Two dead cylinders on a 59ab

Planojc

Planojc

Well-known member
New coil, Distributor and Carb from Charlie NY, new plugs and plug wires on a 59AB. All cylinders have good compression at about 110. Number one and two cylinders show no change when plugs are shorted to ground. Both are getting hot spark to the plugs and through the plugs to the electrode. It acts like no fuel is making its way to the intake valves on those two cylinders. The valves on both cylinders are clean and are opening and closing like they should as seen with a borescope camera. Short of removing the intake, does anyone have any suggestions? I'm running out of options
 
Are the #1 and #2 plugs wet or dry?
You say you have spark, however check your cap and plug wiring order just to verify.
Any sign of mice perhaps blocking within the intake?
 
glennpm said:
Are the #1 and #2 plugs wet or dry?
You say you have spark, however check your cap and plug wiring order just to verify.
Any sign of mice perhaps blocking within the intake?
Click to expand...

Plug wiring order is correct, easy to tell since i'm using a crab distributor. I ran a borescope down the intake but with the 90 degree turn, I could not get far enough down to see any blockage. I'm afraid that I will have to pull the intake to do a complete inspection.
 
clean the main jets, may have picked up some junk, know carb is good but may have broke some stuff loose when changing fuel line.
 
Do you have a vacuum gauge? If so connect it and report vacuum reading , if needles is steady or bouncing .
 
Ggmac said:
Do you have a vacuum gauge? If so connect it and report vacuum reading , if needles is steady or bouncing .
Click to expand...

It’s bouncing between 19 and 20, car shakes and definitely running on just 6 cylinders. Number one and two cylinders are not getting fuel. Tried another carburetor and got same results. I guess it’s time to pull the intake and see if there is blockage.
 
Is there a vacuum fitting between those cylinders on the intake for the distributor brake or windshield wiper ?
 
I know that you said the firing order is correct, but these engines cylinders are numbered differently than most V8s.

http://www.vanpeltsales.com/FH_web/flathead_tuneup32-48_221-239.htm

I thought about your engine, and I don't see how the two cylinders next to each other are not firing with good compression and spark, unless the firing order is mixed up. Maybe the intake is plugged which is unlikely, but anything is possible. I have a bunch of flathead cores out in the garage and some of them have mouse nests in the intakes. You could pull the number one and two plugs and crank the engine to where the intakes are open and blow air in them and see if it comes up and out the intake or even out the next-door cylinder. Then try the exhaust valves when they are open and see if it comes out the exhaust. I'm just grabbing at straws???
 
Inspect the cap for cracks, and check rotor to cap gaps…..Get the area where you have it parked as dark as you can and see if you have a cross-fire leak between wire towers or wires………Mark
 
I had a cracked cap on a sbc, between #5 and #7, which fire one after the other. The crack was lined with carbon dust and trying to fire both cylinders at the same time. Like mentioned, look at cap or swap one out.
 
if compression is good, intake port obstruction would, i think, be unlikely.

in any event, i'd likely be removing the intake manifold...
 
Make 100% sure your plug leads are on the correct cylinder. I had this happen with #7 & #8. Same symptoms. Cold plugs and exhaust. If you don't have a timing mark on your pulley, you can get a rough idea by connecting a timing light to #6 and turn the engine over by hand until the light flashes. (#1 & #6 fire 360 crankshaft degrees apart) Put a mark on the crank pulley and a corresponding one on the timing cover. Now connect the timing light to #1 & it should flash at approximately the same position. If it flashes 90 degrees to the left, you have #1 & #2 mixed up.
Or a severe vacuum leak between #1 & #2.
 
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