Thread: SBC shut down while accelerating?

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The spec sheet for the GMPP engine in my s-10 shows max rpm 5700. A new problem came about a couple of weeks ago and troubleshooting has been unsuccessful thus far. The engine runs strong from idle to about 4,000rpm. It seems that it shuts down and comes back to life after it falls to 3200 to 3500rpm. This occurs mostly WOT acceleration and under a load. Parked in the drive way it will rev to the limit with short bursts of throttle. I have adjusted valves, timed, new performance coil and module, fuel lines, filter, havent changed wires or plugs yet just getting disgusted with the whole thing because its embarrasing when you kill a nissan at the light but then get SMOKED when the shut down comes along. This engine really does justice for the little truck off idle. Would just like to see more top end. Any suggestions?

valve springs

Whats your oil pressure at the time the engine dies??
Could be your lifters are losing pressure,,,your oil pump may be failing to supply enough oil at that RPM.

Check the ign supply plug going into your distributor.
Is it an OE plug that latches in?
Sounds like the engine is torqueing over and making the ignition circuit go 'open'..
Check the ground while you are at it too..
Jeff

sounds like to me your running out of fuel, pump, filter, sock in tank or carb.

Not enough fuel volume.

Install a fuel pressure gauge and see what you have at 4000 rpm.

Be sure and use a pressure isolater so you don't have a pressurized fuel line inside the cockpit.

What kind of fuel pump are you running and what size are your fuel lines?

Thanks for the help guys. The engine spec sheet shows this engine having LT1 (1970 vette) springs. The cam spec is 212/222 @50, 435/460lift. I may need to check for spring damage? While adjusting the lash I didnt notice any out of the ordinary sounds except a minimal amount of lifter noise in #6 when warmed up and above 2200rpm. The fuel pump is factory stock. The fuel lines are 3\8 rubber from pump to carb with wix canister filter inline. I havent paid enough attention to oil psi during shut down, it usually idles about 15psi and 55 (hot) 60 (cold) at cruise. I may need more instruction on the dist. power leads? When I replaced the module, The wiring terminals clip crumbled in my hands and just installed the ends individually to the module. This should be ok since no further malfunction, and that was part of T&E. I'm no expert on these conversions but I see a power block of some kind on the fire wall close to the dist. that has a larger battery source terminaled to it. This is a constant power source with the switch turned off. Is this what I,m looking for?

On the drive home last night I noticed the failure seems to occur when opening the secondaries. It will cruise at 4000 with primaries. Trying to accel. with WOT (secondary) it stalls and surges. No trouble with WOT from idle to 3800-4000.

Running a Holley carb?

Your secondary float level may be too low.

Been there, done that....

Edelbrock 1406 electric choke.

Originally posted by C9x
Running a Holley carb?

Your secondary float level may be too low.

Been there, done that....

Its an Edelbrock #1406. elec. choke.

You can get a flat spot with the Edelbrocks when making an abrupt transition from primaries to secondaries opening.
Abrupt meaning tromping on the throttle as vs rolling it smoothly in.

Running at a higher altitude than you usually do can make the flat spot worse.

It is a flat spot though and it doesn't take long for fuel to start flowing in the secondary circuits and it's more of a bother than a giant pain in the backside.

Many of the Edelbrocks come stock with the orange metering rod spring.
Changing to a pink spring cured the stumble in my 750 Edelbrock.

It helped as well that I jetted the carb - jets and metering rods - leaner for the altitude I'd moved to.
3300' vs 350'.

It does sound like your engine is simply running out of gas and for that reason I'd make a point to check the fuel pressure under load.

Make sure as well you don't have a kinked fuel line.
Rubber and hard line....

Ok, has there been any trouble with rubber fuel lines colapse at high rpm? Doesnt make sense though with the fuel pressure requirement from Edelbrock being 6 to 8 psi. I can get the owners manual from Edelbrock online. Looks like float measurement and adjustment is pretty simple. Think I might start there. Hows the fuel pressure at load test work? Will check for kinks too. Man, when this thing dies, its gone till you let off the secondaries. Just like turning off the key. Dead, notta, nothing. Will tinker with some more. Update yall later. Thanks for all the help.

Secondaries are starving. Clean and set the carb , there's something blocking feed to the secondary bores.

How do I perform fuel pressure check with load?

Borrow a carb from an engine that runs right, then you'll know where the problem is.