Ok.. It's head gasket time!

[Ozzie]

is it mandatory to grind the heads when replacing the head gaskets?

If you mean getting them flat: No. ..but while they are out, it's a good idea to have them checked...which may lead to flattening them.
If you mean preparing the surface: Yes. You don't want to a clean-ish surface on both the head and the block.

[David T]

If you mean getting them flat: No. ..but while they are out, it's a good idea to have them checked...which may lead to flattening them.
If you mean preparing the surface: Yes. You don't want to a clean-ish surface on both the head and the block.

I would check the flatness of the heads and if they are over .002 warped, I would consider it mandatory that they be ground. Requires a good straightedge and a feeler gauge. Typically if the heads got overheated enough to blow the gasket you can figure the heads are going to need grinding. As long as you are grinding them you may as well freshen up the valves and seats. Helps to restore full compression and will give you a better running, smoother motor and more power.
David Teitelbaum

[Delorean Industries]

I have yet to see a set of heads especially original that did not require milling.

[coreydmc]

Ok ill send them to a local shop to be milled, One I install the heads, change the valves and seats and the car is back together again does it require to be tuned to those specs with a dwell meter etc?

[DMC5180]

Ok ill send them to a local shop to be milled, One I install the heads, change the valves and seats and the car is back together again does it require to be tuned to those specs with a dwell meter etc?

That's an interesting question. One would think, if you don't mess with any of the fuel related stuff in the process, you should be fine assuming stock setup. If cams or high compression are involved perhaps not.

I'm interested in reading the answer from the pro's myself.

[coreydmc]

hahahaha. I am interested in the answer also! I have not started this project until I have all the facts down. Especially since I just installed a new cat.

[TTait]

Once you restart the engine, you are most likely to have timing, valve adjustment, and vacuum leak issues, not fuel system issues.

First, worry about oil pressure, and valve clearances - any mistake there will be costly. Next, worry about distributor timing - plug gaps, etc, as very poor combustion can damage your cat. Vacuum leaks next - you won't adjust anything in the fuel system without getting that right first. When those are good, its possible that you will want to do some fuel system adjustments, but in theory nothing significant there will have changed.

Tom

PS - I agree the most direct route for doing this is to just go back to stock, but if you do intend to go stage 2 you pretty much have to replace the head gaskets again - as I understand it they cannot be re-torqued - so if you want stage 2, you will repeat most or all of this job again to do so if you don't do it now.

[David T]

Whenever you do that much work you will want to check all of your adjustments. Especially since you may be fixing vacuum leaks, better adjustment of the valves, etc. All of this will have an effect on the Lambda system and necessitate an adjustment. No sense going half-way and not trying to get the motor to run as well as you can. it is also a check on how well you did all of your work. If you can't get the fuel mixture set right it means you did something wrong. You are also assuming it was set right BEFORE you did all of the work. Big assumption on most Deloreans! BTW, you do not "change" the valve seats and valves. They are ground and lapped. I would also check the timing and advance systems.
David Teitelbaum

[coreydmc]

David- are you saying not to change the valves and seats? I just want to make sure I read your post correctly.

[TTait]

Valves can be changed, but not the seats - the mating surface is milled directly into the head. Instead they get lapped, or resurfaced if you will. The machine shop can do it when they mill the heads, or you can try to do it by hand if you have the patience.