S90 Engine Issue (recent rebuild)

[Tony Aguirre]

S90 engine w/800 miles on fresh rebuild. New everything, CE reconditioned heads, D. Marks rebuilt distributor, Beiker Eng. rebuilt carbs, etc. Runs very smoothly at city cruising speeds. On inclines (mostly freeway) engine will start to sputter going uphill, on level surface driving seems to be OK. When trying to accelerate, car stumbles for a moment and then takes off with good power. Float levels checked twice, timing checked, valves adjusted correctly, carb linkage correctly adjusted, fuel pressure OK. What might be causing this, especially uphill engine miss. BTW, plenty of gas, new fuel filter, new plug wires,etc.

[Richard Towle]

Dirty idle jets, dirty transition circuit, could be dirty main jets...but you arent using the mains while cruising...most likely you need to clean the idle jets.

Rich

[Frederic Prince]

the carbs just come from Bieker, they already have clean all jets, no ?

[Bill Dally]

S90 engine w/800 miles on fresh rebuild. New everything, CE reconditioned heads, D. Marks rebuilt distributor, Beiker Eng. rebuilt carbs, etc. Runs very smoothly at city cruising speeds. On inclines (mostly freeway) engine will start to sputter going uphill, on level surface driving seems to be OK. When trying to accelerate, car stumbles for a moment and then takes off with good power. Float levels checked twice, timing checked, valves adjusted correctly, carb linkage correctly adjusted, fuel pressure OK. What might be causing this, especially uphill engine miss. BTW, plenty of gas, new fuel filter, new plug wires,etc.

Did you measure the volume of gas coming from the accelerator pump when you cycle the throttle. Stumbling on acceleration is usually too much or too little (most often too little) from the accelerator pump.

[Ron LaDow]

Frederick

"the carbs just come from Bieker, they already have clean all jets, no ?"

Hard tellin'. Did Harry clean your tank and fuel lines?
Thanks,
Ron LaDow

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[Guest]

Tony,
At 800 miles the motor needs a full service of oil, valves and filter. This however is not your problem. It sounds like the accelerator pumps are not doing their jobs. Since this is an S90 motor you have Solex P40 carbs. If you look down the throats you will see in each bore a brass tube that is bent downward, this is the accelerator nozzle and it applies fuel down the throat the moment you move the throttle more open. You should see a stream of raw gas being pumped in. This needs to be adjusted to deliver .65 cc per 2 full strokes. You are going to need to get one of the special vials that is made for the adjustment. BTW from Porsche they are $45+. This problem will make cold starting a bit harder also. A quick and dirty way to check this is to look down the throat and give it a full stroke and the nozzle should inject for about 2 seconds.

Alan

Tony Aguirre wrote:

S90 engine w/800 miles on fresh rebuild. New everything, CE reconditioned heads, D. Marks rebuilt distributor, Beiker Eng. rebuilt carbs, etc. Runs very smoothly at city cruising speeds. On inclines (mostly freeway) engine will start to sputter going uphill, on level surface driving seems to be OK. When trying to accelerate, car stumbles for a moment and then takes off with good power. Float levels checked twice, timing checked, valves adjusted correctly, carb linkage correctly adjusted, fuel pressure OK. What might be causing this, especially uphill engine miss. BTW, plenty of gas, new fuel filter, new plug wires,etc.



Tony Aguirre

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[Michael Cass]

Hi Tony.

When I had my A 1600 normal engine rebuilt it had a hesitant flat spot from about 1800rpm to 2300 rpm when giving it some right foot. Like you I had new everything. I did oil changes at 50 miles, 500 miles, 1000 miles then every 1500 miles since. By 3000 miles the flat spot had dissappeared and has not come back. The engine now has about 11,000 miles and is an absolute gem. Now this I believe was simply down to the engine needing to bed in fully so I would suggest that you wait and see.

If it is not due to the above bedding in reason then I would suggest that you check all of your throttle linkage adjustments from the pedal right through to both carbies, to ensure that when you press the loud pedal the throttle on each carb is opening exactly the same. You made no mention of whether or not all of the ball and socket joints on your linkages are new. If they are not then it is near impossible to perfectly synchronise your carbs no matter whether everything else is new or not and this will definately cause hesitation and rough running. Sometimes it is the simplest things that cause niggling problems .

I Hope this helps if this is your problem.

Regards

Michael.

[Norm Miller]

As for a simple volume test tube you can solder a wire to an empty 22 short cartridge case.

Simple, cheap and easy to make. Calibrate it to .6 to .7 cc's.

Norm

[Albert Tiedemann]

Norm is correct on the use of a .22 short cartridge case for a measuring instrument.

If you spend the $45 or so for the correct P25a--an oval GLASS [very, very fragile measurement vial] it works well on all the carburetors except for maybe the 32NDIX with the 24 mm venuri. The space betwee the outlet of the nozzle and the bore of this venturi often did not permit the length of the measurement vial to be properly positioned. In the early days, the .22 caliber short cartridge was the hot lick around this dilema and cheaper --even then--by a goodly amount.

