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620 Land Speed Record

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Is it the 280zx fs5w71 that had the close ratios? Or was it the one with steep OD?

 

 

All of them are 1:1 in fourth AFAIK.

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The '79 280zx was a regular mid ratio same as the previous 280z and the early 620 5 speed and the 810/Maxima. The same. The '80-'83 had the close ratio 1 through 4 gear set. The '80 had a 0.76 over drive and the '81-'83 had the 0.745 over drive. All have the same 1:1 4th

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We currently have a transmission on the shop floor that appears to have extremely similar gearing to the NIsmo box used on the 510 racing applications with a 1:1 5th gear.  The difference is that its shorter, lighter, more durable, readily available, and FAR less expensive.  All I have to do is make the adapter plate and get the clutch to work, and make it fit in the truck, and build a scatter shield.  No biggie, right?  Is it worth the effort for our first year on the track?  Considering our first year may only be a run at the Maxton Mile if salt conditions don't improve, then yes it matters!!!  On the salt, yes it may mean the difference between 129 and 131 mph, success or failure.  

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Today was a boring day of head porting.  It doesn't seem like much, but I roughed in the intake ports, so they are ready for flow bench work.  I initially started by boring each port on the mill to set the port heights (as measured from the head gasket surface).  You can see the step bore in the first photo.  All ports initially cut to 1.485", room to go past 1 1/2" as needed to get the intake/exhaust flow numbers to correspond as needed.  The first exhaust port was also roughed in, so the middle ports could be sized matched next.  

Keep in mind the photos are roughed-in ports, not the pretty CNC look I want when they are all finished.  This is simply a place to start on the flow bench, as a benchmark.  I had no idea how much porting material is actually in these heads.  I can go MUCH larger than this without concern of breaking into water, and likely will once I figure out flow ratios.  Its all about HP, not drivability.  

 

[/url]">http://

">http://datsun%20portin1_zpsaqs0slz8.jpg

[/url]">http://intake%20port_zpsznyz0umv.jpg

[/url]">http://exhaust%20port_zpsromne9ib.jpg

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Just found this thread. Cool build. :thumbup:

No pictures though. I tried to click on them and it says you moved the photos. 

 

Damn photobucket anyway. 

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I fixed it.  Photobucket deleted my images because I had an ad blocker in place when I loaded them.  I had to as they locked up my computer.  Jerks.  

 

So here's the block, ready to go.  Bored and line honed, straps on the mains.  Apparently we're putting together 2 engines, my design, and my engine builder's design.  Until there was a dyno challenge at hand, no progress was being made.  Now the goal is to have 2 running motors by the end of February.  Mine will be a blend of torque and hp, in the 4000-9000 rpm band.  My engine builder (yes the one who let me down prior) is going for all out hp.  We'll share the same intake and 50 mm dual DCOEs.  

This should get interesting.

  [/url]">http://http://s1148.photobucket.com/user/distributorguy/media/datsun%20block_zpsszyz4wws.jpg.html'>datsun%20block_zpsszyz4wws.jpg

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Have you concidered a full belly pan? You could play with air flow there as well. 

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Yes of course.  Not legal in Production class.  A full belly pan is defined in the rule book as covering more than 50% of the undercarriage, if you hear what I'm saying...  Aerodynamically I just don't know what area is best served by covering it.  I suspect the tunnel area would be the best place to add "an oil cover to prevent leaks from hitting the salt." 

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The team came out last night and really put in a good effort.  Lots of nitpicky chassis work done, Heavy duty tow hook made, and a few stickers plastered on the truck for those vendors who helped us in our venture.  We fit the driver in the truck and verified he'll be able to reach all dash switches when in full harness with arm restraints on.  Progress!!!

 

Getting tired of porting.  So many shavings, so much time...

[/url]">http://porting%20dust_zpsvn3qwmd7.jpg

 

Needed a break from the grinding and installed the door net.  Another Bonneville requirement.  

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/doornet_zpsfgnu2kjo.jpg.html'>doornet_zpsfgnu2kjo.jpg

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Spent a couple more hours on the truck today.  Patched a large hole in the box floor where someone had previously mounted a battery.  Also modified and reinstalled the floor sections that were cut away to weld the roll cage to the floor.  I'll just use seam sealer to make the box air tight, as who knows when we may need to cut them back out for ???

