620 Land Speed Record

[distributorguy]

Thanks!  The approach roads are moved quite a ways away from the berm this year, where the salt is thicker.  That road broke a LOT of cars last year!  

 

We will have a dyno video after next Tues to post, hopefully.  Tight schedule, but that's the plan.  I pushed the truck up to about 7500 after the video was taken.  SO much smoother at high rpm, but it was getting a little lean so we just shut it down for the night.  A huge tuning kit will arrive tomorrow.  Fingers crossed.  

[Charlie69]

It would be great to see you set a new world record!

[nickelpistol]

I'll be at Bonneville this year as pit crew for a Vincent Motorcycle. I'll make a point to stop by and say hello. I've been following this thread and I'm excited to see you run this 620 all out!

  

[distributorguy]

We learned a lot last night on the dyno.  Its not a place I've used before - the dyno bolts directly tot he truck's axles.  The dyno operator turned out to be the former owner of the truck, so he's taking this project personally and offering extra help.  Friday we're going back with the original dual Weber carb setup installed for a comparison.  We were having a difficult time getting the mixture under control - with an odd sine-wave type pulse happening every 2000 rpm.  I think its a cyclical pulse problem in the manifold that's causing the carb pistons to rise and fall, since we have to run the SUs without springs or oil in the dashpots to prevent drowning the motor under the application of load.  With a couple modifications, it may become a future EFI manifold...

 

Our dyno session followed a belly tank that's also going to Bonneville, running a Ford 3+ Liter banger with EFI and crank fire ignition - coil next to plug setup.  We made about 10 hp more than them according to the dyno, and the dyno read quite low for both of us.  They used their AEM software to calculate power based on fuel consumption and had a corrected hp number of about 145 at the wheels.  If that's correct, were over 160 at the wheels, and I'd guess that's a little inflated, but not far off base.    We had a relatively flat power band from 5500-9000+ rpm.  By stabilizing the AFR, we should be able to climb another 15 hp?  The goal Fri is to see if we can stabilize AFR at around 13.5:1,  so we're close to ready for Bonneville.  

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[Ben_upde]

Excited to see how this works out!

[Stoffregen Motorsports]

Have you tried a small balance tube between the two pairs of runners to help even out those pulses? It might be worth a shot.

[G-Duax]

Isn't 13.5:1 a little on the lean side?

I roast pistons if my Toyota goes that far off 12:1, and I'm only running 12:1 compression.

[distributorguy]

Yes it is dangerous.  But it'll drop 1.5 points when we get out west at altitude.  Dangerous games, but we tweak for best power, then alter for altitude with a partial run.  

Do you run ceramic coated pistons, chambers, valves, and runners in the head?  We do, and they work.  ?

 

The dyno session yesterday sounded worse than Tuesday, but we made better power numbers - by 10 - 23%.  The odd thing is that it was "peakier" and our power curve and mixture were still all over the place.  That's when I realized the dyno was using an antique Gen 1 LM-1 AFR meter, and a Pentium IV computer.  Crap.  We made 9 jetting changes and pulls, and the numbers were so messed up that it didn't make any sense.  Our emulsion tubes were rich, no matter how lean a set we installed.  Then we'd have a rich spot at 4k on every run that would come and go within a 300 rpm range - it would drop into the 10's every time. WTH?  Frustrating.  

 

What I learned is that our SU manifold WILL be coming with, and it WILL get a chance to run with a few small modifications.  Next year it'll be fuel injected.  For now I'm off to find a different emulsion tube option that's likely influencing the 4k problem.  If anyone cares, out best run was with F16 emulsions, 185 mains, and 130 air correctors, which will likely get changed to 120s.  

[G-Duax]

Detonation won't pop a whole through a ceramic coated dome, but it will still kill a piston.

In this case, melted the aluminum above the ring, the aluminum smeared onto the bore, and locked the ring up, allowing bore flame to pass down the skirt.

