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distributorguy

620 Land Speed Record

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Yes, but only if they are in the ballpark.  If my needle selection is WAY off base to start, I'd be better served to hit the local British repair shop and buy a couple that are close to baseline, then modify as needed.  Plus buy a leaner set to have on hand since you can't go leaner when you run out of jet adjustment.  These jets are cool in that they adjust by screw from the top (very accessible).  I've also got extra springs pulling the jets up into the housing so they won't bounce or end up accidentally going rich.  

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Its actually a modified throttle return spring.  I've been to too many car shows where high end British cars show up and won't run when they pull out of the trailer.  A quick "push" up on the bottom of the jet and they're good to go.  I'm just beating problems before they happen.  Can't blame Lucas for this one.  ?

 

We still have a goal to run the truck on Thursday, for the first time since last August.  Fingers crossed...

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Even the 240Z guys have that problem.

 

A log time ago, I built a set of SU's for my 1275 powered sprite using as many Datsun parts as I could. I even modified the Datsun well jets to work on the British SU's, and they were an improvement. I don't recall why I did all this, but I remember doing it. Boy, I wish I had spare time to tinker like I used to...

 

I also wish I could spare the time to get out to Utah with you guys. Land speed racing is on my bucket list.

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This oddball set of carbs we have is very non-traditional for SU, at least in terms of how the jets are set up.  They're better for racing.  The linkage is far more robust and less likely to bind.  The return springs however totally suck - hence a secondary external spring to keep the jets in position.  We won't use a choke, so there's no reason to ever "pull them down" to richen the fuel mixture.  

I'm still hoping the cam we have is enough to pull the 180 hp+ at the rear wheels we need "in a perfect world" to set the record.  Too much duration.  

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... do your what?

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3 hours ago, datzenmike said:

... do your what?

 

His soiled non sequiturs.

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He must have been referring to old and sticky well jets. And the cleaning process.

 

Given the level of detail here, I'm sure Jeff has already gone through the carbs, so I doubt they're sticky, they just inherently have friction that can hang them up.

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Polished to a fine luster.  Its a brass tube inside a brass sleeve.  They are both polished to the end of their life.  Slippery as a bar of soap on the shower floor.  The springs simply hold the jets in a seated position better than linkages alone.  

The carbs were polished in the same mass finishing machine I use to polish distributor housings on a daily basis.  Better than new.  

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Damn, I forgot you were talking about a carberator for a miniute there. Git'n all hot and bothered. 

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We spent the night getting float issues straightened out.  The gentleman who "rebuilt" the carbs (team member) installed new needle and seat assemblies that were not only made inconsistently, but the fuel passages were way too small and were not allowing fuel into the float bowls in a consistent manner.  A couple hours later with plenty of modification, the fuel level in both carbs matched and we got to crank over the engine.  Unfortunately, despite all the battery and ground cables being new last year, the engine turned over very slowly which lead to the rest of the night being spent cleaning and rewiring.  I'm neither surprised nor upset, but now I'll be out of town for the weekend with no time to get the truck running.  I may also need to add a choke cable to allow more fuel to get through the long runners and down into the engine.  Starting it with this manifold may be problematic until we can get it rough tuned.  For now its still looking lean on start-up, but that's expected with such a slow crank-over speed.  The starter appears good, only drawing the battery down to 10.5V while cranking.  

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I even own the bottles.  We just hadn't gotten that far yet.  After flooding the motor with fuel last year when the regulator O-ring failed, you could say I'm a little apprehensive about hydro-locking the motor with raw fuel.  

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Interesting turn of events last night.  

 

Another night trying things that didn't work to start the engine, so we went back to the basics.  Compression test results dropped from 190 last fall to 100 across the board.  Oh shit!  Never saw that before.  Followed up with a leakdown test to find we're only holding 30% -  70% is flying past the rings.  No water in the oil, no oil in the water, no leakage past the valves.  

 

The block is almost ready to come out of the engine bay.  I hope to have it out by noon (scattershield is going to make it a real bitch) and have it torn down and ready to drop at 1 of 2 local engine shops Friday morning for a rehone.  

 

We suspect this may be caused by:

1.  Tribodyne oil

2.  A poor hone job the first go-round too smooth of a finish and poor oil retention

3.  Cooked rings from poor oil retention and 10k rpm abuse

 

A full inspection will tell the tale.  I'll post pics tomorrow.  It's going to be a long day.  

If anyone has those green intake/exhaust manifold gaskets on hand for a square-port head, I need a couple ASAP.  I'll pay handsomely.  I can't use stock square port gaskets because the fire rings don't fit my header at all.  The stock round port gasket is too small  and would have major exhaust leaks.  

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Rust.  Thank you salt.  You allowed the piston rings to rust into the piston grooves.  We should be beginning the engine reassembly Monday and have it in the truck running on Thursday.  

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You might try getting the air flow for the carbs from the very front, as something is going on with where the carbs are able to pick up salt from the engine bay / wheel area.

Or weld some tabs on that intake header thing, so you can build a sheet metal shield, so only air from the windshield area can get to the carbs, not any turbulence from around the wheel area.

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Every inch of the truck had salt on it.  Inside and out.  I think the key will be to Strip the motor and assess it right after the race. Problem solved.  Just more time and money.  I'm not sure how the new intake could pull air from the front without upsetting the "production" class we're in or making our frontal area larger.  

 

I just got done cleaning and spraying a new ceramic coating on the pistons for detonation protection.  Rings and gaskets (including the green intake/exhaust gaskets) are here so tomorrow I start engine reassembly.  I have the re-honed block and it looks amazing.  By Tuesday evening the engine should be ready to go back in its hole.  The only thing we're waiting on is the new ACL "race" rod bearings for the Honda journal Molnar rods that should be delivered tomorrow.  

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Good news!   The motor is back together and in the truck...

AND IT RUNS!

 

It not only runs,  the fuel mixture was already better than after all the tuning we did last year, and the motor started and ran immediately, no stalling, no issues (so far.)  The best part - it sounds AMAZING with the new 2" SUs and the long runner manifold.  Lopey, powerful, smooth.  This morning will be spent acquiring spare carb needles to try, as well as scheduling a dyno run for Tuesday, if at all possible.  The video is literally 2-3 seconds after it started the very first time with the new carbs and manifold.  Lots of oil in the cylinders, not up to temperature.  65 psi oil pressure at idle. 

 

Remember this motor is 14:1 (or thereabouts) with a huge cam, and carbs off a Triumph TC2000.  Google it.  Its a basic ugly British sedan.  Changing the carb pulse order was well worth the effort!

 

 https://www.youtube.com/watch?v=JwR_DpyK27g&feature=youtu.be

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That sounds nice at idle, and barely off idle.

I would love to hear that engine pulling a load at a higher RPM!

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Looking (and sounding) good!  From the newsletters that the BNI sends out the courses should be pretty good this year.  Hopefully the approach roads are better also!

 

We won't be there this year.  We're headed to the World of Speed event in September.  Best of luck to you guys!

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