Some time ago I took a head (2843169 with spark plug tubes and improved combustion chamber) to a machine shop to have oversized valves cut/installed. The short of it is that we ended up cutting into the water jacket.

So just for fun here are a couple pictures of the head and the visible problem area. Also, if anyone wants the head just come pick it up or pay the shipping.



Look between the yellow marks the dark spot in the corner, that is a hole into the water jacket

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'66 Dodge Dart

I took a long block to a shop once to get it rebuilt and it came back with a different head. They said the same thing happened so instead of waiting to fix mine they just gave me a different one. Apparently you can weld the holes up and start again

So is there a consenceses[sp?] that this is a bad idea... to drill for bigger valves?
I hope Doc or some/anybody throws some insigght into this as I have bigger valves on the shelf waiting for me to do the same thing.

I had Ford 300 valves installed in a 1972 198 head about 13 years ago. No problems. That head is running fine in my brother's van currently. Ford 300 valves are about as big as you can go in a slant head with the stock bore:




Sorry about the crappy pictures. They are the only ones I have.

It looks to me like JoshP's machine shop was digging a little too deep on the exhaust valve seats.

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Casually looking for a Clifford hyperpak intake for cheap.

This issue is more about correctly installing hardened valve seat inserts... more then the actual size of the valves being used.

The correct seat size must be used when installing hardened valve seats into a Slant Six head.
There are many sizes to choose from and that size range includes the thickness as well as the OD - ID diameters.
I tend to use 1 7/16 diameter X .200 thick and have never had a problem breaking into the water jackets.
I have seen a number of "break-thru" issues when trying to use the 1 1/2 OD X .312 thick inserts.

As for simply "opening-up" the factory seat for larger diameter valves, (no hardened seat insert) that is never a problem.
DD

I got some parts from Tony Defeo over the weekend. He has a head at home he was welding mopar "302" V8 closed chambers into. If I go out there I will have a camera.

He is a crazy Mopar "mad scientist!"

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Well Josh never mentioned about having hardened seats installed, but looking at the pics again closer it appears that's what they were doing. At any rate, good info to know and pass along to the machineist.

Why is one pic "as cast" and the other polished?

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Sorry, yes hardened seats for 1.70/1.44 stainless valves. They did mention the shallower seats but said they often fall out. I'll give them a try with my next head.

Doc those 1 7/16 X 0.200 seats, is that ID or OD and would you use them for 1.44" valves?

Rug_Trucker, are you referring to my intake and exhaust seats? If so the exhaust seat was cutout to prepare for hardened seats. Intake seats don't get the hardened steel seats.

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'66 Dodge Dart

That is 1.4375 OD and yes, I use them with the 1.440 O/S exhaust valves.
DD