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Surging slant 6
http://slantsix.org/forum/viewtopic.php?f=19&t=62686
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Author:  Justjack [ Tue Aug 07, 2018 3:37 am ]
Post subject:  Surging slant 6

Hi guys,

I have a Vc Valiant, when I am doing around 50 mph the slant starts to Serge. When I put my foot flat nothing happens but when I lift my foot it clears up. I have put electric ignition on it about 6 months ago with no problems until now, this problem only happens every now and again after driver for about 15 minutes. When I put it in neutral it runs fine, it only seems to happen under load. I was not sure if it is electric problem or fuel. Not sure where to start Can some one please help. :D

Author:  THOR [ Tue Aug 07, 2018 9:14 am ]
Post subject:  Re: Surging slant 6

Hey Justjack,

What carb do you have on it?

If I understand correctly, it will cruise below 50 no problem, but at or above 50 it surges, and when you floor it, nothing really happens.

When you are in neutral and floor it briefly to rev it up, does it hesitate or stutter or backfire? When was the last time you purchased fuel before this started happening? Checked to make sure timing hasn't moved?

It sounds on the surface like the carb is leaning out, starving the engine of fuel, but it's not always the case.

~THOR~

Author:  Justjack [ Tue Aug 07, 2018 4:09 pm ]
Post subject:  Re: Surging slant 6

Hi Thor,

Thank you for your reply.

I have a single barrel Carter carb on it. The fuel is only about 2 weeks old.

When I have it in neutral it runs fine no back fire or hesitation when I rev it. The timing is fine as well that is what I thought it may of moved. I took it out the next day for a drive with no problems.

Author:  THOR [ Tue Aug 07, 2018 6:04 pm ]
Post subject:  Re: Surging slant 6

Could've just been a piece of foreign material (dirt, rubber hose, etc) running through.

Next time it does it having made no further changes to the car, there is a trick to unclogging a carb which is free and takes about 5 minutes. It's not 100%, but I've had great success with the method for your type of issue.

Happy slanting!

~THOR~

Author:  Justjack [ Tue Aug 07, 2018 8:26 pm ]
Post subject:  Re: Surging slant 6

Hi Thor,

Thank you I will give that a try. :lol:

Author:  enrique lopez [ Wed Aug 14, 2019 2:41 pm ]
Post subject:  Re: Surging slant 6

Check your fuel pump. My fuel pump is about to go,, and it sometimes does the same thing.

Author:  Justjack [ Wed Aug 14, 2019 2:53 pm ]
Post subject:  Re: Surging slant 6

Hi mate, thank you I ended up changing the carbie to a Holley and has fixed the problem.

Author:  Louise76 [ Fri Aug 16, 2019 6:53 pm ]
Post subject:  Re: Surging slant 6

FYI- I had the same symptoms at 72 mph only when accelerating. Backed off slightly- ran OK. Accelerated very gently- ran OK. Mental troubleshooting on the freeway returning from a road trip pointed to a carb issue only at high manifold pressure (under high loads). Opened the carburetor up on the work bench and: an internal seal had come loose and fallen out of place, allowing an air leak into the float bowl , but only noticeable at high M.P. Fixed, end of problem. That was my head scratcher.

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