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2inch Jag carbs

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M

MDCanaday

Jedi Knight
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I am planning to put a pair of 2in jag SU's on my 4 this spring.It is highly tweaked and needs the additional breathing.(short of webers)This should be a good step up. The question is has anyone done this??? and if so, what jetting did you use as a starting point??
MD(mad dog)
 
Hello MDC,
I would think that 2 x 1 3\4" would be a better choice unless you are going racing. What do you call highly tweaked?.

Alec
thirsty.gif
 
Alec
This is a post from MDC when he got his TR4 done.

"Any one interested in building little hotter tr 3/tr4 might get a lot of good from my recent project. Re-shapeing the combustion chamber, bigger valves, serious lower end work. Yeilded 151hp at the crank 131ft/lb torque @6500 Overall compression 9 to 1( less than stock) Some idle smoothness was lost to the cam, but not too much. Safe redline 7000 rpm.If you're building on a budget, most of this is not high dollar stuff dont be afraid to ask. It may save you some time too." Maddog

thats about his engine and hopefully the quoting job will work.
Eric
heres the website if you don't believe me
https://www.britishcarforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=5&t=000185

[ 01-27-2004: Message edited by: bigbadbluetr6 ]</p>
 
Hello all,

that is certainly a good output from a 2 (2.2?)litre TR4 engine, but my point is that 1 3\4" S'U's are probably large enough. Take the Jaguar XK engines, the MK 2 3.8 runs on 2 x 1 3\4" S.U.'s and runs 220 bhp (admittedly probably overstated) while the E Type is rated at 265 bhp and although on triple 2" S.U.'s I would say that is from a visual aspect rather than a real requirement. Being S'U's, the oversizing doesn't cause the problems you might find on fixed choke carburettors.
In the search for more H.P. then Webers do gain over S'U's at peak power, so that may be the route to go.

Alec
thirsty.gif


[ 01-28-2004: Message edited by: piman ]</p>
 
Hey Alec,
Ever notice how folks with the big Webers for show have little bitty chokes in them to make them run right?

At least SU's that are too large can still be driven because they just don't open up anymore than is needed.
D
 
Hi Mad Dog! Very interested in your question as I have been working on my fast road TR4 for some time. I have not changed from 13/4 because I want to preserve good throttle response and pulling power from 2000rpm, but it is something I have thought about, especially as it is very easy to modify the existing inlet manifold.
There was some discussion on a Triumph race forum recently about 2 inch carbs, they only seem worthwhile on tracks with longer straights.
Incidentally, I would be interested to know what you use for fuel pump and pressure regulator as I am having trouble getting this right, hoping my new Holley regulator will help.

Simon.
The trouble with racing is they always put the corners at the end of the straights where you're going so darn fast!
 
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