new engine, new problems, please help

[Alf]

i have a recently refreshed .30 over 307, and i am having a few problems getting it to run smooth. here are the specs: 69 307 block, low miles, .30 over, cast flat tops, stock rods and crank, new rod and main bearings and timing chain, the bottom end is not new, but looked very clean. i never pulled the cam, which was stupid, since i've heard 307's wipe cams more frequently than other sbc's. it has a set of 882 heads, 1.94/ 1.50 in. valves, slight cleanup work done by myself. it has a performer intake and a 650 holley spread bore double pumper. the main problem is a horrible stumble. the engine idles fine, and feels fine when cruising, but if suddenly floored it breaks up and does not clear out. i've tracked it down to the ignition, the # 1 and # 4 cylinder's plugs are black and sooty, but not wet, all other plugs check out fine. could this be a wipped cam lobe? faulty ingnition? help is apreciated.

 

thanks.

[MONGO510]

Check for carbon tracks in the distributor. Also check your wires for crossfire. If all is ok there I would pull a rocker cover and check the valve travel on the affected cylinders. If you have a good sye you can watch the valve movement and see if you have a flat cam. If your eye isnt so good compare the valve travel between two similar valves.( 2 intakes, or 2 exhaust) Hope this helps.John

[grumpyvette]

yeah, a TUNE UP ,

replacing the cap,rotor,plugs and adjusting the carb float levels and acellerator pump shot, voluum, to the max setting should improve things, doiing a valve adjustment,and check the ignition timing, if its not something silly like an open vacuum line you forgot to hook up or the distrib not advancing correctly, or an electrical problem

once those check out, Id advise a compression test is run and you check the voltage the ignition receives

plug gap should be about .045 max, and check the plug wires and FIRING order, its abserd but I frequently see plug wires run to the wrong plugs, and the owner says that is never run correctly since the last tune up?????(which is usually about two days ago, before they bring it by

[Alf]

thanks for the replies. i formerly had a stock 305 in my z that had the same carb, distributor, and wires. i figured the carb may not be perfect but it should be in the ballpark. i converted the distributor to the pertronix electronic conversion kit and it ran fine on the 305, but upon tear-down i noticed the magnetic trigger was rubbing on the pickup due to too much advance weight plate play, though the distributor was a rebuilt unit and didnt even have 1000 miles on it, it seemed like they left the clip out that holds the advance plate tight to the shaft. it also has a new borg-warner cap(the one with brass terminals) and a new rotor, the wires had also only been on the 305 for about a month and are Taylor units. the valve adjustment should also be very close if not perfect, since the cam is hydraulic and had already ran in the engine, i ajusted the rockers as i assembled the engine. i did a compression test and all cylinders show at least 150psi. i thought that maybe the coil was not getting enough voltage, but a jumper wire from my batery to the coil showed no improvement. the plug gap is set at .35, and i checked the firing order more than once and it checks out ok. i also tried different plug wires on the two problem cylinders and still no help. the engine also does not consume a drop of oil, so the ring seal must be descent.the main reason i posted was just that it seems so odd that only two random cylinders would be black and sooty but none other, it sounds like a deffective part somewhere along the line to me. maybe the electronic conversion, or cap?