With my car... They could all be related or I could have a few independant issues going on. I'll elaborate a bit. Last year I had some issues with stumbling on full throttle acceleration. It was determined it was a function of my edelbrock carb, so I've gone with a Qjet and rebuilt it over the last winter. Since, I had the engine out, replaced the rear main, had worked on the trans a bit, dealing with leaks for the most part, not anything mechanical. My first issue at the moment is that I have a off idle stumble. With the vehicle in park, and moving the throttle linkage on the carb, I can tell the engine isn't reving up smoothly... it shakes more than it should and does not sound smooth enough, even for the cam I have in. I also have low vacuum. From what I can tell, the carb isn't leaking anywhere. When I first reinstalled the engine and trans, I had set the idle mixture screws to get max vacuum which was around 12". I bought a dialback timing light to set my timing properly, and found I had around 45` of advance. Got it set up around 35` of total advance, and now I'm only pulling around 5" of vacuum. Is it possible I have a vacuum leak (intake manifold possibly?)? Would advancing the timing increase vacuum somehow and have disguised the vacuum leak in the past? The car also puffs out the exhaust, not just on start up, but even fully warm. I have noticed it when I'm at a stop light and I have a tail wind. It's not white clouds, doesn't smell of burnt oil. It does smell of fuel out the exhaust, bad enough that I can smell it on my clothes after being around the car while running. Visually, it's overly noticable, but you can see a haze coming out of the pipes. I am going to be getting a wideband set up installed so I can do some tuning. If it is a vacuum leak, the wideband won't help me out too much at the moment I'm guessing, but it is still something I will want to utilize in the future for tuning. The carb is off of a '73 Olds if I'm not mistaken. My first thought is to diagnose if there is a vacuum leak, then onto timing and carb tuning. Suggestions?
I have issues too: I love beer I own over 25 vehicles I still buy vehicles I love beer Just a hunch: Did you have the vacuum advance disconnected when you found out what your total timing was? Total timing is initial + mechanical advance. Total timing + vacuum advance is your low load cruise timing which I tend to shoot for 46-48 degrees.
Timing was my first thought also. When you set back the total timing you also set back the int. If I understand all the timing threads on the board you have to mod the Dist. to only allow your timing to go to 32-35 advanced at 2500-300rpm keeping your initial timing close to 5.Ive seen where guys had put stops on the plate or changed springs to get the desired results.
2 things you may want to look at: Cam-lobes could be wiped out-my car did the same thing and the old cam had several lobes that were round Bad harmonic balancer can cause the shaking and timing issues. Chris
OK, try to answer a few posts at once. I forgot to add I also love beer, gotta make a trip out to Alberta and pick up some bulk! Initial - 12 Mech - 23 Vacuum advance was disconnected when I was setting the timing. Vacuum line was plugged. I have an adjustable vacuum advance canister too, so I have it set to about 10` advance when it's hooked up. I made a piston stop out of one of my old spark plugs, balancer is correct. I put in two medium springs out of my moroso advance kit, I also have a Crane kit installed with the weights. The springs are supposed to start advancing around 1500 with all in around 2500 I believe.
I had the engine out as I mentioned, had the oil pan off, and didn't see anything in there that caused any concern, I'd imagine if there were lobes worn down, I would have seen alot of filings. Still, something I can check. If I pop off a valve cover, I should see a rocker arm that wouldn't be moving much right?
For starters, open the hood on a dark night. Spray/mist some water on the plug wires, and have someone goose the throttle a few times. You will probably see a light show around the plug wires---tiny blue sparks jumping from the wires. Replace them with ac delco's.
OK I can check them tonight, I've got 8.5mm MSD wires in there right now. Oh and I replaced the plugs last fall with AC Delcos so I'm assuming they're fine. Didn't notice any cracks in the porcelain.
The balancer could be falling apart-my notch lined up perfectly w/TDC and #1 at top of compression stroke. Ended up the balancer was slowly deteriorating-is it getting worse?
I would try to rule out a vacuum leak first and second I would pull all 8 plugs and be sure they are all happy. Does your tah bounce at all when you are at low throttle or idle? If so I bet it is a fouled or faulty plug or wire. You can also use a timing light on all 8 wires to be sure all the plugs are getting good spark.... Look for a consistent even flash.
Good ideas, thanks guys. I tried the water mist on the wires, didn't see anything lighting up and it was real dark. I checked to make sure all of the wires were seated properly on the plugs and dizzy, everything seemed OK. I retimed the car, I was wrong on my previous numbers. I have 16` of initial and total of 34-35`. The car does not rev up smooth like in my previous videos on youtube, it definitely is running as if it is missing. I'll check the wires with my timing light tomorrow and if all looks good there, I'll pull the plugs and check them thoroughly again. I'm not opposed to getting another set of plugs, just to rule it out. I'm not sure what to say about the balancer, I had it off when I changed the cam around two years ago, and probably don't even have 5k miles on it since, but you never know. It doesn't appear to be getting worse, it just doesn't accelerate properly.. bah! :spank:
OK plugs changed, running waaaay better. Still puffing out the back, and I've got about 9" of vacuum... the needle on the vacuum gauge bounces a fair bit, probably from about 8" to 10" on the gauge at idle. The plugs I had in there were AC Delcos, and 2 heat ranges cooler than stock, it was recommended to me by a local guy, but I went with a stock heat range and an NGK plug this time. Still planning on getting a wideband to get the carb set up properly.
It sounds like you are still having a miss, maybe you have a bad wire or crack in the dist. cap? What about the rotor? Take it for a good run and burn out the carbon that must have built up when it was running badly....
I know it is a pain however you could try pulling plugs after a good drive with the new plugs to see if one of them is fouling from either a miss (fuel) or from oil.
Sean, I'm still laughing at your issues. I have never had good luck with AC delco plugs. I like motorcraft or autolite.
