blow through SU carbs?

[whamo]

Has anyone ever heard if it is possible to use a blow through system on an SU carb? It doesnt look like it would be difficult to install a centrifigal blower on an l6 engine, but are the carbs "blow through" friendly? I know you can blow through a carter or holley 4bbl carb. If possible to install a blower without going fuel injected, Id like to try it.

[hls30.com]

Crown Manufacturing and D!ck Barbour made kits back in the day,

Here is a thread from a while back with info on both...

http://www.classiczcars.com/forums/showthread.php?t=22581&highlight=carb+forced+induction

Will

[whamo]

Thanks for the link.... a quick google search found this.

http://www.triumphexperience.com/article/how-to-blow-through-an-su.html

[blue 72]

I've seen a Crown Turbo kit in person. The owner had it on his shed floor. He noted that some special mods had to be done to the float(s) to make it run right. It does push through just one SU carb, and this is years before intercoolers were in vogue. Makes for some tuning nightmares I would guess, but very unique.

[Tony D]

The Crown Kits I have installed were all draw-through, using a single SU on the inlet of the turbo, and blowing into a custom cast manifold piece that bolted on in place of the twin SU's connecting the rear manifold section with the front.

Biggest issue on them is uncontrolled boost if you have the early non-wastegated Rajay Carbs (or the Corvair Carb that was also very popular.) They would blow head gaskets on the Datsun due to running lean, more from not enough fuel because the boost would keep rising if you kept your foot in it. The Corvairs with the Crown Kits were good up to around 17psi with Water Injection, but you eventually had to lift your foot, or redrill the jets/retaper the needles to go above that.

Fitting a wastegate on a Single SU setup will give managable fuel delivery, and can be easily done on a single stock sized SU to around 12psi...but you will have to retaper the jet. To go higher, you really should look into water injection, and boring out the jet diameter to allow for fuel flow....but at 17psi no matter what turbo yo uare using you will have enough heat (despite total vaporisation of the fuel dropping intake charge temperature) that detonation will be a problem. Which is where the water comes in...

Crown Corvair, Crown Datsun...been there, done that! In the 70's and 80's! (The good old days....weren't!)

Edited October 11, 2008 by Tony D

[BURLEIGH]

I set up a blow thru system on my old '73. I used an '81 turbo motor and put my 4 screw round tops on it. I then fabricated a "plenum" that bolted to the two carbs that had an inlet for the turbo and several treaded holes for various accessories. I then just turned the snail on the turbo facing up and conected it to the new plenum with a rubber hose. I did have to modify the carbs a little, but not much. I blocked the float vents, pulled out the throttle shafts and put a small grove in each end on the lathe. I then put an oring that had an OD just barely larger than the shafts. This completely sealed the throats of the carbs up.

I ran the car maybe 5 or 6 times before I needed to use it for a daily driver so I pulled that engine and put the original one back in. I didn't get to do much tuning in, but could tell that there was definately potential there. However, I think if I were to go turbo again I would just seek out the right FI setup. (probly much easier) It was definately fun proving a few friends wrong that said it couldn't be done though. I sold the engine a few years ago, but held on to the plenum and modified carbs just to hang on the wall if nothing else!

Well, good luck with it if you give it a shot. Feel free to PM me if you have any questions.

-Richard