Anyone seen Cobra Jet heads with these mods?

[simonlegree]

I inherited these heads on a 428 wanna be 390 and I've never seen these modifications. What really throws me is the intrusion into the combustion chamber with steel plugs run through the lower exhaust manifold bolt holes. The heads resemble medium riser combustion chambers, have CJ intakes and Med riser exhaust valves. There is light porting and surfacing on both the cylinder side and exhaust manifold side. The heads have all new valves, springs, retainers, keepers , and guides. Someone has done lots of work here and I would like to get some opinions on whether these are useable or crap. Thanks for your opinions guys.
regards
Steve Legree

[Barry_R]

Had a customer supplied set of 427 medium riser heads with similar modification - bolt through to the chamber.
Took a while to understand what was going on.

Imagine this - tech guys put an air pump on a cylinder to check displacement in a race event where such things are specified in the rules.  The owner has a bit more cubic inches than the rules allow.  As he brings it over to tech he mentions to the tech guy that he decided to "put a wrench on the header bolts" 'cuz he heard a leak.  Instead of tightening he loosens them a bit and - somehow the pump will read a lower value...just like magic.

[427mach1]

Anybody think the corners of the steel plug hole would cause hot-spots for pre-ignition?

[FERoadster]

Here is a set of C4 LR heads I had Barry repair a few years ago. Mondello radiused the chambers and there was burn thru in each cylinder.
Could this have been a repair?

Richard >>> FERoadster