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620 Land Speed Record


distributorguy

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This afternoon's long delayed project:  regrind the rocker arms.  While I was at it, I lightened the tips and REM finished them.  Or at least a non-trademarked version of REM finishing.  

 

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/Datsun%20project/D85FB5A4-BB84-45F8-914C-0756BE6C1F65_zps6e6nr3sj.jpg.html'>D85FB5A4-BB84-45F8-914C-0756BE6C1F65_zps

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I just spent the last couple hours mapping out cam and events, using a new Cloyes chain, tensioners, and the 8-hole gear.  I found that holes "A" and "B" seem promising at 111, 114 intake centerline.  Given the cam numbers, which are not what I ordered nor what Schneider put on the cam card, 114 looks the best.  Lower duration, lower lift, lower power.  Sad.  Frustrating.  This won't let us set a record, unless we get everything else right.  It totally screws with the port work on the head too.  Its a $10,000 mistake as the whole trip out to Bonneville was relying on my cam numbers as part of the equation.  At this point there's no way to have a cam ground, heat treated, and set up for our head in time.  Roughly 100 days including assembly, valve shimming, dyno tuning, etc...   I guess we have a goal for next year.   :poop:

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The adjustable timing gear arrived Saturday, so the head went on with the Nismo gasket and ARP studs.  I made a non-spring loaded timing chain tensioner, with a solid brass spacer drilled for oil, adjustable with a stud/nut.  Backlash is about 1/3-1/4 degree at the cam with no oil pressure present.  With this, we can radically change cam timing or gears without worrying about the tensioner popping out of place.  

The adjustable cam gear worked out well - with it being full clocked to the right being at 113.5 (I was shooting for 114)  Intake centerline, and I found the sweet spot for 110 in between marks on the gear face.  When I found the 110 mark, I removed the gear and drilled it for a roll pin through the face to hold the setting, and to be able to reset to that number easily.  

 

Now to deal with the crank scraper and get the oil pump/pickup/pan installed.  Then to dialing in the carbs and linkage so we can fire it up.

 

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/Datsun%20project/7338672A-4ED6-492C-8445-BA0C3EC474B5_zpsgcx6nsyq.jpg.html'>7338672A-4ED6-492C-8445-BA0C3EC474B5_zps

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A solid spacer and a moderate adjustment will allow the oil pressure to take up the slack and act as a cushion instead of the spring.  It was a 30 minute project to mill, drill, & tap the cast iron housing, then make a small brass plug that's drilled end to end and cross drilled for oil pressure.  Now I can swap gear positions in minutes with no spring to frustrate me!  I still have a nice oak block that drops in the hole to hold the chain, but its not fighting a spring.  

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Here's the crude but effective crank scraper I made up just before installing the oil pan last night.  We're also trying to get some photos of cage details pre-approved.  Its a slow process since it all has to be evaluated by a committee.  

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/Datsun%20project/D47373AD-B7F4-44E6-8ECA-1F89AF4C1393_zpskqipnnao.jpg.html'>D47373AD-B7F4-44E6-8ECA-1F89AF4C1393_zps

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  • 2 weeks later...

The truck went to its first car show today.  The 2017 Intermarque Spring Kickoff.  Its the only all-import show in our area.  

We were placed in an area with several other race vehicles.  I drove it 2 blocks from the trailer to its resting place and drew quite a crowd.   :thumbup:

 

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/Datsun%20project/B127762B-216F-4907-A9A7-24AF4F7F3DC3_zpses2dalwn.jpg.html'>B127762B-216F-4907-A9A7-24AF4F7F3DC3_zps

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Mike, the goal is to "scrape" oil as the crank rotates.  Keep the oil mist and spray in the pan instead of lifting it up into the reciprocating assembly.  The added weight of oil adhering to the rods/pistons not only slows acceleration, it adds to any imbalance.  The opposite side is left open for drainback.  Think about how air swirls around the crank as it spins over 8000 rpm.  Oil follows air.  The shearing effect of the crank scraper also has a lot to do with airflow and turbulence in the block, as well as trying to help keep the pump pickup submerged.  The oil dripping from the bearings needs an open window to get back into the pan, and you can use the swirling air around the crank to help push it down.  

My system is ultra-simple.  There will be plenty of opportunity to redesign or add to it for next year.  

