Countach Technical Thread & Questions

I've got hold of the video my mechanic made. From about 1:40 to 3:00 shows the issue best.

What do you guys think? Does this confirm your ideas or give you any news ones?

Thanks again for your help.

 

By any chance do you have a catalytic convertor? If so it might be clogged.

So googling around I did find this.

There is a condition called "standoff" that blows fuel vapor (and it is very visible) out of the carb throat. Technically, at whatever RPM you experience this, there is a reverse pressure wave inside the intake manifold that is blowing back harder than the engine can suck it in! Depending on your cam, venturi size, and other details, you can get standoff at high or low RPM's.

I don't know what size venturis you have, but the first thing I'd do is drop a size and see what happens.

 

No, the car doesn't have a catalytic converter. I very much doubt the cam is not OEM and my mechanic tells me the venturi size is OEM. Although you are not the first person to suggest reducing the venturi size, so maybe that is worth looking at.

I spoke to another Countach specialist today who has not seen this before but suggested that we check the ignition advance curve all the way through the rev range as a starting point.

 

It does look like fuel stand-off but it looks excessive. Having the deck lid off creates a low pressure area over the carbs exaggerating it a bit but I still think it is excessive. I would look at the cam timing, specifically I would be looking to see if the exhaust timing is retarded. Late exhaust timing could cause high cylinder pressures when the intake starts to open resulting in a reversion out the intake.

Thinking more about it. As mentioned above, a plugged exhaust would also cause high cylinder pressures as the inlet opens. Maybe the easiest thing to do first is to remove the muffler and do another run before looking at the timing.

Cheers Jim

 

Thanks Jim,

Both good ideas. Plus it would be fun to hear the car with no muffler - apparently the very first owner used to run a straight through exhaust on my car!

 

I’m looking to replace the AC lines that run the length of the car and run through the left side sill. Anyone have advice on how to do it? I tried pulling the old lines through but it feels like they are clamped. My lines are cut in the engine compartment just before they disappear in the left fender.

Thanks Jim

 

This is job really requires two people and a lot of patience. Lots of one step forward and two back while doing a lot of jiggling. Eventually you will get it. Good news is that you still have the old lines in there. Attach the new lines to the old ones, and use them to pull the new through the maze of tubes.

 

Thanks for the information. I’ll give it another go with a little more effort this time.

Thanks Jim

 

Make sure you use the new rubber hoses with metal tubing inside then use the new generation freon. Did mine 10 years ago and still works great

 

I’m not familiar with that AC hose, I’ll take a look. I do have some hose which matches the factory appearance pretty well.

Thanks Jim

 

Got the AC lines in. They wouldn’t go trying from the front or back. Found a panel covering the rocker panel in the left front wheel well. Working in the wheel well I was able to pull the lines in from the front and push them through the rocker panel. I did about half of it by myself and had help for the second half. Having someone push from the front and occasionally pulling from the back made it so much easier. Not convinced going front to back was the easiest way to do it but it got the job done. Going from the front trunk to the wheel well was the most difficult part.

Cheers Jim