Tuning Webers

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MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Tuning Webers

#1 Post by MaddMart » Wed May 28, 2003 9:33 pm

I have just fitted a pair of DCOE 40's to the Sprint I've just bought. The car was running well with the std. HS6's & a mild road cam.<br>
<br>
I know ultimately I will be better off on a rolling road but I want to get it running well enough to get it there.<br>
<br>
I tried to balance the carbs as best I can (engine still rocking a bit on tickover). I used a colortune to try & get the correct mixture.<br>
<br>
Cylinder no. 1 = nice bluey colour spark, but know matter how much I turned the mixture screw down couldn't get it to go yellow (weak)<br>
Cylinder nos. 2,3&4 yellow spark, couldn't get it blue no matter how far out I turned the mixture screw.<br>
<br>
Venturi size = 34 (couldn't see markings on it so measured the bore)<br>
Air Corrector = 170<br>
Emulsion Tube = F16<br>
Main Jet = 135<br>
Idle Jet = 45 F9<br>
Aux. Vents = 4.5<br>
<br>
The carbs are second hand & came c/w Sprint manifold & K&N's.<br>
<br>
Can anyone put me right on the best way to set these carbs up & have I got the correct jet sizes etc.??<br>
<br>
<br>


<p>1979 Brooklands Green Sprint</p><i></i>

quicksprint
Posts: 10
Joined: Sat Mar 01, 2003 10:22 am

Re: Tuning Webers

#2 Post by quicksprint » Wed May 28, 2003 9:48 pm

I think you will find the 40's are too small for the sprint engine.They will be border line on a 8-valver,low down torque will be ok but you will lose out on top end.<br>
It looks like your idle jets and main jets are too small and the aux venturies should be 36mm,try 160-175 main and 50f8 idle jets.A rolling road session is going to be the best bet BUT i really think you will need to change up to 45's...sorry!!<br>
<br>
From past experience we fitted 40's on engine sizes upto 1600cc,anything over had minimum of 45's.<br>
Try looking in the Triumph Tune guide as it lists recommened jet sizes in relation to state of tuning parts fitted.<!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/intl/aenglish/im ... s/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <br>
<br>
steve.

<p></p><i>Edited by: <A HREF=http://pub52.ezboard.com/bthetriumphdol ... ksprint</A>  <IMG HEIGHT=10 WIDTH=10 SRC="http://emo.spacespider.net/fart.gif" BORDER=0> at: 5/28/03 9:50:48 pm<br></i>

MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Re: Tuning Webers

#3 Post by MaddMart » Wed May 28, 2003 10:36 pm

quicksprint - thanks for the info. I had a feeling the jets were too small.<br>
<br>
What I'm confused about is that you say 40's are too small for the Sprint engine. Surely if the main venturies were 36mm. it wouldn't matter if you were running 40's or 45's. or are there other considerations ?

