As the miles on your car rack up over the years, the performance of your engine will diminish or may not be the same as it was. Even with regular tune-ups and periodic maintenance, an engine’s performance will eventually dwindle over time. Besides engine wear, carbon and sludge build-up are also contributing factors in performance loss. In the days gone by, taking down your cylinder head and having the valves reseated and decarbonized was quite common. The fuel and oil available before were not as high-tech as it is to day.
Other reasons that may require you to take down your engine’s cylinder head might be a blown head gasket, a dropped valve, a cracked cylinder head or a broken timing belt. In the event you do need to take it down, make sure to bring it to a reputable machine shop. A good machine shop, besides checking for warping, would also recommend to have the cylinder head hydro-tested. This test would verify if the head has any leaks. It would also be a good idea to have the head inspected for cracks. The head would most likely be cleaned thoroughly and a special dye would be applied to areas where hairline cracks would normally develop. If a crack is present, the dye would seep into the crack and would make the crack visible. If a crack does appear or a leak is present, it would be better to replace it with a new cylinder head.
If the head does pass the integrity test and would need resurfacing to remove the warped surface, make sure the warping is not excessive. Newer engines have very close tolerances as compared to the older ones. Now, this may sound a bit over-kill but if you resurface the cylinder head too much, the compression ratio of your engine may change. How? If you look at the combustion chamber you would notice it is like a bowl. You would see your intake/exhaust valves and you spark plug hole. As it is, it will hold a certain amount of fluid. It would have a specific diameter (your bore size) and a certain distance from the bottom of the chamber to the bottom face of the cylinder head (mating side to the top of the block). If you remove material or resurface the cylinder head, the dimensions change. The volume of the chamber has decreased. That means that as compared to the previous volume of the chamber, your are now compressing the air and fuel mixture into a smaller space — the result: a bigger bang. It is similar to the old-school engine that has a shaved head. This would be nice if you want more power but with higher head temperatures.
So how would you compensate? For those who don’t want to have any headaches, you can use a thicker head gasket. The extra thickness would compensate for the shaved-off material – that is if the removed material was not in excess. If you are experiencing high engine temperatures after a head job that required resurfacing of the head, this may be one cause. Now if done correctly, once you reassemble everything you should not have any problems.
Nowadays, we don’t hear much of motorists having a top overhaul. That is because we have better fuel, oil and engine designs. I would often hear of cars that have already logged in over 150,000 kilometers having very minimal carbon build up when you peek inside the engine. At one point, your dealer will recommend to have your engine flushed. With the right product and if done correctly, this procedure can reduce the chances of carbon build up and formation of sludge in your engine. If you want to make sure about your engine, have a compression test done just to see how the condition of the cylinders are. Your engine is okay only if and when the variance in pressure between all the cylinders are not more than 10 percent.
Another way of removing or avoiding carbon build in your engine is dong the “Italian Tune-up.” Running an engine at full engine speed or revolutions per minute (rpm just before the redline) helps the engine clean its self. The high revs help dislodge carbon deposits in the engine. It is then expelled out through the exhaust system. This procedure is very helpful for vehicles that are usually driven slowly with the rpm not reaching half way the redline. The Italian tune-up is usually done just before an oil change as some sludge gets to the bottom of the oil pan.
Running you engine at high revs also exercises the engine. It would be healthy to do this procedure once a month, preferably in a highway. This can easily be done by staying in second or third gear for a while and driving for 20 kilometers or so. Just make sure not to go over the speed limit. After a while, you would notice that your engine will feel different and run better. Early mornings would be the best time to do this procedure because there is less traffic. However, your next problem would be where to eat breakfast. If ever you decide to have an Italian tune-up and know of good place to eat, do let us know. It would be good, again, to take a long drive. Drive safely too.