One cylinder looks like its not getting any fuel

[junkyardjeff]

The 351-w I had built for my 55 sunliner sometimes feels like it has a miss at idle,the builder installed a 302 cam but was wondering if I just thought it was a 302 cam and changed the firing firing to a 351 and yes it did have a 302 cam so I pulled the plugs and looked at them.  # 4 plug still looked like a fresh plug and never fired but when I pulled the wire it made a difference so I am wondering if there is a restriction in the intake port or the intake lobe is going flat,I broke the motor in when the zinc was being reduced and knew nothing about it.  I am going to pull the valve cover and see if the rocker arm is moving and check the lift compared to the others.

[wayne petty]

just curious...


is it the last cylinder on the drivers side...     why....  the last two cylinders on the drivers side fire a quarter turn of the crank apart...

the  wires over the left valve cover holder have to be in this order..  7,5,6,8, or the magnetic field can induce an early spark in the last cylinder and cause it to run lean and melt the piston...

you can sometimes see this with a timing light.. as a double flash when the light is clamped on near the spark plug without disturbing the spark plug wires.. you may not see it when clamped on near the cap...


are there any vacuum hoses attached to that intake port... power brake booster leaking...     modulator leaking....   pcv  the incorrect size for the motor..   leaning out that cylinder... ( oversized pcv valves have been a problem for a while)

is there any chance of a vacuum leak from the intake manifold gasket.. to head interface..


how is the carb adaptor to intake manifold gasket?

along with examining the rocker arm motion... and the twisting of the push rods as the motor idles with the valve cover off..   a gentle spin... is what to look for..  spinning madly.. or back and forth.. usually indicates a lifter / cam lobe problem



these are just ideas....   nothing written in stone... or embossed in a valve cover...

[jaybee]

I learned about crossfire on a 351W in just that way.  Loomed up the wires so they looked all nice and pretty on the car I drove in HS.  Dad took one look, moved a couple of wires in the loom and it ran fine.

[junkyardjeff]

Its the last one on the pass side and I always wondered about a vacumn leak as it kind of idles like it has a vacumn leak but could not find one by spraying carb cleaner.  It also slides into third (C-4) at light throttle but not when I give it some gas so I kind of thought there could be vacumn issues,the only vacumn lines are for the modulator valve and wiper motor and has acted the same before hooking up the hose to the wiper motor.  The vacumn wipers wont work too good at idle which is strange but works better when I give it some gas so something is goofy,it has a factory 80s truck cast iron 4 bbl intake and have thought it could be cracked at that cylinder but has decent vacumn (about 19 on the gauge) the last time I checked.

[junkyardjeff]

I went out and looked at it and the vacumn port is on the runner to the last cylinder on the drivers side so I am thinking about pulling the carb and see if there is a restriction in the runner to the cylinder in question along with checking out the rocker arm.

[junkyardjeff]

I pulled a valve cover and its not a cam or rocker arm issue so I am leaning towards a bad intake,it runs ok so I am not going to mess with it as I am going to build a Y block to put back in it.  When I pull the 351 out of the 55 to install it in my 65 custom 500 I will change the cam for a hotter one with a 351 firing order and a new aluminum intake.