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Spitfire Spitfire 1980 intake question???

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J

JagCDN

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Hello,

I am in process to replace stock Stromberg 150 carb. with a 175 type. To do so I bought an used Spit manifold supposely from the same model and grind it to fit 175 CD. But my problem is somewhere else. When I compared both intakes, I noticed that 4 tubes matching head are 1" I.D., for original intake, and 4 head holes are 1.25", a mismatch. More intriguing is that the used intake I bought has 4x 1.25"holes which appears to be a perfect match with head. As this Spit has been bought with a prior life. My question from what car the "original" non-matching manifold is coming from?

Thanks for your input...

Jean
 
I'm sorry no one has responded to this yet, but a picture says 1000 words...
 
As I recall, the 1500 single carb manifold has a big mismatch to the ports in the head.

I *think* the standard size is 1", so you probably just had the normal manifold.

When I started racing in a different club a few years ago, I opened up the manifold runners on my single-carb 1500 to about 1.125" (still not great but better).

The single carb Triumph 1500 manifold is probably one of the worst manifolds ever put on a car....it's horribly restrictive.
 
I have seen this size on some newer manifolds. I think Triumph tried to get the the gas velocity higher to fill the cylinders at low speed at the sacrifice of top end. Look on Ebay for an older manifold with bigger ports. It should be a little better. Or just put twin SUs on it.
 
Jean, I have to agree with tdskip and SpitFrye. I put the dual SU setup on my 73 and have been very happy with them. Now I'm looking for another set for my 79. Check ebay that's where I found mine.
 
Thanks guys,

I have my answer. I fit a MGB 175 CD2SE carb as dual carb set-up on e-bay were prohibitive or junks. I will see if there is some improvement.

In fact intalling nuts on two lower studs is something quite indecent to do...

Thanks all,

Jean G.
P.S. Now I have another problem with that silly carb. with an idle that stays high. It must be those idle coarse( plastic) nut and fine screw, which puzzle me a lot. I could not find the purpose of those nuts...
 
Hello,

A final note to my story.
After polishing inside of manifold and intake ports and enlarging intake's carb port to 1 3/4". I also grinded that 90 deg. bent inside maniflod slightly to have a less sharp angle. I installed that MGB carb.It was not a big deal except to make custom bracket for accelerator cable.
I started the beast and try to adjust carb, everything was running smooth except for that B needle (45H) too lean for Spit( velocity is less strong than B). I am in process to find the right needle. But up to now a Volvo 142 needle gave good results. It is slightly lean at more than 4000 RPM but yield to a decent car. It is a real BOMB when compare with that previous 150 CD and restrictive manifold.

I think that this carb. swap is a good alternative when dual manifold is not easy to find or is prohibitive to buy with 2 SU.

Cheers,
 
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