Carburetor Floats

Tech tips and how to's

Moderators: notoptoy, garth, S Allen

scotcochran
Roadster Newby
Posts: 18
Joined: Sun Aug 05, 2012 1:54 pm
Location: Hollister, CA.
Model: 1500/1600
Year: Low Windshield-64-67.5

Carburetor Floats

Post by scotcochran » Sat Jul 06, 2019 10:33 pm

Hello folks,
I purchased the new plastic floats and I'm ready to place them in the float bowls. Do I need to do any float adjustments or can I just drop them in.?
Any comments appreciated.

C.Costine
Roadster Nut-Site Supporter
Posts: 1080
Joined: Fri Feb 13, 2015 8:08 pm

Re: Carburetor Floats

Post by C.Costine » Sun Jul 07, 2019 5:44 am

scotcochran wrote:
Sat Jul 06, 2019 10:33 pm
Hello folks,
I purchased the new plastic floats and I'm ready to place them in the float bowls. Do I need to do any float adjustments or can I just drop them in.?
Any comments appreciated.
Yes, absolutely! for optimum performance the fuel level in the float bowls needs to be correct. So while there is no recommendation for checking every so many miles, it should certainly be done when you have them open, and since there should be no expectation that the plastic floats will have exactly the same buoyancy as the brass ones, they need to be checked and adjusted.
located in Chester NH
1967 1600 in restoration
2013 Arctic Cat F-1100 turbo
Ford F-350 6.0
Ford 9000 puller, Ford 960 puller, Ford 901show, Ford 971 worker, Oliver 70 waiting its turn

scotcochran
Roadster Newby
Posts: 18
Joined: Sun Aug 05, 2012 1:54 pm
Location: Hollister, CA.
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by scotcochran » Sun Jul 07, 2019 10:10 am

Is there a wiki that tells me how to do this. Looked and cant find one. Thank you for the response.

User avatar
S Allen
Site Admin
Posts: 4024
Joined: Thu Dec 05, 2002 4:57 pm
Location: Knoxville, IA(Lake Redrock)Antioch, CA(Winter Months)
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by S Allen » Sun Jul 07, 2019 11:29 am

There is some info in the FAQ in the wiki.

Question: How do I adjust the floats on the later SUs with the hinged floats?

Answer: Adjustment of the hinged floats can really cause problems if not done properly. Remove the float bowl covers, clean the float bowls, remove old sediment, check and then adjust the float setting if necessary. You can do this by turning the cover upside down and with a 1/8" drill bit. Set the drill bit across the cover. The float tab should just touch the bit. Do not apply force to the float, just let it rest on its own weight. Ensure the needle is moving and seating properly. Reinstall the cover. This should get you real close to optimal setting. Make any adjustments to your idle mixture by turning the very bottom thumb screws counter clockwise to richen and clockwise to lean. You can then check the settings by disconnecting the coil wire, removing the pistons. Crank the engine over several times to get the fuel flowing. Peer down into the jets and the fuel level should be just below the top of the jets and very close to equal.


Steve
66 Stroker-Viper Blue Eventually
67.5 Stroker-Purple
67 SRL311-00279-resto project
Stock '72 240Z-Blue
2002 Ford F250 7.3 Diesel 2WD Hauler
2008 Toyota FJ Cruiser
2009 Smart ForTwo Passion Coupe
2013 Fiat 500 Abarth

scotcochran
Roadster Newby
Posts: 18
Joined: Sun Aug 05, 2012 1:54 pm
Location: Hollister, CA.
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by scotcochran » Sun Jul 07, 2019 12:08 pm

Steve, this is for the hinged floats. I forgot to mention in my post that mine are the free floating type. Not attached to anything. Does this write-up apply to those somehow also?

