Tuning on the off-week

Suspicious of missing out on some straightaway speed, I sought the advice of one of the experienced club members.  We discussed several ideas to explore but settled on doing a leakdown check on the engine.

The process is pretty simple.  You take the cam out of the operation by removing the rocker arms.  This ensures that the valves stay seated (closed) during the test.  Compressed air is introduced through the spark plug hole and we check to see where it tries to get out.

It is normal for the rings on the piston to leak some as they do not form an airtight seal but you should not hear air coming out of the exhaust pipe or the carburetor throat.  During the test on our engine, we could hear a small amount of leakage through the exhaust.  Although it is was detectable, my friend assured me that it was insignificant on the track.  What else could I try?

Spark plugs? I have been running a conventional plug like the one pictured here.

This has the standard ground and I was diligently keeping the gap set properly.  No surprises here.  What about this stuff I read in the forums about a great racing plug for the Animal?  I decided to give it a try.  It has a cut back ground to increase the exposure to the spark.  This is the plug I had in when I visited my friend for the leakdown test.

My friend pulled out yet another upgrade to the plug.  It is radically different and offers even more exposure.  This is similar to what is used in some aircraft engines.  Apparently, it is legal to run so, we will give it a try.

Another upgrade he recommended was a larger air cleaner assembly.  This picture is a side-by-side of the new verses the old.  Obviously, the new has more surface area and will have less restriction.  With the larger restrictor plate, he claimed that this could make a difference for us.  The elongated base also acts as a semi-velocity stack to leverage the inertia if the intake air to "pack" molecules in the engine.

Finally I replaced the drive chain as I understand an old chain can increase drag.  With the stretch between rollers, the rollers don't fit nicely between the teeth and take slightly more power to engage.

With the new air cleaner installed I found it interferes with the right rear tire.  I may have to get creative but for now, I'll have to run the old air cleaner.

I'm again on-shift for the next race but may still be able to get a friend to swap.  I'm looking forward to see if any of this makes a difference.

Race #3

I got a break and found a co-worker willing to trade shifts with me so we could go racing.  I was interested to see if any of my fine-tuning would pay dividends on-track.

The weather was beautiful - sunny, mid-seventies and a light breeze.  It couldn't have been more pleasant unless you could magically make the pollen go away.  There were a total of six in Lian's class ready to race so we had some good competition on the track.

The practice sessions went pretty well and Lian was keeping pace with the rest but it was hard to tell who was fast and who was just riding along.  Lian admitted that she wasn't going hard on the first session and her best time was 22.20 seconds.  She backed that up with a better effort during the second session with a 21.76 second lap.  She complained that even driving hard didn't get her as quick as some of the faster kids on the long straight.

For the heat races, Lian started 4th and 3rd.  In the first heat, Lian was passed at the start by the 5th place racer but held onto 5th and put up some good lap times.  Her best three are below.

I should note here that one of the competitors was a relative rookie and was not moving fast.  He started behind Lian in the first heat but he started on the pole in the Heat 2 - directly in front of her.  When the green flag waved, the outside line went and the 5th place starter followed.  Lian had to wait for them to clear before she could attempt a pass.  She was less aggressive than the other racers and was not confident that she could make a clean pass although she knew she was faster. She was hoping for a blue flag to wave but it never came and Lian finished in the back.

Here she is on the starting grid sporting her new drivers jacket and helmet.  We ordered a dark visor because there are many sunny days ahead...

Starting in the back of the feature, Lian managed to get past that slower driver at the start.  Later that first lap, the 3rd and 4th place drivers bumped causing one to slide wide in a turn and stop.  Lian slipped past cleanly and held on for a 4th place finish.

Despite my efforts, Lian still feels that she is down on power at the end of the straight.  I've discussed this with a few other crew chiefs and I'm hearing mixed signals.  Some don't see that there is a difference on the track, others suggest leakdown testing on the engine to see if a valve is leaking.  I'm even considering a new engine to take any doubt out of the issue.  I'll let you know what I decide in my next post.

Race #2 - washout

Not much to write here beyond the title.  We never even went out on the track for morning practice.  We hoped to at least get the heat races in before the rain started but it arrived earlier than forecast and dampened the track before registration opened.

We made a few changes after last race.  I tightened the valve lash on both the intake and exhaust valves (set at a "tight" 0.002" gap). Installed a cutback racing spark plug and adjusted the carb to a little slower idle but set the mixture so it is a little more responsive.

I will have to let you know how these changes work out next time we make it to the track.  I have to work next race (May 5) and because we are short-handed, I can't get anyone to swap with me.  It's going to be a while before we get to the track.