When I pulled the head off, there was no visible damage, just a couple of aluminum beads, the size of grains of salt at the edge of the piston.

If it hadn't been coated, it would have holed the piston, and wouldn't been able to drive it home from the Texas Mile.

I actually drove this for a week before pulling it down. No smoke, just a persistent ticking noise, which I thought was a cam lobe going flat.

 

[distributorguy]

I know, I know.  But here at 1000' altitude,  setting up for 13.5:1 = about 12:1 at Bonny (4100-7000').  We were doing short dyno pulls, with the load reduced so we were running about 20 second pulls in 4th, at the very longest.  More like 10-15 seconds.  There IS risk involved.  I don't condone this.  But there's more risk in having my drivers never look at the air/fuel gauge and trying to drive through 14:1 or 9.5:1.  At least we have a real baseline for what we need.  Without that, image how much damage you can do on a 3 mile full throttle drag race?  We had 10-11 runs in last year if I recall, and many of them were WAY out of tune.  The pistons survived 100%, with only traces of detonation showing, and no real damage to the land area above the top ring (extremely minor pitting that I polished out before re-coating the tops with a better ceramic.)  This year may play out differently, but a leakdown test will show the damage if it occurs.    

 

Today I have to learn how to use an LM-1 as a datalogger with my laptop.  I've always just used it as a "live feed" while driving.  Hopefully I can find the software and the cable...

Also building the push-start mount for the front of my truck today so we can shove off through 40 mph, and not have to rely on the slightly over-rich emulsion tube rpm range of the race truck.  

 

The newest salt report is the the short courses don't even need to be dragged they're so smooth.  The long courses have small pressure ridges developing and the salt is lifting as it further dries.  A quick drag will make it harder and smoother than its been in more than a decade.  

[distributorguy]

Both of my overnight packages arrived. New leaner SU needles, and a bunch more DCOE tuning parts including 3 mm needle/seat combos because 2.5 wasn't big enough, even at 4.5 psi fuel pressure.  Another 2 sets of emulsion tubes as well, not that they matter  whole lot.  Anything to have leaner options out there.  They're already installed and we can't wait to hit the road for 19 hours.  ?

 

30,000 page views.  Who knew???  Hopefully we don't suck ass again this year.  

[G-Duax]

Good Luck !

[distributorguy]

We made 5 run attempts and only conpleted one.  Achieved 98.5 in 3rd gear and things went south. So far we diagnosed half cylinder pressure in #2 via the exhaust valve, the front crank seal spring was pulled up into the timing chain, and the distributor drive gear lost its index.  Likely sheared the key at the crank gear?  

Going home early.    

[wayno]

Wow, not a good year, sorry to hear this, I liked hearing how you were doing in the past, was looking forward to hearing about it this year also.

If you lost/sheared the crank key for the timing chain that could cause a valve to hit, but there is another separate key/gear for the oil pump which also drives the distributor, so they are separate, the only way I can think of for a valve to hit and have the distributor go out of time is for both keys to shear or have the crank break.

There is also a roll pin holding the drive gear assembly on the bottom of the distributor, that could also effect distributor timing.

Maybe next year you should take an extra engine.

Edited August 13, 2018 by wayno

[datzenmike]

Intakes are larger diameter and will hit a piston top sooner than a smaller exhaust will. Broken valve spring might float an hit. Tough break. May be something small. Don't give up the ship yet. 

[Draker]

Bummer!! I second the spare motor, but that can add up quick. 

 

Looking forward to the diagnosis. Sometimes you have to fail a few times before you succeed. You got this!

[Ben_upde]

Sorry to hear about the hiccups. Hopefully it winds up being minor and you can continue the trials!

[nickelpistol]

Shoot, I was hoping to see you guys get a good run, it's disappointing to travel so far and have to pack up early. We've had some struggles too, broke the rollers today and ruined two starter motors. Luckily we had a spare and the auto parts store had one in stock. Some modifying with an angle grinder on the rollers and we should be able to try again tomorrow after reassembly.

