Head Machine Work Question

[aspekt9]

I'm beginning a rebuild, I'm starting with the head first. The head I have is a 6-bolt it came from a running car so everything in the head seems to be 100% and functioning. I'm going to be rebuilding the head with new springs, valves and seals. My question is, when I send it out to the machine shop do I need anything more than to have them clean it and surface it for an MLS gasket? If they deck it, do they need to re-cut the seats? And if they recut the seats do I need to lap the new valves? I'm going to be doing all the assembly myself.

Thanks

 

[mitsuproracer]

Having it cleaned, pressure tested to make sure there are no cracks or anything, and resurfaced is all you should need.

 

[BogusSVO]

do not let the shop BELT SURFACE?SAND the head... not good at all...
http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html

if they cut/grind the seats, depends on with what equipment they use to cut/grind the seats with weather you may want to lap the valves or not...
http://www.dsmtuners.com/forums/newbie-forum/341297-how-replace-seats-aluminum-head.html

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

have the guides checked and replaced if needed, if replaced the seats will need to be cut.
http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

and you may want to do this oil mod...
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html

here is a great write up, By DSM Wiseman BigWoo
http://www.dsmtuners.com/forums/articles-engine-fuel/303225-engine-machine-work-explained.html

 

[aspekt9]

do not let the shop BELT SURFACE?SAND the head... not good at all...
http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html

if they cut/grind the seats, depends on with what equipment they use to cut/grind the seats with weather you may want to lap the valves or not...
http://www.dsmtuners.com/forums/newbie-forum/341297-how-replace-seats-aluminum-head.html

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

have the guides checked and replaced if needed, if replaced the seats will need to be cut.
http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

and you may want to do this oil mod...
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html

here is a great write up, By DSM Wiseman BigWoo
http://www.dsmtuners.com/forums/articles-engine-fuel/303225-engine-machine-work-explained.html

Thank you!! Incredibly informative, I knew about the belt sander and I made specifically sure that the surface will have a mirror finish specifically for an MLS type gasket. One more question for you, do machine shops usually cut the seats when they surface it? For what reason would they cut them?

 

[BogusSVO]

no, the seats would not be cut for a simple resurface. that would be a Valve job. But at better shops, if the valves protrude past the head deck surface, they should be removed before surfacuing. that may be an add'l cost tho.

quick/cheap shops will just cut the valve heads as they surface the head. that should be advoided.

 

[aspekt9]

Okay I think I'm understanding. So are the valves supposed to sit flush in the head without protruding past the surface? And is there any reason for me to get a valve job? What conditions require a valve job?

 

[BogusSVO]

on the 4g63 head, if the head has been surfaced a few times, or +1mm intake valves, they may protude past the gasket surface.

several reasons to have a Valve job, bent valves, guide replacement from being worn or cracked, high milage, burnt valve, upgrading to +1mm valves. valve seats wide or beat out, damage to valve seat.
are all reasons for a Valve job.

I would measure the head thickness, a "new" head is 5.200 the AERA spec for min thickness is 5.185

even if the head is thin, you can get a thicker HG to restore it to proper thickness

 

[aspekt9]

Okay, since I'm unsure of the miles on the head and how many times it has been resurfaced, if it can still be resurfaced I'll have them do a 3-angle valve job on it since I'm putting all new valves in it. That way I can have peace of mind that everything will seal properly. Does the machinist need the valves to do the 3-angle job?

Thanks a lot, I appreciate the information

 

[BogusSVO]

it is most helpfull if you have the valves, and they are needed if you go with the +1mm valves, that way when the seats are cut, valve tip height can be set, and the seat placement can be set on the valve face