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Colortune for HD8 Carbs?
- Thread starter wangdango
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I knew that about the needle, but the devil on my left shoulder made me write "jet".
Looked at one of the interactive charts and the UN needle (Moss catalog "Rich") is a lttle richer in the idle and mid/upper range than the UH std needle. I'm not well-informed enough to know from looking at the chart whether it fits the "10%" prescription.
People (BCS for instance) have been using this 10% figure for a while without any suggestions for which needle - like it's obvious what needle to use or something.
Since I already own the UN needles, guess I'll install them. Will report back.
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Dial calipers are getting harder to find. I found several digital calipers easily. Seems everything is going digital.
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Bob_Spidell
Yoda
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I think a digital caliper would work fine, as long as it has the depth extension on the end and, yeah, everything IS going digital.
I spent hours tuning my BJ8's carbs after its recent overhaul with Colortune. It idled great, I had 'bunsen blue' and the car ran great on test runs but, when I got on a long trip it started dying when decelerating to idle, after 500 miles or so on the road. I futzed with the carbs on the side of the road--IIRC, I enrichened them a little and opened the throttles a little and the problem went away. I'm convinced the 'final tune' has to be by 'ear.'
I spent hours tuning my BJ8's carbs after its recent overhaul with Colortune. It idled great, I had 'bunsen blue' and the car ran great on test runs but, when I got on a long trip it started dying when decelerating to idle, after 500 miles or so on the road. I futzed with the carbs on the side of the road--IIRC, I enrichened them a little and opened the throttles a little and the problem went away. I'm convinced the 'final tune' has to be by 'ear.'
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I was at HF this past weekend and all they had was the digital...so I was told.
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Bob - are you using the fast idle screw to open the butterflies a little?
This has been argued before. I've never been able to get a steady idle with just the large Slow Running Screw so am ready to try an "unapproved" method.
Bob_Spidell
Yoda
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Yep. After I tried the 'proper' method for hours, I settled for what worked. I've always used the fast idle screws with the slow run open 2 full turns or so; I didn't like the idea of the brass throttle plates hitting the aluminum bores (I've seen carbs--not SUs--with a slight groove worn where the plates rest). When I opened the throttles just a tad with the fast idle screws, the stalling stopped (also enrichened a bit). Also, since I travel cross-county I may go from sea level to 6,000-7,000 feet or more and if the idle slows I can open the slow run screws--and close them up later--more accurately. I think earlier SU versions don't have slow run screws, no? And, SUs don't have 'dashpots' to slow throttle closing, which may cause/contribute to the stalling problem.
Here's my plugs after a warm shutdown after changing the oil; not proper methodology I know, but I had the plugs out for a compression test with 5,200 miles on rebuilt engine:
bob hughes
Luke Skywalker
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I have three colour tunes, mostly from Ebay and use them when I have to, it must be said that the BJ7 uses twin HS6's and I have found that they work fine on these carbs for me. I did lend one to a friend for his mini moke (one of the six trialled by the British Armed Forces) and he could not get it to work for him, he used the lift pin method in the end.
Bob
Bob
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After my engine rebuild with .60 over pistons I contacted BCS, David Nock, and said with 60 over and ethanol gas definitely 10% richer and sent me richer needles. I'm doing some adjusting to get the mixture right, mostly by trial, and hope to have it sorted soon.
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Patrick - Can you pull one of the needles and read the letters on the upper shank?
I also have .060 over pistons, a DWR 8 cam and a bunch of other stuff.
Today I took an 80 mile drive with my UN (Moss Rich) needles installed and the jets down .090" - 2/3 level freeway, 1/3 climb from 1000 ft to 5500 ft -- got 12.7 mpg on premium.
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The screws are .030" per full turn. The initial setting of 2-1/2 turns down is .075". If you're careful to get the jet level with the bridge to start, the turns are quite accurate. I've been doing them and checking with the caliper.
My jet carriers are down a few thou from the bridge so I make sure the top of the jet is level with the bridge to start. If you're careful you can do it without the caliper.
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I'll first check my receipt and get back to you.
Bob_Spidell
Yoda
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That's pretty low mileage; I've documented over 20 road trips averaging 3,500 miles each across the western US, Canada and Mexico in my BJ8--fully loaded with adult passenger, luggage and lots of spares and tools--and I've never seen anything below 15MPG. And, as much as I wanted to, I've not seen much difference running 10% ethanol gas vs. the good stuff (the good stuff seems to mitigate the stumbling after hot start problem). Of course, your engine is hotter than mine (done a compression check yet?).
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I'm still adjusting the carbs. We're starting a heat wave in so cal today; will take a freeway-only trip in a few days and hopefully have mileage more like yours.
Bob_Spidell
Yoda
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I think you might be running Webers(?); I would expect them to get a little less mileage than SUs.
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As usual, the Dial ones were shoved way in the back of the lower shelf near the floor. I purchased one.
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The needles are "UN".
I suspect that I will have to fiddle with mixture adjustment to get them "spot on". I remember one of the mechanics at Hollywood Sport Cars telling me that they used to accelerate to about 55 mph and shut off the engine, coast to the side of the road/track and than check the plugs.Sometimes sandpaper was used on the needles to get the mixture correct when they didn't have one in their inventory that worked.
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Bob - I'm running HD8s; DMD manifold matched to head; .060" over 9.0 Venolia forged pistons; DWR 8 cam; Kirk headers; high-lift rockers; 1.75" Monza exhaust; 3.5 Lempert diff with 28% OD Supra trans.
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Patrick - thank you for checking this out. 'UN' is the one the Moss catalog specs as "rich".