Blow through SU Carb.IT WORKS

[GARRICK.CLARK]

So Guys , does anyone have any how too tips/pics on blowing through a HS8 SU Carb.
I've got some info on the basics but could do with chatting to someone that's done it
Regards G.C

[panel]

Why blow through ?

[GARRICK.CLARK]

I've tried DRAW through. It did work to be fair, but lots of fuel sits in the turbo, hard to start,
My turbo has no carbon seal , I would need to spend a load on a carbon sealed turbo, re design the exhaust for turbo to fit etc.

[69yellowbug]

Id also like to know. I am building a mild 1776 amd want to do a small boost to it.

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[69yellowbug]

.

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[GARRICK.CLARK]

So , I've been looking into the how to blow through an SU HS8.
To Get it to work I had to
Seal the butterfly shaft either end with an O ring.
Fit an O ring under the jet guide
Fit a boost ref port in the float bowl lid.
Fit a pilot tube into the boost pipe at the carb mouth to give the float bowl more pressure than the rest of the carb is getting.
WITH OUT THE PILOT TUBE ON BOOST FUEL ENRICHMENT WONT HAPPEN AT ALL.

[GARRICK.CLARK]

little up date . Had to wait a month to get the butterfly shaft grooved for some O rings. Some shops are real slow doing work. Not good.
I have the motor running now. Got the small vent hole on the SU float bowl lid blanked off.
Then drilled and tapped the lid for a boost feed. 1/4 barb fitting with 8mm barb end.

[GARRICK.CLARK]

Hey Guys. has anyone done blowing through an S.U .
I'D like a chat with someone that has.

[GARRICK.CLARK]

No reply's.
Iooks like I must have the only blow through SU carb motor on this site.
Got it all running now had to do so some more carb tricks on it, e.g put a restrictor at the carb mouth so the pressure that feeds the float bowl is higher than the rest of the carb .( The float bowl pressure feed is taken from a feed that is before the carb mouth). Had to put a heavy dash pot spring in too to stop the piston rising to quick.

[petew]

Only blow through SU I've ever seen...

https://www.youtube.com/watch?v=xtnGItldQWA

Mini metro turbo carb.

[GARRICK.CLARK]

Hi Pete. Yeah your right the metro turbo has an SU , but its a lot different to my carb and are rare as hens teeth.
Hopefully when I drive it to the MOT station it will work out good .

[GARRICK.CLARK]

Got it running good now. Had to fit a PILOT tube in the boost pipe to make the float bowl have more pressure than the rest of the carb. Now it goes rich on boost. With out this you will NEVER get it to richen up under boost.

[GARRICK.CLARK]

Hi chaps. I'm using an S.U CARB. I take a boost signal for the float bowl AT the carb mouth, this does work well. the pipe work from the turbo (NO INTERCOOLER) is about 24 " long. The signal to the float bowl starts as the boost comes on.

What I've done now is fit an intercooler, the pipe work is a lot longer and the internal area of the intercooler slows down the boost pressure that's going to the carb mouth, SO the boost signal to the float bowl is now not as good and not giving me boost enrichment till the turbo builds more pressure to give enrichment. while the turbo is building more boost the AFR goes lean enough to cause a big flat spot. When the boost signal gets strong enough to pressurise the float bowl the flat spot goes away and power comes back.

Is this a good solution.
Move the float bowl signal from the carb mouth and put it right at the turbo out pipe. This will keep the float bowl signal fast and strong AS loads of pipe work and an intercooler will have been by passed

[Clonebug]

Where do you have the intercooler positioned???? You can't have it after the carb and put a fuel mixture through it......that makes it a ticking bomb.

[GARRICK.CLARK]

Hi Clone.
Cooler is before the carb on a blow through. Am gunna put it back to how it was and test it , If it runs how it did before, well I'll have to leave it off.