Engine miss in apex of turn.

[JCSullivan00]

Motor runs fine down the straights, into the turn and at corner exit, but it falls flat on it's face, and almost backfires right at the apex.

New Willys gas carb that was dyno'd on an engine by our engine builder before it went on our car.

Block mount fuel pump, standard regulator, 7psi of pressure.

We checked the pickup, all the lines, fuel filter orientation, checked floats, etc.

Really stumped on this one. Is there anything electrical that could cause this? All the pieces were removed of a race car we junked at the end of the season, and put in a new chassis, and all worked well in that car.

[Lizardracing]

Sell it to a drag racer?

Seriously, Check the Accelerator Pumps.

[JCSullivan00]

I'll check out both of these.

Thanks for the ideas fellas. These things suck to chase.

[powerslide]

Smell the air filter see if its flooding over.

[let-r-eat]

Back the pressure down to 5 and see if it helps?I think it's over running the bowls. What kind of block mount fuel pump?

[JCSullivan00]

We have changed pressure from as low as 5 up to 6.5 lbs with the same problem.

It is a Pro/Cam fuel pump.

The air filter is not saturated with fuel.

[mod88s]

I have had this happen several times with a pro cam pump. I kept raising my float levels and it would work for a week. the fuel pump was going bad. I think it was the spring getting weak, not sure but I would go through a pump a year and each time it did the same thing. If your at the track, raise the float levels. If you have time, replace the pump.

[let-r-eat]

He has fuel pressure so it isn't the pump, I doubt. The Pro Cam pumps are pretty good pumps. I was still leaning toward something causing the engine to over run the bowls. If it's happening as soon as you pick up the throttle I would be searching for something that is causing the over run. Fuel pressure, float level too high, bad regulator surging pressure.If the engine has fuel pressure when the miss is happening it would lead me to believe that something is causing the fuel to over run the bowls.You usually don't get a backfire if things are lean...........No fuel to cause the explosion.I would rule out basic things since you said you had a new Willy's. Of course you get backfires with ignition problems but usually ignition problems *valvetrain and engine condition also are found when the engine is at it's highest load pulling off the corner. This isn't usually when you first pick up the throttle or through the center.

[billyW69]

Had this problem a few years ago with my Willy's carb. Checked everything I could think of couldn't get it fixed till I put on an angled carb spacer. Like this one. http://www.onedirt.com/news/new-angl...e-performance/

Hope this helps
Scott

[mod88s]

My fuel pressure looked great also at idle or even when you would rev up the motor, even when the pump was bad, that's the thing that had me looking else where. I had the EXACT same problem with the same pumps.. Others have had the same thing happen as well. I believe it is the pump.. Try another carb and see what happens to rule out that variable.

[JCSullivan00]

Took the carburetor, regulator and fuel pump to the engine builder and he put it on an engine and dyno'd it with zero issues. I know a dyno doesn't really simulate real world racing, but it is making us take a bigger look at the ignition system.

I'll keep y'all posted about what we find.

[xxxmod]

make sure the secondary butterflys are closing far enough to keep
fuel from getting sucked out of the fuel bowls when you lift.Consider
adding another return spring just for the secondarys.

[kc92]

if your running a msd blaster coil change it bad coil have had this problem

[JCSullivan00]

Picked up a new coil today. I'll also throw another spring on it.

[nthdrt]

had almost same prolbem in a sportmod. Ran balls to wall down the straights but when it got in corner sounded like it was on a rev limiter which didnt have. Came off the corner strong with no prolbems . Went threw alot of things ended up being the carb although i still havent found anything wrong with it . Put a diverent ome on ,no prolbems

[JCSullivan00]

Figured out the issue. Poor connection from the battery to ignition switch.

Don't let drivers do wiring.

[let-r-eat]

Also glad you found it and posted your result. Thanks.