resurface head but how much

[dsmsucks]

Hi I dropped my head off to a machine shop so they can resurface it. They start work on it tomorrow. I just read that there's a limit to how much you can resurface a head. Question is how much do they resurface it?
thanks

 

[tqmx1]

Unless the head is A.F.uped it should take no more than .005" to .010" to clean it up. Before they do it have them lay a straght edge on it to see if it is warped and pressure check it for cracks.

Find out before they put a lot of time into it.

 

[kyanox]

So what if my shop resurfaced it all the way passed the bowl dishes. They gave maybe .1'th for the valve clearance, and there is no room for the pistons to clear the head if they dish out of the cylinders a bit.

So my question is, will a .050 cometic headgasket leave me enough room, or do i need to double up on it.

Chris

 

[1gcrazy]

I probably wouldnt' double up a head gasket... not sure though.

 

[kyanox]

My only concern is when i got the car the head and block had been surfaced so they could install a cometic gasket. I even purchased a new one for this job, but my fear is the pistons don't have enough clearance and will smack the head. They seem to protrude out of the block, but maybe only .001 to .005 and with the head being decked so there is no cylinder bowl at the top, and very little valve clearance im worried im going to smack valves. Now i had the head on once before with a cometic gasket, and didnt hear anything smack and also didnt feel it when hand cranking, but when i first assembled the car the pistons were also about .2 under the top of the block, but now have since expanded or stretched.

 

[Maglin]

Don't double up a HG. Just get a thicker one if you need to. You can bolt the head on with some clay on the piston top. Then just rotate it and take the head off. Measure the clay and that is how far the piston is from the chambers. Then you add the thickness of your HG and that will be your quench area. Less quench is better for performance but you also have to ensure your valves don't hit the pistons with to little quench.

 

[tkelly27]

yup. If you're scared of problems you can order custom copper HG. I forgot where, but they're not super expensive and you can get them pretty thick.

I'm not sure if it's the same with DOHC, but with SOHC if you shave too much off the head your cam timing goes off.

Whatever you do, clay and plastigauge everything and make sure it's within tolerances.

 

[Defiant]

Good god. A cleanup cut on a head won't do enough to matter to the compression. The machinist probably does five a day. Don't think about it.

 

[95blackGsTurbo]

Exactly what Defiant said. They have been doing this for years and just because they may have never done the head before they aren't going to mess it up. If it needs more than .010" machined off they probably will just tell you the head is junk anyways.

 

[kyanox]

Ok so my fear my have come true.

I hear a loud knocking noise now comming from #3 or #4, i gotta get a stethoscope on the block to figure out which one, but could it be the pistons slapping the head after running.

Here's what happened. I got 100 miles on the rebuilt, i been driving no boost, wastegate on spring pressure, i drove to work, didnt go over 4000, engine sounded fine.

I parked, idled for a minute to cool down, then shut the car off. Went into work. When i came out of work, i went to turn the car on to go home, and there was a loud tap tap noise, kinda like a bad rod?

Is it possible i am hitting the head, or spun a bearing?

Again we had .030 clearance between the piston top and the head with the cometic gasket.

 

[Defiant]

Is it possible i am hitting the head,

Nope.

or spun a bearing?

Yup.