cutting out at 3000 rpm clears up around 4000

[Z71hamric]

I have a 94 extended cab i recently built a 350 with flat top pistons rolling thunder edelbrock roller cam old 300horse heads torker2 intake 750 edelbrock carb. I ranthis same setup in my small dirt drag truck minus the roller cam and it ran great. Im running an electric fuel pump with a holley regulator set at 7psi. The truck idles great but when you get on it at about 3000 rpm it starts cutting out I retarded the timing almost to where it would die and made some runs then adjusted the timing about 3 degrees at a time until I found where it ran its best but it still cuts out. Anybody had this problem I have my hei distributor hooked up to the power wire from the original distributor and I also have it hooked up to the stock tach wire. I ran a wire from the tach wire to the purple wire that plugged into the ignition module. Any chance the floats are messed up in the carb and letting gas leak by causing it to flood out or is it just not getting enough gas. Im lost. Cuz once it gets to about 4000 rpm it clears up and hauls a. Please anybody got any ideas

 

[Rusty Nail]

"When you get on it" meaning floor it? Err,"opening secondaries"?

I vote it's in the carb....care to elaborate any?

 

[Rusty Nail]

"When you get on it" meaning floor it? Err,"opening secondaries"?

I vote it's in the carb....care to elaborate any?

 

[Z71hamric]

Both if you slowly accelerate its not as bad but you can still feel it cutting out. When you put it to the floor it cuts out bad around 3000. If you let off the gas then floor it real quick it clears out for just a second then starts cutting out again. Once get over 3800-4000 rpm it clears out

 

[Rusty Nail]

Letting off MARKEDLY produces more engine vacuum.- Clears out for just a second (with an initally higher and decreasing vacuum signal) and as RPM/throttle increases -(less (decreasing) vacuum) problem returns.
That says nothing for why it clears up over a certain RPM, unless what ever is affected by the loss of vacuum either doesn't require it then (closes), or is unaffected at that engine speed.

Can you duplicate the symptoms in PARK and does engine operating temp have any effect?

Brake booster one way check valve.
That's where i would start if you do not see fuel DROPS in park, working the throttle by hand.

But wtf purple wire?

If it ran fine in the other truck, maybe some part in THIS truck is at fault. Insufficient vacuum to operate the known good carb properly?

Ever diagnosed a vacuum line sucking closed? It's kind of like a brake hose collapsing - it happens!