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620 Land Speed Record


distributorguy

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The main caps are all strapped, the block is full of block filler, and the crank was Teflon coated and ground by the best in the business.  Crank was also "deburred" at all critical stress points.  Add a crank scraper, bolster the oil drainage to direct it a little better (and faster), and baffle the pan a bit.  

 

The crank pulley is NOT loose.  Its running a stock pulley, and the flywheel is shaved to about 16 lbs.  We may go lighter, but we can't run aluminum per the rules.  There was no reason to add shims at the pump- this engine had a virgin 1000 miles on it, so nothing had worn.  Drop-in depth for the distributor was modified up top to stabilize the gear from climbing.  It was a stock gear.  I hope to get it apart later today.  3 out of 4 cylinders were well above 98% on a leak-down test, so the new hone and re-ring played out VERY well!!!  

 

I just got done machining a spare crank pulley for a 36-1 trigger wheel.   The next evolution is happening.  EFI, distributorless, dry sump.  No more need for the weak gears at the nose of the crank.  If anyone wants to donate to the cause or buy some of our cool T-shirts,  just say the word.  

 

The 240Z guys ran 166, and the Mazda truck guys hit 183!!!  

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I wish I had an extra $1500 to spend on that system Duax!   I like the concept of having some amount of flywheel mass protecting my engine from our drivers.  Maybe the $300 12 lb flywheel on Ebay? 

We saw the 240Z guys ambitiously miss a shift and bend all their exhaust valves due to an over-rev situation.  We have 3 miles to get up to speed, so our goal is to make more power rather than to get there faster.   

Eventually we'll end up changing to a more efficient transmission, so for now we're trying to make the best of what we have.  All our money is going into the engine and re-working the exhaust at this point.  Transmission and high end clutch are next year?  Unless we get a good donation from somewhere???

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  I read a comment years ago about putting an aluminum can pull tab between the spindle and the distributor. This removed any slack in this sloppy 'screw driver blade' drive. Indeed the Z24i engines and the KA all use a splined set up to remove all jumping around of the spark timing.

 

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My OS was a $150 used one from Japan, shipping via surface was almost as much. 

Didn't even have to replace the disks.

(don't think an L4 even has the beans to hurt a twin disk)

And the 6-bolt versions are even more plentiful than the rather rare 5-bolt version.

 

I'd rather throw myself on a live grenade than put one of those eBay chinese gloss black flywheels onto something that could take my feet off.

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Next time you have the crank out, you may want to consider giving it the knife-edge treatment to lose some weight in rotating mass.

 

Man, I hope you guys get a good run next year. A whole year...that sucks. Too bad there aren't other events you could run in the interim to keep up on the development.

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21 minutes ago, Stoffregen Motorsports said:

I was referring to adding shims to take up the slack on the distributor spindle, not adjust the oil psi.

 

Not the oil pump. Between the spindle top and the distributor.

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Well, the crank will likely be out of the engine some time this week to inspect what happened to the gears up front, and to guarantee the rings don't rust to the pistons again like last year.  There's already a bunch of Kroil in the cylinders.  The head is off, exhaust valve #2 is out.  The damage is minimal.  It appears to simply need a valve job refresh already.  The Manley extreme duty valves look good, but you can clearly see where the valve wasn't sealing.  The fellow who reamed the guides may have gone a little beyond spec, so they will get replaced.  Again.  

 

Our goal is now to avoid using the distributor drive or the stock oil pump.  We'd like to dry sump, but we may wet sump with an external oil pump?  We have yet to decide.  Pulling a vacuum on the block has advantages and disadvantages - especially in a salty environment.     

 

As for lightening the crank and flywheel, the benefits are marginal for the racing we do.  We're looking for peak speed with good durability over 3 miles.  To a large extent, momentum is key.  Light rotating assemblies lose momentum quickly.  When the truck is getting knocked around by wind at high speeds, losing momentum will slow us down.  

 

My goal is to get the truck back to street legal so we can beat the heck out of it locally.  The biggest issue will be getting 114 octane fuel, and the obvious cost involved.    

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Knife edging the crank will help stabilize the rotating assembly at high RPMs, but you already know that. It also reduces windage which can free up hp. I suggested it based on the RPM range you are trying to run that little L20B. Anything over 8000 is high for an L20B.

 

A good harmoic balancer would probably help too. I winder if the NISMO balancer is still available. We used those on the SCCA GT class L series motors, but for the KA24s, we used a balancer from Fluidampr.

 

I honestly don't know what those guys are using these days.

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That would help solve the issue with a belt driven oil pump.  What pulley would you fit to that to line up with the water pump and alternator?  I may have a few old Chev pulleys laying around - which is the bolt pattern, but the offset may be all wrong.  

