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