LQ4BU

This past weekend I raced the NMCA True Street class at Summit Motorsports Park in Norwalk Ohio. Had a blast but am wondering if I may have a fuel or carb issue. I made some jet and timing changes and the car didnt really react at all.

1st run on Friday

Jets 73-83
32 deg timing
20 psi tire

1.61 60'
4.63 330'
7.18 1/8
95.82 mph
9.42 1000'
11.32 1/4
118.27 mph




2nd run on Friday

Jetted up primary to 75
Everything else the same

1.59 60'
4.61 330'
7.16 1/8
95.90 mph
9.40 1000'
11.31 1/4
116.46 mph

/\ Car seemed to hook better, but gained mph at the 1/8 and lost 2 mph at finish???



3rd run on Friday

Jetted up secondary to 85
Lowered tire pressure to 18 psi
Everything else same

1.59 60'
4.62 330'
7.18 1/8
95.65 mph
9.42 1000'
11.33 1/4
117.36 mph

/\ Car slowed down .02 through run but gained almost 1 mph at finish line???


1st run on Saturday

Jets 75-85
36 deg timing
18 psi tire

1.60 60'
4.63 330'
7.18 1/8
96.04 mph
9.41 1000'
11.31 1/4
118.42 mph

Before my 2nd and final test pass on Saturday, I jetted the secondary up to 87 just to see what would happen to the mph. I was expecting it to fall off a bit because I really cant see this motor needing that much so I figured I would do it as a real world test since I had the chance.

Guess what? I guess due to the fact that it was so crowded and they were behind schedule with all the other events going on they canceled our 2nd time trial run and we had to report to the drivers meeting. Then to the 30 mile cruise, and then to the staging lanes, and 3 back to back runs down the track. The only thing you can do is raise or lower your tire pressure. Not allowed to add fuel, not allowed to open your hood or trunk.

So now I'm stuck with 87 jets in my carb and I have no idea what its gonna run.

The 3 passes below all have the same setup:

75-87
36 deg timing
18 psi tire

1.59 60'
4.62 330'
7.18 1/8
95.54 mph
9.42 1000'
11.33 1/4
117.86 mph


1.61 60'
4.65 330'
7.20 1/8
95.87 mph
9.43 1000'
11.33 1/4
117.80 mph


1.62 60'
4.70 330'
7.27 1/8
95.46 mph
9.51 1000'
11.41 1/4
118.33 mph

/\ 60' fell off a bit so it must have spun which
caused the final mph to go up but why did I lose mph at the 1/8th???


The car is obviously extremely consistent, more so when I dont change anything at all. But isnt it odd how consistent it remained even with the the jetting changes? Or am I wrong in expecting to see more differences run to run after changes are made? I'm just wondering if maybe its right at the edge of not getting enough fuel or a carb issue.

I have a Holley Blue with -8 running from it to the engine. I did check the fuel pressure during a full throttle pass earlier in the year and it never dropped below 6psi.

Doug G

Any ideas on the DA ?

How much time between runs ?

LQ4BU

The DA was about 2200-2500 during all of the runs. About 2 hrs between each run on Friday, and then 30 mins between each of the last 3 runs.

I wasnt trying for consistency. I was trying to see if it would go faster, and I wanted to determine what it liked/disliked.

We were not allowed to have laptops or any data gathering equipment in the cars...or I would have logged all my runs which would have really helped.