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Topic: Engine sputtering at WOT

in Forum: C3 Engines

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Engine sputtering at WOT (1/9)
5/27/07 4:14pm

jgoglick

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Huntsville, AL - USA

Vette(s):
1971 convertible,375 HP 350ci,Muncie 4-speed,Edelbrock aluminum heads and RPM air-gap manifold,HEI distrubiter - old school mechanical tach drive. LOUD side exhaust!

Joined: 11/15/2003
Posts: 857

The car accelerates fine at partial throttle. At WOT, it pulls hard but has a "sputter". Also an occasional small backfire happens. THe engine runs great otherwise. Edelbrock carb and manifold if that makes any difference.

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Engine sputtering at WOT (2/9)
5/27/07 5:07pm

71Shark
Former Member
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Edmond, OK - USA

Vette(s):
1971 Brands Hatch Green L48 Coupe Automatic Driver - restored 1995

Joined: 7/13/2006
Posts: 400

Not enough fuel? air?

Engine sputtering at WOT (3/9)
5/27/07 5:15pm

jgoglick

[QUOTE=71Shark]Not enough fuel? air?[/QUOTE]

That was my thinking. Maybe I need to go one size bigger on the secondary jets? Tell me if I'm waaaay of base here... LOL

Engine sputtering at WOT (4/9)
5/27/07 5:25pm

Falcon
Former Member
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Carrollton, TX - USA

Vette(s):
1977 L48 Coupe, Solid top panels,4 speed, leather, tilt, AM/FM/8track(which works) 56,384 miles, Third owner with history

Joined: 10/3/2003
Posts: 31

Just a bit info needed......

1. New carb and intake OR new problem just surfacing ????

2. If new carb....jets may be the answer..

3. If new problem....maybe dirt in the carb....pluged jet.....or even ignition breaking down under heavy load....

More information needed to be of any help ...

Engine sputtering at WOT (5/9)
5/27/07 5:26pm

71Shark
Former Member
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Edmond, OK - USA

Vette(s):
1971 Brands Hatch Green L48 Coupe Automatic Driver - restored 1995

Joined: 7/13/2006
Posts: 400

Probably really draws the air with those pipes if they are open - virtually no back pressure.

Engine sputtering at WOT (6/9)
5/27/07 5:36pm

jgoglick

[QUOTE=Falcon]Just a bit info needed......

1. New carb and intake OR new problem just surfacing ????

2. If new carb....jets may be the answer..

3. If new problem....maybe dirt in the carb....pluged jet.....or even ignition breaking down under heavy load....

More information needed to be of any help ...

[/QUOTE]

1. New carb and intake that came as part of the engine purchase. Problem has always been there, just procrastinating doing something until now.

2. New carb (or at least fairly new - around 6 months old). Problem has always been there.

3. Not a new problem

[QUOTE=71Shark]Probably really draws the air with those pipes if they are open - virtually no back pressure.[/QUOTE]

I bought the engine as a turn-key engine. It was tuned and broken in (of course, not with side pipes - just regular headers).
jgoglick2007-05-27 17:37:15

Engine sputtering at WOT (7/9)
5/27/07 6:02pm

Adams' Apple

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20203

Sounds as if it's running out of fuel @ higher rpms. What type of ignition is on it now? What kind of fuel pump? How much wood could a woodchuck chuck if a woodchuck could chuck wood?
Check the fuel line from the chassis to the fuel pump for kinks. You might wanna put a fuel pressure gauge on it temporarily to see if it's loosing pressure at the time it starts bucking....really sounds like a fuel issue, but could be ign. related, too.

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Engine sputtering at WOT (8/9)
5/27/07 6:54pm

jgoglick

Here is a link to the fuel pump I got. It has an HEI distributer. I'll check for kinks in the fuel line. Oh, and he's chuckin about a cord an hour - he's fast! Rolling%20On%20The%20Floor%20Laughing

Engine sputtering at WOT (9/9)
5/28/07 9:19am

dvicino
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Noblesville, IN - USA

Vette(s):
1968 coupe 327 300 HP

Joined: 5/14/2007
Posts: 6

Do you know at what RPM the problem occurs? Sounds to me like it may not be getting enough advance. Do you know how much timing you have "all in" (>3000 rpm)? I agree, it may be mixture related too, possibly due to the pipes. These things take some effort to tune.

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