<VV> General Information and Tips on Carbs

Sun Jan 22 10:07:35 EST 2023

 Another thing I've noticed is lean belch back more often since the Feds have invoked the 13% ethanol in the gas supplies. I think a further increase in jet size may be necessary to keep up with the higher percentage which had been at 10 percent. I've already noticed an improvement in drivability with .053 -.054 jets in some street applications. The engines need for fuel because of fewer BTU's available with ethanol. Sadly, this all means less MPG's.Paul Fox

    On Sunday, January 22, 2023 at 07:58:03 AM GMT-6, John Sweet via VirtualVairs <virtualvairs at corvair.org> wrote:  

 The needles and seats in my kits that I supply  are 31-514 and I have no problem with them. The other thing to note is that Clark does not supply the Viton pump cups as his are coming from Tiwan.

John Sweet

Sent from Mail for Windows

From: Chuck via VirtualVairs
Sent: Saturday, January 21, 2023 9:58 PM
To: gyoungwolf at earthlink.net; virtualvairs at corvair.org
Subject: Re: <VV> General Information and Tips on Carbs

Great info!  
Thanks, 
Chuck Sadek
Group  Reds

-----Original Message-----
From: VirtualVairs <virtualvairs-bounces at corvair.org> On Behalf Of Grant via
VirtualVairs
Sent: Saturday, January 21, 2023 1:17 PM
To: virtualvairs at corvair.org
Subject: <VV> General Information and Tips on Carbs

Here are a few recent happings/things that might save some angst concerning
our carburetors.
- It seems that many (but not all) of the fuel inlet needles for Rochester
carburetors out there in recent kits (back to about May of last year as far
as I can determine) are too soft and tend to stick in their seats,
preventing fuel from entering the carb. Sometimes tapping will free it up so
fuel can flow and keep it lubricated, but not always. I have reverted to
installing hanger clips on all them so the floats can pull them down instead
of depending on gravity. Kits for them do not include the clips. Most
everyone gets them from Walker Products with the needles number 779 on them.
The part number for the assembles are 15-234. There are some assemblies
15-523 that have the hangers (and the same needle), but the holes are .101",
compared to the stock .086" holes. The larger ones are standard in many
Rochester 2 and 4 BBL carbs. If you have a kit, you can test the needle by
inverting the seat as it would be oriented in the carb and pressing the
needle into it with a bit of pressure.
  If it stays in, don't use it.
- Clarks is no longer suppling replacement throttle shafts for YH
carburetors and I have not found another source or anyone willing to make
them in small quantities. This means shaft bushings will be needed, and you
will need a long reamer that extends through both ends of the TB (or a jig
and drill press) to ensure the hole is straight and true. I have come across
a few bodies where the factory holes were not drilled in the center of the
housing and there is very little metal left after drilling. So, plan ahead
and keep your old shafts. If they are too worn, the bushings can be
installed deeper to get the remaining good part of the shaft inside them.
O-rings can help in a pinch but can only be installed on the pump end of the
shaft without grinding some metal off the lever end of the TB.
- I get quite a few 140 secondary cores where the accelerator pump cup has
been removed, so there is no "squirt" upon quick acceleration. The only
secondary carbs that don't use cups on the pumps were produced in 1968 and
1969. There are some examples out them out there, however, that still need
them. The easy way to tell if your secondary carbs should have them is to
check to see if there is an external rivet at the bottom of the pump cavity.
Rivet means cup, and no rivet means no cup. Regardless, all secondary carbs
with the rivet have only one squirter hole. There is no hole (or passage to
it) on the later A.I.R. carbs. You can swap in earlier ones if you are
experiencing a bog with heavy acceleration.
 - There are still some Rochester kits out there with buna accelerator pumps
that are not ethanol-proof. Improved viton cups were introduced about 5-6
years ago. The way to tell the difference is the color. Buna is black and
viton is blue. The buna cups will harden and stop working in as little as a
year without a fuel additive. The few viton cups I get in cores have all
been in good, flexible condition, but many buna ones are hardened to the
point that they break when removed.  
Hope this helps prevent some frustration for you DIY guys. Happy New Year
Grant - The Carbmeister

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