I just got off the phone with Ford Racing Tech... I just found out that I need to check my block for proper cooling if I am going to use the GT40 Head. The tech guy told me some Early 289-302 blocks will not have the proper cooling passages located on the block to flow correctly into the GT40 head and will require drilling of an 1/8th inch hole, to prevent cooling issues... I'm not sure if anyone else was aware of this so I did some research, apparently Edelbrock was aware as it is in their installation instructions here > http://www.jegs.com/InstallationInstructions/300/350/350-60299.pdf Just a little FYI ..
There is a reply from a guy stating the holes do not need to be drilled...What is the story here? should they be drilled or not? anybody have the GT40's without drilling the holes and have cooling issues? I really do not want to drill if i dont have to. thanks
I would drill the holes. He puts up a good arguement until you really look at the pictures and the Edelbrock instructions. He claims the 302 block he posted does not have the holes but it does. Look at the #1 cylinder and it is there at 2 o'clock just like the instructions show. Use a center punch, a good bit, lots of cutting oil, take your time and don't force it. You will be just fine. That or go buy a new Ford Racing block!!!
I just called ford racing tech again ( im a pita sometimes) and he said I should drill these holes in the head...the holes are already in the block!!
I think they call them steam holes right? Not sure of the purpose but if you can find the right area to drill I think I would. clint
from an engineering and flow point of view it looks like they are to minimize cavitation in the corners of passage. just a somewhat educated guess.
When people put the head gaskets on backwards and have cooling problems is it these holes being blocked that cause the problem? clint
I'm not sure if you can put the gasket on backwards... What the tech was referring to is that the older blocks (ie...1971)have the steam holes they need and worked perfectly for the head that was intended for them, now years later I want to put a set of (ie...1993) GT40 heads on my old block, after several design changes through the years the steam holes on the head dont line up with the steam holes on the block because they were from different years etc. So to prevent any heat build up issues he suggested to drill some holes in the block so they match up with the heads but then after talking a bit more he said it would probably be easier if you just drilled the hole in the head to match the block...
if yur gonna put them on an early block i would drill the holes,cheap insurance if you ask me. i would also have the heads shaved about 30 thou to help with the compresion.mine had 62-63 cc chambers and we knocked them down to 60.
Also the springs on those heads are for a roller cam. You will want to change them if you are using a flat tapper cam. Otherwise you will flatten the cam lobes
