I need to diagnose if oil burning is coming from valve guides or getting sucked from intake.
Plugs are Oily black and engine smokes when started.
Ran great on stand but having issues in car......

Recently, Leak Down was good on suspect cylinder.
Small drip of oil seen between head gasket and block...
No pressure/bubbles in Coolant.

I took some running EGT with infra red Thermometer and had a big swing on middle cylinders up 100 degrees.

Temperature will increase sitting in traffic then lose power......

Low mile Build-
383/496 with 516 fresh worked heads.


Thanks in advance......

If coming from the guides, you mght see oil puddling on top of the valve (the valve in question of course needs to be closed) after the engine has sat for some time.

Specifically, I had a situation on my SB factory heads where using the hard Teflon seals just didn't work right. This was on re-done '596 castings, so proper guide liners installed, new valve job, etc. Needless to say, I could tell that the oil was getting sucked in through the guides, the tell-tale result was the puff of blue smoke on startup and when sitting in traffic (think Woodward Annual Cruise) I literally could see the exhaust starting to show some blue smoke after creeping in traffic for a good 45-60 mins.

Eventually I physically confirmed my suspicion by removing the carb (after the car sat for a few days) and snaking down a USB camera through the intake runner port until I got the the valve stem. Indeed, the oil was all puddled on top of the valve, the runner itself was clean though, so I did not see the oil weeping path coming out of the intake/head junction (assuming that the leak was happenning though a miss-match of the mating surface).

Not knowing what was done to the heads I would guess there was a seal to spring problem. Guides might not of been machined for the seals or the springs were to close to the seals and dug into them. I would check your build and what seals were used.

Pull the carb and intake off and see if the intake ports have oil in them
If so add thicker fiber type intake gaskets
If I was you while you have the intake off I would remove the intake valley pan, intake gasket, and then sit the intake manifold back on the heads and use a feeler gauge to check the clearances between the intake manifold and heads, top and bottom on all four corners If it has a lot of variances have the intake head surface milled to flatten it
I've had to do that more than once on aftermarket new and used aluminum intakes
I've also had to stack intake gaskets (.060 to .120 thick) to seal the intake to the heads It worked well and the motor like it

Thanks for the input. All appreciated.

Ill be back at it this week and use my scope down the ports.
Heads were reworked by an NHRA engine building shop.
I am a bit wary of the PC seals as stated.

I didnt use fibre gaskets and am also now questionalble about the used intake I installed.
Motor ran super kick ass and leaked down well on run in stand, until in car.....

I honestly suspect I will change the heads and cam to reduce compression and meet the owners usage.
Burger Doodles and Cars and Coffees.
Car just runs great, but the heat and oil puffs are frustrating.....

As Cab said, on a big block the very first place I'd suspect is the intake valley gasket pulling oil into the ports from the valley.