Coated Vs. Non-Coated Engine Bearings

I’ve learn engine builds the place the builder swears by coated engine bearings after which different guys will say that they’re only a solution to spend more cash and so they don’t assist in any respect. I’m constructing a giant block Chevy for my Nova and I’d be keen to spend the additional money if there’s a good cause to make use of them. What are your ideas?

P.C.

I’ve a very good pal Lake Pace, Jr. who’s a licensed oil engineer—referred to as a tribologist.

Numerous years in the past, I adopted alongside on a moderately in depth take a look at that he carried out at Shaver Racing Engines in Torrance, California. The take a look at used a 383ci small block Chevy and abused it for a number of hours utilizing a modification of an SAE take a look at designed to run an engine at very low engine speeds at very excessive load.

The plan was to run the small block with a set of typical race bearings after which take a look at the used oil for hint quantities of damage metals. The second take a look at can be run precisely the identical approach with the identical oil however with coated engine bearings. Each units of bearings had been from Clevite and the oil was a mineral base 5w20 oil from Pushed Racing Oil. They used this lighter oil as a solution to additional abuse the bearings from close to contact between the crankshaft and bearings.

The take a look at subjected the small block to spinning at slightly below 1,500 rpm at between 175 and 200 lb.-ft. of toque repeatedly for 3 hours whereas performing a number of WOT dyno pulls up by way of 6,000 rpm. As we talked about, this actually is engine abuse to run an engine at this load at this low of an rpm. However this will even create the form of crankshaft contact with the bearings that may be indicative of hundreds the engine would see over a for much longer time period at larger engine speeds.

Used oil samples had been taken on the conclusion of each units of assessments after which delivered to SpeeDiagnostix for evaluation. There are a number of layers of outcomes from every used oil pattern take a look at however a very powerful numbers that this take a look at was taking a look at had been the damage metals current within the oil.

The crucial put on metals that SpeeDiagnostix stories supplied had been the iron, lead, copper, tin, and aluminum counts. Crucial ones can be the lead, copper, and tin since these symbolize the prevalent metals in engine bearings.

The SpeeDianostix take a look at tracks all these supplies in parts-per-million (ppm). The damage steel complete that features the entire 5 metals for the uncoated bearings got here to 25 ppm whereas the whole for the coated bearings dropped by greater than 50 % to 12 ppm.

The precise numbers are listed within the accompanying chart, but when we break down the numbers particularly for bearing materials to only lead and copper we see these numbers drop much more precipitously. The large one is lead, which plummeted from 11 ppm to 2—that’s an 82 % drop in put on whereas copper put on dropped from 5 to 2 ppm or a 40 % lower.

So it needs to be apparent from this take a look at that spending the cash on coated engine bearings will clearly lead to longer engine bearing life. One facet that this take a look at didn’t duplicate is the damage encountered throughout chilly engine begin. There’s solely a really small quantity of oil on the bearings when the engine is first began after sitting in a single day for instance.

Even the perfect engines require a second or two to generate oil stress when the engine begins. These few seconds sadly can permit a slight quantity of damage every time the engine is began. Coated bearings will supply slightly extra safety towards put on throughout these few moments earlier than oil stress is created.

That is usually why you will note engine builders stress lube race engines earlier than startup to offer these bearings much more likelihood for an extended life. It’s additionally why pre-filling the oil filter is a good suggestion after every oil change—once more to create oil stress slightly sooner to assist these bearings stay slightly bit longer.