   It was great meeting you and your crew, I enjoy talking Datsuns and everyone was really cool. If all goes well I'll see you out there next year.

Thanks for the awesome T shirt!

  Cheers!

 

  Mark

  

[Charlie69]

That sucks but it will help you prep for next year.  Part of going fast!  You will add this problem to your knowledge base and hopefully be able to avoid whatever happened next year.  You gave a good showing.

 

I have a friend that ran Bonneville in the early 70s to the mid 80s on Harley Sporsters, he ran hard for many years and did not achieve his goal, as he ended up in prison.

 

Keep going you are definately learning and doing better with each try.

[distributorguy]

Well, the truck is back safe in the shop.  Tonight we're having a meeting about the next moves.  My goal as of today is to swap the street motor back into the truck so we can develop an EFI system, and work out bugs as I make it street legal for local testing.  Our 2nd engine may actually be done for next year, but I'll get the current one diagnosed in the next few weeks and we'll move forward repairing it as needed.  The valves work as intended, so I suspect the abrupt timing shift actually burned a valve/seat.  The other possibility is that we could have shifted a guide since they're significantly shortened  to flow more air.  We're using custom Manley severe duty valves (ceramic coated), so its got to be something relatively simple.   

The fact that we jumped timing 30 degrees - that can only happen at the crank gear.  Why did that happen?  We'll know soon.  

The 1/8" roll pin in the distributor shaft  only holds the retainer sleeve in place.  Its driven by a screwdriver blade inserted in the end of the shaft.  Since the crank gear appears fragile, maybe its time to add a belt driven oil pump as well, go distributorless, and skip all that fragile crap.  All speculation at this point.  

 

It was great meeting you Mark!  We also had Aaron Kauffman stop by from Arclight Garage - better know from GasMonkey.  That was cool.  Its such a welcoming race environment, but the race conditions are abusive at best.  We'll be back next year.  

[Duke]

Sorry to hear that it didn't go totally to plan.  Talking to a friend that was out there, it seems like the conditions were awesome and the lines were short!  Shame that you guys weren't able to get a good run in.  Next year is the year! (isn't that what everybody says?)

[distributorguy]

The track was really, really hard and fast, until mid afternoon.  It was hotter than the past couple years, and more humid so the density altitude was higher - nearly 8000' versus the real altitude of  4100.  

 

DatzenMike, actually, the exhaust valve is opening at a very fast rate right after TDC, so the exhaust valves are most likely to get bent from hitting a piston - while chasing it down the hole in the first .040" of piston drop.  Both valves are parallel to the piston top in most race engines due to the dome design.  

 

The 240Z guys from Japan had that happen this year, and managed to get over to JDM in Salt Lake for parts.  Rumor had it they were able to get it back together overnight and they might run today.  

[Duke]

1 hour ago, distributorguy said:

The 240Z guys from Japan had that happen this year, and managed to get over to JDM in Salt Lake for parts.  Rumor had it they were able to get it back together overnight and they might run today.  

 

I think that they just ran.  Around 130 through the 2 and slowed after that if I heard right.

[Stoffregen Motorsports]

I wonder if the crank pulley bolt came loose and allowed the stack of drive gears to jiggle around. You're right though, it has to be in the front cover.

 

Are you running a harmonic balancer or a stock type  pulley?

 

Do you shim the distributor drive spindle at the oil pump?

 

Are you using a brass drive for the spindle? The steel ones are not great in racing engines and are known to fail.

[Ben_upde]

I don’t recall seeing what you utilized for bottom end components aside from ultralight rods and custom pistons to spin this guy up to 9k+ rpms. I’ve been toying with the idea of building something capable of revving quite high. Any chamce you could elaborate a bit on the bottom end work done? I understand if you have some secret sauce methods you have used for a competetive edge. Generalized idea information is all i’m after. 

 

Also, hopefully next year treats you better!