Cylinder Wall Finish

In the image below cylinders do look really smooth and they actually are, but just because they are smooth does not mean they will not seal. 

The real factor of ring sealing is the oil that is contained within the cross hatching in the cylinders and the oil on the surface of the rings. Since this application is using chrome plated top ring and each one being low tension they don't need a lot of oil like older types of piston rings.
Engines such as a traditional small block 350 mainly use cast rings that exert a lot more pressure on the cylinder need deeper cross hatching to hold more oil. Those deeper scratches directly relate to the RA (surface roughness) of the cylinder walls. And, with a higher RA the more matte the finish on the cylinder walls. But, keep in mind that the 350 can have finishes just like the one pictured above, but you have to use the rings that specify that RA (low tension, coated, and thin rings)
We often times build viper v10's with surface finishes in the 8-10 range that are "shiny", but since the rings call for it there is almost no blow by pressure.
Along with ring type there is still another factor that drives the surface finish, oil weight. A modern engine that uses RA values below 1.0 also call for zero weight oils. On those engines the cross hatching seems almost nonexistent, but under the microscope there actually are more scratches per square inch. With more scratches per inch they are able to produce much shallower scratches to accommodate the lighter weight oils used.

Examples of RA:
Glass: 2-4 RA
Surfaced aluminum cylinder head: 25-40 RA
Cylinder (honed-cast rings): 20-35 RA
Cylinder (moly low tension): 8-12
Cylinder (Really low tension Laser processed cylinder): <1.0 RA

Easily Damaged Engines

Even though an engine has recently been rebuilt/remanufactured it is not invincible. There are so many small things that can easily damage that new engine within a few minutes:


Cooling system malfunction, which could be caused by clogged radiator, failed thermostat, failed water pump, ruptured hose, etc... Properly flush that radiator and heater core, replace all questionable hoses, replace the thermostat/s, and replace that water pump too.


Oiling system. Most engines keep all of the oil within the engine, but there are more than a few that utilize external oil coolers, which may either be water to oil or air to oil. Either way if the cooler is clogged on the oil side it will most certainly restrict oil to the bearings.  If that engine's initial failure was oil related then all of that material was pumped and lodged in the cooler's passages. And, even if that engine had no issues with the oil system would you really want to install such an important part onto a new engine. Replace the cooler.

Air/Fuel Control Systems. Engines can be damaged by things as simple as a contaminated sensor. MAF sensors that utilize a hot wire to calculate air mass are prone to contamination, because there is hot wire that is a "magnet" to debris. If this wire becomes contaminated that MAF sensor could send false values to the ECM, and those false values could cause the engine to run perpetually lean. Lean conditions have a tendency to overheat the valves and allow them to stretch.


Emission systems. EGR is another system that can easily cause damage to a newly rebuilt engine. If an EGR system uses a valve position sensor instead of a flow sensor it can cause a lean condition. Imagine an ECM that commands the valve to open, the valve may move to the open position, but the passages are clogged; therefore no flow actually happens. Now the ECM assumes that EGR flow is present so it begins to reduce fuel trims to compensate for the smaller amount of new air entering the cylinders. But, if the EGR flow is nonexistent then the engine is still receiving that air; therefore it will produce a lean condition and like above may overheat valves.


Ignition timing. It's a simple procedure that many people assume they know how to do. But, too many engines are damaged due to overly advanced timing. Installing a distributor can vary in difficulty, from idiot proof cam flange types to a little more involved cam gear to distributor gear driven types. The latter requires the installer to first properly identify #1 TDC then install the distributor with the rotor pointing at the #1 position on the CAP no the actual cylinder. After that, too many people don't ever properly set the actual base timing which might be as simple as removing a vacuum hose, loosening a bolt, and turning the distributor all while aiming a timing light at the balancer to watch the flashes. Incorrect ignition timing can cause some pretty major damage such as melted head gasket, melted pistons, or spark plug deterioration. The spark plug coming apart isn't a huge issue until that hard ceramic falls into the cylinder. Overly advanced timing can easily increase combustion temperatures above the melting point of aluminum and head gasket firing rings and it doesn't take much time at all. Below is an example of overly advanced timing which thankfully damaged the head gasket and not the pistons.

So when replacing an engine you or the installer must determine what caused the initial failure. If the oil cooler was clogged and caused bearing damage, you can rebuild the engine and install it, but you will not fix the whole problem until you replace the "causal part". Assess the condition of each item to be installed on the new engine and determine if it needs to be replaced or repaired. And, once the engine is in be sure to adjust idle speed (if necessary) and ignition timing.

Matt W.
North Texas Speed and Machine.  


P.S. Don't forget all new filters. Oil, fuel, and PCV

Valve Seat Boring

Often times the parts you want are not available. You might get something a little too small or a little too big. Being open minded about what you can do to make things perfect for you is an important skill in life.

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So this application was driven by the type of build and modifications required for an increase in performance. The component in question is an exhaust valve seat that maintained the outside diameter but allowed for an increased inside diameter. Directly out of the catalog there were no seats that matched, so I located the best one that could be modified for what I wanted.

