need alky help

Old 06-29-2014, 10:44 AM
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cody6690
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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.
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Old 06-30-2014, 03:39 AM
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curtisreed
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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.

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Old 06-30-2014, 12:27 PM
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cody6690
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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.
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Old 07-01-2014, 03:44 AM
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On alcohol, in my experience lean tends to lose more e.t. than rich. Did the MPH fall off also?
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Old 07-01-2014, 01:41 PM
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cody6690
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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?
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Old 07-03-2014, 05:25 PM
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Keep going up. I'm at around .200 on my methanol 1050's.
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Old 07-06-2014, 08:23 AM
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cody6690
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What size motor are you running?
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Old 07-08-2014, 11:08 AM
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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.
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Old 07-09-2014, 10:37 AM
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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!
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Old 07-14-2014, 01:02 PM
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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
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