[Healeys] SU carb fuel pressure

[warthodson at aol.com]

Thanks for the several comments so far. The background for the inquiry is: A friend has an aftermarket fuel pump that delivers 7-10psi & a pressure regulator set at 2 psi. He also has (3) HS6 carbs. The engine starts, idles & runs fine until he stops & turns off the engine. Like at a gas station. Then upon restarting it runs rough & won't idle unless he pulls the choke partially out, I.E. fast idle, not richer mixture. We assume this is due to heat soaking &/or peculating fuel. I thought raising the pressure might help if the peculating was occurring before the float valve & wanted to know the Max fuel pressure to this model SU. I doubt that it will have any effect. We are also interested in any suggestions you may have. Additional facts:his engine never gets over 190 F when running. He has an electric fan in addition to the original fan. he carbs are not running lean. I am told the timing is correct. 
Thanks,Gary Hodson 



-----Original Message-----
From: Michael Oritt <michael.oritt at gmail.com>
To: warthodson at aol.com; Austin Healey <healeys at autox.team.net>
Sent: Sun, Jun 14, 2020 12:45 pm
Subject: Re: [Healeys] SU carb fuel pressure

Gary--
2 to 4 psi is the common wisdom.  
That said, I had a set of HS6's on the MGA engine in my (now-gone) Elva Courier and no amount of fiddling with floats, lid position, etc. would solve a consistent fuel starvation problem when coming of hard, tight right-handers under full throttle as in turns 1 at VIR, Summit Point, etc.   I finally solved the problem by installing a Holly Blue (high-pressure fuel pump) and reducing pressure via a regulator to about 5.5-6 psi.  Dire predictions notwithstanding I never had an issue  with the floats' being overcome by that pressure and causing leaking.  
I'm not saying anyone should go to such extremes without a good reason but I think the "common wisdom" is just that and not always gospel.  
Best--Michael Oritt
On Sun, Jun 14, 2020 at 12:27 PM warthodson--- via Healeys <healeys at autox.team.net> wrote:

What is the Max recommended fuel pressure (psi) for SU HS 6  Carbs. Is there  also a Min fuel pressure?Gary Hodson_______________________________________________
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