Differences in Machine Work 2- Blocks
I did this before with a set of heads I had. Well, this is a typical 383 block I did for a fellow. He's assembling it, and the block was slightly modified by him previously. std bore HP I think for an A body factory car. like before, I'll do a paragraph, then post the pics.
#1 is the mains. It's pretty basic. It was fitted with studs so it was align honed. However, all my builds get line honed, regardless of use. The reason is, the best machines use this very bore for their reference point. Everything is dont in realtion to the crank's centerline. So that has to be verified to be exactly where its supposed to be. Align honing also make the breaing clearances equal accross the board, because they sizes of the bores are all exactly the same when it's done.
#2 is a close up showing the tapped hole, the finish of the bore, and the dressing of the sharp corners on the mating surface and breaing bore left from honing that need to be removed by hand.
#3 This is the deck surface. This block is a numbers matching, and therefore it's very important to keep the stampings. What you see here, is the step left when the deck is cut. Several things to note here: first, looking carefully, you can se the pattern left by the cutter bit. Tehy resemble the look of turned aluminum. If you run the Cometic or MLS type gaskets, you need a very smooth surface. Old millers cannot be set to cut that fine, and cant leave a finish like this. Also, this is done on a Rottler block machining center. It uses that new straight crank centerline to square deck. Old millers have the machinist use a bubble level (machinist grade) to level the block, and then it cuts. If it's the std sized cutting head, it doesnt cut flat. It cuts deeper in the center of it's cut, than at the sides. What that means is, if the guy leveling isnt perfect, and if the diameter of the head is smaller, your decks will be milled, but not square to the crank, and not as flat as possible. The new machines use a single cutting blade with a variable speed table and spindle speeds, to get a perfectly flat, parallel to the crank centerline, smooth surface. That is the difference between square decking and decking.
#4 is a close up of the finish. The scratches visible are from a green scotchbrite I used to remove some surface rust that showed up while I was drying it.
#5 Shows the lifter bores honed and sized, and all the bolt holes tapped.
#6 shows the new chamfers on the bores. The holes were rough bored on the same Rottler, so again, they are definately in the right place, and exactly 90° to the deck surface and crank centerline. The chamfers have to be done so the new rings slide in during assembly. If there is no chamfer left after overbore, then you can very easily damage the new rings on piston/rod install. Also, the fresh honing finish is visible. Moly rings require a smooth surface to seat quickly. If it's too rough, the rings will simply rub off the moly, and then will take a bunch of careful miles to seat properly.
#7 is a close up (sorry, a little blurry) of the cross hatch. More important than the "45° angle" is the fact that it's not a bright surface. You can see darker grey areas between the deeper scratches. That's where the finer honing stones and finally the plateau hone/brush smoothed out a lot of the roughness. Too rough is no good. Toom smooth is no good. And of course, this was honed with a deck plate in place.
Hopefully you can see the differences between "rebuilt" machining, and performance machining. It used to be that some of these operations were reserved for "competition" engines and big $$ budgets. The accuracy and ease of getting things right has gotten cheaper with time. You should be using a shop that recognizes the difference, and invests in their own quality.
I did this before with a set of heads I had. Well, this is a typical 383 block I did for a fellow. He's assembling it, and the block was slightly modified by him previously. std bore HP I think for an A body factory car. like before, I'll do a paragraph, then post the pics.
#1 is the mains. It's pretty basic. It was fitted with studs so it was align honed. However, all my builds get line honed, regardless of use. The reason is, the best machines use this very bore for their reference point. Everything is dont in realtion to the crank's centerline. So that has to be verified to be exactly where its supposed to be. Align honing also make the breaing clearances equal accross the board, because they sizes of the bores are all exactly the same when it's done.
#2 is a close up showing the tapped hole, the finish of the bore, and the dressing of the sharp corners on the mating surface and breaing bore left from honing that need to be removed by hand.
#3 This is the deck surface. This block is a numbers matching, and therefore it's very important to keep the stampings. What you see here, is the step left when the deck is cut. Several things to note here: first, looking carefully, you can se the pattern left by the cutter bit. Tehy resemble the look of turned aluminum. If you run the Cometic or MLS type gaskets, you need a very smooth surface. Old millers cannot be set to cut that fine, and cant leave a finish like this. Also, this is done on a Rottler block machining center. It uses that new straight crank centerline to square deck. Old millers have the machinist use a bubble level (machinist grade) to level the block, and then it cuts. If it's the std sized cutting head, it doesnt cut flat. It cuts deeper in the center of it's cut, than at the sides. What that means is, if the guy leveling isnt perfect, and if the diameter of the head is smaller, your decks will be milled, but not square to the crank, and not as flat as possible. The new machines use a single cutting blade with a variable speed table and spindle speeds, to get a perfectly flat, parallel to the crank centerline, smooth surface. That is the difference between square decking and decking.
#4 is a close up of the finish. The scratches visible are from a green scotchbrite I used to remove some surface rust that showed up while I was drying it.
#5 Shows the lifter bores honed and sized, and all the bolt holes tapped.
#6 shows the new chamfers on the bores. The holes were rough bored on the same Rottler, so again, they are definately in the right place, and exactly 90° to the deck surface and crank centerline. The chamfers have to be done so the new rings slide in during assembly. If there is no chamfer left after overbore, then you can very easily damage the new rings on piston/rod install. Also, the fresh honing finish is visible. Moly rings require a smooth surface to seat quickly. If it's too rough, the rings will simply rub off the moly, and then will take a bunch of careful miles to seat properly.
#7 is a close up (sorry, a little blurry) of the cross hatch. More important than the "45° angle" is the fact that it's not a bright surface. You can see darker grey areas between the deeper scratches. That's where the finer honing stones and finally the plateau hone/brush smoothed out a lot of the roughness. Too rough is no good. Toom smooth is no good. And of course, this was honed with a deck plate in place.
Hopefully you can see the differences between "rebuilt" machining, and performance machining. It used to be that some of these operations were reserved for "competition" engines and big $$ budgets. The accuracy and ease of getting things right has gotten cheaper with time. You should be using a shop that recognizes the difference, and invests in their own quality.