Block Honing

[Larry Hill]

If you’re going to bore the block before honing have them register the bores off of crankshaft thrust surface. If block will be filled give it time to cure before machining. Don’t forget to check the back of the block to be 90* to crankshaft center line. Also check your trans pump housing bore or bellhousing bore for being on crank center line and perpendicular. That way if the car doesn’t perform as you think it should you can look elsewhere. You know the cylinders are located, straight, round, and perpendicular to the crankshaft.

Sometimes straight, round, and perpendicular takes a while but I think worth the effort. Do what you can, within the rules, to keep the block from twisting.

Just some early morning thoughts.

[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.

[Larry Hill]

My thoughts differ slightly from a lot of folks. I will check an aftermarket block just as closely as I will an OEM block. The best surprise is no surprise.

[Alan Roehrich]

Originally Posted by Larry Hill

My thoughts differ slightly from a lot of folks. I will check an aftermarket block just as closely as I will an OEM block. The best surprise is no surprise.

I do not disagree with my friend the tall man.


What I should have said was that the new aftermarket stuff is usually, good enough that you can simply check for perpendicularity, and then your dimensions will quickly show if there's an error. Every dimension on the aftermarket block will almost certainly required being "kissed" or "dusted". Same with any other aftermarket component, save a camshaft, I know of few people than can do any "adjustment" required on a camshaft, even if they can find an error.

[dragracerray]

Originally Posted by 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.

Alan what is a PAT gage?
Ray

[SBillinson]

"in order to accurately “map” a cylinder bore in order to obtain a clear dimensional picture of how that bore is shaped from top to bottom, a special “PAT” gauge is used."

https://www.championbrands.com/wp-co...2010_42-48.pdf

[Larry Hill]

Thanks for sharing

[Alan Roehrich]

Originally Posted by dragracerray

Alan what is a PAT gage?
Ray

Ray,
The original "PAT" gauge that I speak of was developed by Traco Engineering, a couple of decades back, when they were working with GM in the development of the LS based engine racing program. GM required assistance because they could not get the LS engines to "seal up" and stay sealed up. It turns out that the bores on the LS engines of the time were never truly round. Even in the production engines, when no problem was present. It "appeared" that they were round. On machines, and with gauges, they "measured" round. Well, it turns out a regular "Sunnen style" dial bore gauge doesn't actually measure roundness with any real accuracy. So the "PAT" gauge was developed. The new CNC hones followed shortly thereafter.

[Ralph A Powell]

How did we ever get by back in the day? Yesterday I dug out my my OLD BILL JENKINS SA DESIGN BOOK in the block section Jenkins shows how he hand hones an small block and what stones he uses. Don’t know how we ever got by?

[Alan Roehrich]

Originally Posted by Ralph A Powell

How did we ever get by back in the day? Yesterday I dug out my my OLD BILL JENKINS SA DESIGN BOOK in the block section Jenkins shows how he hand hones an small block and what stones he uses. Don’t know how we ever got by?

I had a pretty close relationship with Jere Stahl the last few years he was around, and as a result, a connection with Bill Jenkins (as in, Jere would tell me that he and Bill were talking about one of my engine programs, and a direction I went with my R&D, and "Bill said to tell you that he thought you were smarter than that" and laugh.) where he would pass along things that he thought that I should look at.


Bill sent me a message one night telling me that we should be using a new Sunnen CNC hone, and we should have individual diamond mandrels for each 0.010" in bore size. That was what they were doing with their engine programs.


Yeah, we've come a long way since he once told me to plumb two Holley blue GPH 110 pumps in series, with 10 gauge wiring, and 0.060" washers under each pressure relief spring in the pumps, because our C/MP popped in high gear. Fixed it, too.


Bill, much like WJ, was absolutely as hilarious as he was brilliant, once you go to know him. But he never hesitated to bust my chops if I screwed up. It was always funny to get "Bill's take on Alan's mistake" from Jere.