I'm having a fuel issue with my newly installed Shorrock supercharger on my TC. Everything is mounted and plumbed but it will not run well or at all, just spitting and coughing.
It appears to be flooding as there is raw fuel dripping out of the intake side of the carb. It's a single H4 with a side draft float bowl unlike on the TC. Recently rebuilt by Joe Curto.
It has a .1 jet, RA needle and a red spring. The float forks are set to 15/32" and the jet is 9 flats down at this time. The fuel level is about .2" below the bridge. Using the same SU fuel pump when the TC had dual carbs.
Anyone have an idea what might be going on?
Thanks, Dave
Supercharger Carburation Issue
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DaveAhrendt
- Posts: 51
- Joined: Mon Jan 07, 2013 10:53 am
Supercharger Carburation Issue
Dave '46 TC 0524
Re: Supercharger Carburation Issue
Is your needle valve shutting of properly when engine running? Sounds like you are within range of fuel height below bridge, but you could go another 1/16" lower? Also important to check "jet drop."
Forget about fork setting and number of flats. (Though 9 flats sounds close) Set it up according to this tech article on page 29--
https://www.namgar.com/images/uploads/C ... er30.1.pdf
Not uncommon for supercharged engine to run a bit rich with SU at idle. Of course it is more important that the mixture is correct when making power.
Forget about fork setting and number of flats. (Though 9 flats sounds close) Set it up according to this tech article on page 29--
https://www.namgar.com/images/uploads/C ... er30.1.pdf
Not uncommon for supercharged engine to run a bit rich with SU at idle. Of course it is more important that the mixture is correct when making power.
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DaveAhrendt
- Posts: 51
- Joined: Mon Jan 07, 2013 10:53 am
Re: Supercharger Carburation Issue
Thanks Duncan,
I've seen that writeup before and it's pretty close to what I have. Problem is that it won't run long enough to do
any investigation. Turns over on the starter then catches and runs for a few seconds then quits all the while coughing
and sometimes sneezing through the carb. When it stops there is a steady drip of fuel from the throat,
Someone commented that they thought it may be a venting issue. I'll try to look into that today. I'm thinking of pulling fuel pump power, removing the float bowl cover and float, manually adding some amount of fuel and try it. If it runs long enough
to run out of fuel without dribbling I'll know if I have a venting issue.
Dave
I've seen that writeup before and it's pretty close to what I have. Problem is that it won't run long enough to do
any investigation. Turns over on the starter then catches and runs for a few seconds then quits all the while coughing
and sometimes sneezing through the carb. When it stops there is a steady drip of fuel from the throat,
Someone commented that they thought it may be a venting issue. I'll try to look into that today. I'm thinking of pulling fuel pump power, removing the float bowl cover and float, manually adding some amount of fuel and try it. If it runs long enough
to run out of fuel without dribbling I'll know if I have a venting issue.
Dave
Dave '46 TC 0524
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John Brownhill
- Posts: 10
- Joined: Mon May 30, 2022 7:39 am
- Location: Castle Donington UK
Re: Supercharger Carburation Issue
Hi Dave,
Although my needle is RC the jet nut is higher than yours perhaps 4-6 flats.
To start I use choke for about 5 seconds.
Things to check:
Dashpot damper cap, SU used 2 systems either a drilled cap or a internal vent drilled through the angled boss next to the cap one or the other not both.
Sticking piston in carb
Dashpot oil, 20 grade should be o.k not 20/50
Float chamber vent
John
Although my needle is RC the jet nut is higher than yours perhaps 4-6 flats.
To start I use choke for about 5 seconds.
Things to check:
Dashpot damper cap, SU used 2 systems either a drilled cap or a internal vent drilled through the angled boss next to the cap one or the other not both.
Sticking piston in carb
Dashpot oil, 20 grade should be o.k not 20/50
Float chamber vent
John