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Twin 40 idf, stock 1600tp, running rich
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rickpereira
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PostPosted: Thu Aug 16, 2012 4:09 am    Post subject: Twin 40 idf, stock 1600tp, running rich Reply with quote

Ok so I bolted up the carbs and took the car around the block,

It idled well at cold and revved well through all the gears, however it was blowing a fair bit of black smoke. It was running fairly rich. You could smell petrol in the exhaust.

And now my oil is also contaminated, and smells of petrol.

I followed the best lean procedure and it was still running rich. Pulling the plugs confirmed it as they were extremely sooty from being cleaned just before the best lean procedure.

The carburettor is set up like this:

Idle jets 52
Venturies 28mm
115 main jets

I am thinking dropping my idle jets to a 50 would help lean the mixture, any ideas that will help get me in the ball park for a stock 1600dp?
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MURZI
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PostPosted: Thu Aug 16, 2012 5:29 am    Post subject: Reply with quote

48-50 on idles
115-120 mains


Check fuel pressure and float levels. You should be close to spot on, unless someone has reamed the jets.
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PostPosted: Thu Aug 16, 2012 8:07 am    Post subject: Reply with quote

What are you running for airs?
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74 Thing
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PostPosted: Thu Aug 16, 2012 8:39 am    Post subject: Reply with quote

Verify fuel pressure and float settings as suggested above.
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rickpereira
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PostPosted: Thu Aug 16, 2012 8:26 pm    Post subject: Reply with quote

ok pulled the carbs out and will be going through the float settings,

i am running a standard fuel pump without a regulator and was getting almost 7psi reading on the gauge,

i know these carbs like 3.5 fuel pressure max. managed to get the fuel pressure down to 3.5 using extra gaskets (just until i can figure out the rich issue)

my air correction jets are 200
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MURZI
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PostPosted: Thu Aug 16, 2012 8:33 pm    Post subject: Reply with quote

Those jets should be really, really close. How many turns from seat are you on the idle jets? And have you set the floats to 10.5-11mm?? If you have not set the floats you will be chasing your tail.

Fuel pressure correction should have helped a lot.
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PostPosted: Thu Aug 16, 2012 8:43 pm    Post subject: Reply with quote

When I bought my 40's from CBPerf they had mains stamped 115 but the actual measurment was 130-135, confirm what you have, bet they have been drilled
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PostPosted: Mon Aug 20, 2012 10:53 am    Post subject: Reply with quote

rickpereira wrote:
ok pulled the carbs out and will be going through the float settings,

i am running a standard fuel pump without a regulator and was getting almost 7psi reading on the gauge,

i know these carbs like 3.5 fuel pressure max. managed to get the fuel pressure down to 3.5 using extra gaskets (just until i can figure out the rich issue)

my air correction jets are 200


There's why you were running rich...7psi fuel pressure. Dumping fuel down the throats. Weber carbs are pretty much like Solex carbs and will not tolerate more than 4psi max.
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rickpereira
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PostPosted: Wed Aug 22, 2012 4:06 am    Post subject: Reply with quote

Sorry I haven reported back guys, I have had the flu for the las couple of days and it really took it out of me this time, I am a lot better now and almost ready to tackle the carb situation, I may get a fuel regulator before doing anything else, although i already have 50 idle jets in my hands and will throw these in after cleaning the plugs, cleaning the carbs, checking the floats and then see how it goes.


I will report back. Hopefully with good news Smile
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PostPosted: Wed Aug 22, 2012 10:40 am    Post subject: Reply with quote

rickpereira wrote:
Sorry I haven reported back guys, I have had the flu for the las couple of days and it really took it out of me this time, I am a lot better now and almost ready to tackle the carb situation, I may get a fuel regulator before doing anything else, although i already have 50 idle jets in my hands and will throw these in after cleaning the plugs, cleaning the carbs, checking the floats and then see how it goes.


