34 pict-3 carb problems

Stinger has no provision for manifold heat? Or, it's not working.

The manifold heat (small pipe under manifold) is essential for acceleration. The heat right under the carb vaporizes the glob of fuel when you put your foot in it. Without the heat, the glob just sits there and the engine stumbles.

In summer, you *might* get away without manifold heat, but it still won't perform as nicely.

Assume you've already checked the accel pump jet and the vac advance/retard is working.

Speedy Jim

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Reply to
Speedy Jim
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72 1600 d.p.,, rebuilt my 34 pict 3, the only mods to engine is I added a "stinger" header system out under the rear,, now it runs great, except I have to push acc. pedal down really slow or it has one hell of a flat spot, then slowly starts reving. my timing is set and have a stock vacuum advance dist. on it, i adjusted idle and everything to benly book specs, is there something i am missing????
Reply to
AXL

The stinger offers virtually NO backpressure, and as a result, you made your engine run LEAN. Step up the main jet size one or two sizes to compensate, or you will burn the valves, maybe even melt the pistons!!!!!!

Jan

Reply to
Jan Andersson

Speedy Jim,

I have to ask this. You are always insisting that the main cause of the poor acceleration is the manifold heat Do you have practical experience on that? I?m asking this, because this is the problem I have. I replaced the vacuum can, electronic ignition rebuilt the engine, fixed the flap inside the air filter, replaced the carburetor this weekend for a new to test and it works much better, but the problem wasn?t completely solved. The ambient temperature is about 13ºC (57ºF). I can wait for the summer to check if it works better (more than 30ºC / 86ºF). The big problem is that, it is necessary a lot of work and money to fix this problem, so I only will go for it, if I?m positively sure that the manifold heat is the problem of my poor acceleration. The manifold was the only part I didn?t replace and the heat tube is obstructed.

Joao

72 Super 1302
Reply to
Joao Eliseu

acceleration

At 13C, I would say the manifold heat is essential. At 30C, it is less of a problem but might still be noticeable.

I didn't believe it either (many years ago) when it happened to me right after replacing the muffler. What could the simple little muffler have to do with it, I asked? But it's true; if the muffler does not create the pressure difference, no hot exhaust will flow through the heat pipe.

If your pipe is blocked (carbon deposits) many times they can be cleaned out with out replacement. Some use an old clutch cable to ream it out, or a torch to burn it out, even hammering on the outside may break the carbon loose.

Speedy Jim

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Reply to
Speedy Jim

I would add to that an overnight soak with cylinder cleaner (the kind meant to break down combustion carbon deposits)...

Reply to
Red Bug

Thanks for your reply. That is one of the thinks that I hate on this cars...even for a simple fix we have to remove the engine...

Joao

72 Super 1302
Reply to
Joao Eliseu

Well, if you remove the muffler, you can run an old clutch cable through the heat pipe without pulling the engine.

Also, blow compressed air through the pipe to detrmine if it is blocked.

Speedy Jim

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Reply to
Speedy Jim

It is blocked... When I rebuilt the engine I test it and it was blocked, but the guy that rebuilt the engine told me that it would only be one week unblocked, so it wouldn?t justify the effort of unblock it. I?m using a stock muffler.

Joao

72 Super 1302
Reply to
Joao Eliseu

That would suggest an engine running so rich that he carbon deposits were quickly building up! Which would be another problem to correct!

Reply to
Red Bug

I will perform the following test:

I will drive it for a few km (miles) to worm up the engine. Then I will heat the manifold with a hair dryer and then I will drive it again to see if I notice any difference. It is a crazy plan, but may be I can prove something. I have to hide myself during the test, because my neighbors will say I?m crazy "He washes the car and dry it with the hair dryer"

Joao

72 Super 1302
Reply to
Joao Eliseu

Not nearly hot enough. You would need a torch flame applied while driving.

Speedy Jim

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Reply to
Speedy Jim

LOL... even on a convertible it would be to dangerous and I guess that I wouldn't find anyone to help me on that

Joao

72 Super 1302
Reply to
Joao Eliseu

Hi Speedy,

I will replace the manifold. The engine has only 600km after rebuilt and I will wait to reach 1500km to do additional maintenance work on it. I will check if the heads are with the right torque, the valves clearance and change the oil. Today the temperature was about 28 ºC and it worked much better but I still feel a little tremble on acceleration and low rotations, so it is an icing problem for sure.

Joao

72 Super 1302
Reply to
Joao Eliseu

I gotta put my .02 in on this.

Carb ice is a real deal at temps in the 70 degree range more so than at

30 degrees or less. The humidity in the air is the culprit. Ask any student pilot or pilot of a small single engine airplane with a carburated engine. I'm presently fine tuning an 34 pict carb and the ambient temps have been in the 70's and every time I mess with it, there is condensation around the base of the carb. I would have never belived it if I hadn't seen it either.

My intake heat pipes have solid gaskets, if someone wants to expalin that, go ahead but thats the way it came. However, I still get enough heat there to keep the carb ice away.

Finally, adding the heat increases the mixture so keep that in mind when adjusting the carb.

< TC
Reply to
tcrdn11

It would much easier if we all use the same units. I mean 29 degree Celsius so it would be around 85ºF. The fuel takes the heat from the manifold to evaporate that is why you see condensation around the base of the carb. If you put a very volatile liquid on your hand, it will be very cold by the same reason.

Joao

72 Super 1302
Reply to
Joao Eliseu

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