Carb mixture adjustment

Tech tips and how to's

Moderators: notoptoy, S Allen, Solex68

User avatar
BBF Roadster
Roadster Fanatic
Posts: 222
Joined: Thu Oct 20, 2011 8:30 pm
Location: Houston TX

Carb mixture adjustment

Post by BBF Roadster »

I'm trying to set the metering nozzles.
Mine are all out of wack.
If they are turned all the way in to lean,
How many turns out toward rich should they be roughly.
I hope someone can help so I can finally get it running.
Thanks
67.5 1600, U20 Swap
69 GTO
70 Barracuda
70 Roadrunner
70 Mustang FB
71 GMC Sprint SP 454
72 El Camino SS 454
Lee2000
Roadster Fanatic
Posts: 361
Joined: Sat Dec 06, 2008 12:25 am

Re: Carb mixture adjustment

Post by Lee2000 »

Are you saying it doesn't run at all right now no matter where you set the jets? Every engine will be different but you might try a base line setting of 1 1/2 to 2 turns out from full lean. Just make sure EVERYTHING else associated with the engine's tuning is set-up and adjusted properly before going hog-wild turning jet screws.
User avatar
jrusso07
Roadsteraholic
Posts: 1691
Joined: Sat Aug 02, 2008 9:02 am
Location: Penn Yan, NY
Model: 2000
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by jrusso07 »

1.5 to 2.5 toward rich is a good start. I tend to go rich as you adjust this out as you set up the system.

You should review this http://www.311s.org/su-setup/su-setup.html" onclick="window.open(this.href);return false;
Joe

1969 SRL311 - Solex
1970 SPL311 - U20 mod
1970 SRL311
User avatar
BBF Roadster
Roadster Fanatic
Posts: 222
Joined: Thu Oct 20, 2011 8:30 pm
Location: Houston TX

Re: Carb mixture adjustment

Post by BBF Roadster »

The engine runs, but has no throttle response, just drones with no power.
I replaced the head and had it rebuilt, so also need to check valve lash.
Thanks for the ball park setting.
67.5 1600, U20 Swap
69 GTO
70 Barracuda
70 Roadrunner
70 Mustang FB
71 GMC Sprint SP 454
72 El Camino SS 454
User avatar
GeoffM
Roadster Fanatic-Site Supporter
Posts: 1593
Joined: Thu May 22, 2008 2:28 pm
Location: Vancouver BC

Re: Carb mixture adjustment

Post by GeoffM »

If you have a micrometer, adjust the nozzles to a depth of .092" to start.

You should read this excellent write-up:
http://www.311s.org/pmwiki-311/pmwiki.p ... sNewSuTech" onclick="window.open(this.href);return false;
Geoff
1969 SPL-311
User avatar
BBF Roadster
Roadster Fanatic
Posts: 222
Joined: Thu Oct 20, 2011 8:30 pm
Location: Houston TX

Re: Carb mixture adjustment

Post by BBF Roadster »

I set the metering nozzles to two turns.
After a hard start again, I noticed a bad spark plug sparking around the ceramic.
Bought a new plug and it idles smoothly now. Yeah

Now when trying to rev the engine, it backfires through the carbs.
Also the distributor is set to full advance, but seems like it needs more advance.
Im very happy that it is closer to driving.
Thanks for any help guys.
67.5 1600, U20 Swap
69 GTO
70 Barracuda
70 Roadrunner
70 Mustang FB
71 GMC Sprint SP 454
72 El Camino SS 454
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8923
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Carb mixture adjustment

Post by Gregs672000 »

Dizzy may be a tooth off. There is a small degree of additional adjustment available by loosening the 8mm bolt that locks down the metal pointer on the dizzy. What is the initial timing set at? What curve? Also, check your firing order 1,3,4,2 counter clockwise. If you are not able to set the timing to where it should be you will have to remove the dizzy and set it correctly... let us know and we will walk you through it.

