A little background. I posted last week about an idling problem that I was having and had several responses and suggestions. Of course, I immediately assumed that I had a Q-Jet problem. I hadn't contacted Lars because I knew that he was not taking on any new carbs so he could concentrate on his new project - a 64 roadster. Much to my surprise and pleasure he suggested that I bring my car over to him since he thought it might just need a simple Q-Jet adjustment. I live about 1/2 hour from him so I leaped at the chance.

So yesterday was the day. After pulling into the Viking Bar & Garage and exchanging a few pleasantries, Lars had the carb off my car and disassembled in about 12 seconds. This carb is one of those dreaded commercially rebuilt units and although not as bad as it could be, it still had several problems. Wrong jets, plugged vent holes and wrong float level are just a few. Lars cleaned everything and put in the proper parts. It took a lot longer to reassemble the carb - about 18 seconds.

After reinstalling on the car and checking vacuum, it became apparent that there was still a problem. So, out comes the distributor!

Now we come to a demonstration of Lars' Primary Directive that not all engine problems should be immediately attributed to the carb. Yeah, my carb definitely needed work, but the distributor also had a problem. Which I am sorry to say, I caused myself when I installed the Crane electronic ignition. The base mounting screws are too long and caused the distributor to turn erratically and get intermittently hung up.

Lars disassembled the distributor, cleaned it, nipped the problem screws, replaced the vacuum breaker, reassembled, installed in the car, set the timing and whaddya know, I have a smooth running, unbelievably responsive Vette.

About 2 hours of fun and informative demonstrations (for me) is all it took. Probably the only thing better than getting a Tuned by Lars carb is being there and seeing the Master at work. I learned that when a problem arises, it's real easy to focus on what seems to be the apparent source, like the carb. There are several systems on the car that work together (duh,) especially the ignition and fuel and everything should be on the radar when troubleshooting. I'll bet a lot of you guys know this, but it was a revelation to me.

Thanks, Lars!

By the way, Alaskan Amber is a good complement with carb work and a Deschutes Black Butte Porter is perfect when working on a distributor.

 

Great fun tinkering with the Vette on a nice weekend morning! It's always enjoyable meeting Forum people, playing with the cars, sharing some tips and techniques, and having a few good beers.

Alan's car was a good example of how many tuning problems can't be solved via e-mail or Forum posts: He had posted some questions earlier about idle speed versus air temperature. His idle speed would never stay the same, in spite of adjusting idle mixtures and playing with the carb. He received a lot of suggestions on how to solve this, but none could have solved the problems we found...

We found 3 primary problems contributing to eratic idle speed:

• First, the carb had been commercially rebuilt, and the builder had installed lead plugs in the idle bleed air holes as well as dropping jet size 7 sizes from the stock size. This caused a "lean hunt" condition, making the idle mixture screws virtually ineffective.
  
• Then, after installing a vacuum gauge on the engine, we found that the vacuum advance control unit on the distributor was not correctly matched to the vacuum the engine would pull at idle. This caused the vacuum advance to never produce the same timing setting after each throttle return to idle.
  
• Finally, the installation of the aftermarket electronic ignition caused the dstributor breaker plate to rub against the distributor housing (the screws for the conversion were too long). The breaker plate, after being erratically moved by the vacuum advance, would jam itself into a new and different timing position every time the vacuum advance moved, never returning to the same timing position 2 times in a row at idle.

So we fixed all the carb issues and jetted it up to the stock jetting for the carb number. Set up float level to .375, raised the secondary rod height to .640", set secondary airvalve windup to 3/4 turn, and popped a new filter into the housing.

The distributor was given a blueprint setup with a new set of springs, a VC1810 vacuum advance control unit, and we snipped the offending screws down to the right length. We then set total timing to 36 degrees, and ended up running the vacuum advance off ported vacuum for best idle due to the very short timing curve on this particular distributor (most applications will run better off manifold vacuum, but this one happened to run best off ported due to the 24 degree initial advance and a short 12-degree advance curve).

These few little changes really woke the car up, and Alan reported some pretty snappy throttle feel after the test run.

Is this fun stuff, or what..?

 

I would just like to say that i am sooooo jelous.

That is all


tim

 

Great job Lars, can't wait to have you set mine up someday...when I put the car back together

 

Wow...I rebuilt my distributor with Lars kit and a Crane module. But the idle is never the same twice... I will check to see if the if the screws are too long...

 

Man I was I was closer Lars! The timming is just something I'm still learning about! I've read everything from you I can get my hands on!

 

Lars is not even a Prince.....he's a freakin' King !!!