[airboat]

Learn from my mistake!
Wrecked this one and had another set I wanted to put on the MK IV on my ski boat so cut this one apart. great combustion chamber however most people ask about removing the vane or ski Jump. the hole I drilled to the left is 3/10" deep and the other is 2/10" deep si I would say yes. Epoxy in hole on the left is from rocker stud boss removed.

[cobalt327]

Holy ****!

Well, thanks for the photos and the ski jump removal verification, but what a drag the head was toast.

The one chunk would make a good ash tray...

[airboat]

YEAH! No ****, and I don't trust it's mate either. It was smaller than a pinhole till I verified where the leak was and dug around with a seal pic. dug around the same spot on another intake and went through also!

[cobalt327]

Originally Posted by airboat

YEAH! No ****, and I don't trust it's mate either. It was smaller than a pinhole till I verified where the leak was and dug around with a seal pic. dug around the same spot on another intake and went through also!

So this was an OEM head? If not whose was it? Or was the leak caused by porting.

[airboat]

Yes OEM Head with hole in waterjacket caused by getting carried away with a carbide burr!

[KA67_72]

Thanks for the pics

Kevin

[airboat]

I built another set of Vortec L29 7400's for the 454 in my ski boat. It just had peanut ports with flat tops about .012" down the hole so I just did rings and bearings with a Comp 270S cam, Stock size Ferria valves and a composite head gasket. I added an Edelbrock Performer and the difference is amazing!! Killer top end!!!

People Have said putting the Vortecs on a Mark IV results in coolant leaks into the engine valley, Not so in this case..

[cobalt327]

Originally Posted by airboat

I built another set of Vortec L29 7400's for the 454 in my ski boat. It just had peanut ports with flat tops about .012" down the hole so I just did rings and bearings with a Comp 270S cam, Stock size Ferria valves and a composite head gasket. I added an Edelbrock Performer and the difference is amazing!! Killer top end!!!

People Have said putting the Vortecs on a Mark IV results in coolant leaks into the engine valley, Not so in this case..

GMPP has also warned of there being leakage from using Mark IV heads on a Gen 5:

Important Technical Note: Use of the adjustable Mark IV cylinder head is not recommended with the new “Gen V engine,” except with Bow Tie racing blocks and all Gen VI with six-bolt composite front covers. Changes in the configuration of the “Gen V’s” coolant transfer passages allows coolant to seep into the lifter valley when the Mark IV head is used.

Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow.

[airboat]

That's great information! I used Mr Gasket "series cooled" gaskets and drilled the coolant passages into the gasket with a Forstner drill bit at very high RPM for paralell cooling. I also opened up the upper holes as on disassembly I noticed some of the holes were plugged or at least partially plugged. This boat is Raw Water cooled and with the thermostat mods I have don it runs at a nice 150 to 160 degrees F. The Mr Gasket head gasket seems like a nice gasket with a rubberized coating, complete OH set was less than $40.00 on sale.