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Hi I’m new here, I’ve been sitting parking on a 1974 Pontiac GTO for about a year. I got it running for the first time in about six months yesterday after I rebuilt my carbs. I have two Holley 600 on a tunnel ram intake. I also replaced my point distributor with an HEI. The engine I have in the car is a 1975 firebird 400. The issue I’m running into is the car idles great but when I give it about half throttle it bogs down and stumbles like it’s gonna die but when I take my foot off the gas it reeves back up to the proper RPM and idles fine. Any advise? I assume it’s something amiss with my ignition system or my carbs.
I need help figuring out why my 400 is overheating It is a 1987 gen3 Fire-bird Formula (reFormulated) with a 1971 Pontiac 400 block casting #481988 bored .030 over with Keith Black dish pistons, crank has been turned .020/.020. Rotating assembly has been balanced, Number 16 heads with new valves and springs, 72cc cambers. Howard's CAM in.482 ex.470, true dual exhaust, new water pump with cast impeller, divider plate clearance set as close as possible to impeller. New 4 core aluminum radiator with 2 10 inch electric fans pulling air and 2 12 inch electric fans pushing air. A/C condenser removed to allow maximum air flow. Removed thermostat, still overheating. Installed a flow restrictor hoping the water was flowing to fast through the radiator for efficient heat transfer. No still HOT. New 180 degree thermostat. With each change it continued to overheat, although the time it takes to overheat varied. I really hope someone here has an idea what I am facing.
Well fellas, I will finally have some more time Saturday to get to tweaking the issues with the '76 GP's idle/accel issues. Started with running terrible and popping back through the carb. After a new fuel pump (smelled fuel in the oil), wix inline filter and new lines, and 2 Rochester carb rebuilds (soaked the parts overnight in the carb solvent the 2nd time as well as installing a new brass float), re gapped the new plugs to .045 that were gapped at .080 by the seller, new vaccum lines, and I also have the new pcv valve and lines (there wasn't one) to install Sat. It now accelerates MUCH better, but idles like it wants to die at stoplights (and does die sometimes) but starts right back up. I thought maybe to tweak the vaccum lines to see how they work best b/c some diagrams show a "t" going to the vac advance with one going to the manifold, and the other going to the carb... and some diagrams just show a single line to the carb. I also don't know it the missing pcv would cause any minor idling or accelerating issues, but I do know that it should be there. the timing is solid. I am going to drain the tank again and refill it with 89 octane fuel to also see if that helps. I am curious though, as it seems to only try to die after it's warmed up. I know there is a choke internal in the intake but it's tough to find a diagram specific enough to list all of the line connections for a 1976 400 2bbl... (most show them for the 4 bbl) If any of y'all have any tips, I'll surely give them a try either tomorrow after work, or Saturday when I do the rest... Have interior pieces to dye inbetween as well so it should be a great Poncho day -- just would feel much better if I could get this baby to run smooth! She's sooo close... Thank y'all for your time, and all of the guidance that you've given. Stevee