I got my recurve kit from Lars last week and finally got a chance to install it this weekend, had to install my headlight switch and speedo drive seal first. :banghead:

Before the recurve I was getting a lot of detonation around 4000rpm+
My vac advance is plugged into ported vac, on the bottom left front of my q-jet, behind a vac delay valve. I still get vac at idle though and I don't understand that.

The car definitely has more power from 2500-3500 rpm! I only advacned the timing to 36 degrees instead of 38 because I was still getting some pinging on WOT, usually after the car shifted into 2nd and 3rd at around 4000 rpm+, but not as bad as before I installed the kit and re-timed the motor. I don't get any pinging at 3/4 throttle or less.

Lars' instructions in the kit mention that premium fuel might be required and I've got a tank of 87 in it now, so I'll stay out of the throttle until I use that gas up.

I also ran a can of GM TOP engine clean through the motor to clean out some carbon deposits that might be causing the ping.

Any tips on eliminating the ping would be appreciated. I'm hoping it's just an octane thing. The octane didn't seem to make a difference before I recurved, I hope it does now. Could that be cause by timing chain slop?

Some of the Forum members and I are heading to an 1/8 mile drag nearby on Wednesday. My best 1/4 was 15.2, that run the 1/8 was 9.7. I'm hoping to be in the 14's for the 1/4 now, so 9.6's would be great in the 1/8!


[Modified by isosceles, 10:07 PM 7/5/2003]

 

Try a tank of high test. Theres a good chance it will erase the pinging. Retarding the timing is another way to eliminate pinging. But retarding the timing usually results in weaker performance. Bottom line is, Pinging is very very bad for any gas engine. If the high test gas cures it and allows you to run the more agressive timing setting, its worth every extra penny. The pinging you hear is the explosion in the cylinder trying to push the piston back down while the piston is still in an upward motion. Think about it. Very destructive to an engine. The high test burns a little slower so it allows the better timing setting, by giving the piston a bit more time to rise to the top before it gets slammed back down by the force of the combustion.

 

Yup ... high test. When I put my kit in in the spring I had pinging as well. Disappeared with 92.

 

I definitely see 14's in your future :). Like Jvette said, higher octane might help, even a mid grade. I'm assuming that you set your total timing at or above it's actual peak and not just where you think it should be. By setting timing at an rpm where all mechanical advance is in, timing chain slop probably isn't an issue. If you want to see a real power increase, get a better cam.

 

Isoceles, I need some help to get my car running this good! :eek:

It's an 80 L48 with the cam done. I am totally unsure what kind of cam it is, because the chap who owned it before me was a little ...uneducated, we will say. Very meticulous cleaner & maintainer, but he didn't go much further than the hood with any knowledge of the car..

Are you getting all this performance out of cleaning up your Q-Jet, or is there another trick or two you could offer as advice?

What kind of gears do you have?

ehhh... :sleep: .. In the winter my L48 might become a boat anchor.

 

Vetterodder, I set my total centrifigal at 36 degrees (no vacuum attached). I revved it to 3500 as per Lars paper, then dialed the mark to zero with my light set to 36. I think I remember you mentioning a cam would do great justice to my L48, and I plan on that next. Since that looks like a pretty big job, I'm taking care of the little stuff first.

Hobbes, I have 3.55 gears. The only mod that I know were done to the car when I bought it is dual exhaust with no cats, through the manifolds with quiet mufflers. I've read Ganey's exhaust thread, I think he said that setup is a big improvement over the stock exhaust. Headers would be even better, but I need a 2004r tranny before I do any exhaust work. My biggest increase in power seemed to come from the Q-jet tuning. My car ran 15.8 in the 1/4 before I rejetted. I followed Lars' paper while figuring WOT metering area. Besides that the only other things I've done were more repairs than enhancements. High flow water pump, power steering pump, AC Delco rapidfire plugs K&N air filter. The Qjet tuning knocked me down to 15.2!