Hi,

After 330000km, my cylinder 4 valve is broken. The mechanic tells me that I need to have the heads rebuilt. What other things can I get done to the heads on the cheap while they'll be off. I'm thinking of having a bit shaved off the bottom to increase the compression ratio since it I always run it on premium fuel. Is there anything else that I can do to increase performance? I just HATE spending heaps of money and not getting any benefit over what it was like before.

 

mmm port and polished head

 

Direct Port Nitrous system.

 

what he said

 

What kind of gains can a VG get from that?

 

Before you spend the dough to have the heads rebuilt, call around and see how much replacing them would be. On my Fiancees Honda ( granted it's an I4 ) it was cheaper to replace the head then to rebuild it.

 

I have a question-if you increase your compression are you get the same gain like when you advance your timing? Also, instead of taking material from the head why don't research for a thinner head gasket? It might me easier and cheaper.....

 

gains from compression and those from timing are two completely different animals of physics....

as for the head gasket -
when u take material off the head, u're also making it true and flat again. u're building compression by reducing the volume of the combustion chamber. also, by the time you torque down your head properly your gasket thickness shouldn't be a contributing factor to your compression ratio. think about it...given that the goal is higher compression, do u really want one of things that keeps coolant out of your cylinder any thinner?

i'm not certain that you're appreciating the scale of how much material is removed frm a head vs how much a gasket is compressed...

 

Actually any good engine builder accounts for the headgasket thickness in their compression calculations.

 

Question on head gaskets while we're on the topic... On my '72 MGB I run a copper head gasket. It's not much of a gasket, it's a frikkin copper sheet. But many MGB owners use them as it does perform much better than the OEM (my OEM valve cover gasket was cork if that says anything). Would using a copper gasket like that increase compression due to it's rather thin construction? Would someone want to try something like that with a newer car (relatively speaking)?