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exhaust open or capped
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Wed Mar 29, 2006 10:59 pm    Post subject: exhaust open or capped Reply with quote

Test and tune day with local group coming with private track rental. Sounds like fun! On our Z site, we have 400 whp running through single 3" . Am I going to gain anything by running open exhaust? Forget long tube tuned primaries. In a tight chassis compromise is the word. Short 1 3/4, with 12" turnouts all mandrel 2.5s into 3" with Aerochamber. Its as good as it will get, but I want as much mph as possible. Worth it? Jetting recommendations open vs capped? Been years since I dragged, more yet with open exhuast. Also any psi recommendations on running Nittos 555 drags? 255s will get a good Z in the 1.50s 60', and low 11s. Unfortunately I have 225s. Don't laugh, but I'm thinking of using 2nd to start where I can hit high 3s 0-60 (24 psi w/ 2500 rpm drop) Starting in first yeilds low 4s. 2nd gear will take more hp, and sticky track might surprise me. ?? Not looking for any world records, just to make some noise and have fun.
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SMOKEmUP
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Joined: 30 May 2002
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1979 Chevrolet Camaro

PostPosted: Wed Mar 29, 2006 11:06 pm    Post subject: Reply with quote

Open exhaust you'll pick up 2 - 3 tenths.

I run my Nitto's between 14 - 16 psi at the track. They don't like a long burnout. Just enough till you start to see the smoke on the sides, then pull up and stage, do not do a little test launch (if you do you just wasted your burnout on the test launch).

I would try starting in first to see how the car hooks. If no traction then try starting in second.

Good Luck! Let us know how you run, I'm interested to hear.
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Thu Mar 30, 2006 9:52 am    Post subject: Reply with quote

smokemup wrote:

Good Luck! Let us know how you run, I'm interested to hear.

not 'till May, I'd bet the air will be pushing 7000+ by then. Maybe being optimistic, I'm guessing mid 12s, 1.7s traction maybe 11s?? Is NHRA tech going to have words with me on a 11 sec run?? mph gussing mid to high teens. G tech lately has shown 123, but we all know they run a bit high. Ha last time I ran was with crap tires and only 7 psi when I first had the Procharger, V6 4.3 2.7 60' Embarassed 105mph high 13s. Eventually got up to 16 psi, but never made the drive back to the track for timeslips. I'm after MPH for hp figuring. This is NOT a drag car, way too stiff. You're all welcome to guess.

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SMOKEmUP
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1979 Chevrolet Camaro

PostPosted: Thu Mar 30, 2006 10:17 am    Post subject: Reply with quote

Refresh my memory on the engine combo and how much it weighs and I'll throw out a guess.
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Thu Mar 30, 2006 11:18 am    Post subject: Smokem up's crystal ball! Reply with quote

OK I know how you love to crunch the Car #sLaughing
383 6" rod, Static CR figured to 10.6:1 with SRP forged, Isky Solid roller 244@.050, .614 on intake/583 exhaust, 108 lsa, Vic Jr, Holley HP750, Off the shelf 68 cc AFR 195s. 1 3/4 short headers, 6 speed Tremec, 2.97/1.94/1.35/1. 3.55 rear. Last time I scaled car with me and things usally rolling around inside, 2720. 225 50 16 Nittos. Racing at 5800 typically around 55-70 degrees second week of may. I'll be jetting for around 7000 ft if its cool. Looking at some racers logs from may june density altitude was 8300-9000+..what they say is a "typical" race day, 70 degrees. Probably running full exhaust, but might take off to see. Car has stiff springs, f/r sway bars. You should be able to nail this one!... and don't hesitate telling me I'm full of $#!+ and it will be lucky to turn a 15 flat. Here's my guess 12.50/116.

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SMOKEmUP
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1979 Chevrolet Camaro

PostPosted: Thu Mar 30, 2006 11:46 am    Post subject: Reply with quote

My guess is 11.66 @ 122.3 mph for a 8300' DA. Provided you can get it to hook up.
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Thu Mar 30, 2006 12:24 pm    Post subject: Reply with quote

smokemup wrote:
My guess is 11.66 @ 122.3 mph for a 8300' DA. Provided you can get it to hook up.

Laughing I like your prediction a lot better. I'm trying to be conservative, been guilty of guessing the other way. I have the usual hard lines, battery tie down coolant catch, 11.99 requires roll bar, suppose they'd toss me out?

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1979 Chevrolet Camaro

PostPosted: Thu Mar 30, 2006 12:43 pm    Post subject: Reply with quote

240Z8 wrote:
smokemup wrote:
My guess is 11.66 @ 122.3 mph for a 8300' DA. Provided you can get it to hook up.

Laughing I like your prediction a lot better. I'm trying to be conservative, been guilty of guessing the other way. I have the usual hard lines, battery tie down coolant catch, 11.99 requires roll bar, suppose they'd toss me out?

Yep!
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240Z8
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Location: Colorado
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1972 Datsun 240Z

PostPosted: Thu Mar 30, 2006 2:22 pm    Post subject: Reply with quote

Cool just called for tech new rules, dropped to 11.49 for roll bars etc. Stock set belts OK, putting in the loop this afternoon.
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1979 Chevrolet Camaro

PostPosted: Thu Mar 30, 2006 3:01 pm    Post subject: Reply with quote

240Z8 wrote:
Cool just called for tech new rules, dropped to 11.49 for roll bars etc. Stock set belts OK, putting in the loop this afternoon.

That's IHRA rules. I thought you said this was an NHRA track? If so did NHRA change the rules?
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85GMCstreetbeast
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1985 Chevrolet GMC

PostPosted: Thu Mar 30, 2006 3:22 pm    Post subject: Reply with quote

I say do some runs capped and then do some runs uncapped. B/c i know of cars that run slower uncapped....
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Thu Mar 30, 2006 6:23 pm    Post subject: Reply with quote

smokemup wrote:
240Z8 wrote:
Cool just called for tech new rules, dropped to 11.49 for roll bars etc. Stock set belts OK, putting in the loop this afternoon.

That's IHRA rules. I thought you said this was an NHRA track? If so did NHRA change the rules?

Its NHRA, Home of the Mile High Nationals! http://bandimere.com/home/index.php I was told they changed it last year. BTW if I run your predictions I'll name my next kid after you... Smoke Jr Wink

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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Thu Mar 30, 2006 9:35 pm    Post subject: Reply with quote

Quote:
I was told they changed it last year. BTW if I run your predictions I'll name my next kid after you... Smoke Jr Wink


That is the best! How bout Little Smoke When the rings go south? Embarassed Adam
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240Z8
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Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Sun Apr 16, 2006 6:12 pm    Post subject: Reply with quote

af2 wrote:
Quote:
I was told they changed it last year. BTW if I run your predictions I'll name my next kid after you... Smoke Jr Wink


That is the best! How bout Little Smoke When the rings go south? Embarassed Adam

Good one, Adam! Guy with 71 Z car, 383, 25 lb heavier, 200 heads, slightly smaller cam, same intake, 750 carb, full length headers, 700R4 just ran a 10.8 @ 125 with a 1.49 60' w/ drag radials. Dallas area. Hmmmm, that's a mile below us.

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Bocephus027
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1972 Ford Mustang

PostPosted: Sun Apr 16, 2006 8:15 pm    Post subject: Reply with quote

240Z8 You going to Test day, Wed to run your car capped and uncapped?
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