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Tried 02 sensors and they are all over the place and did not produce usable data and did not last long. The 02 sensor data was worse in the first half of the run and did start to stable out in the second half but still not producing very useful data. People use Boost to Fuel or Fuel to Boost but that will only put you somewhere in the ballpark. It boils down to plug reading and watching performance indicators.

 

When you say the front half are you meaning the 1/8th mile. If so we read them all the time at 1/8th mile.

 

Templar, yes you can do that but you don’t want the 1/8 mile readings too lean so you can’t get to the 1/4.

TOL, had heated UEGOs. Did not turn them on until the motor was running because they were not retracted. Didn’t want to hit hot sensors with liquid fuel. They still didn’t last long and cost big bucks.

 

If you are smashing your bearing you are detonating, if you are detonating you are losing power and being hard on parts so why tune that way. You do not read inside the spark plug on a blown alcohol motor you don’t care what it is showing down there because you are running the coldest plugs you can get.
Try reading this and see if it helps you put understand
https://www.dragstuff.com/techarticles/reading-alcohol-spark-plugs.html

 

You can tell exactly where you are in the tuneup by reading the spark plugs. I don’t know of anyone that tunes by bearing smash anymore especially in the Promods. We do still check the bearings but not after every run. If you are burning the threads on the plugs then you are way too lean and if more than one thread then watch out.

 

The way I was taught by Steve Harker to read plugs is very similar to what Mike describes in his article, but we look for how much cad is left in the inner beveled area of the plug (referring to a NGK 6061 -10 or -11). Like his article said, close/safe is when you only have a small 'eyebrow' of shine/cad left down inside. Some combinations can get rid of all the cad, but you really have to have a good handle on what jetting your engine wants because at this point you are flirting with burning a piston or detonation. If you are a put a jet in it back at the pit and not 2 pairs back, then stick with some eyebrow of cad or more.

Reading the bearings is very important, but you have to know how to read a V bearing that we all run nowadays. Years ago with the softer M bearings, you could read the 'squish' at the bottom and tell something. I haven't found much info there besides going from safe to detonation - not much in between.

I think it's important to point out that the rolled babbit material that happens every pass SHOULD NOT be part of any measurement. Take a sharp edge or deburring tool and debur the side of the bearings. This should be done if you are reusing the bearing regardless if you are measuring it. Just use a normal pressure and scrape till it's smooth and no more babbit is rolled over the edge. If you are going to try to measure the bottom width of the bearing, you are looking for movement of the hard material on bottom, not the soft material on the top.

Tom Conway taught me the 'across the top' measurement which I describe as measuring across the top of the "U" or what would be the diameter of the bearing half circle. You simply put the calipers on the outsides of the bearing and roll it until it just touches. The diameter of the big end of a hemi rod is 2.500". A new bearing will be about .020 to .035 wider than that so the bearing is tight in the rod or cap. If you are detonating/beating the bearing up, it will hit the bearing at the bottom of the "U" and close the tops of the U in. I have found keeping the bearings around 2.500-2.505 is safe. Closing them up much more than that, you are getting over center. 2.495-2.500 you might be right on the edge. Anything less than 2.490, you are close to disaster. I have seen a bearing 2.470 to 2.469 that kicked the rods the next run (bearings were measured after the fact due to a breakdown in communication). The only instance a bearing will close in without detonation is just too many runs on it. I have been actively tuning cars since 2003, and this measurement has not failed me and has proven to be the most accurate way to find the limit on timing.

Your timing limit is going to be directly connected to how lean the fuel system is and a number of other factors including compression and head temp.

 

I haven't ran coated rod bearings. I doubt it would change the way I read them as it shouldn't have much effect on the bearing closing in if it's beat on.

Now I'm sure they're harder to throw away....

 

Yes you can still smash coated bearings just like uncharted ones.