Hey guys, I have a bit of an issue I've run into while trying to increase the efficiency of my car. Just to get you guys up to speed, I have a 1974 Mercury Comet with a 302 that has been slightly modified with a Weiand stealth intake manifold with a Holley Street Avenger 750CFM carb (I know you'll say it's too large but it works relatively well with low end RPM) Well up until now the car ran and worked pretty well despite not having a vacuum advance. I recently changed the whole distributor in favor of a single diaphragm vacuum advance and now the car is all messed up. I set the engine to TDC when I put the distributor in but for some reason the car DOES NOT like to start. The engine when cranking over sounds like its WAY too far advanced and sometimes actually starts stripping the starter. It usually take at least 6 tries to actually get it to catch. Sometimes i even have to retard the timing so far that the idle nears 500 rpm until I return it to its center position. I believe it's due in-part to the following issue. Now, once I do get it started, it idles beautifully after i get it past the initial cold start (When I finally get it to run it sounds like a top fuel dragster [Popping, spurting, spitting] until it warms up a bit) But that's about as far as it goes. It will only idle through the constant vacuum port on the carburetor, not the ported vacuum. This is where the other trouble comes in. In park/neutral the engine will accelerate smoothly. But in drive or reverse if I accelerate too fast the car stumbles and I believe this is because during acceleration the vacuum drops causing the distributor to retard the timing, not advance it... But it refuses to run on a timed vacuum, unless the engine is always accelerating. How do I fix this? I'm so beyond lost right now its insane. Note: All or most smog provisions have been removed and plugged..
I've tried. That's another issue. I actually dont have a timing mark to base it off of. The Harmonic Balancer seems to be off because the 0* does not come around where the timing marks are on the block so i really am only able to time it by ear.
what distributor did you put in? you need to find top dead center on the balancer. use a piston stop in the #1 spark plug then turn the motor one direction till the piston touches the stop and mark the balancer at the timing pointer. now rotate the motor the other direction till it stops. mark the balancer at the timing pointer. now true top dead center is the exact middle between the two marks. put good mark on the balancer at this spot. i will usually use a file to give it some permanency. also its a good idea to put an index mark on the center hub of the balancer to make sure the outer ring is not moving on it. once you have good timing marks you can then tune it. with out good timing marks your wasting your time.
Sounds like your one tooth off on the distributor. Car should idle great with no vacuum advance hooked up. The vacuum is pulling it to more timing.
I put an A1 Cardone rebuilt in its place, but if I was one tooth off, would it allow me to advance it too far and retard it too far?
stick the old dist. back in and see if it's any better...may be a bad (new) dist. do you have the correct vac. line hooked/plugged?
No, you'd just have to advance/retard the position of the dist to be at the previous timing setting with the orig dist... As others have mentioned you really need to get a known TDC mark on the balancer, otherwise it's guess work and luck at best... Yeah someone will post well I can set it by ear and I can as well, but still like a starting reference point....
Okay. Well I'll try to get a TDC mark with some chalk today and see if I can't just fix the reference point because that would probably help a bit. As for the timing, I am able to advance it and retard it too far and kill the engine. Although it goes further towards advance than it does towards retard. I have to retard it to get it to run but then immediately advAnce it once it does get running.
That's actually what I was thinking as well.. When the old distributer was in it ran fine. Had a couple misses, stumbled a little at idle sometimes, but it worked. It accelerated with no issue (other than the fact that it would not work connected to any vacuum source) so I got a new one to have the vacuum advance working and it broke it.
By disconnecting the vac advance it should run at least as good as it did on the orig dist, if that's not the case, you could have a problem with the replacement... Might be worth checking the condenser, and be sure of the points gap...
It's actually an electronic ignition (go figure..?) that was Original. But perhaps it's is the rebuild quality of it. I'll go try and exchange it. But should it really idle fine without any vacuum connection? It's a single diaphragm advance?
