Bad lifter ?

[antmnte]

The 350 in my Monte is popping on the highway I dont get it around town .Only get it at steady highway speed. Took a look at the plugs and the number 5 is pretty white much whiter than all the rest. I thought it might be ignition so I bypassed the MSD box using a balast resistor for my Mallory dist. got a new coil and new wires and no change. I ran the car with the valve cover off in the driveway and the #5 rocker moves the same as the rest-at idle but again this isnt where the problem is. Should I pull the manifold and change the lifter ? Is there something else I can check? .I cant reproduce the problem with out being on the highway. Thanks for the help.

[Stich496]

hows the timing chain

[antmnte]

Fine only maybe 10K on it and the timing stays put.

[Jimbo17]

I had a intermittent miss in my 350 and I changed plugs, wires, distributor, vacuum lines and just about everything else I could think of without fixing the problem which would only happen every once in a while.

The problem drove me crazy because I could not figure it out.

An old timer I know said I should had a quart of Marvel Mystery Oil.

I asked him why and he said it sounds like you might have sticky lifter so I tried it and I have never had the problem again.

I kept thinking it was something electrical.

Jimbo

[SuperBuickGuy]

white or whiter? white is a coolant leak replace the intake gaskets (it's actually kind of common on SBCs) - why it would be popping - maybe because it's not completely burning the fuel because of the coolant until it's later in the cycle, and when the MSD second strikes it has enough fuel in it to ignite again? - that's my guess. If that's true, it would pop through the exhaust

[realsteelfreak]

Leaking or burnt intake valve?

[milner351]

Do a compression test? that should show you if you have a valve sealing issue.

any signs of pressure in the cooling system?

intake gasket leaking coolant into the intake track is a good idea too.... are you loosing coolant?

[jays67]

compression test will just tell you if that cyl will move air. do a leak down test if you think that is the problem

[milner351]

Yea - what Jay said!

[Barry Donovan]

I had a intermittent miss in my 350 and I changed plugs, wires, distributor, vacuum lines and just about everything else I could think of without fixing the problem which would only happen every once in a while.

The problem drove me crazy because I could not figure it out.

An old timer I know said I should had a quart of Marvel Mystery Oil.

I asked him why and he said it sounds like you might have sticky lifter so I tried it and I have never had the problem again.

I kept thinking it was something electrical.

Jimbo

the marvel has no quit. love that stuff.
even in a sideways everything boxer.
I picked up an egr'd bad cammed slob in 24 years runtime (I guessed atomic grtotesque)

grabs obvious stuff in minutes, keeping it right in keeps it going into tough places to clean..weeks months.

loves the heads.

the op has a good start on checking for lifter..

[antmnte]

Im not losing coolant. Nothing out of the exhaust either, nothing seems weird there. Im going to try the marvel mystery oil and keep and eye on the coolant. I was thinking burnt valve too, maybe.
Any other suggestions, have at it.

[Scott Liggett]

Sounds like the car is leaning out. If the carb is unchanged before the problem, I suggest checking the vacuum advance. Diaphram may be bad.

[antmnte]

I forgot to mention,when i am check that header tube with my ifrared thermometer it is hotter than the others by about 75 deg.

[jays67]

if it was a miss fire it would be colder I had a lifter blow up on my coupe and found it first by checking header tube temps then did a leak down and I backed the valves off as it would not close( I thought it burned a valve) and it closed the lock poped out and the piston in the lifter cam up and cocked and jamed . but the cyl. with the miss was colder then the ones firing as normal

[Scott Liggett]

A hotter header tube is another sign of a lean condition.