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MaxPF's 6.2 build
- Thread starter MaxPF
- Start date
Jason4x4
1/2 ton status
WELL??? It's almost been 2 months since the last update... 
MaxPF
1/2 ton status
Well, the cylinder heads have, uhh, issues 
I bought new guides and seat inserts, and I am waiting on my machinist friend to get them on the CNC. I bought brand new genuine GM diamond precups and installed them. Once on the CNC they will get the guides drilled and reamed for replacements, the seat areas cut for inserts, and the deck will get flycut.
Once they go on the machine I will get pics and post them up.
I bought new guides and seat inserts, and I am waiting on my machinist friend to get them on the CNC. I bought brand new genuine GM diamond precups and installed them. Once on the CNC they will get the guides drilled and reamed for replacements, the seat areas cut for inserts, and the deck will get flycut.Once they go on the machine I will get pics and post them up.
MaxPF
1/2 ton status
I mentioned I got new precups. Well, I finally got the pics off the camera.
Here's the 8 new gen-u-ine GM diamond precups:
$330 for 8 of them suckers Oh well, at least I won't be worrying about reusing cracked cups.
Here's a side-by-side of the Chinese diamond cups (left), the GM diamond cups (middle) and the GM 3 dot+@ 6.2 J code cups (right):
There are a couple things to point out here. First, you can see that the Chinese cups are a rougher casting. The metal is also inferior - the GM cups appear to be Nimonic or Inconel material, while the Chinese cups look like cast iron. In fact, the Chinese cups have started to get spots of rust. Obviously, the throats in the diamond cups are much larger, but if you lok carefully you will notice the interior of the diamond cups have more volume, with a thinner wall on the outside. If you look at the specs for most 6.5's you will see the compression ratio listed as 20.3:1, vs. 21.3:1 for 6.2's. The extra volume required to drop the CR was created by making the swirl chamber in the precup a bit larger.
Here's a pic of the cups installed:
They fit nice and tight, and sit a few thou below the deck. When I get the heads on the CNC the first thing that will be done is taking 10 thou off the deck, which will leave them perfectly flush. You can see where I was cutting the exhaust seats, trying to get them to sit where I wanted on the valve. Ultimately this proved futile - the seats were designed for a .030" oversized valve, and I couldn't get them far enough away from the valve margin to suit me. That is why they are getting seat inserts installed. Since they will already be on the machine I decided to do the intakes as well. Also, in order to eliminate the careful indication of each head to maintain concentricity between the guides and seats I will drill and ream out the integral guides and press in new guide inserts made of superior material. The seats are also made of better material than the induction hardened iron seats: the intakes are hardened steel, while the exhausts are a high nickel alloy similar to what the prechambers are made of. Both should last much longer than the induction hardened seats would have.
Here's the 8 new gen-u-ine GM diamond precups:
$330 for 8 of them suckers
Oh well, at least I won't be worrying about reusing cracked cups.Here's a side-by-side of the Chinese diamond cups (left), the GM diamond cups (middle) and the GM 3 dot+@ 6.2 J code cups (right):
There are a couple things to point out here. First, you can see that the Chinese cups are a rougher casting. The metal is also inferior - the GM cups appear to be Nimonic or Inconel material, while the Chinese cups look like cast iron. In fact, the Chinese cups have started to get spots of rust. Obviously, the throats in the diamond cups are much larger, but if you lok carefully you will notice the interior of the diamond cups have more volume, with a thinner wall on the outside. If you look at the specs for most 6.5's you will see the compression ratio listed as 20.3:1, vs. 21.3:1 for 6.2's. The extra volume required to drop the CR was created by making the swirl chamber in the precup a bit larger.
