Northy
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| posted on 26/4/04 at 07:25 PM |
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Who knows about Weber jets
Trying to sort out my lack of idle, after consulting Mr Andrews web site.
He suggests 50/55f9 Idle jets, I have 55f8's fitted what effect will this have?
Thought I'd check the mains while I was at at:
Main jets: 145
Emulsion Tube: F16
Air corrector: 155
The first two seem fine, but Mr Andrews suggests Main Jet size plus 50 for the Air correctors, so mine seem too small. Would this affect idle at
all?
BTW the chokes are 36mm and the engine is a 2L 8 valve VX SEH
Carbs are Twin 45 Webers.
Anyone know?
Cheers
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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wicket
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| posted on 26/4/04 at 09:37 PM |
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Graham
If you don't get the answer here, try giving Southern Carbs a ring, usually very helpful.
http://www.southerncarbs.co.uk/
Tel: +44 (0)20 8540 2723
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ady8077
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| posted on 26/4/04 at 10:19 PM |
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Hi Graham
According to my speedpro book on webers f8 is slightly leaner than f9
As for air correctors it says there only used at high revs, so they shouldn't affect idle
Cant you get it to idle at any rpm? Dont forget if you've fitted a faster cam it probably wont like idleing below 1000 rpm. And as webers dont
have chokes you'll have to nurse it for a couple of minuits too
Adrian
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Dave Ashurst
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| posted on 26/4/04 at 10:21 PM |
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See my post on your other thread.
Have another try first. I wouldn't change the main jetting yet.
Dave
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britishtrident
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| posted on 27/4/04 at 07:14 AM |
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F9 would be a much better match for your engine.
From experience on Lotus Twincams the difference between f8 and f9 isn''t that enormous that it would stop the engine idling so even F9
might be on the lean side.
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Bob da builder
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| posted on 27/4/04 at 11:22 AM |
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Hey up mate
try EuroCarbs, there in reading. 01189431180.
they have been recommended to me by many different people and speaking to them they now their stuff, infact i have a package of new jets waiting at
home for me right now!!
if you tell them you spec of engine they will tell you the jets that you need, they are also dam good with advice, ie. this happens ... why? and they
seam to give you the right answer to fix the problem!
im off to the MOT this afternoon to hook up to a gas analiser thingy. will let you tnow if they got the correct jets for my carbs.
bob
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MikeP
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| posted on 27/4/04 at 11:59 AM |
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Just to confuse things even further Northy, the idle jets don't control the mixture at idle, the idle screws do. You can run pretty much any
idle jet and still get the car to idle properly.
Dave A's message at the end of your idle thread is good advice. If you can't get the engine to idle with what you've got in there
right now, something else is wrong.
Once you get the car to idle your fun will really start . The idle jets set mixture at the transition between idling and when the main jets come
in. 55F8 should get you driving with that engine and those venturi's. What they *may* cause *if* they're not quite right (it's
hard for them to be completely wrong) is a lean stumble as you accelerate, especially slowly (not to be confused with a bog if you jam open the
throttle suddenly). The air correction jets may cause the engine to run rich at high RPMs - you'll hear the note change if so as you go up near
your top end at wide open throttle. The main jets sound a bit small to me, but you can feel if they're off pretty easily in the mid range if
you swap in different sizes. Once close, you can go up or down a size till you're happiest.
If you start swapping jets, you're going to be spending a lot of time and money, and chase some very tricky and subtle things. What you might
want to do is find someone who can tune webers on a dyno. I'm sure they'll get you set up closer and faster, and for a lot less money
than you'll be into otherwise.
The DIY way is frustrating and expensive, but can be rewarding (eventually). It's a great way to learn how these things work - whether knowning
how weber's work in this day and age is something you can decide on your own .
I'll be happy to help however I can (I've learned a bit about them the DIY way), and I've got some web links that are pretty useful
if you're interested. Definitely pick up one of the weber tuning books as well.
Step one is getting the engine to idle - a little more on the symptoms would be useful. Definitely the butterflies should be open. In fact, you
should hold them open until the engine is warmed up, and then partially close them to try to set the idle. they'll be just slightly open at
idle. You shouldn't need the enrichment circuits unless it's below 0C.
HTH!
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Northy
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| posted on 27/4/04 at 05:35 PM |
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Thank you everyone for your suggestions and help. I'll try again, but won't be until Saturday as the shits hit the fan (again) at work!
Bob, the carbs are brand spanking new (don't ask ) from Eurocarb, and they supposedly set them up for my engine. I aggree from what
I've read here and elsewhere the Idle jets should be Ok, but think they've dropped a bollock with the air correctors Also they are not
my favourate people from recent past experience......
The engine is std, and static timing has been set correctly using a strobe.
Looking forward to Saturday.......
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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NS Dev
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| posted on 27/4/04 at 05:58 PM |
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Just to check the obvious (this won't stop the idle but it will make it very lumpy) have you balanced the carbs up properly?
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Northy
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| posted on 27/4/04 at 06:03 PM |
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But I can't do this properly until it vaugely idles can I, or can I?
Cheers
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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