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620 Land Speed Record


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#81 ByStickel

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Posted 07 August 2015 - 02:54 PM

If it were me, I'd channel my inner Smokey Yunick and I'd cheat like crazy.

 

You could easily chop the top by half and inch and have nobody notice, angling the roof for better aero. And who would realize if the truck happened to be an inch and a half narrower than stock? I say nobody. Cheating is a lost art, and you need to help bring it back!

 

Seriously though, would a King Cab be eligible? I'd imagine that the longer roof would have slightly lower drag, along with putting some mass slightly farther back. Especially when you'll be chopping the top...

 

Good luck with it!.


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#82 mrbigtanker

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Posted 07 August 2015 - 03:10 PM

Sand blasting generates a lot of heat. Unfortunately the worker didn't know this.


What Mike said is absolutely right, it's frowned upon to even do that to body panels period..and if your going to paint not nessecary.

#83 distributorguy

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Posted 14 August 2015 - 04:21 AM

The truck was blasted to remove rust - we use a LOT of road salt up here and many bad things were hidden under the paint.  

 

Nothing new to report here, other than some updated plans for next year.  Now we have time to implement a few more items to make the truck faster.  And I'm practicing at tuning Weber DCOEs on my MGB.  I hope to have that on the dyno before the white crap falls on us in several weeks.  Then I can move on to finish two more small projects before the truck goes back in the shop for the winter.  I also want to make it street legal, so we can debug chassis issues locally, and make it handle for some road race courses - WRL stuff.  I figure a watts link in the back could do wonders with a 4-link, coil over front shocks instead of torsion bars, and a few other items on the wish list.  

 

If anyone has a good 3rd member with a VERY low gear ratio (high numerically) that's ready to run, I'm interested...



#84 datzenmike

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Posted 14 August 2015 - 05:12 AM

The 720 truck ran as low as 3.70, 3.545 and 3.364 in the H-190 size.


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#85 distributorguy

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Posted 19 August 2015 - 06:25 AM

Low ratio, high numerically.  Like a 5-something.  Defies convention, but we are after a specific record and I want to cap out top speed in 4th gear, then drop into 5th and go as far as we can.  Something in the 5.00-5.25 range would be ideal for us for 5th gear.  In 4th gear we'd need a 4.23 or close.  I'd REALLY like to use a 5 speed with 5th as 1:1 but have NO idea where to find that animal.  NISMO made a few...  



#86 datzenmike

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Posted 19 August 2015 - 06:31 AM

All 620 standards were 4.375 except the '79 which was 4.11.. Early '73-'74 L16/18 automatics were 4.625. Some 720 trucks had 4.375


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#87 distributorguy

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Posted 19 August 2015 - 09:09 AM

Funny... our truck has a 4.11 but the parts truck has a damaged 4.375.  Does anyone have a good 4.375 3rd member they'd like to ship to MN?   $$$



#88 510farmer

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Posted 19 August 2015 - 06:04 PM

You know you were talking about drag , not knowing if the tailgate should be up down or half way
They did a study or test on myth busters about that ( I know myth busters Yada yada ) but there test prove that the gate up actually provided less drag due to that when the airflow came over and went down it actually created some type of a air pillow in the open part of the bed and pushed the air over faster over the tail gate
When they had it down it had a few more percentages of drag due to actually elongating the length of the truck
I'm sure in your quest pushing through the wind is more concentrated on the front end
Are you guys aloud to get out the 200mph tape and tape up seams and openings?
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#89 sebpv

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Posted 19 August 2015 - 06:15 PM

At all time a vortex is created in the bed

With the tailgate up: The vortex forces the air to glide over the vortex and tailgate.

With the tailgate down: The vortex entrains more air which creates more drag on the truck, lowering the fuel economy
Blame my french side if you don't understand

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#90 distributorguy

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Posted 20 August 2015 - 07:08 AM

We get to run a bed cover, to eliminate a large amount of the vortex, plus the roll bars will help disturb that vortex from occurring.  No gaffer tape allowed on seams in production class.  But we can "tighten up" seams to the tightest possible production standards.   :thumbup:  Its safe to say the paint is getting scratched when we lift the hood.  

 

The tailgate test is a HUGE function of bed height versus cab height versus length.  Mythbusters only proved the myth for their one model truck they tested.  There are extensive wind tunnel studies online to traipse through if you're interested.  



#91 Stoffregen Motorsports

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Posted 20 August 2015 - 07:44 AM

A Watts Linkage is the best way to control your roll center, so that's a nice way to go. You should first do some math or use an online suspension calculator to see where you may want your roll center, because on a watts linkage, the roll center is the middle of the pivot, so if you get that location wrong, all bets are off.

 

Why not convert to a Toyota rear axle? 4x4 axles come in 6 lug and 3 different widths. The early '79-'85 axles are 55" wide with small drum brakes and small axle tubes. '86-'95 had 58" width and larger axle tubes. The '96-'04 Tacoma rear axle had three differential options including an OEM electric locker which would give you both consistent track manners and on-road driveability.

 

Toyota 5.29 R&P sets are cheap at only $200 a set.

