SU mod that really works

Tech tips and how to's

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SU mod that really works

Post by nismou20 »

So recently I had issues jetting my newly modded SU throttle shafts and found that I had compounding problems cause the car wasn't charging. My charging issue was finally repaired by swapping the old 30 amp to 60 amp GM Alternator to cool side (Passenger). When finally addressing the jetting I found a little sanding of RA needles at the transition from off idle to low/midrange to smooth out the lean condition. I rate this mod one of the best things you can do to a otherwise stock U20. I initially bought a pair of old SU bodies from Peter Harrison in hopes to temporarily seal vacuum leaks at the throttle shafts.I was going to set them aside as backups since my originals on car were leaking badly. Well, seeing posts online from the Brit car world where people have thinned the throttle shafts I thought why not try it on a old Hitachi. If you like to tinker this is such a easy mod where you just grind off the upper half of the shaft just inside the bore after removing the butterfly valve. Removing the linkage from one end of the shaft allows you to slide it right out. There are plastic ribbon type bushings that fall out of the shafts that you reinsert once the mod is done. Follow up with thread locker and new screws to secure the butterfly valves. Get some Orings to fit against the shaft ends and you're pretty much done. If I were to do it again I'd probably use Viton Orings as the rubber ones will most likely dry out from heat and turn brittle. The results are astounding! It is pulling so much more air. It's a different car now. I don't have a Wideband yet to really get an exact AFR but I am really happy with the Butt Dyno! I would venture to say that this same mod will work on the 1600 as well. It transforms the car's midrange /top end. A Win Win!
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Re: SU mod that really works

Post by FergO2k »

Now that is some cool tinkering, good job Tom.
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69 2L, SUs (driver, not susceptible to polish)
02 Tacoma 4 door
Los Alamitos, CA

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Re: SU mod that really works

Post by Linda »

I thought I read that the butterfly screws were really hard to get off....What size are the replacement screws?
If nothing else, putting the o rings on to seal the throttle shaft is a good idea.
68 1600 Los Angeles, CA
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