Hello posting this for my father.

He has a 440 that was running just fine and then he swapped out the heads for a set of Stealth cnc ported version 440 source heads.

The heads were the only things changed on the motor and ever since then the motor has popped out of the exhaust on both sides of the motor. He started replacing everything he could think of: all ignition parts including dist., both carbs(dual 4 setup), fuel pump, head gaskets, intake gaskets.

Timing is 12 initial with 36 total.

Compression test was 190 +/- 10 in all cylinders. Sorry no access to a leak down tester. He did notice a sticking number 8 exhaust valve while running through lash and fixed that with honing the valve guide out to proper clearance. None of the other valves were tight. Adjusted the lash tighter and than really loose but it made no difference. No flattened or wore down lobes.

He is out of ideas as am I. He is sending the heads off Monday to get vacuum tested.

Any help would be appreciated. thank you

I had the same thing when I first swicthed to the Eddy heads and I used the same spark plug that I would use in a factory head.

Once we installed the correct 3/4" reach plugs all was well with the world.

Perhaps you have the same issue. Using the 3/8" reach plug when it should be a 3/4" reach plug.

Thanks Bill I should have mentioned that too. He was using the short reach plugs but switched to the long ones with no change.

He has had about 5 ah ha moments thinking he solved it only to fire it up and listen to the popping. Thankfully he hasn't called the wrecker company and had it towed to the junk yard which he has threatened to do a few times.

I know he probably already has done this but try checking the plug wire firing order. It's not that hard to get two crossed up.

Once you're confident that the plug wires are correct and all other obvious tuning stuff is checked, I'd pull the intake and take a good look at the cam lobes. DAMHIK.

Have you ruled out the fuel delivery system?

Mine did that too.. All stock engine.. Except Performer Intake It was the Holley Carb.. Changed over to a Eddy, fixed the problem.. It was really bad popping,

Check the intake to head seal. Start the car let it warm up and spray all around the intake w/ brake clean or something. Sometimes they suck from the underside too. If you think the cam is going bad you can pull the dipstick and looks for glitter. It will also at some point start to run rough and you'll hear the familiar sounds of lifters chattering.

He has ran through the wires a few times and used a timing light on each to make sure they are firing.

He cant see all the lobes with intake off so he used a dial indicator on each valve bumping it over. Said they were opening close to each other plus or minus .030. Figured the .030 was from not having the dial indicator perfectly inline with the valve.

Fuel is showing 7 psi and fuel in the bowls right up to the threads on sight plug. He checked while running which caused a mess but said the fuel level stayed constant.

What can actually go wrong with a head? valve seats wiggling causing the exhaust not to seat well? No signs of torched valves or seats.

Thanks again for all the help.

Leaky valveseats will cause this.
Do a compression or better a blowby test.

Might also be very lean mixture. How's the vacuum in the engine? Same as before?

He is pretty sure that it isn't a vacuum leak but I pitched an idea to him that he likes and will try after the heads get checked. Make 2 plates to block off the carb holes on the intake and put a fitting in one with the rocker arms off and see if the motor will hold a vacuum.

No clue on idle vacuum from before and now, he never checked.

I wanted him to do a leak down test but no equipment for that right now.

I did ask if it pops through out the rpm range and he said that it fires right up but just doesn't want to take any throttle at all or any load on the motor. Also he pulled both vacuum caps off the base of the carbs and it made zero difference. That makes me think vacuum leak but he can't seem to locate it.

He has had the intake off at least 4 times with a different gasket each time and no change. This is now the 5th month since the head swap and still not running. The knot at the end of his rope is getting closer and closer.

Does the car have power brakes? I would not suspect the heads.

No power brakes. I suspected the heads mainly because that's all he changed and it was running fine before the swap. Also since one of the valve guides was tight enough to hang up a valve right out of the box.

did you try the WD-40 or propane test to find vac leaks?

I would almost guarantee it's lean, that's what's causing the popping. The new heads flow more air and if the intake system is the same, then it's lean.

He did try WD40 on the intake to head, intake to carbs and the split intake gasket(tunnel ram).

Never really thought too much about being lean I figured 2 660cfm on a stock stroke 440 would be more than enough. I'll relay the info. Thanks again.

hyd cam or solid? Do you have adjustable rockers?

Solid flat cam with what looks like very old Isky adjustable rockers.

He said the travel over the valves tips looks good using the blue dye to see it.

Did he by chance pull the timing chain while doing his head swap?