[DeTomaso] Oil Numbers

[JDeRyke at aol.com]

In a message dated 7/1/09 1:38:01 PM, asajay at asajay.com writes:

> For those of us hicks who tend to build our -own- engines.... how do I 
> know what oil is best to 
> use with what clearances?  If rebuild an engine to factory 
> specs (clearances), then I would assume the factory recommended oil.
> 
Generally, the tighter the bearing clearances and the higher the rpms you 
plan to run, the thinner the oil needed. If you 'blue-print' to minimum 
clearances, you probably then need thinner oil, but it really depends on the 
application. Qualifying engines often use 0W5 wt oil that makes an extra 1/2% 
power @9000 rpms; the engine lasts the 5 laps of qualifying.... usually.   
In addition, if you use synthetic-compatible seals & gaskets, you can 
always use synthetic oil except for break-in. Using cheap seals & gaskets, 
synthetic oil may not ever stop leaking but regular oil might work fine. 
Synthetics vary in their properties, too....
Race engines with very high compression can be set up with loose clearances 
for less friction & more power, but then need thicker oil to take up the 
wide clearances and greater impact of combustion, and maybe have lower redline 
rpms. 
All this is not an exact science: one builder said that experience building 
good performance engines comes from the number you built that blew up 
prematurely. Finally, performance engines are comsumable items like headlight 
bulbs. Do not expect to increase power over stock and also increase longevity: 
when one goes up, the other drops. Put another way, the closer to the edge 
you build a motor, the more likely you are to inadvertently fall over the 
edge.... and the 'edge' is hidden by brush so you don't always see it. Good 
luck all- J Deryke



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