[Fot] Fwd: Stutter at 4K rpm

[D V]

Thanks everyone for the replies. I will inspect the pipe to manifold and manifold to head to see if anything is loose or any leaks apparent in the morning.

I actually went down a main jet 145 to 140 and that seemed like it helped some but didn't clear up the issue (which is going leaner; opposite of what Greg said).

It is missing and backfiring when I am full on the gas. I can prevent it by easing into the gas.

I did notice some gas at my air cleaner to velocity stack connection. I wonder if it is a float issue?


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On Oct 15, 2016, at 7:35 PM, Greg Blake <gblake58tr3 at icloud.com<mailto:gblake58tr3 at icloud.com>> wrote:

Don't know if my other email made it to you. Backfires on deceleration can be a lean condition. Have you checked your plugs?  Maybe something got "adjusted" with the bump.

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On Oct 15, 2016, at 12:27 PM, D V <explore8 at outlook.com<mailto:explore8 at outlook.com>> wrote:



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Begin forwarded message:

From: <explore8 at outlook.com<mailto:explore8 at outlook.com>>
Date: October 15, 2016 at 10:30:51 AM CDT
To: <fot at autox.team.net<mailto:fot at autox.team.net>>
Subject: Stutter at 4K rpm

Two races ago I went off track and bent my exhaust pipe enough to break the welded joint near the muffler. In the interest of time, I cut the exhaust at the muffler and secured the pipe to the frame.

At the last race, I noticed the car would backfire at deceleration which I am not surprised but I also noticed a stutter around 4-5k rpm.

At NOLA this weekend it is more pronounced and comes in when shifting hard from 3rd to 4th. After 5k, it clears up and pulls normally.

It doesn't seem to be affected by turns and more related to full throttle vs easing into the gas.

Backpressure from the loss of muffler or unrelated issues?

1300 spitfire with single Weber 40.

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