I dont have any idea of the hours on it but yea I'm surprised this one even cranked with the head gasket blown and it looking like that. All but one of the grommets were completely gone. Lol. Anyway I've got it going to a head shop tomorrow so I'll see what they say. I just didnt have the tools or time to take out all of the valves and all that. How do you seal the prechambers? I'm not sure what a prechamber is?

It's what the fuel injection nozzle capsules fit into in the head. I would remove them before sending it in. Remove the nozzles and you will have to have the special splined tool to remove them, part # 5F8353.

Hi Team,
To My mind this could be the result of not re-torquing the head nuts/bolts after the first start after running up to full operating temp and waiting until cold and re-torque the head nuts/bolts again at 100 hours as recommended by Cat for these models.
The signs of oil weeping and bubbles at the head gasket joint and then continuing to operate the unit could led to this in extreme cases.
My 2 bobs worth.
Cheers,
Eddie B.

Updates yet? Any news from the shop on the head?

"kracked1" wrote:

Updates yet? Any news from the shop on the head?

No update yet. I do believe that the blown head gasket between those cylinders was the result of someone in the past tightening up that bolt too tight. Anyway I havent heard back from the head shop yet but I'll share as soon as I do!

Thanks, we get too many on here that just disappear and we never hear the end of the story.

The guy at the head shop said that exhaust valve on #2 tested at around 5 psi and the others were 8 to 10 psi. I'm not sure whether that is the valve opening pressure or what? Anyway I didnt ask that but he said should be around 23 psi normally so the valves needed replacing because of being too thin to grind down he thought. Any thoughts on that?

Hi kingmike,
something tells me now you were truly talking about PSI to open the valve and not pounds force to open it--often get odd descriptions of goings on here so your newer post confirms that PSI's of air are applied to the port to force the valve open. The lesser Valve spring tensions of the newer valve springs would apply a lesser closing force and so would result in lower PSI readings to open the valves.

In all my years of being a Dealer Trained Cat mechanic I had never heard of this method but I can see advantages to it as you would be testing the seal integrity of the valve too--we usually used a squirt of kero/paraffin in the port if there was a doubt.

We always ground the seat at the spec. angle and the valve head at three quarters of a degree less to give an interference angle line contact fit.
With a finger under the valve stem end, we held the valve about a half an inch off the seat and then banged the valve onto the seat with the side of the fist to check we had a continuous line contact of valve to seat--no lapping required and call it good to go if we had a continuous line contact--never had any comebacks in all the thousands done.


Cheers,
Eddie B.

"edb" wrote:

Hi kingmike,
something tells me now you were truly talking about PSI to open the valve and not pounds force to open it--often get odd descriptions of goings on here so your newer post confirms that PSI's of air are applied to the port to force the valve open. The lesser Valve spring tensions of the newer valve springs would apply a lesser closing force and so would result in lower PSI readings to open the valves.

In all my years of being a Dealer Trained Cat mechanic I had never heard of this method but I can see advantages to it as you would be testing the seal integrity of the valve too--we usually used a squirt of kero/paraffin in the port if there was a doubt.

We always ground the seat at the spec. angle and the valve head at three quarters of a degree less to give an interference angle line contact fit.
With a finger under the valve stem end, we held the valve about a half an inch off the seat and then banged the valve onto the seat with the side of the fist to check we had a continuous line contact of valve to seat--no lapping required and call it good to go if we had a continuous line contact--never had any comebacks in all the thousands done.


Cheers,
Eddie B.

Ok. Yea I dont always know how to word the description in mechanical terms. Haha. Anyway I'm just saying what the guy in the head shop told me. I guess that's the way they do them there and they do thousands per year I'd say at this place. I had all good reviews. Anyway guess thats the reason I couldn't find a spec for the psi- because theres not one! I'm not positive that these valves or springs have ever been changed at all but he didnt say anything about the springs either. Just told me that I needed new valves and seats because the old ones seemed too thin to grind correctly. Should I question that and talk to him more you think?

scan below should get you there--reputable repairer would have asked for these specs. when overhauling the head/valves.
You will have to determine which springs you have --early or late--seems I wrote and posted the specs. on this in the last short while ago.
Early Outer and Inner spring P/No's up to S/No 6U3944 inclusive are:- Outer 5B6030, Inner 1B9704--sorry, I do not have a D4 7U PB to get S/No change out to later P/No's which are:- Outer 5F3112, Inner 5F3111.

Willfit parts have been known to have weld issues at the joint that let go--Have seen a few Cat ones that let go too--usually well rust pitted though.

Cheers,
Eddie B.