Pertronix D186504 distributor
 

Hello,

I am running a 1974 Porsche 914 1.8L engine with Weber 32/36 carburetor (installed by previous owner). Everything is great, except for a bad flat spot right off the idle -- pushing the throttle hard off the idle makes the engine choke, and it even shuts down sometimes. (Not nice at all in traffic.)

Some people suggested that this is a problem with the ignition -- the distributor's advance does not catch up with the accelerating engine. I have the dreaded 009 distributor.

I was wondering if people have tried the Pertronix SVDA (D186504) distributor, and what their experiences were. Originally I tried to buy an Aircooled.net distributor (Bosch, modified), but those are no longer available. ACN recommends now the Pertronix instead.

Any comments? I have tried in vain to fiddle with the idle mixture and idle speed, the flat spot won't go away (or I get it so rich there is no flat spot, but the car won't run well).

Thanks,
Andrei.

Both the 009 and the single-carb setup are difficult to tune in our application. I have no experience with the Pertronix distributor, but if the guys at aircooled.net recommend it, then it probably isn't bad. I would recommend ditching the progressive Weber in favor of dual carbs, or some type of fuel injection.

Though which type depends on how much you like tinkering and how much (if any) the engine has been modified, as well as budget.

--DD

Dave,

how easy is it to switch from the Weber 32/36 setup to a dual carb setup? Which carbs do you recommend? I am not much of a tinkerer, I'd much rather get what I have working properly, by tuning the advance and/or the jets properly.

My only complaint is that with the engine cold, the car stumbles on acceleration at low RPM. Everything else is fine.

Thanks,
Andrei.

Easy? Not sure, frankly. I mean, it should be a matter of tearing the single-carb setup off, and bolting up the manifolds, carbs, air cleaners, and linkage. But there are always details to deal with...

--DD

Now that the weather has warmed up (80 degrees today in Madison) I took it out for a spin. When the engine is warmed up well, it runs like a top, no stumbling. I wonder if there is any way to keep the choke on for a little longer (with the choke on it also does not stumble, it is only when the choke opens up and the engine is still cool, say after 5 minutes of driving in 50-ish degree weather).

Or I have read that increasing the size of the idle jet will make a big difference. Anyone can point me in the direction of where to find the location of the idle jet on the 32/36 Weber? And where can I buy a single jet (I think a 070 is what I need, from what I read)?

That could well fix it,centre mount carbs on any ACVW need a bigger idle jet due to the manifold runner length,these carbs do have an unjustified bad rep IMO,I have personally heard of and seen t4's running well with this set-up.
I think too many people assume they run fine out of the box and don't tune them,a set of #60-65 idle jets should do the trick if not look @ your timing and state of tune.
The 09 isn't the ideal dizzy for the T4,sell off your one to a beetle or bus person.
I recommend the SVDA that ACN sell,go for the dizzy change first.

ANDREIC..........

Everything is great, except for a bad flat spot right off the idle

Some people suggested that this is a problem with the ignition -- the distributor's advance does not catch up with the accelerating engine. I have the dreaded 009 distributor.

I was wondering if people have tried the Pertronix SVDA (D186504) distributor

There are multiple problems using a Weber 32-36 with a flat four air cooled motor.

Icing.....the intake runners are long (too long).....and there is not enough manifold heat for proper fuel/air feed. The fuel wants to puddle and fall out of suspension. This is validated by your "warm day it works ok" scenario. Your jetting could be ok but the jets possibly needs tuning. But first things first......you've got to get more heat to that manifold. Your manifold (maybe...depending on who made it) has a small tube in and out of the bottom of the plenum area of the manifold and goes from one side of the exhaust manifold to the other side of the manifold. You want to change the "other side" that goes to the "other" manifold to the exhaust collector. This way you will have more hot exhaust going thru the tubes to the manifold and not tube to tube which is now just pulsing from tube to tube, and will be flowing more exhaust. This is an easy fix...do this first.

Timing........The distributor issue using a 009......this distributor has no vacuum advance. Bad for a street car but a lot of folks bought them because they thot they were the hot ticket. Usually there is a dead spot just off idle accelerating in first gear from a stop. Set the lead (timing) at 28 crank degrees total when all advance is up.....(about 3000 rmm or more)....idle should be as low as possible with decent idle. Maybe 800-850 rpm. A dist with vacuum will help...maybe. The Pertronix is a good unit but "one size fits all" and the ignition curve might not be optimum for your motor. There are many RATES of advance in disributors that were used O.E. on the flat fours.....and the vacuum can Pertronics uses just maybe an average of those many O.E. units and the carbs vacuum/retard port numbers.

So do the heat flog first.....then idle speed and lead....
Then take a look at the primary idle air jet. A 60 or 65 would be a good start. The idle screw should be about 1.5 to 2 turns out. Turn in all the way....out one turn, start hot motor and slowly turn out till bumpy idle then turn in slowly...IF you have to turn more than about 4 turns for a bumpy idle then go one more (5) air jet.

If you dont want to read up...the Haynes Weber manual , Older shop manuals (Motors etc.) or the Factory Shop Manual...you should find someone who is conversant with 32-36 carbs and air cooled motors. You can spend hours chasing your tail. Good luck.