Here's a pic of the cups installed:
They fit nice and tight, and sit a few thou below the deck. When I get the heads on the CNC the first thing that will be done is taking 10 thou off the deck, which will leave them perfectly flush. You can see where I was cutting the exhaust seats, trying to get them to sit where I wanted on the valve. Ultimately this proved futile - the seats were designed for a .030" oversized valve, and I couldn't get them far enough away from the valve margin to suit me. That is why they are getting seat inserts installed. Since they will already be on the machine I decided to do the intakes as well. Also, in order to eliminate the careful indication of each head to maintain concentricity between the guides and seats I will drill and ream out the integral guides and press in new guide inserts made of superior material. The seats are also made of better material than the induction hardened iron seats: the intakes are hardened steel, while the exhausts are a high nickel alloy similar to what the prechambers are made of. Both should last much longer than the induction hardened seats would have.
BKinzey
1/2 ton status
THAT'S IT!
To hell with my build!
Hurry up and finish yours so I can swipe it!
To hell with my build!
Hurry up and finish yours so I can swipe it!
MaxPF
1/2 ton status
Tacking into the wind
We managed to get one head on the CNC today. The other will have to wait until tomorrow.
The first order of business was adding some dowel pin holes for the rocker shaft pedestals - I should have done this when I cut them down... We also had to cut the guide bosses down to .312". This is enough to locate the rotators. The valve guide seals will go on the .500 guide inserts, which will stick up about a half inch above old cut down guides:
Once that was done for both heads we flipped one over, indicated it in, and got to work on the main part of the job. The first order of business was to deck the head:
Those prechambers are made of some seriously hard stuff. Fortunately, TiN coated carbide inserts are harder, but some CBN (cubic boron nitride) inserts would have probably been better for this application. Still, we managed to get a good smooth finish. It doesn't look as smooth in the close up pics as it really is. For some reason the flash seems to really exaggerate the surface finish.
Finally, we moved on to the main cutting. First, the pockets for the seat inserts were cut. Then a 45 degree cutter was used to unshroud the area around the valves, a 1/2" ball end mill was used to match the throat to the insert ID, and the integral guides were drilled out and reamed to .500" to accept the new press in guides. Here's some cool pics of the cutting taking place (the greenish liquid is water soluble cutting fluid):
Here's the finished product. First are pics of the pedestals with dowel pin holes and the cut down guide bosses that are reamed for new guides:
Deck view:
Closeup of the valve seat pockets, 45 degree unshrouding cuts, and the opened throats:
Here's the inserts next to their respective holes:
Here's one more up close view of an intake pocket. You can see where the ball end mill was dropped into the throat area to open it up:
You can't see it, but there is a sharp edge on the short side radius in the intake ports that I will need to clean up with a die grinder and some sanding cones. Typical stuff when you modify cylinder heads
I'm pretty stoked now. Once the other head is done I can do some deburr and clean up work, install the seats and guides, do the valve job, and bolt 'em on. It sounds liek a lot of work still, but actually it will go pretty fast once this machining is done.
We managed to get one head on the CNC today. The other will have to wait until tomorrow.
The first order of business was adding some dowel pin holes for the rocker shaft pedestals - I should have done this when I cut them down...
We also had to cut the guide bosses down to .312". This is enough to locate the rotators. The valve guide seals will go on the .500 guide inserts, which will stick up about a half inch above old cut down guides:
Once that was done for both heads we flipped one over, indicated it in, and got to work on the main part of the job. The first order of business was to deck the head:
Those prechambers are made of some seriously hard stuff. Fortunately, TiN coated carbide inserts are harder, but some CBN (cubic boron nitride) inserts would have probably been better for this application. Still, we managed to get a good smooth finish. It doesn't look as smooth in the close up pics as it really is. For some reason the flash seems to really exaggerate the surface finish.
