Valve train questions/issues

[laserjock]

So as some of you know, I've had valve train issues with the truck since getting it on the road. I've had a broken rocker bolt and I've had what I would describe as valve float 3 separate occasions.

Background for those not following my build thread or just to recap.

Engine is a Reman 7.3 NA from Promar.
I sent them a typ4 torque cam and comp 910 valve springs to install.

When I broke the rocker bolt I discovered they had shimmed the rockers on the drivers side head with 0.015" shims. When I questioned Mark at Promar about that he said it was to compensate for milling the heads to clean them up and valve recession.

Every time the float has occurred it was just over 3k rpm. I assume it's valve float because I loose a cylinder for a time until the rpms come down. That is usually followed by a few gut wrenching bangs before it goes back to normal. I assume that is valve to piston contact.

It sounds like it's on the passenger side and it sounded like the same place every time. I have not pulled the passenger valve cover yet but that is in the plans.

I have generally a bunch of questions but I'll start with if you were me, what would you do?

In my mind it has to be a weak valve spring but the question is why?

I have my suspicions but I want to hear from you guys.

What say the experts?

 

[riotwarrior]

Seein as we have no specs on head thickness or how deep valves are recessed its quite hard to say.

But if too deep it affects the valve train geometry so rockers dont contact correctly and u may be facing too much tollerance stacking and thus jacking the valve open.

Its all in the details.

I wonder if the cam is a symetrical or Asymetrical lobe...

Anyway if valves not ahimmed to correct amount you wont see correct seated and open pressures as well.

Lots to consider

 

[laserjock]

Bueller? Bueller?

 

[riotwarrior]

Bueller? Bueller?

Omg i spat put my drink laughing

 

[no mufflers]

I don't have much experience in the valve train area so I can't help you much. I would say if you were having enough valve to piston contact that you could hear it then the motor won't last very long. I'm sure you don't like doing it but could you take a video of the sound?

 

[laserjock]

It only made the sound when the valve floated. I picked up a spring compressor tool. If I get time I'll pull the valve cover and check a few things. That's about all I can do in frame. Then I'll call promar with my findings.

 

[Thewespaul]

My gut tells me you have some valves that really like your pistons, in several builds that have used the type four cam people have found evidence of piston valve contact even if they heard nothing out of the ordinary. I don't think the springs are the issue as they have held more boost and rpm then you have thrown at it yet. And these engines under nomal circumstance have no issue buzzing past 3k.
I would think that with the tight valve to piston tolerances these engines have stacked with a milled head stacked with a performance cam there just isn't enough shim to make up for it

 

[no mufflers]

yeah I think that's about it. it happened to my old motor and I would have never known until I took it apart.

 

[laserjock]

I hope I can wait till winter to tear it down but it's sounding/feeling like that's the road we are heading down. First thing first. Check the easy things first right?

 

[F350camper]

I'll start with if you were me, what would you do?

Your theory seems sound to me, especially with your previous broken rocker bolt and bent push rod on the other side.

For an additional data point though I would try to eliminate the fuel system as a culprit. A stuck injector will make some crazy terrible noises. I think I would see if I could bring it to 3k+ against compression down a hill and see what it sounds like.

 

[Thewespaul]

Maybe wait to tear into it until the new type four can is released, but then again you don't want an unreliable truck and don't want to bang up a new engine. It's a tough call.

 

[tjsea]

I say check to make sure they shimmed the springs correctly first. I know when I was checking out mine that the typ4 cam has ALOT more lift which means it's going to take more spring to close it at higher rpm.

 

[laserjock]

Did some reading this morning. Sounds exactly like valve float on a hydraulic lifter as described by a guy on HAMB.

Miss for a few seconds until the hydraulic lifters bleed down then normal. The bang I heard was probably piston valve *********** as the lifter bled down. Probably have another bent pushrod at a minimum.

Sigh. Guess I need to suck it up and do this.

 

[no mufflers]

I think you had said it but, pull that valve cover and see what you got going on. if you find nothing then I would do what rob said and try it in a few different scenarios.

 

[Hydro-idi]

Sounds like you have a big problem that needs to be addressed. I've had similar problems in the past. You need to pull the heads off that engine to see what's going on. I can bet that the valves are hitting pistons.
I would verify that you have normal oil pressure at high rpms. If it's unusually high, I can bet that the lifters are pumping up too much, causing valve-piston contact.
If your oil pressure checks out okay, pull the heads and get them checked out by a machine shop. If cylinder heads are within spec, problem is the torque cam.