The most common rocker used to be the forged version these have bushes in them and can be used on any and all size motors. The very early rocker arms do not actually have any sort of bush in them and must be replaced when worn these are typically the pressed steel type which are not very strong in the first place. When these parts are worn, setting the valve clearance is very difficult and if you run the engine with poorly adjusted valves not only will you lose horsepower but you can also burn a valve. it is important to note the condition of your existing rocker shaft and arms. High performance cams achieve their objective by increasing valve lift, among other factors, This is great, but the stock rocker actually pushes the valve sideways as well as down and the higher the lift the greater the side loads on the stem and guide.Įvery performance gain has a price, but this high performance penalty can be offset with the use of modern roller tipped rockers! While on the subject of rockers. Why Performance Modifications Affect Value Job FrequenciesĪnother factor in the need for more frequent valve jobs is the increasingly common use of high performance camshafts.
Bronze guides will not last as long, but stem wear will be greatly reduced. Most original and early cars have steel guides, which might last longer but can wear the valve stem. The problem with unleaded gas not only affects the valve seats, but just as significantly the guides the lack of lubrication in the unleaded gas causes excessive wear. The second reason for a valve job is the valve guides. The valve is dependent upon intimate and total contact with the valve seat to dissipate the heat anything that prevents this contact will allow the valve to heat up and eventually burn! The impurities in the air and gas often get trapped between the valve and the seat in the head under worst conditions stopping the valve from closing, but more commonly being smashed enough to allow just a little seepage of hot gases.
Īnd by the way, we have a great article on Performance Cylinder Heads ) (We have a good article on Do I Need A Valve Job if you're still unsure.) And if you're needing a new cylinder head check out our Cylinder Head. The most experienced people will tell you that the best way to maintain your engine performance is to accept the fact that valve jobs need to be done 2 or 3 times more often than rings and bearings! And this data base was concluded when leaded gas was the norm! Now that unleaded is all you can get, valve jobs are needed even more often!īut regardless of the why, the point is every once in awhile, they have to be done. Doing A Valve Job? Then You Gotta Know Your Cylinder Headįirst of all, everybody has their own opinion on this subject of doing a Valve Job.
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