Finally, we moved on to the main cutting. First, the pockets for the seat inserts were cut. Then a 45 degree cutter was used to unshroud the area around the valves, a 1/2" ball end mill was used to match the throat to the insert ID, and the integral guides were drilled out and reamed to .500" to accept the new press in guides. Here's some cool pics of the cutting taking place (the greenish liquid is water soluble cutting fluid):
Here's the finished product. First are pics of the pedestals with dowel pin holes and the cut down guide bosses that are reamed for new guides:
Deck view:
Closeup of the valve seat pockets, 45 degree unshrouding cuts, and the opened throats:
Here's the inserts next to their respective holes:
Here's one more up close view of an intake pocket. You can see where the ball end mill was dropped into the throat area to open it up:
You can't see it, but there is a sharp edge on the short side radius in the intake ports that I will need to clean up with a die grinder and some sanding cones. Typical stuff when you modify cylinder heads
I'm pretty stoked now. Once the other head is done I can do some deburr and clean up work, install the seats and guides, do the valve job, and bolt 'em on. It sounds liek a lot of work still, but actually it will go pretty fast once this machining is done.
Disturbingly sick work as usual. 
WOW
original balzer
1/2 ton status
Awesome work Max! I just wish I understood what is going on exactly LOL.
I think your next project should be completely building your very own diesel engine from a block of steel.
I think your next project should be completely building your very own diesel engine from a block of steel.
MaxPF
1/2 ton status
seats & guides
I got the bit of grinding in the ports out of the way. I also used a fine rotary stone in a high speed air dremel to get rid of the sharp edges at the mouth of the precups, since I was afraid they might burn away otherwise. I didn't remove much material, just enough to turn the knife edges formed during surfacing into finely rounded edges.
Next it was time to install guides. They get driven in from the rocker side using a driver tool I made and an air hammer. Here's a pic of one installed and an adjacent empty hole which is reamed to .500". The guide inserts are .502" OD, giving a .002" press fit using commonly available .500" reamers:
The short boss on the spring pocket was left there to center the valve rotators, which have a .625" ID.
The guides were chilled to -40F to shrink them slightly, which makes driving them in a bit easier, but they still don't fall in by any stretch. The driver tool I built has a counterbore in it which is .625" deep. I simply drive the guide in until it stops on the boss and it leaves the guides at the height where I want them:
If you look you will see that these replacement guides have grooves inside of them, which are supposed to retain oil. That, plus the fact that they are quite a bit harder than the head material means they wear better and last longer. Add in the roller tipped rockers and guide wear should be virtually eliminated.
The seats are a hefty .005" press fit for the exhausts and .0065" for the intakes. They require a BFH for installation, even after chilling to -40F. If I had liquid nitrogen handy I could have chilled them in that and they would have literally dropped into their holes, but most machine shops drive them in like I did. I made another tool for this job. It is a driver with steps for the two different inserts as well as clearance, and a 3/8" hole that fits over the valve guide pilots. Here's a pic of the tool with an exhaust seat on it, ready to go:
The discolored splotches on the insert is frost. The tool is chilled also so it doesn't heat up the insert. A few whacks with a 3lb hammer and it is in:
Those are the pilots used to center the tool, and later to center the seat cutter when doing the valve job. Here's an intake seat ready to go:
Here they are, all snug in their holes:
Next step is to ream the new guides to size, They are close, but a tad snug on the valve stems. Then I can do the valve job. The intake seats won't take much to get them ready, but the exhaust seats need a considerable amount of material removed to get the valve set to the proper height. Here's how they sit right now:
The plan is to set the intakes, and then drop the exhaust down until it matches the intake and cc the chambers. From there I can decide if I need to drop them more or just finish them up at that height. I will also cc the prechambers so I can compute my compression ratio. Right now, with as much as I unshrouded the valves I have no idea what the CR is going to be...
I got the bit of grinding in the ports out of the way. I also used a fine rotary stone in a high speed air dremel to get rid of the sharp edges at the mouth of the precups, since I was afraid they might burn away otherwise. I didn't remove much material, just enough to turn the knife edges formed during surfacing into finely rounded edges.
