View single post by Esprit2
 Posted: 12-01-2015 05:52 pm
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
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Koit,

If you were talking about a Lotus 907/ 912 engine, there's enough Dellorto history with those engines, both Jensen-Healey and Lotus versions, that we could tell you what set-up will work. And there may be a Volvo forum with similar Dellorto history for the B30; but on this forum, the B30 is just not something we talk about.

In the jetting table in message #4 above, the first two generic columns are what the standard formulas indicate for an engine with 496cc per cylinder that delivers peak power at 5500 rpm... in the broadest of terms. Since your carbs are already 45C's with 36 chokes, try something based on the first column... which seems to be what you're doing...
So I will start with:
Emulsion tube 7772.5
7484 main jet size 145
7485 air corrector jet size 180
Emulsion tube 7850.7
By the book, the 7772.5 Emulsion Tube is about right for an engine with a one-cylinder displacement of 450-575cc, which covers the B30's 496 cc/cyl. However, the 45C / 36 Choke combination is large for a "near-stock' sedan engine of that size, so flow velocities will be slow, which will create a weak vacuum. That could lead to an overall lean condition. I'm not suggesting you start with a richer Emulsion Tube. I'm just saying that if you end up fighting an overall lean condition in the future, that it might help to go richer on the Emulsion Tube.

The J-H version of the 907 used DHLA 40s with 35 chokes. However, for Lotus own version of the 907, they used a 45E/ 36 Choke that's similar to your carbs. The 907 & B30 are very close to the same cylinder displacement (493 Vs 496 cc/cyl), but very different in tuning (peak power at 6900 rpm Vs 5500). While I expect the final jetting set-ups to be different, I will point out that Lotus used a richer 7772-8 Main Emulsion Tube.

In the chart below, the first column is the generic 'Power' set-up from message #4, and the second column is Lotus' 45E / 36 Choke set-up. Just keep in mind that much of the J-H community shuns the 'Lotus' set-up as over-carbureted, and the J-H factory used DHLA 40 carbs with 35 chokes. In the end, I suspect you'll find the 45C's with 36 chokes are a bit much for a near-stock B30. If it has been hotrodded, then they might be about right, but you haven't indicated that's the case.

Since your 45C carbs currently have 7772-7 Emulsion Tubes (?), it might be worth saving the initial expense and trying the first round with the existing tubes. If the mixture is still too rich (the plugs are now black and carbon fouled), then you can spend the money and go with a little leaner tube on your second try.

Your current Main Jet isn't far off the generic 'Power' value, but the Idle Air Corrector is small. Small means less air and a richer mixture. If you don't mind chipping away in small steps, installing larger Main Air Correctors with the current Emulsion Tubes might be a good first step.

The Lotus 45E / 36 Choke's Main Jet is larger than the generic B30 'Power' recommendation, but the Idle Air Corrector is also much larger... much more air to keep the Air/Fuel ratio in check. The Lotus Air Corrector might actually be larger than optimal, since by that point in time they were running into more strict emissions standards, and mixtures were a little lean to meet mandated standards rather than give best running or power.

............................... Generic ......... LOTUS (not JH)
Engine .................... Volvo B30 ...... 907 ................ Your B30
Displacement (cc/cyl) 496 ............... 493 ................ 496
Power Peak RPM ...... 5500 .............. 6900 .............. 5500
Tuned for: ............... Power ............ Power
Carb Type ............... DHLA 40 / 45 .. DHLA 45 ......... DHLA 45
Choke ..................... 36 mm ........... 36 mm ........... 36 mm
Venturi Reduction %.. 0.90 / 0.80 ..... 0.80 ............... 0.80

Main Jet ................... 145 ................ 135 (160) ....... 150
Main Air Corrector .... 180 ................ 150 (230) ....... 160
Ratio, Air Corr/ Jet ... 1.241 .............. 1.11 (1.44) ..... 1.067
.............................................................................. 180 SpeedPro
Ratio, Air Corr/ Jet .................................................. 1.200

Main Emulsion Tube.. 7772-6/ -5 ....... 7772-8 ........... 7772.7
.............................................................................. 7772.4 SpeedPro

Idle Jet ..................... 50 ................... 50 ................ 60
............................................. I prefer 55 ................ 50-55 SpeedPro
Idle Air Corrector ...... 7850-2 ............ 7850-2 .......... 7850.9
............................................. I Prefer 7850-7 ......... 7850.6 SpeedPro
................................ 2nd richest ....... 3rd richest .... 3rd leanest
Idle Jet Holder ................................... 7850-7

Float Wgt (gram) .............................. 10.0 ............... ??.?
Float Hgt (mm) ................................. 16.5-17.0 ........ 14.5-15.0 ??
Float Valve ....................................... 170 ................ 170
Pump Jet .................. 40 .................. 38V 42H .......... 40

Auxiliary Venturis ...... 7848.2 ............ 8011.1 ........... 8011.1
Aux Vent sized for ... <550 cc/ cyl .... >550 cc/ cyl ... >550 cc/ cyl
............................................................................... a size too big
Aux Venturi should be ............................................... 8011.2 SpeedPro

Pump Delivery in 20 Strokes .............. 8.0cc
Pump Lever Clearance (mm) .............. 0.1 +/- 0.05
Fuel Delivery Pressure (psi) ............... 1.5-2.5

*~*~*
This is how my floats are set, as I did it by the book I had. The car has mechanical fuel pump from the crank so I don't think thas going to be an issue. So I can check the fuel levels again in the carb bodies. I will also not that I changed the needle valves one seemd to have leaked so I changed them for all the carbs.
In the fuel inlet valve, which needle style did you use? Stock Dellorto valves are all brass, while aftermarket valves have a Viton rubber tip. Both work. But the rubber tip takes a compression set after a short while, which allows the float and the fuel level to rise a bit. If you used a rubber tipped needle, then it's best to re-set the float/ fuel height after they've been in service a few days to a couple of weeks.

Your photo shows the cover in the correct position, with the cover gasket in place, for setting the float height. And as far as I can tell in the photo, that one is set to 14.5-15.0 mm. That's all good as far as it goes. However, as I mentioned above, Dellorto floats were available in several weights (Weber uses only one), and each weight requires a different height. You have not stated what your float weights are, so I can't say if 15.0 mm is correct.
10 g = 16.5 - 17.0 mm Float Height
8.5g = 15.5 - 16.0 mm Float Height
7.0g = 14.5 - 15.0 mm Float Height
25.0 mm = Float Drop, common for all.

Des Hammill's book is probably the best amateur guide on the market for Dellortos; however, it's not perfect. One flaw is that he states an over-simplified one float height, like it's singular and gospel. It's not. It varies according to float weight. So, what is the weight of the floats that are installed?

Or, as I wrote in message #4 above, the best approach is to simply set the fuel level to 27mm/ 1.063” down from the top of the jet pedestal in the float bowl.

Good luck,
Tim Engel

Last edited on 12-01-2015 07:08 pm by Esprit2