 

The used axles range in price from $50 for an early axle or a Tacoma axle with locker for $400.



#92 distributorguy

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Posted 21 August 2015 - 04:22 AM

If I get around to building a Watts linkage, I'll make the roll center adjustable since mathematically correct may not be how I want the truck to handle.  This game is all about traction combined with rolling resistance - not an easy pairing.  

 

I don't know the width of the factory axle off the top of my head, but I only have room to go narrower, not wider.  Since the factory gear ratio will work for now (until we convert to a 6 speed tranny with custom gearing) it makes no sense to switch.  



#93 DaBlist

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Posted 21 August 2015 - 09:33 AM

Once you know what RPM your HP and torque peaks are you can gear for that. No benefit only losses to spinning gears, drive lines etc, faster than you need. Some manual transmissions use more power to spin in overdrive than a direct 1 to 1 ratio so high numerically gears is usually the wrong way to go. Numerically high rearend gears also have more mass to spin than a ratio in the threes.

When you are going for a record you need all the little things in your favor.


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#94 distributorguy

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Posted 21 August 2015 - 10:08 AM

Wind resistance is our biggest challenge.  Its essentially going to rob us of a potential 35 mph.  The record holding 240Z just broke their record by 6mph by finding an old NISMO gear box that's close ratio, 1:1 in 5th.  I have a game plan when the budget allows that will better that by a gear.  I'm hoping that 5th gear will give us a short surge of speed at the end of the run.  I'm gearing for 135-140 mph in 4th at 8k, cam peaks hp at 8500.  Torque at 2000 rpm should exceed max torque on a stock motor, peak near 5000.  We'll consistently run 4500-8000 rpm range, push it further if we need to.  Keep in mind most folks are gearing for over 200 mph.  Think 1/8 mile drag racing for the speed we're trying to achieve, but with enough durability to run for 3+ miles at WOT.  

 

When we convert to a modified class in the future and all cards are off the table, then we go 2.00 diff, 800-1000 hp, and LONG gearing in the tranny.  Until then, we're building a sprint car.  



#95 distributorguy

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Posted 17 September 2015 - 04:43 PM

Not much progress.  We're trying to assemble a game plan for more upgrades and how to get the engine done to our liking.  Straightened up a couple body issues last night, otherwise its been in mothballs. 

 

Photobucket issues.  Hopefully one of these works?

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http://i1148.photobu...zpsbnq9zfwp.jpg

http://<a href="http...zfwp.jpg"/></a>



#96 datzenmike

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Posted 17 September 2015 - 07:35 PM

 The record holding 240Z just broke their record by 6mph by finding an old NISMO gear box that's close ratio, 1:1 in 5th.  I have a game plan when the budget allows that will better that by a gear.  I'm hoping that 5th gear will give us a short surge of speed at the end of the run.  I'm gearing for 135-140 mph in 4th at 8k, cam peaks hp at 8500.  Torque at 2000 rpm should exceed max torque on a stock motor, peak near 5000.  We'll consistently run 4500-8000 rpm range, push it further if we need to.  Keep in mind most folks are gearing for over 200 mph.  Think 1/8 mile drag racing for the speed we're trying to achieve, but with enough durability to run for 3+ miles at WOT.  

 

When we convert to a modified class in the future and all cards are off the table, then we go 2.00 diff, 800-1000 hp, and LONG gearing in the tranny.  Until then, we're building a sprint car.  

 

1:1 is 1:1 in any transmission.

 

A 4 speed in top gear will be exactly the same as that NISMO DD 5 speed in fifth.


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#97 distributorguy

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Posted 18 September 2015 - 04:37 AM

You CAN achieve a higher top speed if the gearing to get there is improved.  You need EVERY gear to play along.  Too large a drop between 2nd and 3rd for example will result in a bog by falling out of the hp range of the cam, and these are very temperamental motors - purpose built.  Our power band, by design, will be 5000-8500 rpm.  If we can stay above 6000 rpm at all times, we will be faster, helping to keep our power output higher than our wind resistance.  That's where a close ratio 5 speed can pay dividends (mostly from the 4-5 shift), and I think we have an option on the table. We may have 3 miles to pull off a record, but it goes by pretty quick!  We need to be near top speed at 1 mile, and this is NOT built as a drag strip truck!

 

Yes, 1:1 is what it is.  The journey to get there matters however.  If 4th gear is 1.2:1, we can have that leverage to overcome drag much better than if its 1.8:1.  Then 5th gear is icing on the cake - a free "push" to a record.  



#98 distributorguy

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Posted 18 November 2015 - 01:12 PM

Only a little cosmetic progress on the truck since July.  Since we're in "production class" no body modifications are allowed except a hood scoop up to 11" tall.  I'm still working with that.  

Photobucket hates my spam filter and is fighting me.  hopefully one of these works:

http://i1148.photobu...zpsyzjraydr.jpg

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[/URL]">http://datsunstripes_zpsyzjraydr.jpg



#99 FlyinPat

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Posted 18 November 2015 - 07:04 PM

So awesome! Keep up the good work!

#100 ]2eDeYe

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Posted 19 November 2015 - 10:32 AM

Looks great :cool: 


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