[/url]">http://box%20patches_zpsbcrstvek.jpg

 

Also mounted a large tow plate as required by the rule book.  

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/tow%20hook_zpscwsq68zi.jpg.html'>tow%20hook_zpscwsq68zi.jpg

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I think you need a Rat-N-Wrenches to adorn that grill. 

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If you look up when a chevy S10 had a record in the larger displacement class, you will see that they only run a bed cover over the rear half of the bed. The idea is that it allowed a larger diameter of air to swirl behind the cab.

I always thought that if the front portion of the bed had an upside down arch shape, it would inhance the swirl.

 

And the also ran a large dry ice cooled intercooler in the covered portion of the bed, and piped it to the intake on the engine.

 

This was 15-20 years ago.

 

I've also seen people duct high pressure air from in front of the windshield (from the oem grill opening there), through the car's interior, to the back of the car, to lessen drag. Ducting was huge.......

 

It looks like your on the right path with gearing, to be near max rpm on the engine, at your target speed.

Does the production class rules allow you to run a quick change rear end ?

That would making minute gear changes in case you are just a tad off, and those rear ends, and gear sets are all over eBay for cheap.

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We can run any differential. as long as its the same "type" as original, in this case meaning a straight axle, not IRS.  It would be nice to run a narrower axle as well, so we can switch back and forth between LSR tires and something with grip for the Maxton Mile.  I'm not sure what you mean when you say QCRs can be found cheap?  Cheap usually means damaged goods, not inexpensive.  

 

Venting is now very limited in production class.  We do have big vents running from the cowl into the interior.  I will also get back to work on the hood scoop design now that our 2nd pair of hood pins arrived yesterday.  We're allowed an 11" tall hood scoop, but have to weigh air flow, engine bay cooling, drag, and aesthetics.  We haven't come up with a great way to inspect air flow with different height scoop designs to effectively decrease the 45 degree wall called a windshield.  

 

The swirl behind the cab is tricky.  It applies a negative pressure to the back of the cab (bad) but can also provide downforce to the box floor (good.)  With all the research that has been done, I've seen most trucks running the front 1/3 of the box open, although most now run a full cover.  We were thinking about running the cover up to the cross bracing, with a removable front section for testing.  I have yet to see anyone run the tailgate partially down and fixed like a wing - there are no rules against it.  Rules state that you can run with or without a tailgate, up or down.  More experimenting.  

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The 620 has a heater that can be removed if allowed or set on cool to allow cowl air into the cab. There re also air vents on each side of the dash that would also bleed air from the cowl when opened. Hell pull the ducting hoses off so the heater and grills don't restrict the flow.

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I believe Mythbusters did a show on pick up tailgates.  If I remember correctly, long bed trucks benefited from tailgate down,  Short bed trucks benefited from tailgate up.  Short bed trucks generated a vortex by the blocking action of the tailgate, the vortex swirled behind the cab, and stayed with the truck, and helped guide slipstream air over the tailgate.

 

Now, how that translates to a 620, Well, as they all say, your results may differ.

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The interior is gutted to make room for the cage.  Gutted.  There's a shell of a dash, with metal duct hoses running from the cowl to the dash vents where the air can be directed to the driver.  Fresh air in the cab is required in case the Halon extinguisher is used.  A small 12V electric fan will be mounted under the dash pointing at the driver.  The Cool Shirt cooler sits on the passenger side floor, circulating cold water through the driver's safety suit.  

 

Today I just made a custom trailer hitch, to mount our push bar from.  Even if we can fit a starter to the engine, It will be nice to have the option if needed.  The band saw is chewing on the actual push bar right now.  The trailer hitch is all but touch-up painted in place.  We'll use a roller on the end of the push bar to prevent side-to-side movement of the push truck from shoving the race truck left and right.  Essentially a wooden pad will be mounted to the snow plow hitch on the front of my Superduty Ford to mate with the push bar.   [/url]">http://http://s1148.photobucket.com/user/distributorguy/media/hitch_zpsd5nhfghj.jpg.html'>hitch_zpsd5nhfghj.jpg

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Not much progress.                                                              datsun%20sunset_zpsbnq9zfwp.jpg

 

 

Thats OK.

