67 pontiac 400 popping through exhaust

[bwalsh67firebird400]

Hi I am new to this and this is my first thread. I recently bought a #'s matching 67 firebird 400 4 speed. I drove the car for about an hour (car ran great) and then filled it up with gas, about an hour later the car started running really rough and stalling. Barely able to limp it home stalled 5 times on the way home and flooded really bad.
I changed the oil, checked the points gap, replaced the points set gap, replaced plugs,wires,cap,rotor, plugs are gapped to .035. the engine now upon start up pops from the exhaust haven't driven since however i tried to adjust the qjet no change. It will pop while just idling if you accelerate not under load, ive tried adjusting timing this can make it worse or a little better. I got frustrated with the points so i installed an ignitor 2 with no change of course. I noticed that it seemed to be running out of fuel so i installed a holley red electric fuel pump and regulator last night (had it laying around for my chevelle, now I know ive got lots of fuel, set psi to about 5.5psi to 6psi. My first firebird at wits end not sure what to do, going to do a compression check today (should have done first).
ANY HELP IS GREATLY APPRECIATED!!!
Thanks.

 

[melsg5]

what octane gas did you put in the car? When you had the distributor apart to install the ingnitor 2 did you check if the advance weights are moving freely and fully return? Are you setting initial timing with the vacuum advance disconnected and what are you setting the timing to? Have you checked the fuel pressure with a gauge? Check the plug wires with a ohm meter should have no more than 1k ohms per foot of wire length. Do you have another ignition coil to swap out the current one? Let us know the result of the compression test.

 

[bwalsh67firebird400]

it was 94 octane. now 87 in it. i forgot to check the weights going to today. spark plug wires are new but will check today. tried setting timing to 6 deg btdc, then fiddled from there it idles fine at 1000 rpm when warming up but as soon as idle drops it starts popping, rotated the distributor a bit and popping goes away. maybe the advance weights are stuck. ill check that next and let you know what i find.

 

[bwalsh67firebird400]

one other question when i installed the ignitor i used a flame thrower coil but i used the same wiring from the coil (less the ballast resistor) could this be related to the resistance wire?

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[melsg5]

you cannt put 87 octane in a stock 1967 Pontiac engine! That engine is around 10:1 compression and needs high octane unless you want to blow the motor. What are the instructions that came with the aftermarket parts, do they specify not to use the resistor wire? Either way you had the problem before you put the aftermarket parts in. Whatever you do if this is a matching numbers car do not throw away any of the original parts. The whole problem could be the 87 octane gas!

 

[bwalsh67firebird400]

I thought it might be a fuel issue which is why I drained the premium out to try some regular. I readjusted the timing on the engine today and got it running good. Only thing is I'm way below the 14 deg btdc mark on my timing cover. Not sure why, but it runs good now like that. Loads of power through all 4 gears really puts you in your seat now. That being said it still pops in the exhaust, today it's in the muffler shop getting new exhaust. A buddy of mine came over to help me out and he explained that the old mufflers on it are a double wrap design inside when these deteriorate and crack they store un burnt fuel which then ignites and subsequently pops. I drove the car for about two hours, no pinging nothing. Didn't have time to do comp test yet gotta do that in a few days when I'm back from work.

 

[melsg5]

you still havent checked if advance mechanism is stuck? that would explain why you are dialing in so much advance. You are doing it with the vacuum to the advance disconnected? You set the points using a dwell meter for 30 degrees before adjusting the timing? once you have the timing straightened out we should move on to how to adjust the idle speed and mixture.

 

[raguza123]

Is this a stock 400? It sounds like it isn't stock and your timing was retarted. I have a 67 326 and I run it at 12 BTC with a electronic conversion kit in it and always use nothing less than 91 octane, 87 is horrible.
What are using for your adv. Ported or full manifold vac.?
Go to Harbor Freight tools and get yourself a dail in timing light help set your timing at 12 deg btc.

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[melsg5]

The correct way to set the timing is not by initial but by total mechanical advance. Purchase a Mr. Gasket spring and weight kit for points type distributors. Remove the distributor from the vehicle and replace the nylon advance stop bushing, if it's still there, with the bronze bushing in the kit. Reinstall the distributor without the advance springs and do not connect the vacuum advance and set the dial back timing light to 36 degrees. Start the engine and set the timing to zero degrees. This gives you the 36 degree total advance. Now install the gold colored springs that came in the kit and check what your initial timing is and make a record of it. Reconnect the vacuum advance and drive the car. If you get any surging at low speeds the vacuum advance can has to be changed to one that provides less advance.