User avatar
S Allen
Site Admin
Posts: 4024
Joined: Thu Dec 05, 2002 4:57 pm
Location: Knoxville, IA(Lake Redrock)Antioch, CA(Winter Months)
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by S Allen » Sun Jul 07, 2019 12:31 pm

No, this is for the hinged floats. The service manuals in the tech wiki should have what you are looking for. There are either screen or print versions available. Here is the Clymer manual screen version.


Clymer Service Manual


Steve
66 Stroker-Viper Blue Eventually
67.5 Stroker-Purple
67 SRL311-00279-resto project
Stock '72 240Z-Blue
2002 Ford F250 7.3 Diesel 2WD Hauler
2008 Toyota FJ Cruiser
2009 Smart ForTwo Passion Coupe
2013 Fiat 500 Abarth

scotcochran
Roadster Newby
Posts: 18
Joined: Sun Aug 05, 2012 1:54 pm
Location: Hollister, CA.
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by scotcochran » Sun Jul 07, 2019 6:02 pm

Thank you Steve.

User avatar
ted heaton
Roadster Fanatic-Site Supporter
Posts: 1534
Joined: Wed Nov 01, 2006 5:01 pm
Location: Bellevue Washington
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by ted heaton » Sun Jul 07, 2019 11:27 pm

S Allen wrote:
Sun Jul 07, 2019 11:29 am
There is some info in the FAQ in the wiki.

Question: How do I adjust the floats on the later SUs with the hinged floats?

Answer: Peer down into the jets and the fuel level should be just below the top of the jets and very close to equal.


Steve
The pertinent section of Steve's link is quoted above. The "book" distance spec between the bottom of the inlet needle and the arm
that the float pushes on is for the original inlet needle valves. The current replacement valves may NOT be the same length as the original.
Unless you use washers under the valve to make it the same length, the original specs are wrong. Adjust the float height so the fuel level is about
2 mm below the top of the jets. Apparently the OEM Nissan inlet needle valves are no longer available.
All the recent ones I have used were NOT the same length as the original.
Dean states that his valves are the correct length.

Ted
Ted Heaton
Bellevue, Washington
DROPS (Datsun Roadster Owners of Puget Sound)
SPL31003054 1964 1500
SPL31112958 1967.5 1600 S15 SR20DET
SRL31105015 1968 2000 S13 SR20DET
SRL31112326 1969 2000 Honda VTEC

fairladyproducts.com
Roadster Fanatic
Posts: 215
Joined: Thu Aug 16, 2007 9:29 pm
Location: SOCAL

Re: Carburetor Floats

Post by fairladyproducts.com » Mon Jul 08, 2019 1:33 pm

Ted wrote:

"The pertinent section of Steve's link is quoted above. The "book" distance spec between the bottom of the inlet needle and the arm
that the float pushes on is for the original inlet needle valves. The current replacement valves may NOT be the same length as the original.
Unless you use washers under the valve to make it the same length, the original specs are wrong. Adjust the float height so the fuel level is about
2 mm below the top of the jets. Apparently the OEM Nissan inlet needle valves are no longer available.
All the recent ones I have used were NOT the same length as the original. ...."

I have some new genuine Nissan ones available. Price is $35 each Bar codes included.

Stan
MVC-011S.JPG
You do not have the required permissions to view the files attached to this post.

scotcochran
Roadster Newby
Posts: 18
Joined: Sun Aug 05, 2012 1:54 pm
Location: Hollister, CA.
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Carburetor Floats

Post by scotcochran » Mon Jul 08, 2019 10:27 pm

Ok, so I think I'm confused now. How do I see the fuel level to adjust it? Today I set the float arm height at 15mm from the base as it shows in the book.
It doesn't look like they changed my inlet needles so I assume they are the originals.
What concerns me is that the float arm that I am supposed to adjust, were way out of adjustment by about 3mm. Don't know why. I don't know how the floats ever hit them since they were partially sunk. This makes me want to adjust the fuel height as you stated instead. So...did I miss something? Maybe my brain is over thinking this. Are there instructions on this method somewhere or do I use the first method the book states where it seems I need a tool of some sort.