hey fellas this a new thread on my engine miss i've been trying to track down. i pulled the head thinking a valve was bent, and checked all the pushrods just to be sure none were bent, and none were, straight as arrows. i flipped the head over and looked at all the valves and they all look okay. So next i poured distilled water on the valves to see if any weren't sealing(i heard of this method from a diesel shop) but none of the valves seemed to show any different than the others, and all held the water pretty well. so now what????


jason

 

Get it magnafluxed?

 

i might have too, but im wondering if there is a way to check for one of the valves being bent with an (at home method) im trying to figure out why my truck has a miss, and i cant figure it out although i think its missing more with the stock injectors i put in than my 435s. Im starting to think that the 435s might have had a small injector miss and my stock ones have an obivious miss??? im so confused!!!!

jason

 

Do you see any obvious contact with a piston?

 

I just pressure up the intake and exhaust side with compressed air. It should seal up to 60 psi. It easy to find bad valves and cracks. I doubt that the problem. I had a bad head crack, the motor ran good just didn't make any boost. Its more than likely related to the fuel system. Have you flow checked the injectors and see how the spray pattern looks.

 

Hey Mike d, no contact with the pistons, at least i cant see any marks or srcatches.

Hey Mike holeman, i took my 435 injectors to a shop and they said they were dirty and had low pressure, (220-230) and one was drippy, basically they wanted to rebuild them for 650 bucks!!!. i figured they were crooks and since my truck never had this issue before i replaced my HG that my injectors would be fine so i put them back in. The stock injectors i honestly have no idea about them so im gonna get the head pressure tested, since its off anyways and go from there.


jaosn

 

hi
well i never heard of using water for a leak test , and i personaly would not use it .
dry the combuston chamber side and use some diesel fuel to fill each port to test the leak rate of each valve .

next indicate the cam lobe lift for each lobe to check for a bad cam .

next have the valve springs tested for spring psi to find a week or broken one .
let us know ?

 

next indicate the cam lobe lift for each lobe to check for a bad cam .

how do you check for a bad cam??

the valve springs are only 2 years old so they should be fine.

The only thing thats got me stumped is that it ran fine before the head gasket popped. and it was a small gasket break, right on the edge of the head, never mixed coolant and oil or even got into the cylinders. So i just can't figure why i got the miss, i didn't change anything??? thanks


jason

 

I would take both sets of injectors to an other diesel shop and get them both pop tested that way you can know for sure if that has anything to do with your problem

 

For a home valve seat crack and/or bad valves you can do a pressure check to look for cracks. I put a piece of sheet metal under the air grid. Put in two air horn gaskets, torque up the four air horn bolts. The intake air chamber must have the intake plate be on and torqued up correctly with the stock gasket. There should be lots of 1/2, or 1/4 plugs in the air chamber. Put in air chuck and start applying pressure. If you have a bad valve, air will just blow thru. On the exhaust side, put the exhaust manifold gasket on. Get a T03 spacer and put a metal sheet on top of exhaust gasket. If you have a pyro hole in the exhaust manifold, plumb in air into that hole. I built a 1/4 T03 blocker plate with a 1/2in NPT hole just to do this check. I like to make sure everything is air tight. If the head is ok, you should have no air leaking from any cylinders. My test is best done with the valve are closed (loosen the rocker arms), just in case you put the head back on. If you have a leak, the air should blow thru the injector hole. I do this with my truck regularly, I hate head cracks and bad valves. Liquid sorta only works on the really bad valve seats.

I would try another set of injectors. Sounds like you're current set isn't pop-off at the right pressure and are not seating properely to get a good flow pattern. For $600 you can buy a new set. New 215 or 370 are cheap, you should price out a set for new 6.7L

 

being that you said it started after you changed the head gasket it could be the gasket, i changed one on a tractor one time that i had fire rings in and when i sat the head on one of the rings moved a little and i never seen it anyways when i started it it missed really bad you couldnt see it leaking or anything, you might want to check your gasket really close, probably not the issue but you never know, sounds more like a fuel issue but check it and see.

 

wow great tips, i took the head to a good machine shop this morning though, and they said it was fine so i talked to new era and im getting a new set of 435s, im pretty sure they were causing the stumble, since the problem got worse with the stock injectors, which i were a lot worse than the 435s, which only had a slight miss. so in a couiple days i'll repost with the new injectors and let ya'll now how it runs thanks for all the replys



jason

 

Buddy, I've been there too. Last summer I killed off three head gaskets. Working on #4,

 

220-230 is very low if that is in lbs pressure. They also should not be drippy.

 

That would likely be BAR. Spec is 260. I hear they run better a bit higher, around 280.