[60man]

Originally Posted by twinturrbo406

... here are our Tiger heads with the insert ... it has turned out really nice and the surface is seamless ... it is a bit tricky blending the inserts by hand, as you are literally hovering over the alloy seats with a carbide-burr (()) but it is a slow process ... and based on the results of the others engines we've seen using this mod, i see no reason why it wont work as intended for these heads ... and it also makes for a very nice "repair" for any heads that have had any issues in this area, regardless of make ...

Looking good ....Question....any thoughts on adding the additional water hole/passage above center bolt...AKA: 421 mod..?? Is it possible with insert..Would it help prolong gasket life even more ??
Would like to hear Calvin's & Glen's opinion ..Thanks

[Glenn Sedig]

Originally Posted by 60man

Looking good ....Question....any thoughts on adding the additional water hole/passage above center bolt...AKA: 421 mod..?? Is it possible with insert..Would it help prolong gasket life even more ??
Would like to hear Calvin's & Glen's opinion ..Thanks

I think extra water can't hurt. I would put the hole under the insert unless you can hit the radiused end of the insert dead center with the drill bit. The insert is tough enough that if you don't hit center the drill will wonder off to the side. Also the amount of press fit on the ends of the inserts has been calculated to stay pressed at temps up to 600 degrees even with the different rates of expansion. Drilling the into the ends would give less area of contact for the press.