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 Posted: 07-10-2005 12:44 pm
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Ron Earp
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I went to prep my car for fire up and my rear carb leaked a serious amount of gas out when I pressurized the system with 3.25 psi of fuel. I removed the carb thinking the float valve was stuck (tapping did not resolve it).

Once off I then consulted my manual on float specs. There are none. They are specs for two types of Delortos but nothing on float specs for the Strombergs. I have not consulted the TR8 manual (same carbs) yet but wil later today to see what it might say.

Anyone have some float height specs, and more importantly - WHERE to measure the specification? I could fiddle around and guess through trial and error where the height should be, but I'd like to avoid that if possible.  And, is there any replacement for that ball valve that acts as a proper float valve? I would really like to see a high quality spring loaded needle valve there.

Thanks much,

Ron

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 Posted: 07-10-2005 05:33 pm
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Mark Rosenbaum
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The float setting spec should be stated in the carb rebuild kit.  This dimension is 0.688" (11/16").  Both carbs should use sealing washers of the same thickness, and, naturally, the same float setting.

The float height is determined with the carb body inverted so the float is at the top, and is measured from the fuel bowl gasket surface on the carb body (without the gasket), to the highest point of the float (which should be the corner region furthest from the pivot pin).  I generally use a vernier caliper with a depth rod to gauge this dimension.

There are two types of fuel inlet valve available: the Grose valve which uses a ball to shut off the fuel, and the conventional type which uses a constrained metal needle but no spring.  With the low fuel pressures required by Strombergs, I am not sure one would want a spring that helped keep the fuel inlet valve closed.

Each ZE15K rebuild kit should contain a new valve of the needle type.  Individual valves are also available.  I've attached a photo of the variant with the screen at the inlet.  This screen is unnecessary if one uses a fuel filter at the inlet to the tee that feeds both carbs.

 

Attachment: fuel inlet valve 12855 with screen.jpg (Downloaded 84 times)

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 Posted: 07-10-2005 09:33 pm
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Ron Earp
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Thanks Mark! My kits had the ball valve type, so I am not sure what gives. I would like to have the needle valve type for sure. So, are the specs for the needle valve type? I noted in the TR8 manual 0.625 to 0.627 was correct for the ball valve types, exact same carbs except for emissions tags, but otherwise the same.

I need to switch to the needle valve type, I don't trust those ball valves at all for some reason.  Every other carb I've taken apart that works like this has spring loaded needle valves and work on 2.5-4psi of pressure, so you don't have to worry about having springs in them and not getting fuel. I like the springs because it will insure fuel won't leak whilst the car sits, not something I trust with the ball valve.

Ron

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 Posted: 07-10-2005 11:12 pm
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Mark Rosenbaum
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All the kits I've used over the past 5 years have been from Delta.  All were marked ZE15K (see attached photo) and all had the needle type valves with black rubber tips on the needles.  None of these had a spring inside, and AFAIK none of these leak until the rubber tips are worn out (assuming proper fuel pressure and good floats, of course).  If the kit-maker is using modern materials, and the fuel is free of rust flakes, the fuel inlet valves could conceivably outlast the car.

I have seen several variants of the needle valve with a bare brass tip.  These probably should be avoided as they are far less forgiving than the soft-tipped ones.

I suppose if you really wanted to, you could disassemble the inlet valves and modify them to add tiny springs.  Lacking proof that this was really necessary, I wouldn't bother.

You have to be careful what kit you buy.  According to the TRF catalogs, the kit for the TR6/TR250 with Strombergs (TRF P/N ZEMS577A) and the kit for the TR4/TR4A (TRF P/N ZECD3), both use Grose valves.  Presumably Moss sells the same kits under their own part number system.  Don't know what is being sold for Volvos or TR8s.

Since Delta's price for carb kits is competitive or better, in your position I'd just buy from them, in bulk if necessary, and not worry about other sources.  (Usual disclaimers.)  If you rebuild your carbs every season, pretty soon you'll have a garage full of perfectly good but slightly used carb parts that should satisfy any plausible need for spares.  Alternately, buy a second set of carbs, rebuild them and tune them for the car, then put them up for spares.  It's much quicker to R&R a carb than it is to troubleshoot one -- and there is never any spare time on race day.

BTW, one trick that should improve your Stromberg fuel/air mix consistency under severe cornering is to make sure that both floats weigh the same.  Floats weigh 14.0 grams nominal, and should be matched to within 0.15 gram.

 

Attachment: carb kit ze15k.jpg (Downloaded 73 times)

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 Posted: 07-11-2005 12:59 am
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Ron Earp
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Mark,

I have a kit from JAE and it has the old ball valves. These carbs I have were tweaked and flowed from a fellow in the NE that fools with them a lot and while new, he used the ball valves too. I'll order a couple of kits from Delta. I suppose with moving them around etc. the tabs became bent on the floats and caused them to hold the valve open - sure looks like it. I'll check it out tonight.

I definitely mean to have some spare carbs around and will start hunting a set up. I had four on a recent Jaguar V12 I just sold the other day but they were different enough in linkages that I didn't want to worry about them. There are enough JH carbs second hand that it pays just to get a set of the real deal.

Ron

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