Cylinders 1&2 colder than 3&4 and lack of power

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Miguel Antonetti
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Cylinders 1&2 colder than 3&4 and lack of power

#1 Post by Miguel Antonetti » Sat Oct 13, 2018 1:38 pm

Dropped the engine to fix a leaky oil cooler on my 356 C, change break points, condenser, and plugs. Now it idles fine but cylinders 1&2 are colder and there's lack of power and missing under acceleration. Checked and cleaned carb, break points again, changed the condenser, new dist cap and rotor... Could new plugs be bad, but 2? I didn't touch the fuel pump, but could it be the it not pumping enough?
Any hints would be highly appreciated...

Many thanks!!!!

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Mike Wilson
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#2 Post by Mike Wilson » Sat Oct 13, 2018 1:44 pm

Check to see if you have spark to #1 and 2. Also check to see if fuel is being delivered to those carbs when you manually activate the throttle rod.

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#3 Post by Vic Skirmants » Sat Oct 13, 2018 1:50 pm

Make sure the plug wires didn't get switched; don't laugh; I did that last year on my race car.

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#4 Post by Mike Wilson » Sat Oct 13, 2018 2:08 pm

Good point, Vic. I've done that as well.

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#5 Post by Miguel Antonetti » Sat Oct 13, 2018 2:53 pm

I just tried another condenser and the same... but noticed a surge on the rpms in idle around 2.5K, not cyclic but an intermittent surge of may be 200 rpms... going crazy here...:(

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#6 Post by Miguel Antonetti » Sat Oct 13, 2018 2:58 pm

Mike, there's spark at the dizzi when unplugging the plug wires.. how do I test the carb for by hand?

Vic, I checked the wires - ok.

Could it be fuel pump delivery? However I believe both sides (1&2 and 3&4) would do the same, right?

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#7 Post by C J Murray » Sat Oct 13, 2018 2:59 pm

Vic Skirmants wrote:Make sure the plug wires didn't get switched; don't laugh; I did that last year on my race car.
I did that when you weren't looking!
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#8 Post by David Jones » Sat Oct 13, 2018 3:10 pm

Take a straw and put it in the vent hole and push down to see if the bowl is full of fuel because I have had floats stick in the bowl and hold the float valve closed. If the float moves then make a mark on the straw where it enters the vent tube then run the engine and see if it changes position. That will tell you if fuel is actually getting to the carb, especially if you hold the float down you will flood the engine. You also could have something blocking the flow into the float valve.
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#9 Post by John Ward » Sat Oct 13, 2018 3:13 pm

Did you pull the carb or the manifold off on that side when you pulled the fan housing off ?
Sometime, you`ll get an air leak and that would cause that bank to have problems
 

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#10 Post by C J Murray » Sat Oct 13, 2018 3:14 pm

Most likely it is limited to only the work that you just did but...

Blockage in the 1/2 fuel path before the float bowl, after the T split in the steel line. Collapsed hose forward of fan shroud. Hose chunks blocking needle valve.

If the fuel pump can get fuel to the 3/4 carb it should also reach the 1/2 carb.

Double check the plug wires. It is easy to have them crossed under the generator which causes confusion. I also have screwed that up in the past. Hold the #2 wire near the cap then hold it near the plug end, then give gentle tugs back and forth left to right and you will then be certain.
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#11 Post by Wes Bender » Sat Oct 13, 2018 4:07 pm

Pull the plugs on #1 & #2 and make sure the gap hasn't been closed.
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#12 Post by Mike Wilson » Sat Oct 13, 2018 5:40 pm

You could also pull the top off the carb to see if there is fuel in the bowls and check the float needle valve.

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#13 Post by Eric Wills » Sat Oct 13, 2018 7:02 pm

Run the car with the air cleaners off. Look to see if excess fuel is being dumped into the right side carb. Float valves can stick both open and closed. Stuck open and the cylinders on that side will be flooded with fuel but the car will still run, but rough. Temps will also go down as it is WAY too rich. Just a possible cause. Good luck.

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Re: Cylinders 1&2 colder than 3&4 and lack of power

#14 Post by C J Murray » Sat Oct 13, 2018 7:43 pm

Wes Bender wrote:Pull the plugs on #1 & #2 and make sure the gap hasn't been closed.
Good point. Extended tip plugs in an engine with a tight squish might close up. Were the old plugs the same tip type?
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Re: Cylinders 1&2 colder than 3&4 and lack of power

#15 Post by C J Murray » Sat Oct 13, 2018 7:45 pm

Eric Wills wrote:Run the car with the air cleaners off. Look to see if excess fuel is being dumped into the right side carb. Float valves can stick both open and closed. Stuck open and the cylinders on that side will be flooded with fuel but the car will still run, but rough. Temps will also go down as it is WAY too rich. Just a possible cause. Good luck.

EW
Another good point. Should show black smoke though.
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