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Strombergs -- higher altitude operation  Rating:  Rating
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 Posted: 04-02-2009 04:46 pm
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Dakota123
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My "new" '73 JH is due to arrive here in Colorado today, after living all of its life at sea level.  What can I expect from the Strombergs when I go to drive it off the trailer?  Will it even start?

Does anyone have a feel for what jets I will need for operating at 6,000 - 7,000 ft?  A starting place is all I'm after...

Thanks in advance,

Mike

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 Posted: 04-02-2009 05:53 pm
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Jensen Healey
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A simple adjustment should be all you need. No need to buy any parts but you will need the Stromberg tool. Call Delta.

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 Posted: 06-21-2009 01:05 am
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Dakota123
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I failed the Colorado smog check -- thought I would try it to see where I was at, since the car was actually running well.

I did a partial rebuild on the Strombergs, since the adjusters were frozen on both carbs and the front carb wouldn't hold damper oil for more than a few minutes**.  I changed the diaphrams and adjuster o-rings. 

After doing that limited work, I can get neither carb to exhibit the expected behaviour when rich (i.e. lift the piston slighlty and get a brief rise in idle).  I can get them only to a point where there is a slight stumble on raising the piston, which should mean that they are slightly too lean, no?  If I continue to richen (CW), I get worsening idle, burning eyes -- but always a stumble when lifting the piston.

Both adjuster screws are only about one turn rich from full lean (full CCW).  I attribute this to the fact that I'm at 6,200 ft. 

Idle is even and smooth at 950-1,000 rpms -- a bit of cam lope at 900 rpms or lower. It runs great with no hesitation or misfire under acceleration.    Timing is at 10^ BTDC, ignition system is in great shape.  (I'll drop timing to 0^ before taking it back for a recheck, based on advise of others.)  Not a true 'plug cut' since I drove back home after doing a test run, but all four plugs are light brown.

Before I did the partial rebuild, both carbs were slightly rich but on lifting the piston, idle speed did indeed increase. 

So what could be going on that the carbs are not doing what they are "supposed" to be doing?  Since the car is running really well, I'll probably leave well enough alone (assuming it passes smog this time), but I find this really puzzling.  Aybody been there, done that?

Mike

Edited; I had CW and CCW backwards.

 

** After putting it back together the first time and still having the damper oil disappear, I tore it apart again and noticed that the hex hole for the allen wrench went all the way through the screw.  "That's not gonna work."

Last edited on 06-21-2009 05:31 am by Dakota123

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 Posted: 06-27-2009 07:57 pm
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Dakota123
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In the interest of closing this out (I'm sure everyone was waiting with baited breath) she did indeed pass... with flying colors, no less.

Significantly less than 200 ppm HC and less than 3% CO at both 1,000 rpms and 2500 rpms.  Actually, these numbers are so good that I'm left wondering if the test wasn't flawed, but I'll take it.

I did back the timing down to 2^BTDC, the lowest I could get on the fine adjust knob alone (brilliant thing, that knob), based on the advice of Tim Engle.  Otherwise, I left the mixture at best idle quality.

 

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 Posted: 07-09-2009 03:58 pm
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Dakota123
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A tip for improving the damper oil seal of the jet adjuster screw -- even after replacing the o-rings in mine, I couldn't keep oil in the dampers for more than a couple of days.  I cut one finger off of a nitrile (otherwise known as buna-N) exam glove and cut off the tip, so that a small sleave is left.  I inserted that and the adjuster into the bore and voila, two weeks with no loss of oil at all.  Nitrile is oil-resistant so I'm hoping these hold up for some time to come...

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