Tuning Webers

[Dave]

I've got a list of two sets of jet sizes one for 45's the other for 48's 170hp spec i'll give you both.<br>
<br>
fitted 48;s 170hp <br>
<br>
choke 36 36<br>
diffuser 1<br>
main jet 148 148<br>
idle jet 55 60<br>
pump jet 40 45<br>
starter jet 70 70<br>
main emulsion 7772 6 6<br>
starter emulsion 7482 1 1<br>
main air correction jet 170 170<br>
idle holder 7850 1 1<br>
needle valves metal 170.1<br>
floats 7298 1 1<br>
<br>
the 45s are running with a sprintspares 7ty1 (sp1016r) cam which is as follows duration 292 degrees<br>
<br>
timing vl/vc fl tdl<br>
<br>
in 40/72 .380/.008 106 .100<br>
ex 76/36 .360/.010 110 .96<br>
<br>
This seems to run fine the pugs are the right colour anyway, Don't forget to replace the rubber O rings as a matter of course and never ever tighten the mountings more than around 15 lb ft You should not need to put any effort into tightening the nuts otherwise the body will fracture.

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[Dave]

wrong thread

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[speedracer]

Excuse my ignorance but I didn't think it was possible to use Colourtune with a sprint motor given the depth of the plugs/tubes etc ... obviously it is. <br>
<br>
Mart, have you used some special setup? <br>
<br>
I'm embarrased to admit it but i'm having diffuculty tuning my 1 3/4" SUs ... <!--EZCODE EMOTICON START :o --><img src=http://www.ezboard.com/intl/aenglish/im ... rassed.gif ALT=":o"><!--EZCODE EMOTICON END--> <br>
<br>
speedracer

<p><!--EZCODE LINK START--><a href="http://www.triumphowners.com/2">1975 Dolly Sprint</a><!--EZCODE LINK END--></p><i></i>

[feralsprint]

speedracer dont be embarrased in our country riddled with cars fitted with Strombergs and carters there are a hell of a lot of supposed trained mechanics that have no idea about tuning SUs, especially multiple carbies. If you have the right needles already tuning and balancing should only take 10-20 minute max and no special tools needed just some spanners (small for undoing linkages ) what is the problem idle or running

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[MaddMart]

speedracer - All I do is put the colourtune spark plug in my plug socket (which should hold it in) and insert into tube (don't over-tighten - just tweak it). Then, this is the fiddly bit, you have to screw the extension to the spark plug.<br>
<br>
As for tuning the SU's, I know the theory I just can't seem to master the practical side.

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[SMIFTER]

As someone else said......<br>
<br>
SU's suck. Literally!!!!<br>
<br>
I could never get the buggers spot on but its amazing the difference dodgy carb rubbers make - even some that look OK can be suspect!

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

[Malc]

We live an learn, clever way to install a clour tune plug thingy, very clever. I have had a colourtune and a Sprint for 20 years and they've never met !!!!

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[Stephen Grellet]

1/ I think 40s would be ok for road use, possibly up to 6000 rpm<br>
2/ An engine being set while the car is static will tend to give too lean a reading when running.<br>
3/ I would go to a rolling road that has a good reputation with Webers. Because the jets are expensive you could spend a small fortune trying to get the correct mixture. The garage should have a range of jets that they will change until they get it right, and then you should only be charged for the jets you use.<br>
4/ Buy a Weber Tuning Manual from Webcon. This gives very good details on sizing carbs, jets and chokes etc for various engine sizes and rev ranges.

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[Dave]

a useful trick is to spray something like wd40 round the suspect area. If you get a change in in engine revs you have a leak. The oil seals the leaks momentarily.

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[MaddMart]

That's it, I've had enough <!--EZCODE EMOTICON START :( --><img src=http://www.ezboard.com/intl/aenglish/im ... /frown.gif ALT=":("><!--EZCODE EMOTICON END--> I've got them set the best I can. I'm going to book the Sprint in for a Rolling Road session. It's a 6 week waiting list so that will give me time to get a couple of other items sorted. <!--EZCODE EMOTICON START :) --><img src=http://www.ezboard.com/intl/aenglish/im ... /smile.gif ALT=":)"><!--EZCODE EMOTICON END--> <br>
<br>
Thanks everyone for your comments/ideas. I will let you know in due course what jets/chokes I end up with.<br>
<br>
Martin

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

[John Skinner]

Speaking of rolling roads, has anyone got any recommendations for rolling road virgins in the southeast? I was thinking maybe cambridge motorsport cos they seem to tune older cars...

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[Richard]

<br>
Red Line Tuning in Colnbrook / Heathrow are good. they're very close to Heathrow. Tony has been there for years and knows his stuff.

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[MaddMart]

Had the Sprint on the Rolling Road yesterday. Thanks to Dave @ Interpro, Bristol, a very knowledgeable chap. Soon had the Sprint firing on all cylinders <!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/intl/aenglish/im ... /laugh.gif ALT=":lol"><!--EZCODE EMOTICON END--> <br>
<br>
Compression test results were :- 180, 170, 185 & 175.<br>
<br>
Jetting:-<br>
Pump Jets = 45<br>
Mains = 135<br>
Emulsion Tubes = F16<br>
Air Correcters = 170<br>
Idle Jets = 50f9<br>
Chokes = 36<br>
<br>
The final output was 148 bhp @ the flywheel (108 @ wheels) @ 5800 rpm with 136 lbft torque @ 4800 rpm.<br>
<br>
What a difference compared to my near standard Sprint. Definately needs the Sierra brake upgrade.<br>
<br>
Quote me happy <!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/intl/aenglish/im ... /happy.gif ALT=":D"><!--EZCODE EMOTICON END-->

<p>1974 French Blue Sprint<br>
1979 Brooklands Green Sprint</p><i></i>