After honing 4 of the cylinders a good bit there were still scratches visible. So I'm just going to do a full rebuild on it. Working on ordering the kit now but need some help.

I know I'm going with .040 over bore Mahle Marine pistons, but the main and rod bearings I'm not sure if I should go ahead and get .010 over bearings and have it turned or not. Oil pressure was never below 40psi at idle so I assume the crank is in good shape.

Second question is with the head gasket. I will likely have the block and head decked .010 to be sure there is a good flat mating surface. So that will be a total of .020 less clearance. Can I use a stock width head gasket or will piston to head clearance be an issue? If so I'll just go with a .020 thicker marine gasket.

Let me know asap so I can get the kit ordered!

 

Why don't you take it apart and mic it out? It is always my druthers to run standard if within tolerance. Remember that over and under size require machining off metal. I would get the info, order the correct parts and then build a good reliable engine, My opinion of course ...Mark

 

will that overbore and block decking raise compression?

 

No because I'll go with a thicker head gasket to get clearance back where it should be, and the marine pistons have a much larger bowl. So compression will be close to stock or only very slightly lower.

 

Just got some news I may have a buyer for a bunch of Baylor Brake Controls I have. IF I do sell them it will go into my truck fund, and I'll be able to completley finish is up!!! Paint, body, injectors, twin turbos, the options will be nearly endless!!!!

I'm crossing my fingers till I find out.......

 

O-rings? Studs?

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No o-rings. Decking the head and block to ensure they are perfectly flat, and some good A1 studs.

 

You more than likely won't have to take .010" off to get a flat surface. The machine shop will take off however much is necessary until it's entirely flat. For example, the shop I took my head to machined .001" with each pass until it was true. In the end, they had only machined .006". I put a standard gasket under it. The amount of compression it lost is not nearly enough to make a difference.

 

I believe you gain compression, as you made the chamber smaller.

 

No chamber, so surfacing the head will not change anything until you get way past where you should. The deck is where you will raise compression or risk hitting the piston. Have them check the deck before automatically decking it.
Are you going to run Marine Injectors then? If not, I am not sure I would use the Marine pistons as the spray pattern would be directed more towards the bottom of the bowl. At the very minimum, I would contact a well respected Diesel performance guy and go over the plan.

I would also wait until I had it apart and measured before I ordered the kit, you would get it before the machine work was done in any event.

You might also want to see if the first overbore size would clean everything up ( .020 ) because you have no room to rebore later without sleeving.

 

Stock piston protrusion is around 0.025" and the stock HG is about 0.060" thick. So if you did cut a full 0.020" off, the piston would be getting close (0.025") to the head w/ stock HG. It will affect the piston to valve clearance as well(Are you changing the cam?). These diesel engines run very tight clearances compared to gas stuff.

Decking the head will raise the compression some because there is a small recess around the valves.

I would also say go only 0.020" for now, save for later/ next time.

 

I'm going .040 first time. I dont plan of putting the kind of miles or hours on it to require reboring it again later. If it gets to needing rebuilt again I'll likely go with a different setup then.

I went with the marine pistons at the advice of a couple engine builders. The one thing I didnt get a straight answer on though is reballancing the rotating assembly with the marine pistons. Should I get it all reballanced?

Also, what should I set my ring gap to? I'm thinking about .015-.017. Is that enough or too much?

 

Your absolutly right about not having to take off .010 to get the surfaces flat. The reason I'm going with that though is simplicity. I can either wait and see how much gets taken off, then figure out if I need a thicker gasket, or keep it simple, go .010 on both, and install the .020 thicker gasket to be back to stock P to V clearance.

 

You might as well have the rotating assembly balanced!

 

One word of advise. VE's love compression...try not to dip below 16.5:1 if you can help it. 15.3:1 with the marines is gonna hurt efficiency quite a bit.

Balancing is a must!