[Fot] SU HS6 problems during hard braking

Sun Jul 14 06:06:14 MDT 2019

Ok this is a long shot but.  

I was have a similar issue in the TR3 recently and it turned out I had a combination of issues that led to a very over rich condition. 

I use the Holley chrome fuel pressure regulator and I have a fuel isolator in the engine bay with a fuel pressure gauge in the dash. One weekend, the rubber diaphragm in the regulator started leaking and I did not have a replacement. I borrowed one from a buddy who’s car was on the trailer. Turns out, his regulator had the high pressure spring that can’t regulate fuel bellow about 5 psi. As luck would have it, I also had a bubble in my gauge isolator line. The bubble was causing a false low pressure reading so I kept cranking it up at the regulator. This was a frustrating process as the car starting progressively bogging down after hard braking and hard cornering, which is where I do about 90% of my passing. It’s embarrassing to admit now, but this took me two race weekends to figure out. Finally I decided to take apart the gauge isolation system and start over. Once back together, the true pressure reading indicated 8 psi. Next I took apart the borrowed regulator to rebuild it with the kit and I discovered the high pressure spring. Rebuilt with the appropriate spring and all is right. 

Like I said, long shot, but it’s worth sharing in case it helps you think through some related change you might have made recently. It’s amazing how simple the fix typically turns out. 

Good luck. 

Greg

Sent from my iPhone

> On Jul 13, 2019, at 11:49 PM, Bill Dentinger via Fot <fot at autox.team.net> wrote:
> 
> Years ago we went through a period where an additive in racing gas was causing a leak in the float seams on new replacement floats.  At the end of a session your ‘new’ floats could be full of gas. Old floats were sought after.  Harold Baker, one of Duck Waddle’s crew made us some custom aluminum ones that worked perfect.  We got through the season.   And eventually they fixed the issue. Bill Dentinger
> 
> Sent from AOL Mobile Mail
> 
> On Saturday, July 13, 2019, Steven Belfer via Fot <fot at autox.team.net> wrote:
> 
> Probably not related but the brass floats can develop a pinhole leak. It probably sinks and stays on the bottom 
> 
> ~Steve
> 
> 
>> On Jul 13, 2019, at 8:09 PM, Tony Drews via Fot <fot at autox.team.net> wrote:
>> 
> 
> 
> We experienced this, but getting the pivots in the orientation you have them was the fix for us (in a TR-4).  You can try a different top orientation though, assuming you have the float bowls with the 3 screws.  The front carb is likely the problem - under braking the fuel goes to the front so the float drops.  As soon as you stop braking the float bowl is overfull.
> 
> Regards, Tony
> 
>> On 7/13/2019 8:37 PM, Jason Sukey via Fot wrote:
> 
> The floats pivot so the swing front to back.   On the rear carb the pivot pin is nearest the firewall, on the front carb the pivot pin is nearest the radiator.
> 
> Thanks,
> Jason
> 
> On Sat, Jul 13, 2019, 9:29 PM Greg Blake <gblake58tr3 at icloud.com> wrote:
> What is the orientation of the pivot on the floats?  
> 
> Sent from my iPhone
> 
> On Jul 13, 2019, at 8:17 PM, Jason Sukey via Fot <fot at autox.team.net> wrote:
> 
>> Phil, I'm running 2 psi.  My fuel pressure gauge stays consistent during the entire run.
>> 
>> Thanks,
>> Jason
>> 
>> On Sat, Jul 13, 2019, 9:15 PM Phil Gott <vfracing at aol.com> wrote:
>> Jason;
>> What sort of Fuel pressure are you running? Should be 1 1/2 to 3 psi, although a Spitfire driver and I run 6 with no apparent ill effect. More than that could be causing you some of this problem.
>> Phil Gott
>> 
>> Sent from my iPhone
>> 
>> > On Jul 13, 2019, at 8:57 PM, Jason Sukey via Fot <fot at autox.team.net> wrote:
>> > 
>> > Hello FOT,
>> >      Running my GT6 at the PVGP historics this weekend.  I've sorted the braking system and installed new tires since the last time out.  Now that I'm actually able to brake hard, I'm suffering from what seems to be fuel flooding, possible sloshing in the float bowls and dumping out the jet into the intake...
>> > 
>> > During and immediately after a hard braking zone, the engine goes completely "off" and I can smell raw fuel.  After a few seconds it clears out and runs strong in all other conditions, no indication of over rich or starving for fuel. Starts normally, no issues idling.
>> > 
>> > Original fuel level in the floats was about 1/8" below the top of the jet.  By reducing the fuel level in the bowls from there, the problem has somewhat improved, but it's still significant.  Every session I adjust them a little further, but I'm not sure this is the right fix...maybe a band aid.
>> > 
>> > Has anyone experienced this with the HS carbs?  
>> > 
>> > Jason Sukey
>> > 
>> > 
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