Next it was time to install guides. They get driven in from the rocker side using a driver tool I made and an air hammer. Here's a pic of one installed and an adjacent empty hole which is reamed to .500". The guide inserts are .502" OD, giving a .002" press fit using commonly available .500" reamers:
The short boss on the spring pocket was left there to center the valve rotators, which have a .625" ID.
The guides were chilled to -40F to shrink them slightly, which makes driving them in a bit easier, but they still don't fall in by any stretch. The driver tool I built has a counterbore in it which is .625" deep. I simply drive the guide in until it stops on the boss and it leaves the guides at the height where I want them:
If you look you will see that these replacement guides have grooves inside of them, which are supposed to retain oil. That, plus the fact that they are quite a bit harder than the head material means they wear better and last longer. Add in the roller tipped rockers and guide wear should be virtually eliminated.
The seats are a hefty .005" press fit for the exhausts and .0065" for the intakes. They require a BFH for installation, even after chilling to -40F. If I had liquid nitrogen handy I could have chilled them in that and they would have literally dropped into their holes, but most machine shops drive them in like I did. I made another tool for this job. It is a driver with steps for the two different inserts as well as clearance, and a 3/8" hole that fits over the valve guide pilots. Here's a pic of the tool with an exhaust seat on it, ready to go:
The discolored splotches on the insert is frost. The tool is chilled also so it doesn't heat up the insert. A few whacks with a 3lb hammer and it is in:
Those are the pilots used to center the tool, and later to center the seat cutter when doing the valve job. Here's an intake seat ready to go:
Here they are, all snug in their holes:
Next step is to ream the new guides to size, They are close, but a tad snug on the valve stems. Then I can do the valve job. The intake seats won't take much to get them ready, but the exhaust seats need a considerable amount of material removed to get the valve set to the proper height. Here's how they sit right now:
The plan is to set the intakes, and then drop the exhaust down until it matches the intake and cc the chambers. From there I can decide if I need to drop them more or just finish them up at that height. I will also cc the prechambers so I can compute my compression ratio. Right now, with as much as I unshrouded the valves I have no idea what the CR is going to be...
Jason4x4
1/2 ton status
that's a nice air hammer, Where'd you get it?
and did you really get them to -40?
and did you really get them to -40?
MaxPF
1/2 ton status
I dunno
Near enough. I chilled 'em in the freezer, then put them on an ice&salt slurry pack, which should theoretically be -40 or so. I was going to use dry ice & acetone, which is like -108F or so, but I didn't have any acetone left and I was too cheap to buy more
Easy enough to get them to -40 -- I just put them outside for about 20 minutes
smalltruckbigcid
1/2 ton status
Max- whats your recipe for the slurry you made
MaxPF
1/2 ton status
Ice, water, and as much salt as I could dissolve in the water. There is probably an optimum solution, but I just used the SWAG method.
In other news, I ordered a pair of guide reamers today. If they get here by the weekend I should have some more pics to post up.
y5mgisi
1 ton status
wow i dont know how i missed this but subscribed!
thedrip
1/2 ton status
We're waiting for an update!
DEMON44
Low-Tech Redneck
Awesome work Max! I just wish I understood what is going on exactly LOL.
I think your next project should be completely building your very own diesel engine from a block of steel.
funny you should mention that........a magazine artice recently just profiled that. a guy machined his own cummins engine block from solid steel. I guess it makes 1900hp or something of that nature. now the billet rods are the weak link.
That's nothing new:
In the 80's I was always reading about guys that were building their own blocks and heads, even aluminum blocks with inserts and aluminum heads, intakes, pretty much everything from scratch, in their garage, and making amazing powers.
At the time it was corvairs and VW engines I was interested in.
DEMON44
Low-Tech Redneck
I didn't imply that it was new.........but you talk of these cute little engines.
no one machines their own SBC or BBC blocks from a billet cube. and certainly no normal person does that for a 5.9L cummins. the cost of the cube of steel big enough to make a 6B cummins block alone must have been astronomical.
