Mint 400

[John Collard]

Jerry,
I can't see the photos.

John Collard

[chicagojerry]

hope these help some with what the before and after like like on the dome.  jerry birky does these mods with the original tool bit passed down from dane leimbach from back in the day when he and carl cranke were doing it. dane turned me on to it about 7 or 8 years ago.  i have been doing it to virtually every 400 motor i build now, including guy cooper's. the price is really reasonable and the outcome well worth it




http://s769.photobucket.com/user/chicagojerry/media/IMG_0457_zp

[Jerry Birky]

Hi John, here are the photo's i tried to send yesterday of the 400 head machining procedure.
  Jerry

[John Collard]

Many thanks to the 2 Jerrys, all is revealed. I guessed it was like this but confirmation is always nice.
The previous owner had fitted 2 head gaskets to try and soften the power delivery, that's fine providing the head doesn't leak afterwards, machining the chamber is a better solution providing I don't go too far.
Jerry, I'd be happy to let you do it for me but you're the wrong side of the Atlantic.

Regards,  John Collard

[Daniel P. McEntee]

It looks like you basically double the depth of the chamfer that runs from the head surface to the combustion chamber and increases the volume of the whole dome. The bit is custom ground to the shape of the finished bevel? A mandrel is made to screw into the spark lug hole that allows you to chuck it concentrically, but man! How much chatter racket does that make when the bit is at full contact? If you wanted to a lot of these, I have an idea on how to make a fixture that offers more support, but just don't know how to articulate it.
  Thanks for the clarification. I don't know if my '77 400 has that done, but will look into having that done of the next build.
  Type at you  later,
  Dan McEntee