Hi guys, I just used a TDC stop to verify TDC on my harmonic balancer is true TDC. It was off by several degrees because it is a cruddy old balancer but I now have true TDC marked very accurately. I have a rebuilt CCC LG4 Qjet on a 1987 305 TPI stock long block. If I set the base timing to the 6 BTDC that the 1983 LG4 computer I am using calls for (with the EST disconnected to set), and then reconnect the EST and drive the car, it bogs SO BAD that it will backfire and stall if you floor it quickly while driving. If you ease into the gas it will hesitate but go. If I bump the base timing 6+ degrees more than the stock spec the car no longer hesitates and it runs great. What the hell? A stock 305 should not need this much timing. I am having a hard time getting the dwell to show the tune is rich enough. Could added base timing be covering up my lean condition? The problem is that when I over advance the timing from the stock spec the car runs really great.

 

wow, you're having ALL KINDS of problems with that cc-qjet...You've started lots of threads about this... sheesh, that sucks!


Perhaps ask on the TPI board, what the TPI motors usually take stock, as it is a TPI long block, with carb induction. Like if someone put a timing light on their stock TPI motor, what timing it'd be pulling at idle. I'm not sure what would have more effect on the need of base timing, long block (cam and heads), or the carb and intake. I know the cam isn't much different than the LG4 one, but it is slightly different so....

I'm having a tough time seeing the problem here...

 

Just put it where it runs the best, and don't get so worked up over the "number".

The ENGINE knows what its "right" timing is, better than the timing light does.

 

I actually burn chips for the TPI engines. I have the 3d timing curve right in front of me. The TPI engines do run quite a bit of timing early in the curve but I don't know that it wasn't just for emissions purposes, and not because the engine absolutely needed it. I am going to just bring the timing up to where it runs right and not worry about it for now. I hate the CCC Qjet like it's my job. It sucks so much.

 

Of course it sucks. It operates on vacuum.

Maybe I've got some special karma unit that has presented me with a grand total of one problem in the almost 7 years I've run it, but I doubt it. I've heard the ECMs improved a little with age, but I doubt yours is so much less capable than mine. As has been stated, give it the timing it wants - where's the downside there?

However, I wouldn't hesitate to replace a damper that has a slipped ring. There are plenty of downsides to delaying that.

 

I re-indexed the slipped ring. It was off by exactly 6 degrees. So now I have 6 deg. more timing than when I thought I was at stock timing before, but it is still not enough to make the engine happy. It likes to have something like 15 BTDC base timing with the EST wire disconnected. This gives it way too much total timing I imagine, but the part throttle response is excellent. I don't know that too much timing is not covering up the fact that I can't get the dwell to be rich enough. I am almost ready to adapt a TPS to a Holley spread bore carb. I can't take too much more of this.

 

All fixed. The timing was not the problem. I bought a new balancer and installed it just for ha has anyway. I had a fuel leak from the tank to the 3/8" supply line in the rear of the car. It would drip while running. I fixed the leak and the car runs awesome. I'm guessing the fuel was getting tons and tons of air bubbles in it because of the leak on the feed side of the fuel system. With 6-8 BTDC timing the car is very responsive and lays down rubber on dry pavement easily, without using the brakes. I haven't checked the dwell but with the IAB at 3 turns out and the idle screws in the base at 3 turns out it runs very well and starts soooo easily.

 

Good news. Let us know how the dwell is responding so I know you're good.

 

I had to bring the idle mixture screws in to 2.5 turns from seated. This allowed me to get a ranging 25-30 dwell with the engine idling. Turning the base plate idle mixture screws in, or turning the IAB out, both resulted in the dwell reading increasing, I assume to add fuel because I was leaning the mixture out. The car drives excellent and has killer throttle response. I have never seen a carb that was this touchy before, these things really must suck on modified engines without lots of work.

 

Your dwell response to IAB still puzzles me, but looks like you're there now.

Good job.

 

Mechanical fuel pumps and carbs hate air leaks. Turns the fuel into "capuccino foam". The pump doesn't work as efficiently and when the "foam" gets into the foat bowl it floats all around and generally hoses up the carb's basic ability to properly meter fuel. It was designed to meter LIQUID fuel, not a foamy mix.

 

Yeah the dwell is kinda weird but it's definitely closed loop and it's definitely ranging and responding to IAB/mixture screw changes. I can bottom the dwell out near zero screwing the IAB all the way in, or I can bring it over 30 bringing the IAB most of the way out. This is repeatable. I have had several Qjet CCC carbs on this engine and they all behaved this way regarding dwell.

 

Damon's response is a little cryptic but I'm inferring that it may not be a bad idea to check your fuel line. You can pull your fuel line off at the carb and let it pump a bit while the engine idles with the fuel left in the bowl. Observe the amount, quality and possibly pressure if you have a guage.

On the other hand, if it's not broke...

 

naf Damon is referring to a fuel leak that I have already fixed.