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The seats had the same 1.062" OD but had an ID that was about .085" too small. I could have installed the seats in the cylinder head and then bored them to the desired dimension, but the center is based on the center of a pilot, so they would all be different once installed and machined. And, our machine cannot bore a seat that small, the OD is only slightly larger than an inch.

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So to make them all the same I decided to perform the boring before the seats were installed in the head. This process began with designing and building a fixture to hold the seats.

The fixture first was squared with a shoulder so it could be mounted in a vise on the mill and be square to the machine. After flipping the top was slotted to allow a flexible clamp. After the slotting the next step was to machine the bore that the seat would "sit". That bore was nearly the same size as the seat so it required a little tapping to get it in. Below the seat I machined a counter bore to allow the boring head a little over-travel after finishing the seat boring. The final fixture construction step was to drill two holes off center to accomodate two clamping bolts which squeeze the seats in the fixture. Now it's built so lets do some machining.

Matt W.
North Texas Speed and Machine

1940 Nash La Fayette Water Pump

  As with any engine rebuild or restoration your are going to need parts, but when a car or truck was built over 70 years ago those parts might be hard to come by.
Many companies have offer restoration parts for those old cars so getting, piston rings, bearings, gaskets, and the like were easy to source. But, not everything has worked out so well.
 As with many restoration builds we begin with a conversation about the history of the car, any know problems, and why they want it rebuilt. This vehicle had its own story and reason to rebuild, but it had one ever-present issue. It almost always over-heated when it ran. The customer had the radiator cleaned and recored with no change so we had been tasked with rebuilding and figuring out why the engine was constantly over-heating.
  Another special condition was that we received this job already disassembled.

The impeller was not even attached to the shaft.

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As we sifted through the included parts we definitely found the source of the over-heating. Upon inspection of the water pump we found the water pump impeller not attached to the water pump shaft. It was just dangling inside the water pump housing. It also looked like swiss cheese from someone previously trying to repair the pump with set screws, roll pins, and wood screws (not definite about that one, but wouldn't put it past them)

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A short look on the internet and the Hemmings motor news ended without a good supply of a new or used part to replace ours. So we were left with reverse engineering and fabricating one ourselves. This ended up being the best option, because the housing was in such good shape and all that was needed was the impeller and shaft. So here we go. I started by measuring every dimension and taking notes on housing dimensions to see if there was room for improvement. It's a simple straight fin centrifugal impeller that ingests the water in the center (inducer) and exhausts it through its outer circumference (exducer).

CAD of the component ready for CAM

I decided to construct it from aluminum for a few reasons: easier to machine than cast iron, easier to get (already had aluminum), and with modern coolants corrosion should be nil. I did increase it thickness by about .050" and its OD by about .050" really to take into account the loss do to erosion.

Center drilling for the hole which will be the x0y0 of the component.

Mounted to the fixture to do the profile of the impeller.

The stock dimensions are 3"x3"x2". The first procedure was to face the top and two sides so the piece could be held square within the vise. After the facing of the three sides it was flipped over and clamped into the vise. Once over and clamped with the center located the center hole was drilled and reamed which created my zero positions for the x and y axis.  Now, being that the part was about 1.200" too thick I needed to cut down the top to the actual thickness of the impeller. With the part now at the final thickness there needs to be a counter bore cut concentric with the center hole.

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So all of the machining is done on one side of the impeller and the perimeter needs to be machined for the fins and inducer step. I did this by facing another piece of aluminum and drilling it to accept a 1/2" bolt so the machined part could be held in the center. This allowed full access to the perimeter for milling.

CNC milling of the impeller.

And here the final part. The next step will be machining of the pump shaft and reaming of the housing bushing for truing.

Video of the action above

Matt W.
North Texas Speed and Machine
www.ntxmachine.com

D16Y8 Engine Build Pt. 4

Part 4 will focus on the Honing of the cylinders on the D16.

The cylinders have been machined on the cnc to within @.007" of the final size. The remainder will be honed out. Honing is a process very similar in operation to sanding. Instead of flexible abrasive paper we use a vitrified abrasive grinding stone. As it cycles up and down in the cylinder it grinds away the metal leaving scratches in the cylinder(cross hatch).

The first stones used are an abrasive equivalent to a 70 grit sand paper. This step will remove the metal at a pretty quick rate but will produce a surface finish thats way too rough for piston rings at 60 rms. With the rough stones I bring the diameter to within .0015" then it's time to step to a finer stone.

The next stone is equivalent to a 220 grit paper and can produce a cylinder wall with a 22-32 rms. At this point old style cast piston rings are happy with deep grooves to hold a lot of oil. With the the 220's the cylinder is honed to within .0005 of final size.

The second to last step will be a 280 grit equivalent that is capable of a 16-23 rms finish, which is really smooth. Now the cylinder will be honed to its final size of 2.963", which will give me a .0025" piston to wall clearance.