<p>1979 Brooklands Green Sprint</p><i></i>

SMIFTER
Posts: 846
Joined: Wed Feb 12, 2003 3:04 pm

Re: Tuning Webers

#4 Post by SMIFTER » Thu May 29, 2003 8:45 am

Gotta get rid of my 40's and bolt my 45's on asap then!!!<br>
<br>


<p>http://www.smifter1971.pwp.blueyonder.c ... </p><i></i>

quicksprint
Posts: 10
Joined: Sat Mar 01, 2003 10:22 am

Re: Tuning Webers

#5 Post by quicksprint » Thu May 29, 2003 12:37 pm

Because 40mm is less than the 1 3/4" SU's you have taken off.Thats why the early tuners and Leyland ST fitted 2" su's to the group 1 cars and 45's to the group 2's !!<br>
2" =50mm approx<br>
1 3/4"= 45mm approx<br>
Asprint engine will demand a lot of air when used as it should be so the ability to give extra fuel is needed hence why 45's are the best all round size,with 48's the next step up or 50's if you are crazy!!<br>
<br>
"The 40's can be fitted BUT will tend to lose out on top end breathing if any more than a standard road camshaft is used.<br>
The power increase available is much better if the 45's are used,even on a basically standard car,as they can cope with higher demands from a more modified engine"<br>
<br>
Above was an extract taken from the Triumph tuning guide.<br>
According to the guide for 40's you need ...<br>
Choke:36mm<br>
Aux.venturi:4.5<br>
Main jet:155<br>
Emulsion tube:f16<br>
Air jet:170<br>
Idle jet:55f9<br>
Pump jet:45<br>
Back bleed:20<br>
<br>
Hope this is of some help,and all i can say is that 45's sure did work on mine<!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/intl/aenglish/im ... s/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/intl/aenglish/im ... s/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/intl/aenglish/im ... s/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <br>
<br>
steve

<p></p><i></i>

MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Re: Tuning Webers

#6 Post by MaddMart » Thu May 29, 2003 1:11 pm

Thanks Steve (I think) <!--EZCODE EMOTICON START :( --><img src=http://www.ezboard.com/intl/aenglish/im ... /frown.gif ALT=":("><!--EZCODE EMOTICON END--> <br>
I'll have to keep the 40's for now & re-jet them.<br>
<br>
Martin

<p>1979 Brooklands Green Sprint</p><i></i>

quicksprint
Posts: 10
Joined: Sat Mar 01, 2003 10:22 am

Re: Tuning Webers

#7 Post by quicksprint » Thu May 29, 2003 1:34 pm

No problem...you could at a later date sell them to someone with an 1850 !!!! <!--EZCODE EMOTICON START :eek --><img src=http://www.ezboard.com/intl/aenglish/im ... ns/eek.gif ALT=":eek"><!--EZCODE EMOTICON END-->

<p></p><i></i>

SMIFTER
Posts: 846
Joined: Wed Feb 12, 2003 3:04 pm

Re: Tuning Webers

#8 Post by SMIFTER » Thu May 29, 2003 2:23 pm

Steve<br>
<br>
Sorry to be an anorak but 40's actually have a similar area to HS8's - there are twice as many chokes on webers!!<br>
<br>
My understanding is that 40's are good for up to 160BHP, hence why you see many 2.0 8 valve engines such as TR7's and pinto's running them.<br>
<br>
They work quite nicely on my standard sprint engine and give bags of torque but I accept they will have to come off when I've fitted the STR91 cam etc as they wont be able to keep up with the increased mixture demands the higher lift/duration will give. <br>
<br>
Good News - I think Martins car is probably on the limit of 40's having a mild cam fitted.<br>
<br>
Mart - bad news - 45's are more sought after therefore cost a lot more cash secondhand. Typically double the price of 40's.

<p>http://www.smifter1971.pwp.blueyonder.c ... </p><i></i>

John Skinner
Posts: 93
Joined: Thu May 29, 2003 5:40 pm

chokes

#9 Post by John Skinner » Thu May 29, 2003 5:40 pm

RE your question about what the difference is between 36 chokes in a 40 or 45. I have been reading alot about tuning Webers recently and my understanding is that the general cut-off point between whether to use 40s or 45s is between about 34 and 36mm chokes. Basically if you are using the largest available sized chokes in a 40 (or any size for that matter), it is less like a choke and more like a straight pipe. So a 36 choke is supposed to work better in a 45 than a 40 as it is more choke like.<br>
Nothing I read recommended using larger than a 36 in a 40. As far as I remember a lot of Alfa 2L cars had twin 40's as standard with 32mm chokes...a completely different engine to a dolly though! and a standard state of tune...

