Drew2010
Full Access Member
There was no machining.
Valve marks on pistons?
- Thread starter Drew2010
- Start date
There was no machining.
PwrSmoke
Full Access Member
Meaning you checked head thickness, piston level and valve protrusion? If those are good, all that's left is the cam because that was the wild-card that started it all. I can potentially see that a reground cam (if that's what it was) could have a problem if to much was taken off the base circle. Not much leeway for error on a diesel. This is something that can be checked... here's how(I think)...
When I went thru the paranoia with my head work, I found washers that were the thickness of a compressed head gasket (FelPro= 0.065" according to their gasket guru). I replace the valve springs with light test springs. After putting a thin layer of Play Dough over the piston crowns, I installed the head using those shims instead of a gasket and the rocker gear. I then ran the engine thru a few revolutions by hand. I estimated I had a good 0.012" of clearance between the piston and valve (hard to get an accurate measure of Play Dough thickness.) Yeah, this was a PITA. If you don't find any obvious answers, it may be a worthwhile PITA in your case.
You can pull the OP relief valve pretty easily from the filter housing. If it's stuck, it will be obvious. It's kind of a remote possibility, judging from my fairly extensive general engine experience, but I don't have a broad base of experience with the IDIs (even though I had some training from Ford on them back in the day), so it may be more likely than I know in this case. Worth checking!
Whatever else, as I'm sure you already know, this is a biggie and you gotta dog it until you find an answer. Hang tough!
Just a tip....dust the tops of pistons with baby powder if yer using the play dough/clay method, helps stop sticking, I would suggest though in this case perhaps some plasta gauge http://www.plastigaugeusa.com/ for safety sake.
I would suggest checking block deck height, piston deck height and head thickness along with pushrod length too. Heck even the mounting bosses for the rocker assembly...double triple check every single measurement you can.
JM2CW,
I would suggest checking block deck height, piston deck height and head thickness along with pushrod length too. Heck even the mounting bosses for the rocker assembly...double triple check every single measurement you can.
JM2CW,
Drew2010
Full Access Member
Well, I havent checked any measurements, but I did get the other head off, one piston was pretty bad like the other side, 3 were mild, and one looked like it hadnt hit at all.
This thing is really throwing me.
This thing is really throwing me.
I bet at the such tight minimum clearances these have , the VR headgaskets are thinner Than what you took off, engine history, ? used, reman, any idea.
Drew2010
Full Access Member
Engine is used with 150,000 miles, Didn't these come with VR gaskets?
The thought crossed my mind to put rod and main bearings it it, maybe between slight wear in bearings, along with the new cam, it is pushing things just a little too far, I talked about this issue with a buddy of mine who is pretty familiar with machine work, he seemed to think taking the pistons out and shaving just a 2 or 3 thousandths and weight balancing them would also do the trick, any ideas if this is a possibility? or would that cause issues with the cutouts in the pistons.
icanfixall
Official GMM hand model
Milling the pistons is not an issue but not much can safely be removed. These are factory mahle stock pistons. Thats the oem maker for all the 7.3 turbo and non turbo engines. They all have a dome thickness of 560 to 580 thousands. Don't remove more than 15 or 20 thousands. Some have done as much as 125 and seem to be getting away with it but. Your removing too much material and the top ring will suffer from the extra heat it sees. This information was told to me by an engineer from mahle. I think they know what they are doing. I took 14 thousands off my mahle low compression pistons. The low comp is 10 thousands lower in the bore because the pin is machined that much higher in the piston. Sorry to say it but you have plenty of measurements to be taken before you find out whats going on.
Drew2010
Full Access Member
Yeah Gary, Seems like theres alot of precise measurements to take, fun fun...
Looks like I need to find a magnetic dial indicator... this doesnt sound like fun.
But from the sounds of it, If it comes down to it, taking a few thousandths off the tops of the pistons wont hurt, as long as you dont take too much off...
I dont think its the cam, there isnt that much more lift built into it, any sign of the key broken or anything, this is really wierd. shaving the pistons 20 wont hurt
If you wanna pull the cam let me know and I will get another on the way to you and they can check it on this awesome machine to see if it is the problem, if it isnt Ill have good deal on a used torque cam. its prettty close to coming out at this point.
If you wanna pull the cam let me know and I will get another on the way to you and they can check it on this awesome machine to see if it is the problem, if it isnt Ill have good deal on a used torque cam. its prettty close to coming out at this point.
Drew2010
Full Access Member
Russ,I will check the key as soon as I can, probably not until monday... I have an 8 page paper due Tuesday that I havent started yet, damn college kids, lol. I am going to talk to my machine shop monday or tuesday, if they dont have any idea, I will pull it and get it off your way. How long do you think it would take? Maybe you have one on hand already.
Great Service BTW, you get two
If I were to get the pistons shaved a little, that isnt a very expensive service is it?
racer30
Full Access Member
If it was a turbo engine the stock gaskets compress to .065 The new vr's are about .035 from what I have found. The stock turbo gaskets being unavailable realy sucks. Just pulling it down and regasketing the engine you loose .030 of space and increase CR .42 per .010 so its a big pain in the but not having a (thicker) gasket available.
I think all the oem gaskets were thicker. and that could be the problem. being as it ran good and its all the pistons.
racer30
Full Access Member
Thats my thoughts also, The gaskets are a real problem for this situation. One of the resons I will be cutting My pistons. I won't be holding my breath for a thicker gasket to be made before I get mine done.
Drew2010
Full Access Member
wow, thats a big difference, my engine is not a turbo motor, but still, I didnt realize these new gaskets were thinner. Maybe Ill have the pistons shaved a little anyway I think about 10 thousandths would fix my problem, if you can go 20 without worries, maybe Ill do that, anyone have a ballpark estimate to have them done?
icanfixall
Official GMM hand model
Yes... I already posted the max to be cut off a piston. Its 20 thousands and not a thousands more without the risk of issues I spoke of. Felpro head gaskets are 10 thousands thicker than oem whatever it was. Take your used head gasket to the shop and have them measure it before we condem the vitctor reinz. Northern Autoparts and Summit sell a piston height gauge like what you want. It looks like the letter U and has magnetic feet on it. A harbor Freight $18.00 dial indicater will work well for this. I have the tool but its loaned out at this time... Just make sure the block deck is clean and then place it acros the cylinder bore after you have it set. Then crank up the piston and see what the piston is above the deck height. Very simple. Once your done with the new tool sell it to others here building an engine. This is a must have tool like a torque wrench. Without actually knowing whats going on with piston height your running blind.
