View original topic: Kadrons "popping" when I hit the throttle...why?
fifthcenturycheese Wed Feb 20, 2019 7:35 pm

The motor:

Dual Kadrons (new) Berg linkage
Pertronix flamethrower SVDA + flamethrower coil
110 engle cam
8:1 compression
Timing 7.5 initial
91 octane
pump shots on both kadrons measure to .6 cc
idle jets 55 , mains 135's
carbs synched, butterflies match...

Installed vacuum port on driver side kadron and changed out German 009 with Pertronix flamethrower. Very pleased with results so far, stumble has smoothed out, but when throttle is punched I get a pop from both sides. Not everytime, but a couple times. I feel like I am real close to having it dialed in... Any suggestions on what is happening here? Thanks, Mike

Mikedrevguy Wed Feb 20, 2019 7:50 pm

How are they synced?

APPLEGREENVW Wed Feb 20, 2019 7:59 pm

What's the fuel pressure?

vwracerdave Wed Feb 20, 2019 8:07 pm

With 8.0 compression ratio I'd try some 87 octane gas.

nsracing Wed Feb 20, 2019 8:14 pm

Are you sure the distributor is advancing properly?

Also, you might want to add more squirt --maybe you need to adjust the fuel advance.

yes, check the synchronization on the carbs.

fifthcenturycheese Wed Feb 20, 2019 8:32 pm

Fuel pressure is around or slightly above 1.5 lbs.

modok Wed Feb 20, 2019 9:30 pm

Appears you haven't installed the airfiter or........ the rest of the car yet.
Won't even be able to get it warmed up with no load on the engine.

oprn Wed Feb 20, 2019 10:00 pm

modok wrote: Won't even be able to get it warmed up with no load on the engine.
Excellent point!

Also make sure you have the thermostat and flaps installed and working correctly. My Kadrons would not stop popping and farting at part throttle until the engine was fully warmed up - as in - several miles at highway speed. Then without the thermostat they would start popping again after 4 or 5 sets of lights back in town and the engine was too cool again.

Once I added the thermostat there was no more popping in town.

fifthcenturycheese Wed Feb 20, 2019 11:16 pm

Modok and Oprn:

Took the engine out to do some adjustments, but I guess I am at the point where I can now "install the rest of the car"...I'm still on my learning curve. Thanks for the input. You guys are absolutely correct, the engine has not been getting hot enough, thermostat is installed and works perfectly.

Will install and post results.

Thanks, Mike

andk5591 Thu Feb 21, 2019 6:17 am

Yeah - it should run a bit crappy until fully warmed up unless you have it jetted too fat.

andk5591 Thu Feb 21, 2019 6:18 am

Yeah - it should run a bit crappy until fully warmed up unless you have it jetted too fat.

Alstrup Thu Feb 21, 2019 8:30 am

Yeah, not enough cr and not enough timing at idle.
The timing is easy to change. Set it up for 10-12 degrees at idle and limit the advance to 30 max 32 without vacum. That'll help some. The rest is jetting.

fifthcenturycheese Sun Mar 31, 2019 10:57 pm

So, the engine went back in the car and I am extremely pleased with the results! The Pertronix 034 svda cured the problem. The engine needs to warm up for the Kadrons to operate efficiently. The svda really smoothed out the performance of the engine over the German 009. Opening the "already provided" vacuum port was very easy to do without having to send the carburetor off somewhere for a while and at no added expense! Just need a black distributor cap!

fifthcenturycheese Mon Apr 01, 2019 5:45 pm

With black cap!

earthquake Thu Apr 04, 2019 1:12 am

Do the discharge tubes for the accelerator pump squirt straight down the vent?
Some times they need to be tweaked over a bit because the squirt on top of the Aux vent and just kinda splash fuel allover when you open the throttle.


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