Oversize valve install - finding water

[Lagniappe]

I've been researching installing 1.75 intake and 1.50 exhaust valves since I need to have hardened seats put in for a daily driver install. But the Classic Inlines comment on the valve purchase page which I copy below concerned me. For any of you guys that have gone to the bigger valves, is this a problem?

"When machining for oversized valve seats, don't be surprised if you cut into the water jacket, especially when machining the #1 exhaust seat. However this can usually be repaired by building up the wall thickness (welding) on the backside, by working through the t-stat access hole."

I have a spare C9DE 6090 M head from a 200 and a spare D0DE 6090 A head from a 170, but I don't want to trash one or pay for too many tries at machining them either.

Thanks!

 

[CNC-Dude]

Many practices and techniques are still done because of tradition instead of necessity. Many machine shops no longer recommend installing hardened seats because the reasons for them to be installed in the first place 40 years ago no longer exists. Many have found that installing them creates issues that aren't there to begin with, so seek the advise of your machine shop before you just tell them to do it, they may educate you as to why this is no longer needed.

 

[CZLN6]

HOwdy Back:

The need for installing hardened valve seats will have alot to do with your intended use. Extended high rpm driving may require hardened seats. Cruising and occasional spirited driving, not so much.

As far as getting into the water jacket, it is very (extremely) unlikely on the C9 or D0 head castings. If you do please let us know. With FoMoCo, i've learned to never say "Never".

Adios, David

 

[Lagniappe]

Thanks guys, I've discussed the issue with the machinist who's going to work over the cylinder head, and he says that it's crap shoot whether we get into the water jacket or not. However, for my planned (non-racing/daily driving) use I will probably not notice the difference performance wise. So we're going with the standard valves and seats.