First thing you need to do is get that body twist fixed. If thats your car in the avatar.

 

Run methanol or E85

 

Yep , some form of alcohol . Temps effect swing a lot less .

 

I can contest to this. With with water grains being the only factor with Alcohol. Just last weekend at Bandimere my truck ran 10.557-10.587 with a DA of 9500ish feet and 95deg temps with 30.00ish water Grains. Just a few weeks befor mu truck ran the same ET with 8400ish Da with 85ish temps and 45.00ish water grains.

My truck will almost Xerox time slips if I don't have a head or tail wind.

 

Alky
Loose convertor
Get that car to leave flat as a pancake without the twist
Guages for water/tranny temp and be sure to stage at same temp every pass..Alot of cars are very transmission temp sensative.

I always got car good and hot engine/tranny/rear end driving around track an hour before 1st round time trials so car can heat soak and cool to mimic between round temps/times to cool

Data data data, log every bit of weather from your weather station possible each pass, after awhiIle a pattern will show as to what affects car more, da, air temp, humidty, water grains.

 

Long stroke, over-gear, under-cam, under-cylinder head, synthetic fluids, water temp, trans temp, oil temp, intake temp, flat hood (or, at least, no outside air), 3 speed (no glide, unless REALLY light or REALLY fast), weight transfer, radial tire (only if the car NEVER spins with a bias ply first), fuel injection, oxygenated fuel. It's not just 1 thing, it's everything.

 

On the no outside air ? Why is this ? I pull the hood on my gas truck and have ducted outside air in my other . Seems a lot more predictable when monitoring weather.

 

How much should or does a car change from good air to bad. Mine don't seem to swing much more than .15 in the 1/4 from spring to summer....but I always blame the wind some cause good air at Indy usually means a headwind.

 

No one said I would have to know math.

 

After bracket racing 44 years I would say on a day that you described, everyone competitor suffers. It's a crap shoot to dial in.

 

The car does leave a lot flatter lately.
Problem is that my .60 has all of a sudden started to vary.
Used to be 1.53's 95% of the time.
Now it's 155's-1.58's
I think it's heat or engine related.
(Could a different heat range of spark plug possibly matter? That's the only I've changed recently)

I drive the car 37 miles to the track, so it's plenty heat soaked to start off with.

 

Problem is that my .60 has all of a sudden started to vary.
Used to be 1.53's 95% of the time.
Now it's 155's-1.58's

There's your problem. How old are the tires?

 

data log every thing is best . been times i got the call to run a gamblers race had to unload the car look at my notes (thats right no lap top) and have been with in a couple hundreds . and another note no hood scoop and run a open filter air cleaner

 

My cars all have ran consistant when at the finish line my EGTs are 1300. This worked on my 331 hp SRT4 Neon, my 350 hp nitrous fed Turbo GLH, and even my lowly...near stock...carbed Horizon. I also have the jetting on the Horizon set up so I can stay as little as a few seconds on the convertor or as long as a couple of minutes and the EGTS at the starting line are the same, but lower than the 1300. I also power brake it up after the dry hops to get all the slack out of the drivetrain, still a street driven car so not fully tied in. Another thing is that my water temps are always the same on every run, as are the trans temps.

 

Shoot my car on Alky jumps around when the humidity changes. Can't figure my problem out so I can't help ya with yours.lol

 

it could be fat if it slows a lot when the humidity goes up, mine might slows only .01 with a big swing in humidity, I leaned mine up a hair at Bristol and the rest the weekend car wouldn't change et unless the 60ft changed

 

it needs to be little fat, way fat is an issue, i leaned my up 10 sizes and it was great but it does show just over 1200* 1/8

 

Well the carb was built for a sbc 383 10.1 motor. My new motor is a sbc 383 13.1 with a slightly bigger cam. Was told that now it's rich, that sounds weird to me. But I'll try to lean it out a bit

 

should be good on a ngk 8, I ran 9s in my 15-1 406, now its 12.5 so im going back to 8s

 

I run ar134 plugs. Not ngk like I should I guess. The ar134 are shorter so that's why I like them. I tried the ngk number 8 and seen no difference so I went back to what help clear headers better

 

that works, no change means its close

 

Gonna lean it out 10 jets Thursday after a run and see if it picks up. If it doesn't change any mph then should I leave iit or keep dropping jet.

 

Are you saying you are gonna drop 10 main jet sizes? That is a LOT.

 

I'd leave it

 

that's like 1 step on alcohol, same as about 2 on gas, I've swung mine 20 and seen very little change

 

Yep 10 Alky isn't very much. Actually I only have a set of 154s I guess so it will only be 6 sizes down

 

J pat do you have a primary power valve if so could be ruptured if so get rid of it and put a block in it go up 12 jet sizes and see what happens I have NEVER ran P VALVES in my gas or alky carbs front or rear and have had pretty got results!

 

No they r both blocked and jetted at 160. Carb was perfect when apd built it for my other sbc. Only moved 8 numbers from early spring to late fall no matter what the weather did. On this motor as of now it has gone from 10.03- 10.22 so far.

 

never on alky, but I do have a q950 that is faster with front PV on pumpgas, not sure why, my holley hp750 I always ran blocked 78/80, some reason the 950 like it

 

when does it run the fastest

 

well looking back at my weather station it seems that when the vapor pressure is super low like in the 30s it seems to be fast. But if it goes to 50s it will slow. Bp and humidity I am still looking at, still getting use to logging weather data. When it went 10.03-10.05 the weather was super cool in the 50 degree range and the da was 2000 ft or so. But it has been 10.08 at 95 degrees and 4000 da. So I'm pretty puzzled. When using a my weather station what should u use to predict runs. DA, Humidity or VP. Those the the options it gives me. I was told not to look at DA on alky