Re: [HSS] Further to Marvel Carburetor Jets

Unknown

Tom Goodman wrote:

>

> --- In HudsonSuperSix16-29@egroups.com, Geoff & Marg Clark

> <geoffclark@x> wrote:

> > Tom Goodman wrote:

> > >

> > > Background: Standard Jets for Marvel "VB" Carburetors are

> specified

> > > in the book that Pete so generously shared as follows:

> > >

> > > High Speed Jet P/N 49-140-D-28

> > > or 49-160-D-28

> > >

> > > Intermediate HS Jet P/N 49-220-E-24

> > > or 49-180-E-24

> > >

> > > (the reason for the "or" is that Marvel made a change mid-run to

> get

> > > better performance, I suppose)

> > >

> > > Now: According to the Marvel book (P 13), jets should be changed

> for

> > > high altitude operation. We already knew that and Geoff

> suggested a

> > > real good way to do that with wire hanging into the opening of the

> > > jet.

> > >

> > > Marvel's suggestion for High Altitude operation is to use the

> > > following jets:

> > >

> > > High Speed Jet P/N 49-130-D-28

> > >

> > > Intermediate HS Jet 49-170-E-24

> > >

> > > Question: Does the second number in the part number indicate the

> jet

> > > size? For instance, in a 49-130-D-28, is the jet size .013"?

> That

> > > sure would stand to reason as far as I am concerned. If so, this

> > > gives me some indication of (1) what I have and (2) what I need

> to do.

> > >

> > > Thanks for enduring all of this and for your responses.

> > >

> > > Tom

> > >

> > >

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> > Regarding sozes, yes, the middle figure designates size, but I have

> > never bothered measuring the actual size of the hole, but the larger

> > number is a bigger hole. I have reduced the main sizes as

> mentioned

> > before. If anyone had a set of numbered drills then the actual

> > diameter could be ascertained by inserting the right number drill

> in the

> > jet and measuring the dirlll with a micrometer or dial gauge, but I

> go

> > by the "hit and miss" method, and it works fine. Remember that it

> is a

> > combination of float level, flapper spring tension, and jet size

> that we

> > have to consider, and all three have to be spot-on to get your

> Marvel

> > working correctly, taking into account also the height above sea

> level.

> > Have fun!

> > Geoff.

>

> Well, I am really confused now. I have two carbs and I took the jets

> out of both of them. According to the numbers stamped on the jets

> they are 160's for the high speed jets and 180's for the intermediate

> jets. This fits the recommended values in the Marvel book. HOWEVER,

> when I actually measured a jet (yeah, I measured the right end) it is

> 0.038 inches. The intermediate jet is marked 180 and actually

> measures about 0.045 inches. I am beginning to believe that either

> the jets have been bored out or that the marking is NOT intended to

> be indicative of the diameter of the jet nozzle as I originally

> suspected. By the way, I used both optical comparator and pin gauges

> to measure the diameters.

>

> The engineer in me was trying to calculate the correct size wire to

> drop in as you suggested, Geoff, to change the jet size but this

> measurement vs. marking correlation does not make sense to me. Does

> anybody have a suggestion as to what the diameter "should" be for the

> 49-160-D-28 jet, the 49-180-E-24 jet and for the "high altitude"

> replacements: 49-130-D-28 and 49-170-E-28???

>

> It is a puzzlement so far to me.

>

> Thanks in advance.

>

> Tom

>

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Tom, the measurement you give indicates that the jet numbers are in

relation to the size, in that a larger number has a larger hole than the

smaller number. I had ascertained this by the "eye-ometer" test.

The measurements you give are approxiametely 1/4 of the number. I.e.

180 divided by 4 = 45 (in thousands of an inch) and 1/4 of 160 = 40.

(you measure .038, could you be .002 wrong?) A 5 amp fuse wire is

.008" so if you insert one strand into the intermediate jet you are

reducing the fuel flow (theoretically) by nearly 20%. 10 amp wire is

approx .013, which should reduce by 33%. In actual fact this is what

happens, as I improved the fuel economy of a '29 Hudson 30%, (from 12

to 16 m.p.g.) by inserting 10 amp fuse wire in both the high and

intermediate speed jets. Power and performance was not affected at

all, in fact was better if anything as previously it was running far too

rich. This is because the specific gravity of our modern fuel is

lighter than it was in 1929. Have fun!

Geoff.