Air Fuel Help, Think I'm running to lean |
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Air Fuel Help, Think I'm running to lean |
Jetsetsurfshop |
Mar 1 2014, 04:50 PM
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#1
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
Quick one guys. At a track event and I think i'm running to lean.
What is ideal? I know we've killed this topic to death! I'm terrible at the search function. Please help (IMG:style_emoticons/default/driving.gif) |
Jetsetsurfshop |
Mar 1 2014, 04:52 PM
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#2
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
13.4 A/F
135 main jets on 45 webers |
brant |
Mar 1 2014, 06:07 PM
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#3
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914 Wizard Group: Members Posts: 11,618 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
at full throttle it will be rich and then get leaner and leaner towards redline
you want between 12.5 to 12.9ish... at the lean point of redline so it will likely be more rich at 4k.. or 5k than redline what rpm were you getting your readings? dyno pulls start around 3k ish... then give the motor time to clean out and have consistent full throttle to watch the AF ratio under load running lean at redline is a sure way to hurt the motor an do you mean 44 webers? the velocity (affected by choke size) has a lot to do with how well the carbs atomize at tip in.... and thus what jets will work best. Which main venturi size are you. if you leave the chokes alone you will want bigger mains if you put large chokes in you can pick up a few hp at redline by giving up midrange. But this is standard operation for a race motor that ideal is going to redline every shift. bigger chokes also require bigger mains |
Jetsetsurfshop |
Mar 1 2014, 06:12 PM
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#4
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
at full throttle it will be rich and then get leaner and leaner towards redline you want between 12.5 to 12.9ish... at the lean point of redline so it will likely be more rich at 4k.. or 5k than redline what rpm were you getting your readings? dyno pulls start around 3k ish... then give the motor time to clean out and have consistent full throttle to watch the AF ratio under load running lean at redline is a sure way to hurt the motor rpm is 5500-6500 with the 13.4 Thats with 135 mains I don't have a 140 set. I do have a 145 set. Is it that simple? Thanks Brant. I'd figured you'd speak up. Shane 40idf sorry really tired. |
brant |
Mar 1 2014, 06:30 PM
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#5
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914 Wizard Group: Members Posts: 11,618 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
I would absolutely throw the 145's in.
they are probably the right ones... but if they are too big or you pick up a midrange stumble you can buy something else. if it does pick up a midrange stumble, you may be able to play with air correction/emulsion tubes or idles to fine tune it out the biggest jets that dont destroy the midrange are the most power and the same technique applies to chokes. this will not make a fun street car... but will inch towards HP for the track. |
ChrisFoley |
Mar 2 2014, 08:18 AM
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#6
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I am Tangerine Racing Group: Members Posts: 7,920 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
Shane,
with your displacement and camshaft, you're giving up a lot of potential using 40IDFs without doing substantial mods to the carbs. Big primary venturis like the 36mm chokes I use don't work too well in 40IDFs unless the top plate is opened up and the secondary vent support ring is trimmed. 44IDFs have a more open inlet to the carb throats and don't need any mods to flow much more air. In regard to your jet sizes, I wouldn't hesitate to try the 145 mains and also increase the air correction jet size as needed to compensate for any over-rich condition which might occur. The ideal jets will likely end up around .25mm apart. For example - 150 mains:175 a/c |
Jetsetsurfshop |
Mar 2 2014, 08:34 AM
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#7
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
I'm sure my random fuel mixture isn't helping.
What fuel would you guys run with 10:5 to 1 compression ratio? Thx Chris for your help too. My dad "the real mechanic" is not with me or I'd be bothering him. |
ChrisFoley |
Mar 3 2014, 08:03 AM
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#8
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I am Tangerine Racing Group: Members Posts: 7,920 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
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ThePaintedMan |
Mar 3 2014, 09:11 AM
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#9
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
I agree with everything that's said, particularly Chris's suggestion about the 44s. For that displacement, you're much more in the range of 32-36 mm main chokes (venturis). If you're running 40s, it's very likely that your venturis are 28mm, or at most, 32mm. I think that 36mm are pretty hard to find for a Weber 40.
I have a set of 44s that I'm going to be selling soon once I finish rebuilding them. They're currently setup with 36mm vents and you can swap over all of your jets to them, including the 145 mains. Or I can do it for you if you're interested. |
Jetsetsurfshop |
Mar 4 2014, 02:33 PM
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#10
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
Do the 44s fit on the same manifolds?
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ThePaintedMan |
Mar 4 2014, 03:01 PM
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#11
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
Almost certainly. Most of the manifolds around were made to accept up to Weber or Dellorto 48s.
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bulitt |
Mar 5 2014, 10:58 AM
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#12
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Achtzylinder Group: Members Posts: 4,188 Joined: 2-October 11 Member No.: 13,632 Region Association: South East States |
You can also purchase a carb drill set and drill each jet progressively until you hit on the right size. Then order the correct ones.
(IMG:http://www.914world.com/bbs2/uploads/post-13632-1350646430.jpg) |
ThePaintedMan |
Mar 5 2014, 01:18 PM
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#13
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
You can also purchase a carb drill set and drill each jet progressively until you hit on the right size. Then order the correct ones. That works too. Though it won't net you the full potential that the larger carbs will, you can go this route and get the jetting more fine-tuned. I've got a set of jets that were filled and drilled previously, but they're currently somewhere around 1.25. You could open them up to your current size and go from there. That way you wouldn't be drilling an original set of jets. |
r_towle |
Mar 5 2014, 09:52 PM
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#14
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Custom Member Group: Members Posts: 24,571 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
what displacement is the motor?
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NICCKK11 |
Mar 5 2014, 11:50 PM
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#15
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Newbie Group: Members Posts: 1 Joined: 5-March 14 From: india" Member No.: 17,080 Region Association: None |
Hi,
Welcome to this forum site. Here you can find lots of things for your question. I suggest you, you have to ask same to any other expert. I am sorry for not able to answer your question. ............. Top Ten classified websites |
bulitt |
Mar 6 2014, 04:25 PM
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#16
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Achtzylinder Group: Members Posts: 4,188 Joined: 2-October 11 Member No.: 13,632 Region Association: South East States |
Nuther... (IMG:style_emoticons/default/spam.gif) (IMG:style_emoticons/default/spam.gif) (IMG:style_emoticons/default/spam.gif) (IMG:style_emoticons/default/pissoff.gif)
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Jetsetsurfshop |
Mar 7 2014, 12:22 PM
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#17
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
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r_towle |
Mar 7 2014, 07:11 PM
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#18
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Custom Member Group: Members Posts: 24,571 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
Thank you, I can't help with your issue, these guys can though.
I am just going to learn whatever setup you land upon. Rich |
brant |
Mar 7 2014, 09:58 PM
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#19
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914 Wizard Group: Members Posts: 11,618 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Shane. I didn't realize the motor displacement. What size chokes? I'm guessing you have a lot of easy horsepower left in your induction. Bigger mains and chokes.
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Jetsetsurfshop |
Mar 8 2014, 02:03 PM
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#20
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
Thanks for the help and advise everyone. Working on the carbs next week. (IMG:style_emoticons/default/smash.gif)
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