<p></p><i></i>

Richard
Posts: 196
Joined: Wed Mar 05, 2003 9:38 pm

Weber

#10 Post by Richard » Thu May 29, 2003 10:13 pm

<br>
this is written by a Robin Hood owner ..... very useful<br>
<br>
<!--EZCODE AUTOLINK START--><a href="http://members.aol.com/dvandrews/webers ... <!--EZCODE AUTOLINK END--><br>
<br>
may take a few secs to load - it's worth it !

<p></p><i></i>

MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Suck it and see

#11 Post by MaddMart » Fri May 30, 2003 7:45 pm

Thank you all for your comments. I think I will re-jet the 40's based on the settings Steve has supplied above & let you know the results in the near future.<br>
<br>
Martin

<p>1974 French Blue Sprint</p><i>Edited by: <A HREF=http://pub52.ezboard.com/bthetriumphdol ... addMart</A>  <IMG SRC="http://www.aqpd91.dsl.pipex.com/NewSprint.jpg" BORDER=0> at: 5/30/03 7:46:17 pm<br></i>

MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Re: Tuning Webers

#12 Post by MaddMart » Fri Jun 27, 2003 8:15 pm

Right, I've fitted 36mm. chokes & all jets as per quicksprint/TriumphTune list.<br>
<br>
Engine ticks over fine but loads of smoke coming from the exhaust. I checked the plugs & they were all sooted up after running the engine for about 10 mins. obviously running rich me thinks. <!--EZCODE EMOTICON START : --><img src=http://www.ezboard.com/intl/aenglish/im ... ohwell.gif ALT=":"><!--EZCODE EMOTICON END--> I tried to get the mixture right using colourtune. All 4 cylinders were showing a yellow spark (rich mixture) & I couldn't adjust the mixture to show a blue one.<br>
<br>
Can anyone shed some light on this ??

<p>1974 French Blue Sprint</p><i>Edited by: <A HREF=http://pub52.ezboard.com/bthetriumphdol ... addMart</A>  <IMG SRC="http://www.aqpd91.dsl.pipex.com/NewSprint.jpg" BORDER=0> at: 28/6/03 8:28 pm<br></i>

redalan1971
Posts: 55
Joined: Fri Jun 27, 2003 11:13 pm

webbers

#13 Post by redalan1971 » Fri Jun 27, 2003 11:13 pm

i suggest that you contact peter cox at triumphtune as he has a list of settings that should be appropriate, i spoke to him re some settings for dellorto 45's and as in the triumph tune manual they suggest only 34mm chokes until you reach the sprint cam as it is much better for low down power 36mm chokes are only recommended on sprint profiles.<br>


<p></p><i></i>

SMIFTER
Posts: 846
Joined: Wed Feb 12, 2003 3:04 pm

Accept Defeat!!!

#14 Post by SMIFTER » Sat Jun 28, 2003 10:06 am

Mart<br>
<br>
2 words<br>
<br>
Rolling Road!!<br>
<br>
<br>
You know it makes sense!<br>


<p><!--EZCODE LINK START--><a href="http://www.smifter1971.pwp.blueyonder.c ... >Smifter's Dolomite Sprint Website</a><!--EZCODE LINK END--></p><i></i>

MaddMart
Posts: 1154
Joined: Tue Apr 15, 2003 8:35 pm

Re: webbers

#15 Post by MaddMart » Sat Jun 28, 2003 10:52 am

redalan - I used these settings because these are the recommendations in the Triumph Tune Performance Manual which are ok for anything up to a road cam (TT10104) which is what I have. <!--EZCODE EMOTICON START :) --><img src=http://www.ezboard.com/intl/aenglish/im ... /smile.gif ALT=":)"><!--EZCODE EMOTICON END--> <br>
<br>
Graeme - I know I need to use a rolling road but I was hoping I could set the mixture half decently myself for now. <!--EZCODE EMOTICON START :) --><img src=http://www.ezboard.com/intl/aenglish/im ... /smile.gif ALT=":)"><!--EZCODE EMOTICON END-->

<p>1974 French Blue Sprint</p><i></i>

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