I need someone to set me straight on why car is popping.

Here are the symptoms.
1. Engine makes small popping (backfires?) when I decelerate in 3rd and 2nd gears. Popping is not loud like a backfire, but it is annoying me. The sound happens after I take my foot off the accelerator pedal and begin to slow in the lower gear. Not at the same time I take my foot of the pedal. No sounds when I give the car gas.

2. I have tried leaning out the mixture on my carbs with little change. Timing is correct. No obivious exhaust leaks. Valves are set at .006" for exhaust and .004" for intake.

3. Engine setup is as follows: 1776 cc, dual Kadrons, engine built for 87 octane, fuel pressure regulator set at 2.5.

4. One interesting thing is that I pinched off the balancing tube when I adjusted the carbs, per instructions. When I released the clamp the idle dropped considerably.

I am going crazy trying to figure out the cause and have tried so many things to correct it that I am confusing myself. I hate hearing the pops when I am slowing down at a light. Cars that look as good as ours should not sound like crud.

Any help or suggestions would be greatly appreciated.

Hi John; When my starts a poppin,its usually time to adjust the valves. I don't know if this will help, but it sounds as though you have tried every thing you could think of.

I also have changed my exhaust about three times now because I have split the mufflers wide open after agressive driving on my road trips.

Most likely the intake needs tightened up or you need to take the carbs and intake off and have them trued up (flat on gasket surface) then install new intake gaskets and torque the bolts down using a torque gauge to insure proper tightening. I think you will find that either it has loosened up and just needs tightened or that if its already tight getting the surface trued back up and installing new gaskets should do it. Don't use the metal kind except in the winter.

My car was behaving in the exactly the same way with its kadrons.
Turned out that the carbs were out of balance with each other and one side of the engine was leading the other at idle.

Balancing the carbs, with an airflow meter, solved the problem.

Try leaving the balance tube off entirely, plug the holes in the manifold, and super-tune and sinc the carbs. We had some terrible problems with the Kads first time around, and now run them sans balance tube. I guess that the temps and expansion rates with the VW motor are all over the place, to the point that we were idling on the driver's side alone. The heat from the #3 port was throwing everything off. With the balance tube in place one side was drawing vacuum and fuel from the other and we had a rich and lean condition in the same engine.

Without the tube, the problem went away, the carbs sinc properly and the engine stays in tune much longer.

Luck,

TC

Team Evil
Your reply sounds like a good place to start since I notice such a difference in the tuning when the balance tube was pinched or not. Do I just remove the balancing tube and leave the fittings open or should I get some special part for each fitting? I don't want to compound my problem by getting something in the carb through the balancing tube fitting.

You'd need to seal off the balance pipe fittings in the manifolds if you're not going to use it.

AJSim's site is quite helpful for kadron tuning

www.lowbugget.com/help_section.html

Note he recommends not pinching the balance pipe for tuning (if your going to run the engine with a balance pipe).

John,

Our Kads came from AJ without the fitting for balance tubes. If you don't want to commit to permanently sealing the holes in the manifolds with a metal plug. You could get a rubber cork and silicone it into the fitting, or use a short piece of hose and fit a bolt into it with silicone or plug the holes for the balance tube in any reasonable fashion that seems to make sense to you.

If you don't seal the holes the vacuum leak would prevent any sort of accurate tuning, and the permanent lean condition would burn your exhaust valves down to nothing. That, or the excess heat would melt everything left standing.

Plug the holes in the manifolds, permantly or otherwise, and super-tune the carbs to a fine balance. Disconnect all of the linkage and do each carb separately, then reconnect and be sure that they bottom out, and respond in concert.

The Kads don't respond all that well to a unisinc because of the intake horn being so large, the air simply stacks up too much above the venturies, you can get them close, but you'd be better/best off going to lowbugget .com and checking the tuning/balancing procedure there, or email Sims for info.

Luck,

TC