Head gasket

[Goose57]

Thanks Husker, Yes that’s the cylinder. I did see that crack. Also how shiny it was around the crack. I did receive info on this site And read on another sites that’s typical on these motors. I believe the others have these cracks also. Is there even a coolant passage behind that area? It was hard for me to get back there to inspect the cylinder walls on #7. I even used a mirror and put the piston on the bottom. I was going to check it good again after getting the motor out. Anybody out there know the weight of these motors? I’m not sure if my cheap HF picker would handle it. I was planning on pulling the bumper and
radiator support. Thoughts. Thanks again Gus

 

[jrsavoie]

Thanks Husker, Yes that’s the cylinder. I did see that crack. Also how shiny it was around the crack. I did receive info on this site And read on another sites that’s typical on these motors. I believe the others have these cracks also. Is there even a coolant passage behind that area? It was hard for me to get back there to inspect the cylinder walls on #7. I even used a mirror and put the piston on the bottom. I was going to check it good again after getting the motor out. Anybody out there know the weight of these motors? I’m not sure if my cheap HF picker would handle it. I was planning on pulling the bumper and
radiator support. Thoughts. Thanks again Gus

Get a heavy duty pick or gantry.
Don't risk injury to you or your vehicle.
Bad things happened to a local not long ago.

 

[denata]

Have you used Penitrant or magnetic powder to look for cracks in the cylinder? I used 'Magnaflux', clearly showed a crack on the head. I could not find it on the cylinder.

 

[denata]

A crack in the head can be easily repaired with a 10mm diameter brass tube. Remove the plug, press a piece of tubing about 3 inches long with glued Loctite.
Then insert a new plug. (part# 14025517 )

 

[denata]

It is easy to pull out the plug, drill a 6mm hole. Grind off the edges of a small nut, insert a long bolt through the hole in the hole, screw the turned nut through the hole in the head. pull the bolt - the plug will pop out.

 

[denata]

This is where the tube is inserted.

 

[MrMarty51]

LockNstitch makes a kit just for the 6.2 and the 6.5 cylinder head common crack between the valves.

Order # L6269K, Diesel Head Water Passage Sleeve Kits On Lock-N-Stitch

Browse Order # L6269K, Diesel Head Water Passage Sleeve Kits in the Lock-N-Stitch catalog including Order #,Item Name,Description,Shipping Weight,Kit Contents (Replacements)

castingrepair.locknstitch.com

 

[Husker6.5]

Thanks Husker, Yes that’s the cylinder. I did see that crack. Also how shiny it was around the crack. I did receive info on this site And read on another sites that’s typical on these motors. I believe the others have these cracks also. Is there even a coolant passage behind that area? It was hard for me to get back there to inspect the cylinder walls on #7. I even used a mirror and put the piston on the bottom. I was going to check it good again after getting the motor out. Anybody out there know the weight of these motors? I’m not sure if my cheap HF picker would handle it. I was planning on pulling the bumper and
radiator support. Thoughts. Thanks again Gus

YES THERE IS A COOLANT PASSAGE BETWEEN THE VALVES! YES, THAT IS WHERE THE COOLANT HAS LEAKED OUT AND BEEN BURNED DURING COMBUSTION! IF YOU "READ" ABOUT THESE CRACKS ON THIS AND OTHER FORUMS, THEN YOU'D KNOW THAT LEAKING COOLANT FROM CRACKS BETWEEN THE VALVE SEATS IS EVEN MORE COMMON THAN LEAKING FROM BLOWN HEAD GASKETS!

Replace/repair that cracked head and you've fixed your coolant issue. You do NOT need to pull your engine to replace that head!

 

[Will L.]

100% agree. Your compression is low, engine is getting tired. Unless you plan to spend $20,000 doing a super nice build- fix the head with the brass tube method (i posted a link to company that sells this as a kit- just do a search) do all 4 cylinders while it is out.


Or replace the head. But know that unless you get a new set of p400 heads the new heads will crack again. I can’t see putting p400 heads on that tired of an engine.
The cheaper heads have a lot of history of needing machining when brand new- not cheaper long term. So it becomes optimizer or p400 as only logical answer.

The good news with the low compression is you can drop in a big boy turbo safely believe it or not! You will have more blow by- but just do the provent200 knock off and buy the real provent filter. Eliminate the cdr and you just need to drain that captured oil and pour back in every so many fill ups of fuel.

The other head probably isn’t too far behind needing same treatment so plan accordingly

 

[SnowDrift]

My P400 heads needed milled when they were new from the factory. .003" warp when new.

 

[Goose57]

Wow,Thanks guys for all the input, Yes Will I agree about not putting P400,s on a tired engine.
Doing the head repairs is above my pay grade. And you still have a worn out motor. I agree on putting in a new motor. Are the cracks between the seats on the factory heads due to heat or just bad designing of the heads? If it is just the heat is there any thing you can do to improve cooling to the back cylinders if I choose to go with an Optimizer? After I got the passenger head off I did see a blocked off plate on the rear of the block what seemed to be over a cooling passage. $10-12 grand sounds better than
$20-22 grand. you know I am retired LOL . Thanks again Gus.

 

[denata]

Buy HUMVEE on sale military surplus , pull out the engine from there.

 

[Will L.]

Yes it is a design flaw. The p400 head has the best fix available. Unfortunately we cannot buy a complete new p400 engine. New Optimizer engine will have slightly better heads than the gm heads, but will still crack. Hence the expense- buy an optimizer and p400 heads. Sell the new optimizer heads to get back some of the money.

Tons of people tried messing with the rear head coolant ports- it creates worse problems to cracking the block. Gm tried a bunch of variations. Learn about “balanced water pump system”. Keep the coolant equal on both sides and ensure the temp NEVER breaks 220. If you were to examine all 8 locations you will see cracking in others also- just that one went first for you.
There is coatings you can have done to aid in some of the issues including this.

On new optimizer heads if you don’t buy the p400 heads, have the new optimizer ones get this brass tube treatment. If you can’t do it- pay a machine shop. That can hold the answer for your current heads if you want.