valve tapping in 440

[charger2fast4u]

my 440 has a valve tap its a stock rebuild with 6 pack internals its coming from the drivers side of the motor i took the valve cover off and looked for any obvious signs the head had a puddle of oil around the bottom of it and a light coat across the rockers and spring components whats some of the causes of valve tap? how can they be checked?

[Chryco Psycho]

could be a weak hyd lifter , if you push down on the pushrod side of rocker & it moves the lifter is not holding pressure

[b5blue]

 Mine has it too. I'm looking into Smith Bros. adjustable push rods. As rebuild tolerances stack up or change new factory standards the lifters run out of room to compensate. As the lobes on a cam really can not be any higher then the bore of the cam bearings a higher lift cam has a LOWER at rest diameter (The "off lift" part of the cam.) to achieve that greater lift.
We all tend to use a higher lift then the "stock" cam so with non adjustable rockers on a Hyd. cam setup the lifters may sit lower than required for your rebuild. That's why cut to fit push rods are offered for our motors, to correct the layout of the geometry. I had always planned to use Crane Ductile Iron Adjustable Rockers and ball cup push rods to dial in this slack but they are out of production for years now.
The tolerances of installed valve height after a valve job varies as the seats and valves get cut to further screw with push rod length along with surfacing or milling the heads, block deck height and head gasket thickness. As I was thinking of changing the heads on my engine later I was looking for an adjustable solution rather then a set of custom cut push rods that would be of no use if I did.   

[firefighter3931]

could be a weak hyd lifter , if you push down on the pushrod side of rocker & it moves the lifter is not holding pressure

weak or partially collapsed hyd lifter is the most likely cause 



Ron

[Challenger340]

If Known ?

WHO's Lifters are being used ?
Who's BOX were they packaged in ?

Lunati BOX ?
Engle BOX ?
Comp Box ?
Crane Box ?
Hughes Box ?

Just curious.
I had some time, so I did some "testing" with some various Hydraulic Lifters on the Dyno recently. Thats right, HYDRAULIC Lifters, which I don't use much, but I was finding some concerns need to be addressed, given, Flat tappet Cam rates have increased substantially.

[charger2fast4u]

Questions I can't answer I bought the car with the motor in it the po had it rebuilt to stock as far as I know nothing special ran good for awhile but started getting a slight tap and then my motor started acting up and backfires now if you give it to much throttle not sure if they are related was  thinking maybe  I got a bad cam lobe or bad lifter so to check if its a bad lifter I will push down on the lifter side of the rocker and if it moves I have bad lifters? Should the lifters be tight against the cam lobes at all times during a full cam rotation? Still learning as I go so bear with me

[Challenger340]

Questions I can't answer I bought the car with the motor in it the po had it rebuilt to stock as far as I know nothing special ran good for awhile but started getting a slight tap and then my motor started acting up and backfires now if you give it to much throttle not sure if they are related was  thinking maybe  I got a bad cam lobe or bad lifter so to check if its a bad lifter I will push down on the lifter side of the rocker and if it moves I have bad lifters? Should the lifters be tight against the cam lobes at all times during a full cam rotation? Still learning as I go so bear with me

Backfire under load is a Symptom of a BBAD cam lobe.
Could also be other things,
but,
if you also have a ticking Lifter in conjunstion with the backfire under Load, good bet you killed a Cam lobe.

[charger2fast4u]

I'm hoping for the best that It's not a cam lobe I have a holley lean rich fuel indicator hooked up and it has 3 lights on it for lean normal and rich always ran good until recently  It started running lean I adjusted the floats and messed with the screws changed plugs and still reads lean then it slowly started to run rough when you drive it now its to the point you give it a decent amount of throttle and it will buck and backfire

[Chryco Psycho]

With a strong magnet you can pull all the lifters without removing the intake & inspect them , you will know if it ate a lobe on the cam

[charger2fast4u]

I'll have to pull the rockers and pull out the lifters and check for any signs of a wiped cam lobe what are some reasons that a cam lobe gets wiped out? I usually used castrol 10-30 oil with a small bottle of zddp additive per 5 quarts of oil I didn't ever find any metal flakes when I drained the oil  I was thinking it was either carb needed adjusted or something in the ignition system was the reason for the backfiring maybe bad plug wires or coil maybe the ignition box itself it has the mopar Orange electronic ignition box  and read about them going out but now its sounding more like a cam lobe may be the issue

[Challenger340]

Do you have a Dial Indicator with a magnetic base ?

Saves alot of time BEFORE actually tearing apart, or pulling Lifters, when trying to diagnose a bad Cam Lobe,
to simply,
MEASURE your Valve Lift at each Valve as you roll the engine over.

Because the Lift area of the Lobe goes away FIRST, before the base circle on the Cam, you will notice a dramatic loss of lift on the culprit lobe ?
BTW,
it is that loss of lift that causes the backfire, because that combustion pressure is not getting directed properly during the Cam events.

Measure the lift, you'll know if you have to go further from there.

[charger2fast4u]

thanks for the suggestion using the dial indicator much easier then pulling the lifters where do you usually set the dial base while checking the lift? i think it may have the stock cam but am not certain good time to find out what was the stock cam specs for a 1970 440 6 pack motor?