tc944

84 N/A. Car runs great at the beginning of the session and keeps up with my 88 with no problems. After three laps or so, he begins to drop back and I never see him again. My lap times are pretty consistent so I am not leaving him with my driving ability. It runs fine the whole time, no missing or anything like that. As soon as we got back to the paddock we jacked up the car and made sure there was no drag from the brakes or the wheel bearings. This happened every session.

I am thinking a fuel pressure problem?

951and944S

Sounds like it.
Whens the last time the fuel filter was replaced and/or the tank strainer been checked or replaced...?
Especially a steel tank on early cars, I would look at those first.

Have you tried running several laps with the fuel cap loosened....?
Maybe the tank isn't vented properly for some reason and it comes under vacuum after a few laps.

T

tc944

Thanks for the info. Filter looks very old, we will be replacing it and checking the tank strainer.

Never dawned on me to check for blocked vent, but I will check that also.

tc944

Quick update:

Spent some time checking over the car this weekend.

Checked flow from tank: good,
Replaced fuel filter: old one seemed ok but changed to be sure.
Checked fuel pressures according to Clark's, everything good.

I found that the band clamp on the throttle body side of the J boot had lost the bolt. The boot was still attached but was loose. Hopefully this will fix the low power problem. It could definitely explain the loss of power without any miss fires or rough running.

Waiting for the next track day to test.

T&T Racing

The loose connection is a source for unmetered air entering the intake manifold and making less vacuum pressure at the AFM. This reduces the amount of fuel injected because the AFM is not % open for the required demand. Should see an improvement.

tc944

UPDATE:

Finally figured it out. Feeling pretty stupid about what the problem was but posting this to help anyone else if a search brings them here..

We tried and checked everything and the car continued to have the problem. When we would come back into the paddock, the car wouldn't want to roll but by the time we got out of the car and jacked it up, the wheels would spin.
Finally, I stood ready with the jack and lifted the car as soon as it came in. When I tried turning the front wheels it took all of my strength to turn them. Thirty seconds later the wheels turned freely.

After a little investigation I realized that when I replaced the master cylinder, I adjusted the brake travel incorrectly with virtually no free play. Re-set the pedal with some play and the car did great.

Lesson learned.

Nowanker

Thanks for the update!
Too many times, someone has a problem, goes to the forums for help... and vanishes.
Great you were able to solve the problem, even better that you passed on your hard-earned knowledge!

StoogeMoe

So it was dragging brakes? Weren't your rotors super hot?