The injection quantity early on was only .2 cc/2 strokes, so there was plenty of cartridge to hold the quantity to be measured. However, the .22 short or even the long or long rifle case will not hold .6-.7 ml [1ml=1cc]

Proof: .65/1000 * 1/3.78 * 231/1 = .22^2* 3.1416...*1/4 *Z

where Z = length of cartridge case

Find Z=1.044 inches For .2 ml, find Z=.321 inches

For the Zenith carbs this is an acceptable substitute. For carbs with a spec of .45-.65 ml
another measurement scheme is needed unless you want to spring for the factory tool.
I made my own for the Solex 40 PBII-4 and one similar but proportioned for the Zenith. A lot less expensive then the $45 one mentioned by Alan.

But--like all things that are made in small quantity, 10 is usually the lower limit unless you are flush enough to afford 95,000 coupes, 135,000 cabriolets and 200,000 Speedsters --pushrod all, of course

[Ron LaDow]

Ab wrote:
"If you spend the $45 or so for the correct P25a--an oval GLASS
[very, very fragile measurement vial] it works well on all the
carburetors except for maybe the 32NDIX with the 24 mm venuri. The
space betwee the outlet of the nozzle and the bore of this venturi
often did not permit the length of the measurement vial to be
properly positioned.

I don't know if it's on the Registry web page (Barry?), but in the magazine article on reboping Zeniths, there's a photo of a deli straw bent, taped and marked for .3cc.
Thanks,
Ron LaDow

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[Guest]

First check that the accelerator nozzles are squirting fuel into the
throats when the throttle is moved.

Alan

Michael Cass wrote:

Hi Tony.

When I had my A 1600 normal engine rebuilt it had a hesitant flat spot
from about 1800rpm to 2300 rpm when giving it some right foot. Like
you I had new everything. I did oil changes at 50 miles, 500 miles,
1000 miles then every 1500 miles since. By 3000 miles the flat spot
had dissappeared and has not come back. The engine now has about
11,000 miles and is an absolute gem. Now this I believe was simply
down to the engine needing to bed in fully so I would suggest that you
wait and see.

If it is not due to the above bedding in reason then I would suggest
that you check all of your throttle linkage adjustments from the pedal
right through to both carbies, to ensure that when you press the loud
pedal the throttle on each carb is opening exactly the same. You made
no mention of whether or not all of the ball and socket joints on your
linkages are new. If they are not then it is near impossible to
perfectly synchronise your carbs no matter whether everything else is
new or not and this will definately cause hesitation and rough
running. Sometimes it is the simplest things that cause niggling
problems Wink.

I Hope this helps if this is your problem.

Regards

Michael.


------------------------------------------------------------------------

59 Porsche 356A Coupe
59 VW Kombi
60 VW kombi
61 VW Karmann Ghia Coupe
02 Toyota Townace SBV ( aka. The Unspeakable)




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[David Menere]

For my Solex carbs, years ago i used a hypodermic syringe to deliver the required 0.65ml into a ballpoint pen cap, cut to length so it was just full at that amount, wound some thin wire around it and put a dab of contact glue on the wire to prevent the wire and cap separating. You might have to go through the household supply of pens to find the shape that will best fit into the barrel ...

[Guest]

A good substitute, and in fact it looks like the original, is to use
the glass portion of an eyedropper. Place it on a length of wire and
over a gas flame melt the tip closed. Calibrate it in your way and use
some very fine wire to hold in in the throat of the carb. Beats paying
$45+ for the real one and the eyedropper is much stronger. BTW if you
must have the real one they are still available from Porsche.

Alan


David Menere wrote:

For my Solex carbs, years ago i used a hypodermic syringe to deliver
the required 0.65ml into a ballpoint pen cap, cut to length so it was
just full at that amount, wound some thin wire around it and put a dab
of contact glue on the wire to prevent the wire and cap separating.
You might have to go through the household supply of pens to find the
shape that will best fit into the barrel ...


------------------------------------------------------------------------

David Menere
356SC




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[Freddy Rabbat]

Tony,
Check if the Venturis were not assembled upside down...
Best,

[Ken Daugherty]

The barrel of a plastic hypodermic syringe makes a good vial.
Melt the bottom closed and push a hot wire thru the plastic for a
handle.
No danger of breaking.
(There are certain parts of Louisville where you can pick up one
off the street)
Ken Daugherty
kend356@insightbb.com


-----Original Message-----
From: Alan Klingen [mailto:stable356@earthlink.net]
Sent: Sunday, May 04, 2008 8:36 PM
To: 356talk@356registry.com
Subject: [356Talk] Re: S90 Engine Issue (recent rebuild)


A good substitute, and in fact it looks like the original, is to use
the glass portion of an eyedropper. Place it on a length of wire and
over a gas flame melt the tip closed. Calibrate it in your way and use
some very fine wire to hold in in the throat of the carb. Beats paying
$45+ for the real one and the eyedropper is much stronger. BTW if you
must have the real one they are still available from Porsche.

Alan


David Menere wrote:

For my Solex carbs, years ago i used a hypodermic syringe to deliver
the required 0.65ml into a ballpoint pen cap, cut to length so it was
just full at that amount, wound some thin wire around it and put a dab

of contact glue on the wire to prevent the wire and cap separating.
You might have to go through the household supply of pens to find the
shape that will best fit into the barrel ...


----------------------------------------------------------------------
--

David Menere
356SC

------------------------
Alan Klingen
Owner, The Stable




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