Author Topic: 1st 11 second pass  (Read 411 times)

hdinch

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1st 11 second pass
« on: October 15, 2019, 07:05:50 PM »
Well after a year away from the track made it back hoping to see an 11. Made a few changes including the fuel pump. Went to a RobbMC over the carter, both mechanical. I also rebuilt my Turbo 400 as it was starting to slip. Also had the converter slightly upgraded to a higher stall since I had the trans out and the shop would do one free change. Doesn't work as well with my overdrive however. So at the track the car lays down hard in 2nd gear. Check the fuel pump and pressure is down from 7 it was set at when I left home (drove it to the track). I made an adjustment back out to the track layed down in 3rd. I made one more adjustment to the fuel pressure putting it at 8.5 according to the engine gauge and knew thats the best I would get from a field adjustment. I went on to blow away first gear but made a solid pass. So last pass after many track delays and 2 hours later I get to make a final pass. My goal was to hit an 11. I had an early shift to 3rd and thought well no way...however my ticket said 11.980. So I made it! I was happy in the fact that I got there and I know it should have a couple more tenths with a good clean pass. My mph is still lacking.
1st pass 13.2
2nd pass 12.6
3rd pass 13.1
4th pass 11.9

https://youtu.be/xCOiQjvNsyI
 

FormTA

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Re: 1st 11 second pass
« Reply #1 on: October 15, 2019, 07:55:14 PM »
Looks good, sounds good. What gear are you running? You said overdrive, is that a gear vendors unit?
79 Trans am 301 (work in progress) LS swap n progress
79 Formula 301 (Work in progress)
67 RS Camaro (Work in progress)
See the recurring theme???

Names, Luke. If I hear anyone telling me they're my father....

hdinch

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Re: 1st 11 second pass
« Reply #2 on: October 15, 2019, 08:06:52 PM »
Running a 3:73 gear with a gear Vendors unit.  I really enjoy having the overdrive. Makes hwy speeds much more friendly.

b_hill_86

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Re: 1st 11 second pass
« Reply #3 on: October 15, 2019, 08:16:20 PM »
That looked like it ripped! SOMEDAY a gear vendors will be in my future.
-Brian-

1977 Trans Am 400 4 speed

NOT A TA

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Re: 1st 11 second pass
« Reply #4 on: October 15, 2019, 09:53:07 PM »
Nice!  Put some skinny's on the front and you'll be solidly in the 11's.
John Paige
Lab-14.com

Re: 1st 11 second pass
« Reply #4 on: October 15, 2019, 09:53:07 PM »

hdinch

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Re: 1st 11 second pass
« Reply #5 on: October 16, 2019, 05:20:20 AM »
  Good suggestion, I was thinking of some ways to try and get a couple tenths.  How much can a front tire change actually get you?  What is a good size to go with?  I have 15 inch rims on the back. 

NOT A TA

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Re: 1st 11 second pass
« Reply #6 on: October 16, 2019, 09:09:45 AM »
Probably a couple tenths depending on the weight difference. Wheel/tire weights and diameters make a bigger difference than just taking weight out of the car because you're also trying to increase the rotating speed of the mass. A bit of googling of "Moment of Inertia" (MOI) will give you  good explanations and formulas if you're interested.

I tested my bird at the strip with the 17" road course wheels/tires and a set of 15" Centerline Auto Drag's with Mickey ET Streets back to back at a couple different drag strips just because I like experimenting and the difference was about .4.   I'd run 14.3's on the Yokohama DOT R's and 13.9's on the Mickeys. Traction wasn't a problem with either tire but 60' times were lower with the slicks/skinny's because of the reduced MOI and weight.

Gotta get my moneys worth out of Photobucket and everyone likes old pics so here ya go!





 
John Paige
Lab-14.com

Jack

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Re: 1st 11 second pass
« Reply #7 on: October 16, 2019, 09:29:33 AM »
What do you have for an engine? Mods?




Regards, Jack

hdinch

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Re: 1st 11 second pass
« Reply #8 on: October 16, 2019, 09:49:06 AM »
Probably a couple tenths depending on the weight difference. Wheel/tire weights and diameters make a bigger difference than just taking weight out of the car because you're also trying to increase the rotating speed of the mass. A bit of googling of "Moment of Inertia" (MOI) will give you  good explanations and formulas if you're interested.

I tested my bird at the strip with the 17" road course wheels/tires and a set of 15" Centerline Auto Drag's with Mickey ET Streets back to back at a couple different drag strips just because I like experimenting and the difference was about .4.   I'd run 14.3's on the Yokohama DOT R's and 13.9's on the Mickeys. Traction wasn't a problem with either tire but 60' times were lower with the slicks/skinny's because of the reduced MOI and weight.

Gotta get my moneys worth out of Photobucket and everyone likes old pics so here ya go!





What size did you run up front?  I have 17's now as regular driving tires.  I put on the 15's drag radials for the track.  If I even got 2 tenths going to 15's in the front that would be worth it.  Looking online finding inexpensive rims https://www.amazon.com/American-Racing-Custom-Machined-5x120-7mm/dp/B000CIJNDU   Something like these either 15 X 6 or 15 X5.    4 tenths is huge! Nice Bird...72?

oldskool

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Re: 1st 11 second pass
« Reply #9 on: October 16, 2019, 09:49:17 AM »
Wow, side-pipes !  Haven't seen any of those in a long time.  They looked really at home on some of the Vettes. But, when they were really popular, guys put 'em on LOTS of different cars.

