Technical Part-throttle popping through exhaust under load?

Remember the Olds has a non-adjustable rocker are system with the lifter taking up all slack. If you take the head off it might be to your advantage to just fix what is wrong and put it back together if you don’t have the time and resources to do a complete at this time and don’t mix up the pushrods. Good luck.

 

I think the proper repair here is to just pull the head and get a valve job done, and then re***emble. Thankfully not an issue of time or resources, I just want the car reliable so I can drive it and not worry about it. It's a pain in the *** job but nothing that couldn't be handled over the course of a few evenings.

Might be worth trying to snake the cam out and replace that too with some new lifters.

 

You're getting enough compression at times to light the fire, unless the popping is coming from another hole. Last burnt ex valve I had was a SBC, 0 compression but no popping. Also had a SBF with a valve sunk so far into the seat the lifter was fully collapsed and it still was leaking. Again no popping. You might put a straight edge across your valve tops. Also maybe just some carbon breaking loose sticking on the seat. In any case I would compress air the hole and see where it's leaking before dis***embly.

 

And THAT'S why they call him "Blowby"!

 

Also, Jeff from Elderly Iron has some good methods for un-sticking the sticky bits on a stuck engine. Some good diagnostic tips too.

 

Hell I wanna see part 3 now...

 

Part 3 is great. I'm gonna go home and beat my valvetrain like it owes me money.

 

Ummmm . . . Now you did notice that he had a wood block between the valve stem and his hammer, didn't you?

 

Haha, yes, I did note that. Problem I will have is accessing cylinder #7 with said hammer. Damn autronic eye module is huge.

 

Before you decide to pull the engine apart do a "leak-down" test to find out where the compression is going. If you don't have an adapter you can make one by pounding the porcelain out of an old spark plug with a hammer and punch, then welding or brazing the shell to an air chuck ******. As the rockers on your engine are non-adjustable you'll have to remove the rocker ***emblies to get both valves to stay closed, then using the adapter fill the cylinder with air and listen for where the air is escaping. If it's out of the carb, it's an intake valve, if it's out the tailpipe, exhaust, if it comes out the oil filler, piston or rings, if the air comes out an adjacent cylinder, head gasket. The reason you check everything before taking the engine apart is once it's a pile of pieces you may not be able to tell what went wrong. The guy down the street from me had a small-block Ford that was pushing water (actually, erupting, as in volcano) out the radiator after the engine warmed up. The usual suspects are head gasket, cracked head or block but before I could get down there with my handy-dandy adapter he had it torn down and guess, what?, both head gaskets and heads look perfect, didn't see any sign of water in any of the cylinders (water will steam the carbon off of the cylinder head and valves), no obvious cracks in cylinder deck or bores. Because there's no way to figure out where the water was coming from he's looking for another engine to build.

 

I'm pretty sure my Compression gauge comes apart and can accept an air fitting, which I will certainly do tonight. The adjacent cylinder (#5) is actually pretty healthy and held 145 psi of compression for about an hour before I released it and closed the shop for the night. I'd imagine if the head gasket was blown between the two cylinders it would leak in the reverse, though the head gasket could feasibly also be blown off the side and be leaking the compression out entirely and towards the firewall. That being said, I have driven this car about 100 miles, and it has never once gotten hot on me or used any coolant, even driving around on a damn near 100 degree day with the a/c on. So while I obviously can't say for certain, based on the totality of the cir***stances, my inclination is that this is valve related. And more specifically exhaust valve, if not also intake. If it truly is just a matter of getting the valve to move enough to seat and seal, I'm going to at least give it a shot to free it up before I pull the head off. Worst case scenario is it doesn't work, or I break a part that I was going to wind up having to replace anyway.

 

If your gauge stem has a Schrader valve insert make sure to pull it out first.

 

The leak down test is what you need to use now... with that you'll be able to tell if all you have is a valve issue; in which case pull the head and fix it. But, air blowing into the crankcase will indicate further issues you'll have to investigate.

 

When leak testing the cylinder with compressed air, (caps lock on) LOOSEN OR REMOVE THE RADIATOR CAP AND PLACE A FENDER COVER OR FURNITURE MOVING PAD ACROSS THE TOP OF THE RADIATOR. IF THERE IS A HEAD GASKET LEAK INTO THE COOLING SYSTEM, PRESSURIZING THE CYLINDER WITH THE RADIATOR SEALED WILL ALSO PRESSURIZE THE COOLING SYSTEM AND CAN DAMAGE COOLANT HOSES, RADIATOR AND/OR HEATER CORE. THIS CAN BE A REAL ISSUE ESPECIALLY IF THE ENGINE IS AT OPERATING TEMPERATURE WHILE PRESSURE TESTING WHEN IT TRIES TO QUICKLY PUSH OUT A COUPLE GALLONS OF SCALDING HOT COOLANT OR WATER.

(Caps lock released)

 

Just wanted to follow-up on this thread and thank everyone for the amazing help. Cylinder 7 wound up having a bent intake valve. I ****ed it up, pulled the head, and when I remove the valve I noticed that it had a pronounced lean and a smiley face in the top of the piston. I replaced both valves, springs and retainers on that cylinder, and got full compression back in that cylinder. It's also holding a steady 17 inches of vacuum now at idle, a far cry from the wildly fluctuating readings between 5-15 before. I got it all ****oned up before and took it for a nice drive, with no popping or backfiring.

This was an excellent lesson for me in engine diagnostics, the use of a vacuum and compression gauge, and ascertaining what and where my true problem was. I want to thank everyone that responded to this thread for the help. Every day is a school day.

 

From many of us , I'm sure , I'm glad you were able to learn , at this point , the most valuable thing to share is knowledge , its gratifying to hear someone will be carrying that knowledge forward !.

 

Glad to hear you got it all sorted out!

 

Glad to hear you're back up and running...