The final step in the honing is using a plateau hone brush that will break all of the peaks of the scratches left by the honing stones. This process used to be done by the piston rings and that was called "break in". But, when the piston rings performed this process they would get scratched in the process. So with an abrasive impregnated nylon brush I performed a plateau hone.

And that's honing a block.
For a video www.YouTube.com/abletrot
Matt W.
www.ntxmachine.com

D16y8 Engine Build Pt. 3

For this installment I will addressed two machining processes. 1st the surfacing of the sleeves. 2nd boring of the cylinders.

1. After the sleeves were clamped in place for about 24 hours it was time to remove the clamps and continue machining. Recommended procedures for sleeve installation requires that the sleeves actually protrude beyond the deck @.001", this is done to allow for any settling, if any. As you have read in an earlier post the deck has been surfaced. The before measurement gave me about .022" of an inch above deck so a few passes then netted me .001" protrusion. That's done let's move on.

2. Boring of the cylinders is normally not very exciting except when blueprinting a block for performance. Our cnc locates the cylinders using a touch probe, this is acceptable for a regular rebuild. But, for this one I checked the numbers and found the end to end spacing really close and the side to side spacing varied by .007". Normally that doesn't bother me but I went ahead and corrected the positions for the best possible spacing. I also went ahead and bored it to accommodate 75.25mm because of my special b series rods have been narrowed enough to make them fit in the bore. More on them later.
Until next time,
Matt W.
Ntx Machine.

Synthetic Engine Oil

I remember the advent of Synthetic oils back in the late 80's and 90's and they were labeled the best thing for engines Period.
Synthetics have come a long way and have made their way into almost every automobile manufacturer's line-up. With partial synthetics in Ford's first version of 5W20 to fully synthetic Mobile in every Corvette made. Needless to say they have great benefits over conventional. Higher temperature capacities, lower viscosities without reduced film strength, and better thermal stability to name a few.

But, there is one item of contention "Break in". Should an engine go through its break-in on synthetic oils?

Lets first think about what "Break in" is. When a metal cylinder (aluminum or cast iron) is first bored then honed it leaves the surface broken and jagged. There are processes to reduce the jagged texture of the cylinder but there are still microscopic edges of metal that need to be "Broken in" by what ever opposing surface they meet. Upon the first start the piston rings travel up and down the cylinder and with each pass they remove the peaks of metal created by honing, and that process is one part of "Break in".  Another process within "Break in" has to do with flat tappet camshafts. The flat tappet lifter does not slide up and down the camshaft lobe it actually rolls/spins up and down the lobe. This is caused by a 1-3 degree taper on the cam lobes and a convex surface on the bottom of the lifter. This action is similar to tilting a barrel on one corner and turning it up a ramp. It's easier to roll it than try to slide it up the ramp.

Within the process there must be material removal to create plateaus in cylinders, wear patterns on lifters/pushrods/rockers, and wash out the resulting swarf to produce a well "Broken in" engine. It will have better sealing piston rings and long lasting lifters to name a few. This action is allowed by the reduced lubricity of a Conventional oil.  No one will argue against synthetics having more lubricity than conventional oil, but the more lubricity is the issue.

Many piston ring manufacturers recommend against synthetics because they are too slippery and will not allow the piston rings to create the perfect mating surface.  Now understand that they are not saying that an engine will not "Seat" the rings on synthetic, but they are saying that they RECOMMEND conventional oils. And, if you buy their rings you have to follow their rules.

Total Seal: http://totalseal.com/TechPage.aspx#trGaplessPistRings
Je Pistons: http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf
Deves: http://www.deves.com/tips.php

The following is my opinion as far as engine break-in goes for piston rings.

1st step starts with proper cylinder finishing. Appropriate honing stones should be used according to piston ring dimensions, structure, material, and coatings. The cast piston rings of the old days require a rougher finish which will create deeper valleys to hold more oil. On the other end, newer chrome or moly coated piston rings of 1.2mm thickness require a very fine finish that creates shallower valleys due to the reduced pressure they exert on the cylinder.

2nd step is done immediately after honing and it is a process that helps to reduce the initial break-in time and stress placed on the rings. If they have to break off the peaks of the honing then they will be scratched in the process. Plateau honing will basically knock those peaks off and create a plateau, and this will prevent heavy scratches on the rings.

3rd Conventional oil that is close in viscosity to what is required by either the manufacturer or the engine builder/machinist. If you have a flat tappet camshaft then a good break in oil additive would be in your best interest.

4th Reasonable driving. Don't drive it how you intend to after break-in. Be that hard or easy. The cylinders and rings need sufficient pressure against each other to properly lap them together. Once at operating temperature, accelerate from 30mph to 50mph approximately 10 times. Do this close to wide open throttle while keeping rpm's below 10% of redline. At this point the engine is essentially broken-in. Now drive the vehicle somewhat normally for the next 500 miles (no high boost, red line shifting etc..) once at 500 miles change the oil and filter to what ever type of oil you decide and happy driving.

Matt. W.
NTX Machine
 P.S. Check with the cam manufacturer for their break-in procedure, because they will be the one you call when the cam goes flat.