I will report back. Hopefully with good news Smile


if you shimmed your pump to get 3.5, you dont need a regulator do you? Confused
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rickpereira
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PostPosted: Wed Aug 22, 2012 12:56 pm    Post subject: Reply with quote

Probably not, but I would like to be able to dial it in more precisely. I have found that having the pump idle at 3.5 means that when I rev the engine hard the pressure drops dramatically, hoping that with the regulator it won't be the case
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rickpereira
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PostPosted: Sat Aug 25, 2012 2:48 am    Post subject: Reply with quote

ok so today i pulled the carbs apart and cleaned them out, they were a little dirtyn nothing to drastic (probably happened because i forgot to clean out the fuel line Embarassed ).

checked the bowls and they were set at 15mm and a drop of 28mm so i set them both to 10mm float level and 32mm drop, replaced the idle jets to the new 50's cleaned out all the main jets, emulsion tubes ect..ect..

so i didnt get to fix the manifolds and carburetor"s back but may do so this week sometime.

i am going to double check my valve clearances and change the oil which is contaminated with fuel, and set the timing so i can get a fresh start on tuning these carbs

i was also told that 98 octane fuel tends to foul plugs on older carburetored cars and to stick to 95 octane, so i may syphon the tank and put some fresh 95octane fuel in there.

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PostPosted: Sat Aug 25, 2012 3:58 am    Post subject: Reply with quote

1, if you get a fuel pressure regulator , dont get the cheap ones with the dial, they dont work.

2, unless you have high compression, dont bother with high octane gas its will give less power and burn less completely.

3, check you spark is powerful, so you dont get false rich look from unburnt fuel due to weak spark.
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rickpereira
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PostPosted: Sat Aug 25, 2012 4:11 am    Post subject: Reply with quote

How do I check how powerful the spark is? I have a new petronix flame thrower distributor, coil and Bosch leads and spark plugs
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rickpereira
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PostPosted: Thu Aug 30, 2012 3:38 pm    Post subject: Reply with quote

ok so i changed my oil, cleaned my plugs, cleaned the carburetors, checked my valve clearences, set my static timing.

i will try to tune the carbies today. wish me luck
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rickpereira
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PostPosted: Thu Aug 30, 2012 7:16 pm    Post subject: Reply with quote

got the car started and then and through the best lean procedure to find that the 1and 2 cylinder carburettors are not responsive to screwing the idle mixture screw all the way in, so in effect i can never get a reaction from cylinders 1 and 2

cylinders 3 and 4 however i get a strong reaction and get the cylinder stumbling and hunting, so then i back the screw off 1/4 turn.

i suspected a air leak in the manifold of cylinders 1 and 2 but sprayed wd40 all around and had no reaction.

another thing .. if i screw in cylinder 4 to where it is stumbling and then turn it in some more to kill that cylinder off the engine will die, which leads me to believe cylinders 1 and 2 aren't pulling their weight,

what to do?
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rickpereira
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PostPosted: Thu Aug 30, 2012 8:16 pm    Post subject: Reply with quote

Ok do on these two problematic carbs I can completely cover the velocity stacks and nothing happens, the motor doesn't stumble or stall when with cylinders 3&4 will stall the motor, so it is apparent that I have a leak somewhere. Sigh pull carbies off again
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PostPosted: Thu Aug 30, 2012 9:05 pm    Post subject: Reply with quote

A couple of thoughts......first, take heed of what 66brm said. Did you actually measure your main jets to see if they are what is stamped on them? Second, in reading what you've posted, you never mentioned that you synchronized your carbs. Did you? With the linkage disconnected from both carbs?
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rickpereira
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PostPosted: Thu Aug 30, 2012 9:57 pm    Post subject: Reply with quote

I bought brand new jets from a reputable carburettor specialist who checked over my other jets as well so I know I am running the correct jets. Also I did synchronism the carbies and they are both set at 4 on the snail synchronizer Before I tried to lean the carbies out. It seems pulling the plugs on cylinders 1 and two has no effect on the engine either
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rickpereira
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PostPosted: Fri Aug 31, 2012 12:52 am    Post subject: Reply with quote

well decided to swap carburettors over from left to right to rule our problematic carburetor.

the carbies decided to start behaving themselves and i was able to tune them at idle.

problem is that while driving they backfired quite a bit through the carbies Sad

knowing that this is a lean condition , i enriched the mixture 1/8 turn on all jets and this minimised the popping ,but it is still there and now i have rich running conditions again. Sad

Back to square one
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