I have my truck(2004 GMC with 265K miles) in the shop right now getting new head gaskets. The mechanic said he contacted the local Chevy Dealer's "expert" and was told the heads cannot be resurfaced on duramax engines. Everyone I spoke to said they can and thats why the different thickness gaskets. Sound like the dealer want me to buy new heads. What do you guys think?
Head Resurfacing
- Thread starter WVlogger
- Start date
They can be machined quite a bit if your machine shop knows what they're doing. You have to recess the valves & seats back to spec after taking a good amount off the surface, and if you take enough off, you have to machine the intake surface so the clamshells still line up, I am told.
I've had many LB7 heads surfaced without issue. By the time you pay for the valve seat recession and a valve job on top of it, it isn't cheap, but it is cheaper than getting new heads or having to pull it all back apart because warped stock heads were just slapped back on.
The different gasket thicknesses are to account for varying piston protrusion from engine to engine. The Grade C is the largest, and you can generally just run Grade C gaskets without issue, but if you know what it had on before, just use the same grade. You can also measure the piston protrusion and look up what gasket is needed. Each bank is done individually, so it isn't uncommon for an engine to have two different gasket thicknesses.
I've had many LB7 heads surfaced without issue. By the time you pay for the valve seat recession and a valve job on top of it, it isn't cheap, but it is cheaper than getting new heads or having to pull it all back apart because warped stock heads were just slapped back on.
The different gasket thicknesses are to account for varying piston protrusion from engine to engine. The Grade C is the largest, and you can generally just run Grade C gaskets without issue, but if you know what it had on before, just use the same grade. You can also measure the piston protrusion and look up what gasket is needed. Each bank is done individually, so it isn't uncommon for an engine to have two different gasket thicknesses.
Heads
I do a LOT of head gasket jobs and I would never do them without milling them!!!!! You have to use a competent shop. I really cant believe a dealer would do a job like that and not do it correct. The heads will be dented/grooved were the gaskets fire is.
I do a LOT of head gasket jobs and I would never do them without milling them!!!!! You have to use a competent shop. I really cant believe a dealer would do a job like that and not do it correct. The heads will be dented/grooved were the gaskets fire is.
When I did my LB7 I had the decked. Took 10 thousandths off and used grade c gaskets. I didn’t have any issues but that doesn’t mean it was right
Our machinist here resurfaces the dmax heads if the fire ring has left marks in the head. If the marks are to bad he orders new castings without valves. Then all he has to do is cut the valves and re assemble. The castings come with new guides and seats in them for $480 / each. He tells me the seats are alot of work to remove and install on the dmax and its around the same money to just get blanks. The 1st thing he does when he gets a set of heads in is checks the surface and then measures how deep the valve protrusion is. Spec is minimum .039 - maximum .054 if I remember correct. If the heads are out of spec he orders the new blanks. The guy has been doing head work for 31 years and has a real good reputation.
I think if the shop that you have your truck at, worked on many Dmaxes they would have just sent your heads to a reputable shop to have them checked to see if they are warped , guide clearance , cracks , spring pressure and if all is good ,seals ,grind valves and seats , take off .0035 to clean them up and you are good to go ! A guy on the SOCAL tec line two months ago told me they do not like to take any heads for core that have been cut more than .0035 because they will need to do a .0035 clean up which would put them at .0070 very near your .0079 post that you talked about . If your heads are beyond specs , post #8 has great advice ! Good luck !!!
Thanks for all your input. There's a lot of knowledge out there. The machine shop said there was something with the fire ring that needed resurfacing. They don't get many Duramaxes here so y'all input is golden.