Trouble with surging. Building 1971 cutlass s with 350 rocket. Bored out to 4.125. Using DSS FX series high compression pistons. Comp cams extremene energy cam and lifter set cl42-222-4. Summit Racing Blueprint HEI distributor. Edelbrock performer intake. Torque Master 2000 stall Torque converter. Holley 600 carburetor with 70 jets. #6 cylinder heads....Engine idles beautifully and has great throttle response while in neutral or park but when in gear and trying to accelerate it lacks power amd surges and stumbles. Have adjusted base timing and vacuum advance to no avail. Thinking the 600 carburetor may not be supplying enough fuel for build but not sure what direction to take next

 

Consider a AFR gauge set up. You could be way out on the tune. What timing are you running? Ported or manifold vacuum advance?

 

^^^^^^

 

is it a new carb or used one? how much throttle are you giving it when you say it surges? is it more like a hesitation?

sounds like a secondary lean problem, air valve on secondary set to loose or a a combination of both.

is your accelerator pump giving a good pump shot?
here’s the trouble shooting guide and tuning chart. the tuning book is great for setting them up, very easy to follow

 

Sorry I put edelbrock carb on accident. Running a holley 600. Had 66 jets and installed 70s hoping would help. Surging is constant from about 1/4 accelerator to full throttle and gets worse the more i get into it. Ive set timing all over trying to fix issue and doesn't seem to help. Running vacuum advance off of ported or manifold vacuum or disconnected and okugged seems to have little affect on surge.

 

Buy a wideband O2/ air fuel meter and see what it tells you.
You can chase this as much as you want. Just buy the meter.

 

First, quit playing with the timing. Set it, and move on.

 

I will try meter to see what it shows, only issue is it is presently open header because have not got it running good enough to make drive up the road to exhaust shop so not sure how I will go about installing sniffer for the gauge

 

I would order a gasket set for the 600 holley you have and go through it. Spray some carb cleaner to make sure none of the circuits are plugged. Square off the primary transfer slots, close the secondaries almost all the way, and then verify the accelerator pump(s) is adjusted correctly with the choke fully open. If the accelerator pump arm is adjusted when the choke is closed and the fast idle is engaged, it can lead to problems in getting the proper pump shot when the engine is warm and the choke is open. Set the idle mix screws out about a turn and a half to start, and lean it out from there. Plenty of guides online if needed.

 

what model number 600? it’ll be stamped on the front of the choke air horn

is it double pumper or vac secondary?

new or used?

 

Are there any known issues with gasket sealing a square bore carb to a Performer 350 intake manifold?


And apologies if I offend you, but why use an essentially stock intake on a performance build instead of a Performer RPM?

 

Was a new holley 600. Tore carb down and cleaned everything when putting in bigger jets. Replaced carb gasket when removed and seemed to have no issues with fitment or leakage. Used that performer intake as it was included with bunch of spare parts when I bought car.

 

Any chance there may be issue from vacuum modulator on transmission? About only place getting vacuum that i have not checked or tried to cap off to test change to surging

 

There could be a vacuum leak anywhere in the modulator vacuum line. I think if the modulator itself fails, ATF will get sucked into the intake.

 

I agree with installing a AFR. Id also suggest installing a fuel pressure gauge, at least temporarily. You may be chasing a fuel delivery issue. If do, you will never get the carb right if the engine is always thirsty. Plumb it in, tape the gauge to the windshield where you can see it while driving.

 

That's a great starting point.