strange running condition
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Junior Member
Joined: Mar 2018
Posts: 39
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From: Texas
strange running condition
85 distributor/coils spark wires(new)
13b s4 6 port, no air restriction sleeves
Racing beat intake with Mikuni carburetor(similar to weber)
vacuum advance hooked up
bought this engine used and assembled it with all new internal parts, I checked all the jet sizes in the carburetor, all good. timing is set. fuel pressure at 4psi. fuel filter clean. ive fiddled with idle and float a bit but not much change was shown.
if I let it idle then give it acceleration it will rev high but if I go to rev again it tries to die. ive clwaned the carburetor with carb cleaner etc but next im going to inspect every jet closely for cleaning.
what do you guys think based off the videos?
https://youtu.be/9xk_OcijmIU
https://youtu.be/T1k9EBo8izU
13b s4 6 port, no air restriction sleeves
Racing beat intake with Mikuni carburetor(similar to weber)
vacuum advance hooked up
bought this engine used and assembled it with all new internal parts, I checked all the jet sizes in the carburetor, all good. timing is set. fuel pressure at 4psi. fuel filter clean. ive fiddled with idle and float a bit but not much change was shown.
if I let it idle then give it acceleration it will rev high but if I go to rev again it tries to die. ive clwaned the carburetor with carb cleaner etc but next im going to inspect every jet closely for cleaning.
what do you guys think based off the videos?
https://youtu.be/9xk_OcijmIU
https://youtu.be/T1k9EBo8izU
The sleeves that you're talking about are not air restriction sleeves. They are opened by actuators at higher rpm's to allow addition air into the engine that is subsequently stored in the dynamic chamber. The engine is designed to run using all of the components for the 6 port system. Is the intake manifold built for the S4 N/A 6 port engine?
It almost sounds like the engine is not getting enough fuel. Its choking at any heave ounce of throttle application. Why is your fuel pressure at 4psi? I would think at least 6psi would be in a good operating range.
It almost sounds like the engine is not getting enough fuel. Its choking at any heave ounce of throttle application. Why is your fuel pressure at 4psi? I would think at least 6psi would be in a good operating range.
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Joined: Nov 2017
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From: Beaverton, OR
Not sure about that set-up exactly, but IMHO it sounds like the accelerator pump is miss-adjusted. I had a similar problem, but it was the Nikki's vent solenoid having died that caused the bowls to be under high vacuum under load. Out of curiosity, have you checked timing?
Thread Starter
Junior Member
Joined: Mar 2018
Posts: 39
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From: Texas
Not sure about that set-up exactly, but IMHO it sounds like the accelerator pump is miss-adjusted. I had a similar problem, but it was the Nikki's vent solenoid having died that caused the bowls to be under high vacuum under load. Out of curiosity, have you checked timing?
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3D Printed
Joined: Nov 2017
Posts: 1,127
Likes: 278
From: Beaverton, OR
Again, not sure about the Mikuni, but can you see the AP nozzels? If so, while the car is off pump the gas a couple times and see if fuel comes squirting out of them. It should be a decent amount and if there isn't any, something in the circut is most likely clogged. It could also be out of adjustment or the spring could be missing or installed on the wrong side of the diagram like you said.
Keep us posted.
Keep us posted.
Thread Starter
Junior Member
Joined: Mar 2018
Posts: 39
Likes: 0
From: Texas
Again, not sure about the Mikuni, but can you see the AP nozzels? If so, while the car is off pump the gas a couple times and see if fuel comes squirting out of them. It should be a decent amount and if there isn't any, something in the circut is most likely clogged. It could also be out of adjustment or the spring could be missing or installed on the wrong side of the diagram like you said.
Keep us posted.
Keep us posted.
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