Still trying to find my surging problem. Any rpm (worse at lower rpms) any speeds (harder to feel in 4th gear but its there). Seems to idle a hair worse. The power seems to be lacking a tad when I stomp on it.

Full restore with just about everything new 3 years ago with about 20,000 miles. Everything was running great before this happen.

Things Ive tried, 1 thing at a time:
Completely changed out every component of the Ignition.
Tried with and without vacuum advance - no diff
Different carb (Tried an edelbrock performer - seem to almost make it worse)
Took trans out - m20 all looks good
New u-joints
Rebuilt rear end, new axels, bearings, posi clutches
Shut off rear brakes
Checked front wheels
Vacuum at idle = steady 8"
Cam = Edelbrock RPM

Questions:
Just got in from checking the fuel pressure (edelbrock EDL-1722, not race version - 6psi). I put my vacuum gauge/fuel pump tester into the splitter for the 2 bowls (speed demon 750 mech) and got a steady 9 psi. Should only be 6psi. Could the gauge be off that much? Can the pump fail and make more pressure causing my problem?

How much slop should there be between the cam and distributor gear? I can rotate it backwards some. Both distributors have good gears. Can the cam gear itself be bad? That sound possible? Timing light seems to follow the rough idle, doesnt look all over the place.

Been chasing this for 2 months now...AHHH! Miss my car :(

Thanks all
Tim

Timing light seems to follow the rough idle, doesn't look all over the place.

Been chasing this for 2 months now...AHHH! Miss my car :(

Thanks all
Tim

Looks like your timing (advance mechanism) is wandering. Try getting the idle down to almost stalling, then set it at 20 deg. If the RPM picks up at idle then turn it down again. You want 20 deg on the crank without any of the mechanical coming into play.

Then speed up the engine to 3000 RPM and make sure you have less than 38 (big block). do all of this with the vacuum advance disconnected. After you get this all confirmed, then hook up the vacuum advance to manifold vacuum. The total with crank, mech., and vacuum should be in the near 50* area.

Then after all this is done start tuning the carb. Its ignition first then fuel :yes:.

I tried 2 different distributors. Nothing changed. I tried with and without vacuum advance. Nothing changed. Car was dyno tuned (I did not leave its side) and was running perfect for 5 months, I haven't messed with anything. All timing events are still the same as then. It likes 13 initial 31 total, which it is at right now. Any more and power fell. It was perfect until this started. Its not a tuning thing, been there..done that many times :) Something went bad....Something is failing. Hence the fuel pump and cam gear question.

Fel pump maybe driving the needle/seat open leading to a rich condition? What carb and what do the plugs look like?

Have you checked and retightened the intake bolts? A vacuum leak will cause a surge as well.

My Eddy RPM cam in my 327 with AirGap intake and RPM heads needs a lot more than 13 degrees initial timing and 31 total. And its a huge difference with and w/o vac advance.

The fuel pressure readings don't make sense. Are you saying your fuel pump tested at 6psi or are you quoting the spec.

Where exactly, RPM wise, are you getting the surge. Off idle, part throttle, hard accel?

BTW, 3 years ago and 20,000 miles I wouldn't consider new anymore. So you might have to go through some of these parts again.

when did the problem start? was there any other work done about that time?

is there any evidence of the carb running over, unable to control the fuel level in the bowls? Booster venturiis dripping? Fuel dripping out of the throttle shafts?

Does it surge at 40 MPH steady state? 30MPH?

when did the problem start? was there any other work done about that time?

is there any evidence of the carb running over, unable to control the fuel level in the bowls? Booster venturiis dripping? Fuel dripping out of the throttle shafts?

Does it surge at 40 MPH steady state? 30MPH?

Zeke 67:
"Just got in from checking the fuel pressure (edelbrock EDL-1722, not race version - 6psi). I put my vacuum gauge/fuel pump tester into the splitter for the 2 bowls (speed demon 750 mech) and got a steady 9psi, should only be 6psi max per edelbrock. Could the gauge be off that much? Can the pump fail and make more pressure causing my problem?"

Tom:
No work done, started 2 months ago out of no where. It surges at all MPH and all RPM, in every gear. Harder to feel above 3500rpm, but its there. Can really feel it when in 1st holding 2000rpm. Bucks/surges like crazy.

Sounds like a lean condition. You may have an intake leak to the inside of the engine. This will cause surging. Also you may have a leak in your brake booster. Just some suggestions to look for. Try blocking off the booster line and see if it goes away. Unfortunately you will need to remove the intake to check for the other.
Bill

Everything Edelbrock starts with the correct fuel pressure. These carbs have a small fuel bowl volume, so too little or too much fuel pressure affects the fuel metering. You can do no carb tuning on an Eddy until you get this dialed in.

Add a fuel pressure regulator first. I'm not saying this will fix the surge, but you can't do any more carb tuning until this is fixed -- you won't have a reference to make changes off of.