cody6690

We are running alky in a 548 ci BBC using a carb. Yesterday we made 1 time trial as we had problems on first time trial. On 2nd time trial around 3pm in high 80 degree weather car ran 8.92 in the 1/4. We went up for first round around 7. Car had exact same 60' but slowed up to 8.96. Does anyone know what would have made the car slow up as temps started to drop? Please only serious comments.

curtisreed

Do you track the weather data? If the air got better and you are close to being on the edge of you fuel / air ratio, then you could have gone just a bit lean. Do you have O2 sensors? Just a quick guess on my part.

Curtis

cody6690

No o2 sensor. But I did have someone else tell me that they thought it was lean. Just wanted to keep some more opinions before we made a change. Normally we keep track of weather. We did the time trial but didn't for first round.

curtisreed

On alcohol, in my experience lean tends to lose more e.t. than rich. Did the MPH fall off also?

cody6690

we lost less than a mile an hour so basically no. we are gonna make a change. we are at 172 jets right now thinking about going to 180. does that seem like an alright change?

jmarksdragster

Keep going up. I'm at around .200 on my methanol 1050's.

cody6690

What size motor are you running?

jmarksdragster

It was dyno'ed at BLP on an 800 HP BBC, 540ci. It's also been on the track in a 700 HP SBF. With methanol you need a lot of fuel through the boosters.

cody6690

OK so we are in the same ball park then. We are gonna make the change and I'll let everyone know what happens. Thanks again!

cody6690

Changed jets from 172 to 180. and car still slowed up. temps didn't really change. And they glued the track between each run.

Time Trial 1- 1.2539 60ft; 5.6709 1/8 mile; 121.00 mph; 83°F; 42% humidity; 2:48 pm
Time Trial 2- 1.2602 60ft; 5.6783 1/8 mile; 120.59 mph; 84°F; 45% humidity; 4:00 pm
Elimination 1- 1.2709 60ft; 5.7118 1/8 mile; 119.98 mph; 84°F; 52% humidity; 5:13 pm
Elimination 2- 1.2691 60ft; 5.7259 1/8 mile; 119.67 mph; Don't have temps; 6:18 pm