I did order a 3-stage oil pump yesterday, and designed the caliper brackets for the original rear axle we ran last year (with the Detroit Locker).  Progress.  

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Not sure who made the Nismo balancer - most of that stuff was outsourced.  I've got an ATI on its way (may be the same as Nismo?), along with a HTD drive crank pulley (direct fit) to go with the Barnes pump.  In the online images, it looks like the ATI damper may have a single V-groove in it.  If not, we still need to fit the 36-1 trigger wheel and at that point I'll figure out all the pulleys at once.  Its a BBC bolt pattern, which will make all this pretty simple.  Then some hard core plumbing.  I hope to get all this tackled in the next 4-6 weeks. 

 

I'm currently using a 1600 water pump and pulley, and a petite Mazda/Ford alternator with a HUGE pulley on it.  I could just make a pulley as well.  I have a nice 6" round block of aluminum sitting here.  A little 5" OD pulley would be cool.  Slow things down a bit.  

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Boy, I can't find a pic of the original Datsun Comp crank damper anywhere. It was about 7" diameter and had the belt behind the damper. Beautiful looking piece, but since I can't find any pics, they must be hard to find.

 

Oh well, sounds like you've got a plan anyway.

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That's how the 240/260/280 ATI damper is made.  I can't find my old Nismo catalog either to see if the part number matches ATI.  Likely 917720 or 918040?  

Hopefully all these parts will mate up without too much coaxing.  If tomorrow goes well the valve job will be done as well as the disc brake conversion on the stock 3.89 diff with the Detroit Locker.  The goal is to have at least 2 axles with gear ratio options that can be bolted in and out - without breaking into the hydraulic system.  

 

Next week:  dry sump oiling once all the parts arrive.  

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Since I put this set up on my 620, I'm wondering why I didn't do it 10 years ago.....

And the serpentine drive on my real hot rod (the Toyota), will most definitely be changed.

This could easily drive an oil pump also, I just wouldn't machine the teeth of the pulleys, they come 40mm wide.

And I could have made the crank pulley register longer, to be able to stack pulleys.

 

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Nope.  No time, and its too expensive.  

This is the same speed I worked at last year, and we still weren't ready on time.  I hope to get the EFI running and sorted so we can street drive the truck in the Spring, to help get it further sorted and tuned.  I have to dig up 1000 hours of spare time in less than a year.  If I don't start now, it'll never happen.  

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The quick damage diagnosis from last night:  

The exhaust valve seat receded into the head slightly on #2, and #3 is following suit.  Both "settled in" a little toward each other and upward, in the center of the head, with #2 being far more "out of square" to the valve face.  Must be a hot spot there?  The #2 valve head is just a hair non-concentric.  I'll face all the valves, grind the tips to an even height after a quick valve job refresh, and touch up all the seats now that they're settled in to where they are likely to stay.  I hate doing valve jobs, but there's power to be made here so I'll struggle through it.  I'm not sure why I didn't round the edges of the new exhaust valve heads when they were installed, but I won't forget this time.  

 

The distributor drive gear teeth are all severely worn, in a very irregular pattern.  its obvious that the gear got hot and had some wear issues at high rpm - most likely from an abundance of oil hydraulicly (is that a word?) separating the gears at speed.  The thrust face is destroyed.  The crank gear showed far less damage than the driven gear, which will not be used in this engine any longer, but it still had substantial wear for only running under 50 miles.  Barnes dry sump, here we come!

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The point of filling the block is that it moves less.  Heat has never been an issue for us.  In fact, with all the ceramics we have a bigger problem with the block being able to accept any heat.  It runs cold.  Dry sump will allow us to heat the oil as a benefit.  A laser temp gauge shows the head is pretty consistent in temp - no hot spot in the center to be found.  A typical reading is 350 or so at the header, 250-280 at the head adjacent.  150 or so on the plug side.  On  an average run, our engine temp drops from 65 to around 130, which normally would indicate over fueling, but we're actually running pretty lean.  Without the filled block and modified main caps, we would have broken the crank by now.  Coolant capacity is still near 2 gallons like a typical SBC - and this is only half an engine.  ?

 

The spline drive and oil pump are here, but so is a new puppy, so I need some sleep.  10 week old Irish Terrier if you care.  

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Hahaha!!!!  Nothing like being up at midnight (exhausted), then back up at 5 am.  Sleep deprivation like having a baby around.  I'll regain energy as I find more time to exercise with her!!!

 

The next time at Bonny will be better organized.  I took a few things for granted this year.  It was more chaotic renting a 20' trailer instead of a 26' as well.  Plus it was WAY hotter this year.  Next year I'll be in better shape and so will the truck.  It'll also be making more power.  

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