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 Daytona's 'improved' Inlet Needle & Seat? 
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Joined: Sun Jun 23, 2013 1:41 pm
Posts: 375
Location: Phila. Penn.
I decided to order up a rebuild kit from Daytona Parts as they claim to be USA made and ethanol resistant. This is for a Motorcraft 2150, so the usual Holley type sources weren't an option.

The kit came with an inlet valve with a flat bottomed needle and raised seat. They claim it is more tolerant of contaminants, dirt and provides a more stabile fuel level in the bowl. H'm, really?
A copy of their claim is on their website here: ... valve.html

At first I thought this was something for off-roading, but after reading the above, it doesn't seem to be. They must make a version for most common carburetors.

What do you think?

File comment: Daytona Parts flat bottomed needle valve and inverted seat.
Daytona-015S.JPG [ 39.21 KiB | Viewed 554 times ]
Fri Jan 22, 2016 11:35 am
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I replaced one of those in a neighbors Edelbrock AFB, didn't work right.

Fri Jan 22, 2016 3:46 pm
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Variations of a horizontal seat and the associated claims of SSS have been around a long as carburetors. In practice, it soon becomes obvious that to be able to tolerate the same fuel pressure fluctuations encountered in a vehicle due to pump pulsing, G forces and heat (vapor pressure) the horizontal seat orifice needs to be smaller in diameter than a seat for a conventional tapered needle (or a ball).

Fri Jan 22, 2016 5:05 pm

Joined: Sun Jun 23, 2013 1:41 pm
Posts: 375
Location: Phila. Penn.
jmarkaudio wrote:
I replaced one of those in a neighbors Edelbrock AFB, didn't work right.

Interesting. Now you know who where it probably came from. I figured it would work, just not do what they claim and at high flows create more turbulence.

tuner wrote:

...the horizontal seat orifice needs to be smaller in diameter than a seat for a conventional tapered needle (or a ball)

Next time I'm at the shop I'll compare the inside diameter against a normal one.

The statement that seemed most suspect to me was that a with a normal inlet valve, fuel level goes up in direct proportion to rpm due rising pump pressure. As far as I can tell, the typical mechanical diaphram pump produces the highest pressure when deadheaded. While at a given pressure it will flow more as rpm increases (limited by the internal valve sizes), it seems to me the float would hold the valve shut as soon as needed, unless the inlet pressure made too great a force.

Based on what both of you have posted, I'm not even inclined to give it try.

Last edited by Mattax on Fri Jan 22, 2016 11:02 pm, edited 2 times in total.

Fri Jan 22, 2016 9:49 pm
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Mattax wrote:

$ecret $quirrel $hit

"SSSS" is even more Top Secret and can be translated two (or more) ways (as many as your imagination provides), $uper $ecret $quirrel $hit or $upposedly $ecret $quirrrel $hit.

Fri Jan 22, 2016 10:11 pm

Joined: Thu Mar 28, 2013 6:09 am
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LMAO!!!!!!!!!! You have a way with words/abbreviations................... :thumbr: :thumbr:

Sat Jan 23, 2016 9:18 am

Joined: Sun Jun 23, 2013 1:41 pm
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Location: Phila. Penn.
Thanks Tuner.
I think it is a bit generational and environment Barry. I think I'm about 5-10 years behind. I'd heard the phrase before, although only as Secret not supposedly but couldn't put it together with the triple S.

I should add that I have a general aversion to seals that depend on resiliance. Worked on too many cars and houses to see what happens to many of these seals over time. Metal on metal with or without a thin gasket, or wood to wood with the right detailing is almost always best, but of course the devil is in the details. A properly designed o-ring seal is quite good, and poor finish or lack of flatness on wood or metal will be near impossible to make tight.

Sat Jan 23, 2016 10:30 am
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The 'mechanical pump pressure goes up as RPM increases' thing is based on most people not knowing how a mechanical pump actually works (or more accurately, thinking they know when they really don't*).

