat ends and the head begins. I have an old Kwik-way model M seat cutting set up. My plan is to use a cutter that is slightly smaller then the seat OD to remove most of the seat and hope that the remains come out easily. Are the seats going to be harder then my cutters?

 

[jaluhn83]

I wouldn't worry too much about it. A 0.020" increase in recession (assuming it's that much for every valve) drops the CR about 0.7 - 21.5 to 20.7 according to my math. There's some estimation in that, but bottom line is not a huge difference and will actually be a bit better for turboing. Probably has some impact on airflow and combustion propagation, but again no significant difference. Maybe a slight bit harder to cold start, but pretty minimal.

What manual are you using? My manuals (IH 7.3 & Ford 6.9) have 0.042-0.054 intake & 0.051-0.063 exhaust.

Only the exhausts have inserts, intake are direct machined (at least per my book, I'm can't say it's true of all 7.3s).

I personally would have a machine shop do seats - too easy to mess up without a good head machine, and if one comes loose because the bore/interference is slightly off it's going to blow up the engine. If I had to do them I'd try welding a bead on the inside of the seats (be very careful to not hit the head itself) and shrink them out that way.

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