TheSamba.com :: View topic - 30 pict 1 on dp 1600- bogs down and pops when cold

Tue Jul 01, 2025 10:25 pm

When the engine has been ran for awhile, (hot) it runs great, happily gets up to highway speeds and revs very nicely. It runs good and revs good when cold too, but when I put a load on the engine it bogs down (basically no acceleration) and pops a little bit. It mainly happens in 2nd gear at lower rpms.

I did follow the procedure for setting the idle mixture. I believe you start 2.5 turns out, then turn in until the idle drops, then back out to achieve max idle again. All while hot and the choke is completely off.

Engine specs:
Vw 1600 dp
30 pict 1 carb- 125 main, 60 idle, 115 air (I know it is a little small, but it should work) I also have a 130 main I put in and when I did that it had almost no power.
Pertronix coil and 009 electronic ignition, timing set to 30 degrees total advance

Am I running too rich or too lean? I am 3000 ft above sea level if that helps any.
Do I need to adjust my electric choke? I know a lot of people who have gotten rid of electric chokes due to problems like this.

Tue Jul 01, 2025 11:35 pm

Pops out the carb or the muffler? Typically too lean out the carb and too rich when out the muffler.

Wed Jul 02, 2025 11:38 am

I am running a 30PICT-2 WITH THE MATCHING VW DISTRIBUTOR on my 1641 SP. Runs really sweet at all times under all conditions. I put a wide band on just to see where the mixtures were... guess what? It's squarely in the 13's all around! VW seems to have got it right.

I am thinking you have a vacuum leak.

Wed Jul 02, 2025 12:46 pm

What is the best way to check for a vacuum leak? If I have a vacuum leak wouldn’t it pop out of the carb due to more air? I guess it could explain it due to thermal expansion.

Wed Jul 02, 2025 12:47 pm

Also it does pop out of the exhaust, but when I tried putting a bigger main jet in it was popping from the carb???

Thu Jul 03, 2025 3:17 am

Spray something combustible around all the connections on the intake. The engine will tell you if there is a leak.

I wouldn't rule out spark scatter either from sloppy or worn distributor parts. Could have cross firing on the cap too.

I just had my timing light on my Buddy's Buggy. Spark was steady at idle but the higher I rev-ed it the more unstable it was. One of those cheap no-brand electronic distributors. You know the one, white cap and module on the side, $65 I think I saw them advertised a few years back.

If you seriously want to know what the mixture is beg borrow or steal a wide band and weld a bung in your exhaust.

Thu Jul 03, 2025 3:25 am

Hang on a minute! Is this a type 3 engine that you put a single carb on? Lets see a picture of the conversion please! I want to know what you are doing for intake manifold heat.

Thu Jul 03, 2025 2:25 pm

BenderTheRobot wrote: What is the best way to check for a vacuum leak? If I have a vacuum leak wouldn’t it pop out of the carb due to more air? I guess it could explain it due to thermal expansion.

As stated above, use a combustible spray of some sort. But be careful as a wild spark could light it up!

I use starting fluid, through the straw end of a can. I have also used a hand held plumbers torch with MAPP gas. Anything works as long as you can get the mixture pinpointed.

Or if that is scary. A smoke test. Take a big drag off of a pipe full of tobacco and blow the smoke into the carb opening. Do it a few times and see if smoke comes out somewhere it should not!

Thu Jul 03, 2025 3:25 pm

No, not a t3. Would be interesting to see though. I will try the starting fluid. Thanks!

Fri Jul 04, 2025 5:19 am

Carburettor is a bit small for a 1600 DP. It is usually a 34PICT-3.

Was it once an SP engine and did you keep the same distributor? The distributor timing curves are different..

Fri Jul 04, 2025 8:10 am

The answer is in his first post.