The cam lobe only retracts the diaphragm, that's the intake stroke. The cam lobe moves away, and the big spring pushes the diaphragm back to the neutral position which is what generates the output flow. If the outlet is deadheaded, i.e. the pressure never falls after the intake stroke, the diaphragm stays in the same retracted position. If there's no flow the diaphragm & spring never move. When not deadheaded, the spring only pushes the diaphragm out just enough to maintain the pressure. Most of their claims are based on similar misunderstandings of how stuff actually works.

Are these the same folks who make those Tornado swirl-generators?

*"What gets us into trouble isn't what we don't know, it's what we know for sure that just ain't so." --Mark Twain

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Sun Jan 24, 2016 10:17 am

Joined: Sun Jun 23, 2013 1:41 pm
Posts: 375
Location: Phila. Penn.
That's the best explanation I've seen. I was never sure but assumed the spring was only for pressure control; that is, in direct contact with the arm. Since I couldn't find rebuild kits back when, I never took them that far apart. Now, thanks to the internet, I can see you're absolutely right about the arm pulling and the spring providing the return push.

from Modifying a Carter 6270 for supercharged Studebaker

There are also really good pictures of a pump internals in this Carter 3508S rebuilding thread. This is also for a Studebaker, but the Ford and aftermarket Chrysler pumps by Carter are very similar - in fact the housings might be the same. This author is also astute enough to recognize the role of the spring in regulation.

The mistake I see alot is in understanding the advertised ratings. So its probably worthwhile restating what your explanation tells us.
Maximum pressure occurs at zero flow. If the pressure is too high, then the float bowl inlet valves can be forced open. In which case an inline pressure regulator is often added, and those IMO are often restrictions at high flow, and therefore a less than ideal solution. There probably is a reason why some fuel pumps have max pressures above what any of the common float and valve can hold back. Anyone know what the reason is? The M6270 "Competition" pump for example has a 7.5 psi pressure rating, and the new Holleys have a rating of 6.5 to 8psi. I have no idea why they have such a wide range (random supply of springs?) or why anything over 6.5 psi would even be wanted. But there it is.

The Flow Rating is the maximum freeflow output. Since all mechanical pumps see some resistance to flow both in and out, the free flow potential is of limited use. Around 2003, Holley came out with a new line of mechanical pumps and actually provided pump output curves. Below is one from their '110 gph' series. It shows both free flow and the much more useful flow against a restriction developing 4.5 psi. 3-5 psi is ballpark pressure going down the track for a lot of us.
File comment: Holley 110 gph Mechanical Fuel Pumps
f110GPHchrt.jpg [ 42.88 KiB | Viewed 485 times ]

Since that time, Holley seems to have decided that such useful information should be removed from their website. :wft?:

Without a chart, some reasonable observations can be made.
Volume moved with each stroke is dependent on the diaphram diameter and movement, along with inlet and outlet valves sizes. More valves or bigger pump diameter should have more potential volumetric flow. This is a problem on 70 up Chrysler small blocks, but most other engines seem to have room for 6 valve pumps (3 in, 3 out) if needed.

The other option is to send the pumps to a place that can actually test them. Not sure how common this is, but Ryan Brown was doing this, mostly for circle track folks. I sent 3 pumps for testing and thought his service was reasonably priced and well worth it. Interestingly, the slope is not always positive, and certainly not a direct correlation to rpm. The M6270 dropped a bit and then flat lined from 3000 to 4500 rpm, and the 6 valve MP pump dropped a little from 3500 to 4000 rpm.

Last edited by Mattax on Sun Aug 06, 2017 2:54 pm, edited 2 times in total.

Mon Jan 25, 2016 6:16 pm
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Might as well add the graphs from Ryan Brown's testing mentioned above.
The Carter M6290 is a 3 valve pump with 1/4 NPT inlet/outlet ports. Max (deadhead) pressure measured as advertised 7.5 psi. ...and this caused periodic problems when I used it on the street and in autocross.
The p4529368 a 6 valve pump with 3/8 npt inlet/outlet ports. Max pressure supposed to be 9.5 psi, but maybe that was a typo because it proved to be a much more civilized 7 psi.
File comment: Flow tests for two mechanical pumps
fuelpumpflowtests2.jpg [ 101.73 KiB | Viewed 465 times ]

Tue Jan 26, 2016 11:34 am
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