R or U motor?
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
BBF Roadster
Roadster Fanatic
Posts: 222
Joined: Thu Oct 20, 2011 8:30 pm
Location: Houston TX

Re: Carb mixture adjustment

Post by BBF Roadster »

Thanks to everyone.
I pulled the distributor and started over.
The oil drive was 180 off,then I cleaned and greased the distriburator so the vacuum advance would work.
Now it idles smooth and revs like a beast.
Now I will hook up the new clutch cylinders and get my first attempt to drive this car.
But I better not go far since I have no brakes yet. Lol
67.5 1600, U20 Swap
69 GTO
70 Barracuda
70 Roadrunner
70 Mustang FB
71 GMC Sprint SP 454
72 El Camino SS 454
jamesw
Roadsteraholic
Posts: 2754
Joined: Thu Aug 05, 2010 11:06 am
Location: Houston TX

Re: Carb mixture adjustment

Post by jamesw »

That's what the e-brake is for on these cars (in south TX where it's flat).

Just make sure the e-brake is CONNECTED first though :-)

Good to hear you got her running smoothly.

James
SRL311-00275
'96 Porsche 993 C4
2001 Excursion 7.3l
User avatar
v8_ranch
Roadster Fanatic
Posts: 109
Joined: Sat Oct 10, 2020 11:13 pm
Location: Jackson, TN
Model: 2000
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by v8_ranch »

I know this is an old thread, but just wanted to say thanks! It affirms everything I have sort of stumbled into today working on my 68, after getting confused by reading a lot of other information about what to expect from the SU carbs.
Shane

1968 SRL Project
User avatar
Linda
Fraternal Den Mother-RIP
Posts: 7807
Joined: Sat Nov 05, 2005 11:37 pm
Location: Los Angeles
Model: 1500/1600
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by Linda »

I think the .092 nozzle depth mentioned is confused with the .092 nozzle opening size for the 1600, as stated in the Tech Wiki article.

http://www.311s.org/pmwiki-311/pmwiki.p ... sNewSuTech

Linda

You are reading, which is GOOD :D
Last edited by Linda on Tue Nov 03, 2020 8:33 pm, edited 1 time in total.
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
User avatar
v8_ranch
Roadster Fanatic
Posts: 109
Joined: Sat Oct 10, 2020 11:13 pm
Location: Jackson, TN
Model: 2000
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by v8_ranch »

Yeah, I saw that as well, but was mostly looking at the baseline settings for mixture adjustment. Still trying to find a depth for the 2000, but I guess it probably doesn't matter if you know the approximate number of turns...
Shane

1968 SRL Project
User avatar
Linda
Fraternal Den Mother-RIP
Posts: 7807
Joined: Sat Nov 05, 2005 11:37 pm
Location: Los Angeles
Model: 1500/1600
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by Linda »

Problem for me with “approx number of turns” is it is too “approximate” and therefor hard to “match” the carbs as well. I always thought “2 turns” etc was easy to duplicate, but measuring showed something else.
I suppose you could do “ 2 turns out” or whatever, then pull the domes and try to match per a measurement, then reassemble and run. Keep doing that till correct. Tedious, but once set the carbs should be good. Matching is important per ZTherapy instructions so I figure it is worth pursuing, but others might not care...
Linda

Nozzle size for 2000 is.100 per TW
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
User avatar
v8_ranch
Roadster Fanatic
Posts: 109
Joined: Sat Oct 10, 2020 11:13 pm
Location: Jackson, TN
Model: 2000
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by v8_ranch »

Linda wrote: Tue Nov 03, 2020 8:36 pm Problem for me with “approx number of turns” is it is too “approximate” and therefor hard to “match” the carbs as well. I always thought “2 turns” etc was easy to duplicate, but measuring showed something else.
I suppose you could do “ 2 turns out” or whatever, then pull the domes and try to match per a measurement, then reassemble and run. Keep doing that till correct. Tedious, but once set the carbs should be good. Matching is important per ZTherapy instructions so I figure it is worth pursuing, but others might not care...
Linda

Nozzle size for 2000 is.100 per TW
Good thinking...
Shane

1968 SRL Project
User avatar
spl310
Roadster Guru
Posts: 13202
Joined: Sun Dec 29, 2002 10:38 pm
Location: In front of this keyboard... in Jacksonville, Florida!

Re: Carb mixture adjustment

Post by spl310 »

If you want absolute accuracy, get a Gunson Colortune.
"Wow, a Roadster!" Stuart Little

1967.5 2000
1967.5 2000
1964 1500
1964 1500
1967.5 1600
1968 chassis
2006 Acura MDX
2013 Volkswagen Jetta TDI wagon
1995 F350 Powerstroke!
More...
Post Reply