For drag fronts, the idea is lighter rotating mass AND smaller contact patch. The smaller contact patch along with high air pressure will reduce rolling resistance.

There are different types of front drag tires. The lightest are thin, light, & have a sort of a rounded tread, rather than flat all the way across. So, as air pressure increases, the contact patch size & rolling resistance decreases.

The Moroso Drag Specials come in 3 sizes. The shortest will be lighter & have a smaller tread width. But, they will also require that the tire, wheel, & brake rotor rotate faster than with taller tires. To say it another way, the shorter tires will be doing more rpm all the way down the track. How much ET difference would there be between the different heights ? I have no idea.

One problem with lightweight racing tires & wheels is that they are not cheap. So, low budget guys must go with something cheaper. The last pair of drag fronts I bought were street 185/65R15's. I chose these because they were the smallest cheap tires the tire store I used had, at the time. Don't remember the brand name of those tires. They were what i call "no-name" tires. They worked just fine on my 11 sec Ventura.

Drag wheels are real similar to drag tires. The super lightweight wheels are not cheap. Even the small fronts can cost over $200 each. So, for low budget guys, some of the Summit or Jegs wheels are probably the cheapest compromise.

Not sure, but Jegs MAY have the cheapest lightweight 15x4 front wheels available.

https://www.jegs.com/p/JEGS/JEGS-SSR-Star-Wheels/3663732/10002/-1

https://www.jegs.com/p/JEGS/JEGS-Sport-Star-Cast-Aluminum-Wheels/1231935/10002/-1

Here are some that are around $100 & less.

https://www.summitracing.com/search/part-type/wheels/wheel-bolt-pattern-app/5-x-4-3-4-in/wheel-diameter/15-in/price-range/50-100?N=wheel-width-in%3A3-500-in_3-750-in_4-000-in%2Bprice-range%3A50-100&SortBy=Default&SortOrder=Default

https://www.jegs.com/p/JEGS/JEGS-SSR-Mag-Wheels/3629201/10002/-1

These are $127.

https://www.summitracing.com/parts/are-vn5155461/overview/
« Last Edit: October 16, 2019, 10:50:30 AM by oldskool »

hdinch

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Re: 1st 11 second pass
« Reply #10 on: October 16, 2019, 09:53:29 AM »
What do you have for an engine? Mods?

Im running a 461 stroker, 850 carb and 3:73 rear.  Turbo 400 and a 3400 stall approx.  Roller cam and Kaufman heads.  Very street able.  Full weight car nothing removed. Also Caltracs and adjustable shocks with frame-rail connectors.  Thats about it.

Garry

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Re: 1st 11 second pass
« Reply #11 on: October 16, 2019, 12:57:43 PM »
The problem with mechanical pumps is they absorb heat from the motor. Heat kills HP. What you described in your first post could be caused by this. Congrats on the 11s.

Garry

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Re: 1st 11 second pass
« Reply #12 on: October 16, 2019, 01:41:21 PM »
If you really wanted to test my theory they sell secondary fuel systems for nitrous that fit under your hood.

hdinch

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Re: 1st 11 second pass
« Reply #13 on: October 16, 2019, 03:17:36 PM »
  The fuel pump I have now is a RobbMC rated to 1100 hp, I just need to put a regulator in the car and turn up the fuel pressure.  I bought this one instead of the 550 hp version in case I ever decided to put a 150 shot on the car.  So that should take care of it.  I just need to find a place to mount it once it gets here.

NOT A TA

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Re: 1st 11 second pass
« Reply #14 on: October 16, 2019, 05:35:47 PM »
I have 26 X 7.5 Mickey T 15's for front. Think the wheels are 3.5? Never run them on the street, drag only.

.4 was swapping all 4 wheels. The RR wheels were 17 X 9.5 and 17 X 11 with 315's out back and 275's up front. So swapping out just the fronts isn't likely to get much more than a couple tenths. This was with a mild 400 Pontiac, T-350 with stock convertor, and 3.73 rear gears with stock posi. 
John Paige
Lab-14.com

Re: 1st 11 second pass
« Reply #14 on: October 16, 2019, 05:35:47 PM »



hdinch

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Re: 1st 11 second pass
« Reply #15 on: October 16, 2019, 06:47:40 PM »
So something like this set https://www.jegs.com/i/JEGS/555/680251/10002/-1
                                      https://www.jegs.com/i/Mickey-Thompson/672/3002/10002/-1

A 28 tire would provide more value ET wise?  Not too concerned about reaction time.  A couple tenths is actually alot, and at this point I need to pull small adjustments where I can. My goal is to be consistent mid 11's.

oldskool

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Re: 1st 11 second pass
« Reply #16 on: October 16, 2019, 07:25:56 PM »
The Moroso tires are lighter. Not saying they are stronger or better, in any way. But they ARE lighter. Less rotating weight.

https://www.jegs.com/p/Moroso/Moroso-Front-Drag-Tires/746893/10002/-1

Re: 1st 11 second pass
« Reply #16 on: October 16, 2019, 07:25:56 PM »
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