Block Honing

[Alan Roehrich]

The tall man is correct here on all points.


If you're starting with a new aftermarket block, then your path is short and straight, you just need to set your deck height and bore size, then it's off to the hone.


If this is a production block, then it's a whole different ball of wax. Assume that it's already been thoroughly cleaned, to the point where the water jacket has been acid washed, and the usual checks have been performed for wear and damage.


The first step is a thorough sonic test. Once the block passes that, I always pour next.I use regular stock head bolts and cheap gaskets, for this. I bolt one head on, and then pour the first side, immediately bolt the head on over it. This I let cure in at least 60 degree F ambient temp, for 24-48 hours. Then I pour the other side. This time, it sits for at least two weeks.


After that, if you can find someone trustworthy, who has a CNC program for your block, you're fortunate, you can get your block trued up, as Mr. Hill describes. Next best choice is someone with the necessary Block-Tru, Bore-Tru, and other fixtures by BHJ to true up your block. Your first step is to get the crank bore perpendicular to the bellhousing flange and indexed to the block dowel pins. Now, if you have the means, you can also verify that the cam bore is parallel to the crank bore, here. Then it's off to properly size the main bores. Hopefully, an align hone will do that. I finish my crank bores in the second step because everything else indexes from there. My next step is to Block-Tru the deck surface to the main bore. Then Bore-Tru, here you correctly locate all 8 cylinders (if you have that many). And you bore to size, leaving the requisite hone stock to finish the bores.


Since we're concerned about honing here I'm just going to make this note about lifter boresafter you deal with honing your block, if it isn't a new aftermarket block, you're going to want to bush the lefter bores with a Lifter-Tru setup, and even if it is an aftermarket block, bushings may be required for your lifters).



And now we come to honing. Can you get the "perfect bore" with a CV 616 or similar hone? Pretty close, assuming you have a skilled operator, with the necessary patience and the requisite measuring tools. And there's the sticking point. Most shops that don't have a CNC hone, also don't have a PAT gauge, and a regular dial bore gauge cannot actually measure whether a bore is round. Never mind straight. That's where the CNC machine becomes a necessity for approaching perfection. It can measure its work in ways that a human cannot measure his.


If you go look on youtube, you'll find about a dozen videos posted by the guys at Total Seal on just this subject. Do yourself a big favor, and watch them all. It tells you about the CNC machines, the older equipment, and the profilometer. All priceless information.


Hope this helps you, good luck.