440bb 40psi cyl6 not firing help!!

[TruckManiaMike]

The lifter plunger may have leaked down. On start up there could be enough clearance to allow the pushrod to come out. How long had the engine been setting since run?
Doug

We had started the motor for a minute 2 years ago, not long enough to get warm but it sounded off then too. But before that it sat 2-3 years since they drove it home. The two guys that bought it are both very knowledgeable engine builders and they didn’t say anything about it missing on a cylinder….i would think they would have caught it if it was an issue upon purchase in 2019…

 

[dvw]

It probably just happened when last started.
Doug

 

[pnora]

I tried moving the linkage before moving booster…. No go…

Valve cover will not come off with a big block and that booster. The booster is the wrong one for a big block. You would need the smaller diameter tandem booster.

 

[Dave6T4]

Roll that pushrod on a piece of glass or your countertop to see if it is truly not bent. They don't have to be bent much, to start acting like a spring.

 

[TruckManiaMike]

Roll that pushrod on a piece of glass or your countertop to see if it is truly not bent. They don't have to be bent much, to start acting like a spring.

I did on the table and it rolled great.

 

[TruckManiaMike]

Valve cover will not come off with a big block and that booster. The booster is the wrong one for a big block. You would need the smaller diameter tandem booster.

do you have a link to something that would be compatible to swap with? Would love to never have to take it back off again…that was a major Pain In The A$$ haha

 

[pnora]

do you have a link to something that would be compatible to swap with? Would love to never have to take it back off again…that was a major Pain In The A$$ haha

Big block trucks had them. but 78 was the last year. Lots of 3/4 ton used them and I think up to 93 will fit. The master might have to be changed also depending on yow it bolts to the booster

 

[TruckManiaMike]

It's all alluding to a possible stuck valve, pushrod fell out, lifter popped up. Side benefit; the other bad cylinder has stuck valve issues. Pull both rocker shish kabobs and check valve heights with a straight edge

Pulled rocker shush kabob and got pics with straight edge…seems awful uneven what does it mean? Seems on the cylinders with low compression the exhaust valves are sticking up higher…

Compression test again for easy reference to pictures…
8-160
6-40
4-120
2-120
1-150
3-90
5-150
7-170

 

[Dave6T4]

I used to get smaller diameter dual diaphragm boosters out of Dodge B-vans. Pop the hood and there it is on a right angle bracket. The booster nuts are easily accessible. No more climbing around under car dashes.

 

[Don Frelier]

Take a small block of hardwood and a medium sized hammer and give the low ones a few whacks. See if they come up. You might want to lift the valve seal and spray some penetrant od the valve stem above the guide.

 

[khryslerkid]

If your valves are not opening and closing I don't believe you'll get a good reading. It's like when you don't open the throttle when doing a compression test there's no air being drawn into the cylinder to make compression.

You could adapt a air hose to your tester line and put each cylinder under pressure. You can listen for air coming up into the carb (open intake valve) or air going out the exhaust (open exhaust valve).

 

[rick68b5]

Do yourself a favor and pull it and rebuild it correctly there's absolutely no reason to have then shims under the rocker shafts I'm sure the rest of it is just as sweet as that work.

 

[RemCharger]

@PRHeads ?
Looks like the valves are sunk. Back in the day a shade shop would take the assembled head to a belt grinder and equalize the valve stems lol. But they're pretty out of whack.
Rocker shaft shims are ok for the correct application( head milled, pushrods too long,.. less lifter preload for higher rpm etc..) but not too sure what the builder was shimming for

 

[TruckManiaMike]

@PRHeads ?
Looks like the valves are sunk. Back in the day a shade shop would take the assembled head to a belt grinder and equalize the valve stems lol. But they're pretty out of whack.
Rocker shaft shims are ok for the correct application( head milled, pushrods too long,.. less lifter preload for higher rpm etc..) but not too sure what the builder was shimming for

After listening to a couple videos online of cammed 440’s it definitely has a big cam in it. I was reading some other forum post saying that when you put a big cam with stock rockers it helps to shim the rocker shaft up so maybe it’s there to help ‍

 

[RemCharger]

After listening to a couple videos online of cammed 440’s it definitely has a big cam in it. I was reading some other forum post saying that when you put a big cam with stock rockers it helps to shim the rocker shaft up so maybe it’s there to help ‍

It's all about setting the preload on a hydraulic cam. Checking it while assembling is part of a performance build. If you had adjustable rockers it would take care of that.

 

[TruckManiaMike]

Take a small block of hardwood and a medium sized hammer and give the low ones a few whacks. See if they come up. You might want to lift the valve seal and spray some penetrant od the valve stem above the guide.

Sprayed the valves with pb blaster then tapped all the valves with a piece of wood and a hammer. I got all positive sounding shuts from the valves, the sunk valves did not seem to go up at all maybe a little bit I can’t tell. Thinking that’s the best I can do for now. And will reassemble the rocker shafts and valve covers Friday and see if it runs right. Have a leak down tester on the way to check for leaks in cylinders 3&6.

 

[TruckManiaMike]

This is how it sounds almost exactly

 

[pnora]

Your heads are messed up. They need to come off and be rebuilt or replaced.

 

[TruckManiaMike]

Your heads are messed up. They need to come off and be rebuilt or replaced.

What makes you think the head is messed up? Maybe just need new valves and an adjustable rocker assembly?

 

[RemCharger]

What makes you think the head is messed up? Maybe just need new valves and an adjustable rocker assembly?

Pnora and rick68b5 are right, those are pretty bad. The seats are sunk