Found a lot of great posts here about timing, lean mixtures, TDC and setting up for "initial starting" before tuning.... but I'm at my wits end... 3 days so far... gas fires, fireballs, popping, serious backfire through carb and engine will BARELY idle when I feather the throttle so I can't get out of the car to adjust timing and set the carb. ... and the battery and valves probably cannot take much more of the cranking and backfires. My nicely polished Speed Demon is now all black. It's a 302 with a Weiand intake and a Speed Demon 650 w/no choke. I set TDC with #1 plug and by "eyeballing" 10-12 degrees advance the distributor was jammed against the rad hose so I pulled it out and rotated it slightly and put the plug wires back on the proper posts. I bench set the Demon before mounting it because the last time i started the car it was idling around 3000 rpm. Set the primaries and secondaries to about .020 air gap through the bleeds underneath the butterflies, set each mixture screw to 1 full turn out, and the accel pumps are 'just' touching and seem to squirt right away when the throttle is moved. The gas level in both glass windows is near the center mark (now that I dropped them all the way to stop gas from belching out of the vent tubes). The vacuum lines for ignition advance might not be working (too much or too little vacuum) but I cannot get the engine to run on it's own for more than 10 seconds so I can't adjust the carb or even see where the timing is at, or whether the vacuum advance is even working. It won't idle and it won't rev up at all. Sucked on the hose and the advance pot moves easily. Rechecked the order of the spark plug wires not twice but three times. I also put in a Pertronix elec. ignition - cleaned all the contacts to make sure it was firing. Few questions if anyone can help: 1. Someone mentioned a distributor that was 180 out - is this relevant? If you rotate the engine once is the distributor in the exact same spot or is it a few degrees different? Is a wad of toilet paper good to help figure out which is the compression stroke (in case it gets sucked into the cylinder)? 2. I'm using the 2 port vacuum check valve (forgot the name - the thing that splits vacuum into 2 ports) located on the top of the thermostat housing... so can I assume that on a cold engine there is NO vacuum advance when it first starts and just mechanical advance. If I just plug all the vacuum lines completely and set the distributor to 10 or 12 degrees shouldn't it run adequately? 3. There is an in-line plug right before the distributor vacuum pot that seems to block all the vacuum. No matter how hard I suck or blow I can't get 'er diaphragm to move. I love how that last sentence just stands out on it's own, eh? 4. I've tried "enrichening" the four mixture screws 1/4 and 1/2 turn up and also leaning them 1/8 to 1/4 turn (simultaneously both ways) since the Demon is a pretty over sized continuous 4 barrel for a stock motor. Carb seems to be seated tightly on the intake - and I also have a 1" spacer on it. 1 turn full out for the mixture screws is supposed to be the initial setting and they are often tuned down to nearly 3/4 turn after warm up - but I can't seem to get that far. Also - very hard to see the timing mark - haven't cleaned the engine and there's grease, rust and spider webs everywhere underneath and I can't get under the car where it's sitting. Should TDC be exactly on the mark on the crank (my 6 cyl. Comet has a different indicator than this V-8 one - TOC is top of center or is it supposed to be numerical?). Thanks if anyone has suggestions! Almost broke a finger on the car today so tomorrow I have to cook a full-course Turkey Day Dinner with 9 fingers and a huge band aid - but I plan on diving under the hood of the Comet again as soon as everyone leaves. Not sure if I have some other major problem that needs to be addressed to get the car running on it's own. Whisky
if the dist was out 180 it wouldn't run at all, what firing order are you using, 1 5 4 2 6 3 7 8, or the 351 order 1 3 7 2 6 5 4 8. are you using the frist plug on the right bank for # 1, to find TDC remove #1 plug, place you finger over the plulg hole and turn the engine with a socket on the crank end, be sure to turn it the correct direction, when you feel pressure on your finger, ite comming up on compression, then watch the timing marks, when the pointer lines up with the mark on the cover, you have TDC, place the plug wires in the correct position, dist turns counter clock wise looking down at it.
Fuel level should be at the bottom of the site plug or just trickling out the carb when the site plug is removed.
