Chuff, Chuff, Chuff

[Mike053]

1988 f250 7.3 idi

Middle of the desert, pull over for fuel and I hear this LOUD chuffing. Truck still runs, but with reduced power. I’m able to limp home. Chuffing from air intake. I measuring compression, cylinder 2 has 0 psi. Push rods not bent, rocker assembly appears OK.

With rocker assembly removed, I measure, the best I can with a micrometer, from the head to the top of the valve assembly. and it appears the intake valve sits .05” lower than the exhaust valve. I’m thinking either the valve is stuck in the valve guide, or there is debris caught under the valve head. A brass drift and a hammer blow on the valve stem does nothing. Pulling the head is not an option for me. I’m looking for comments and suggestions how to proceed. Any possibility of removing valve spring and attempting to free the valve without pulling the head?

 

[Nero]

Use a sand mallet instead. Plastic hammer that's full of sand for weight. Use them all the time when testing heads, won't hurt the valve.

 

[Kevin 007]

Could it have blown a head gasket between two cylinders? Seen this a few times, causing a no compression and chuff sound. Otherwise lots of lifter and valve guide issues causing the chuff, but usually not resulting in 0 compression

 

[Nero]

You would have zero compression on two cylinders if it was a gasket issue between two holes. Chuffing out the intake makes me believe there's an intake valve issue.

 

[Mike053]

Could it have blown a head gasket between two cylinders? Seen this a few times, causing a no compression and chuff sound. Otherwise lots of lifter and valve guide issues causing the chuff, but usually not resulting in 0 compression

Adjacent cylinder compression = 400psi, so I'm leaning toward the "stuck in guide" scenario. Trying to find a tool that will let me remove spring without removing head from truck.

 

[Mike053]

Use a sand mallet instead. Plastic hammer that's full of sand for weight. Use them all the time when testing heads, won't hurt the valve.

I like this suggestion. Won't hurt the valve, and good for my frustration. I'll try this afternoon and let you know. If I can free it up, and give it liberal dose of mystery oil perhaps....

 

[BlindAmbition]

@Mike053 Linked below is the tool I used to swap my springs out for Comp Cams springs without removing the head. Worked great. Bring the piston to TDC and then use the tool. Might be worth using a different bolt so that you do not strip the one that holds the rocker arm down.

https://www.oreillyauto.com/detail/c/performance-tool/performance-tool-spring-compressor/pfm0/w84002

 

[KansasIDI]

Could it have blown a head gasket between two cylinders? Seen this a few times, causing a no compression and chuff sound. Otherwise lots of lifter and valve guide issues causing the chuff, but usually not resulting in 0 compression

I had this happen on my 6.9, through an oil passage

 

[IDIBRONCO]

Don't use the O'Reilly's one. Go to Harbor Freight and buy valve spring compressor SKU# 59343. The will do the trick and it will hold the spring in place without any extra effort from you. They're not great, but they do work. I've used one a few times.

 

[The_Josh_Bear]

Could it be a collapsed lifter?
I've never dealt with one myself, but I've read about them a few times. I guess it's a low probability given the engine was running at the time of failure.

 

[KansasIDI]

Could it be a collapsed lifter?
I've never dealt with one myself, but I've read about them a few times. I guess it's a low probability given the engine was running at the time of failure.

I have had lifter issues, am wondering if my 7.3 is starting to develop one… hope not… but it is making a clicky chuff. With the turbo, no air out of the intake, so can’t gauge by that. I actually think my exhaust still isn’t sealed up, but it sounds more like a lifter than a exhaust leak. I also frequently run my engine at 3k for long periods of time… so… yeah…

I should’ve replaced lifters when going through the motor… but, I didn’t… it isn’t a bad click, I am really having a hard time figuring it out…

 

[IDIBRONCO]

I have had lifter issues, am wondering if my 7.3 is starting to develop one… hope not… but it is making a clicky chuff. With the turbo, no air out of the intake, so can’t gauge by that. I actually think my exhaust still isn’t sealed up, but it sounds more like a lifter than a exhaust leak. I also frequently run my engine at 3k for long periods of time… so… yeah…

I should’ve replaced lifters when going through the motor… but, I didn’t… it isn’t a bad click, I am really having a hard time figuring it out…

I don't remember right now, but if you installed stiffer valve springs, then those can give you issues if you happen to have a weak lifter spring. I ended up replacing mine because of that. It had run just fine before the overhaul, but after, one intake lifter wouldn't open it's valve.

 

[KansasIDI]

I don't remember right now, but if you installed stiffer valve springs, then those can give you issues if you happen to have a weak lifter spring. I ended up replacing mine because of that. It had run just fine before the overhaul, but after, one intake lifter wouldn't open it's valve.

Ah. Might be my problem. Engine doesn’t shake, and sound seems to be drowned out by 2500 rpm

 

[KansasIDI]

At least it doesn’t click as bad as my neighbors brand new Hemi

 

[IDIBRONCO]

Well no surprise there!