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Was thinking if one is good, two would....? Mostly it would block air movement down into the pan. The other side doesn't have to totally seal just channel oil splatter away from the crank and drip into the pan through vent holes near the block side. 

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Last night we got a fair amount of work done on the truck.  All the roll cage bolts were changed from grade 5 to grade 8 per requirement (although I don't agree with the reasoning due to loss of shear strength), the original style grille we acquired from a member here was cleaned and repaired with epoxy so we can get that installed, we removed the bellhousing section of a 5-speed to send out for a custom ballistic blanket fitting, and the Detroit Locker was installed with the new higher gear set (numerically lower).  

Woot!

Note the instructions on the cardboard.  We eventually followed them.  

 

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/Datsun%20project/B051A525-3760-47B4-9F6D-1AAECDBBCB49_zpsylc1wsoz.jpg.html'>B051A525-3760-47B4-9F6D-1AAECDBBCB49_zps

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Adding twin DCOE 50's to an L20b is not for the faint of heart.  Not only do you have to use 45 DCOE manifolds and port them, weld them, adapt them to fit, but the carbs are physically bigger and don't fit on the manifolds after they are installed until after you install jamb nuts on the shafts, as the factory nuts that hold the linkages collide.  

 

Then you have to modify the linkages to fit and work.  Now there's no room for a throttle bracket or dual return springs anywhere, and the pivot points on the manifolds don't align, so you make offset bronze bushings for a linkage rod, as well as custom brackets to run Heim joints.  So far I'm maybe 4-5 hours from it physically working, and I haven't dealt with fuel lines yet.  Fun!!!  And this is with a full machine shop to play in!

 

[/url]">http://043D0ABF-9DCC-4CE8-83B0-FDDBACAC8AC2_zps

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The real answer is: I don't know.  whatever came in them so far.  Until I get it up and running and figure out a baseline, I'll use what I have.  They're huge.  Then again, so are the ports in the head, and so is the exhaust manifold.  This is going to be set up for rpm only - 4000 will be as low as we go.  Always into the air correctors.  Hopefully I can limit tuning at Bonneville to air correctors only.  Hell, these things don't even have a choke.  I was hoping to use that for enrichment while driving, but no such luck.  

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The 'choke' on this style carb is the slip in venturi.

I've seen really large throttle bore carbs, with tinny venturies in them.

And I think the booster venturies come in different sizes also.

Just another tuning option.

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I know what the chokes are.  I just meant there's no enrichment circuit, where you would hook up a choke cable.  The chokes are huge.  I just couldn't read the numbers on them because when I read your post I forgot my reading glasses in the house and I was in the shop.  They are huge chokes.  Huge.  Very thin.  And I'm contemplating running them in my mass finishing machine until they are silky smooth.  But that means I'll just have to re-safety wire them.  Too many more important issues on the agenda.  

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Adding twin DCOE 50's to an L20b is not for the faint of heart.  Not only do you have to use 45 DCOE manifolds and port them, weld them, adapt them to fit, but the carbs are physically bigger and don't fit on the manifolds after they are installed until after you install jamb nuts on the shafts, as the factory nuts that hold the linkages collide.  

 

Then you have to modify the linkages to fit and work.  Now there's no room for a throttle bracket or dual return springs anywhere, and the pivot points on the manifolds don't align, so you make offset bronze bushings for a linkage rod, as well as custom brackets to run Heim joints.  So far I'm maybe 4-5 hours from it physically working, and I haven't dealt with fuel lines yet.  Fun!!!  And this is with a full machine shop to play in!

It depends on which manifold you use. Some of them had wider spacing than others.

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A friend of mine brought over a brand new Nissan Motorsports dual carb manifold yesterday. It still has the 99996 part number sticker on it. That's the best one to use, but yes, they are very hard to find.

 

You may seriously want to consider running some sort of soft mount behind those carbs. You can still get the offset isolators new. Though they're not as soft as the non-offset isolators that Nissan Motorsports used to sell, I cut them in a lathe to soften them up.

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I couldn't use that manifold if I wanted to.  I moved the ports in the head.   :thumbup:

 

I've had issues with isolators causing vacuum leaks.  I'd rather add bracing to a stiff air box to prevent vibration instead.  Fewer problems overall, at least for me.  I have a set, but I can't force myself to use them.  I've always ended up taking them back off.  

 

My rod ends for the carb linkage just showed up - in time for me to leave for a long weekend.  I guess I have along list of things to attend to when I return.  

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