This is correct if you pull a spark plug or 2 they may be wet from running rich Sounds like the timing chain may have jumped a tooth or 2, going to have to find timing mark and set it at zero pull #1 spark plug and see if it is on top and take distributor cap off and see if rotor is pointing at #1 on cap. Hopefully this is not the case but something to check Speed Demons are a little tricky to adjust with the 4 corner idle set up until you get used to them.
i have seen motors kinda run 180 out. when you turn the crank one full turn the dist will turn 180 degrees. try pulling the dist. out and turn the rotor so that its exactly 180 degrees when you put it back in. check that you have all the vac. ports on the carb pluged. there usualy is a big one under the rear fuel bowl that is used for pcv or power brakes. go ahead and turn the idle speed screw up a few turns so it should idle around 1500 rpm. what else have you done to this motor sence it last ran right?
I have as well. Won't run well or long but if you feather the throttle right it will run a little while 180 out. Done it. If you use the thumb over the number one spark plug hole to test for tdc you stand a 50-50 chance of stabbing the distributor 180 out. There is enough back pressure in the exhaust system to force your thumb off the hole to convince you it is at TDC. Only way to know 100% sure is by watching the valves while you turn the engine over. clint
if there is enough exhaust back pressure to force your thumb off the plug hole turning the engine over with a wrench, you've got an exhause valve not opening.
Not necessarily true...Valve overlap on the exhaust stroke will give you a puff out the plug hole when you turn the engine over...Gotta pull a rocker cover and verify #1 cyl valves are closed to be certain. Compression stroke will "blow" your finger out of the hole. Hence the reason some get the dist 180 off.
If you use the rockers to get it to TDC you don't have to count on compression to "blow your thumb off" the plug hole. Just turn the engine over with the driver's side valve cover off until the #6 (second cylinder, 3rd and 4th valve) are in the middle of overlap. (the exhaust valve moving up "closing" at the same time the intake starts down "opening") That should be TDC on the compression stroke on #1 cylinder. For each revolution of the crank the cam turns exactly 1/2 turn. It is easy to drop the distributor in 180 off because it runs off the cam 1:1. That means the distributor only makes a half turn for each turn of the crankshaft.
Thanks for all the replies!.... I'm using 1-5-4-2-6-3-7-8. I noticed with the backfiring that it actually blew two of the rubber plugs off the carb; so tomorrow I'm gonna re-check and and plug ALL the vacuum lines then try again - in daylight this time (working in the dark is how I almost broke a finger). I'm guessing that the large tube to the PCV (back of the carb) can just be plugged for the time being - since it's pretty loose and could be upsetting the balance of the carb? The carb has 2 ports for vacuum advance - one is ported (timed with the throttle to advance ignition?), and the other is manifold vacuum advance - I suppose I use the manifold vacuum advance?
you have a timing issue for sure Forget the carb for now. Make sure the dizzy is in correctly and confirm ( through whatever method you like to use) TDC. Don't be "off a tooth" on the dizzy, get it right. Make sure of your firing order and wiring order. Set carb air bleeds at a base setting for that particular carb. Holley is usually 1 1/2 turns off of seated, not sure about Demons. That will get you a baseline setting that the car should run off of. You can fine tune the carb later. If none of this solves the problem , then I'd be looking at the timing set as a potential cause.
AWESOME... she's running; thanks for all the feedback Kewl... got the car running ON IT'S OWN today - no feathering the throttle to keep it running. One of the tees under the back of the carb was disconnected, the disti was still slightly off and base-line adjusting a Demon is tricky. Finally realized that when the oil-pump drive shaft is "loose" and wobbles around so much you can't get the distributor back in - all you have to do is push down on it with a long 1/4" drive extension to make it stand up. But as pointed out elsewhere; the real bugger turned out to be the 6 sided (hence 60 degree increments) of the oil shaft make re-aligning the distributor a bit tricky. Took a few cranks with a BIG 1/2" socket to make it seat in the right place. But when I got it in and marked the intake manifold with a sharpie, eyeballing the timing at first and then eventually getting a timing gun once it was running smoothly, it was dead on 6 degrees. It'll take a road test to see how far to move the timing (people say much more than 12 degrees with a bigger carb???). Car started right away - no backfiring - at 3,000 rpm idle. Demon baseline settings are (I guess) too much for a 302... now down to less than 3/4 turn out on each mixture and had to practically close the butterflies. Vacuum advance doesn't work and it surges, but at least it's close enough to pull into the garage and fix the tranny then do some bodywork and paint before winter. Now I have gauges installed and stopped the oil leaks and gas leaks; so it doesn't smoke as much and hopefully the only fires now are INSIDE the cylinders. Wondered about the wiring for the Pertronix ignition and hi tension leads that were getting chewed up by the alternator blades, but there is no misfire at all and the timing is dead steady. Awesome way to end a weekend! Thanks for the replies here...
