O ringing is relatively simple if you have the tools, or are willing to pay to have it done.

I start by O ringing the block. You can carefully get the OD of the wire between the cylinders very close but they must have some room.

I have seen 2 BBC blocks where the bores were not equally spaced. Take some preliminary measurements as see how much meat you have between the cylinders and how equal thay are.


I used to have an Isky O ring tool. It made me good money. I groove the block with an .039 groove and make it .035 deep. This will be your reciever groove. Once you have all 8 cylinders cut I cut some very close but slightly short (.060 short) wires. I keep the wire because I will use them again. I then use some machinist bluing around the combustion chambers. While that is doing, I take my slightly short wires and gently tap those wires into the block.

With the bluing dry on the head, I install all 8 wires around a cylinder. Gently tap with a hammer, making sure you don't flatten the wire. Next take the head and mount it to the block. I usually torque the head down to about 60-70 % of what the bolt (or better yet the stud calls for) a half in head stud torques about 100 pounds. So, torque the heads down to the block with the wires installed and let them sit for about an hour. Untorque the heads and mount one on your mill fixture.

I then set up my fixture in the mill. I level the head in both directions and then get an indicator on the head and and make sure it is flat. I shroud mention the head SHOULD have its final surface DONE before you cut the grooves in them. With the head mounted in the mill and indicated in, I installed a custom cutter that was made by my friend and mentor Wayne. He made two sizes and it covered about everything we ran across. He made a round tool holder and milled a slot in the holder and then drilled and tapped a 1/4x20 thread in it.

Next he made a tool holder (actually two of them, one for each diameter of O ringing tool. It consists of a .500 wide bar that has a .250 slot milled down dead center. On the cutter end he made a tool holder to hold the grooving tool with a screw. The tool holder was then TIG welded to the .500 wide bar at a right angle.

With the tooling made and the head marked by torquing it to the block with the wire in it, mount the head in the fixture and level the head in both directions.

I start at one end and work to the other. Using an .039 cutter, simply line up your O ringing tool over the first cylinder you want to start with. Take your time and line the cutter up perfectly over the clean lines you see on the head where the bluing is gone.

Once you are happy with being centered over the wire witness, slowly feed down until you just touch. Lightly feed very slow until you have a very light, clean full cut around the chamber. Let's say you went .003 down to get a clean start. We need to go .025 deep for our .041 wire. You went .003 deep so you need to go down another .022 and then stop.

Do that 7 more times and your done with that part.

I take a razor blade and just lightly go around the edges of the grooves just to clean them up a bit.

Now, make up 8 new wires and make them all a half to one inch bigger than they need to be. File one cut end square and start tapping the wire into the groove. I like to start and end the wire where the lowest amount of pressure is so the seam doesn't cause a leak. Keep gently tapping and try not to make flat spots on the wire. Once you get close to the ends meeting very carefully trim off the end. Use a sharp flat file to square the wire end as square as you can get it. In a perfect world, you can end up with a zero gap. If the gap is too long, it will force the wire up out of the groove. If this happens, shorten the wire a bit more. You can have as much as .040 gap for N/A stuff and no more than .020 for blown, turbo and nitrous.

Once you have all the wires in, you simply remove carefully and save the wires in the deck of the block. Save them as most likely you will need them again.

Now you will have the wire in the head. That helps support the head where the grooves get close. I use the grooves in the block as reciever grooves. You can do it the other way, but you can get a head hot enough to go soft and with no wire in the groove in the head it will fold up and lose your seal.

Certainly, you can weld it all back up and fix it, but you almost never have that issue if you put the wire in the head and use the groove in the block as the reciever groove.