 

     CAN WE HAVE MORE OF THESE?    :thumbup:    We need a walk around as it stands. And more interior. Your dash is bad ass!

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hitch_zpsd5nhfghj.jpg

 

Why can I see light between your lowering blocks and leaf springs? .. the U-bolts also look like they could be for a larger diameter axle tube?

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Why can I see light between your lowering blocks and leaf springs? .. the U-bolts also look like they could be for a larger diameter axle tube?

 

This is a good call INDY510, something looks like it is mounted wrong, the U-bolts don't look tight either, there is supposed to be a overload bumper on top of the axle under the u-bolts that also aligns the u-bolts so they align straight up and down, the ones in this photo look tilted outwards at the top.

Shit could get real loose if something moves and settles on to the alignment peg/pegs, the right side looks outright dangerous to me, the spacer didn't drop on to the alignment peg/bolt head sticking out of the leaf.

 

The interior is gutted to make room for the cage.  Gutted.  There's a shell of a dash, with metal duct hoses running from the cowl to the dash vents where the air can be directed to the driver.  Fresh air in the cab is required in case the Halon extinguisher is used.  A small 12V electric fan will be mounted under the dash pointing at the driver.  The Cool Shirt cooler sits on the passenger side floor, circulating cold water through the driver's safety suit.  

 

Today I just made a custom trailer hitch, to mount our push bar from.  Even if we can fit a starter to the engine, It will be nice to have the option if needed.  The band saw is chewing on the actual push bar right now.  The trailer hitch is all but touch-up painted in place.  We'll use a roller on the end of the push bar to prevent side-to-side movement of the push truck from shoving the race truck left and right.  Essentially a wooden pad will be mounted to the snow plow hitch on the front of my Superduty Ford to mate with the push bar.   [/url]">http://hitch_zpsd5nhfghj.jpg

 

 

Why can I see light between your lowering blocks and leaf springs? .. the U-bolts also look like they could be for a larger diameter axle tube?

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A week ago I got the springs back from being de-arched another 3", so we could ditch the 3" lowering blocks and go to 0-2" blocks as needed with additional weight.  In a rush to get the truck back on the ground for our Thursday night team meeting, I just quick bolted them together, and to be honest my deep well socket would only go that tight.  I have a different set of U-bolts, but they were in cold storage (hovering around 0 degrees here.)  When the wind chill is back above zero I'll go grab the misc. parts we need to finish about a dozen small projects for Thursday again.  The U-bolts are the right size, just skewed from hanging under the axle loose.  Every fastener on the suspension is aircraft locking, so there is NO worry of the u-bolts coming loose once they are properly installed.  That'll happen either when the floor warms up or when I can get back on the hoist in the unheated building (much easier!!!)  I'm surprised no one commented that the u-bolts hang lower than a flat tire would allow for ground clearance.  That would be a catastrophe!  

Besides, the photo was of the hitch.  You weren't supposed to notice.... :devil:

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Here's the finished push bar.  

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/pushbar_zps4lwey9f9.jpg.html'>pushbar_zps4lwey9f9.jpg

 

I'll try to take more interior photos, but that's really, really difficult.  Lighting sucks and its severely cramped.   The back lexan window still has film on it until we're done welding the final gussets on the cage, if we ever finish?  

 

If anyone makes the "rat and crossed wrenches" in decal form or in a steel laser cutout, we'd proudly represent!  The grille skull is not allowed per rules because it block airflow, but it unclips in 2 seconds.  

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I'm not sure who has the file or actually cut them out, but a few people received a laser cut metal rat and wrenches for different aspects of the Canby raffle truck last year.

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There are a couple engine machining projects I don't have the equipment to perform, so while I'm waiting for parts co come back, I'm getting the rest of the engine ready.  Here are a few new photos just for the fun of it.  

Rebuilding and recurving the distributor fro the 15:1 compression.  

[/url]">http://distributor_zps1nkripiy.jpg

1600 water pump and pulley is lighter and slower turning than the later clutch type pump.  Offset appears to be identical.  

[/url]">http://cover_zpsxbknslan.jpg

Shaved flywheel minus 7 1/2 lbs.  Still heavy, but better.  

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/datsun%20flywhgeel_zpsj3wv7y4e.jpg.html'>datsun%20flywhgeel_zpsj3wv7y4e.jpg

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