milling the deck hieght??

[myblack98gst]

Hey whats up people I am going to start a re-build on a 6-bolt to go into my 98.. the block blew a ring so I am going to have to bore it out..... DARN!!! haha. well anyways I was think about going all the way to .040. and I was wondering if anybody knew the piston valve clearances to see if maybe I could shave the deck or head a small amount to bump the compression up a few points.

Basically I am looking to buid a more powerfull base motor. I am going to be using the eagle automotive rebuild kit with 1g rods and 2g pistons.

Let me know what you think based on your real experience.

Is it a bad idea to go .040 with the bore?
Should I try shaving the deck to bump compression?

Oh yeah I will be using the 2g head off my motor

 

[allwheelTSI]

i do not know piston to valve clearance because i am an idiot,but i do know that shaving the deck height or head would not bump your compression up anywheres near "a few points".

and 3 points would have you at 11.5:1 you don't want that unless you have a huge turbo to spool or you are one helluva tuner.

if you can,ditch that awful flowing 2g head for a better flowing 1g model.

 

[myblack98gst]

Sorry I said that wrong I meant a few points by .1 points so go from a 8.5 to a 8.8 or 9.0

 

[AdrenilineCrash]

im with allwheelTSi, ditch the 2g head if you can and get a 1g. they arent too hard to come by and wont be too expensive.

-mike

 

[myblack98gst]

okay I may try to find a 1g head.....


does anyone know how far I can safely go on shaving the deck or the head??

or if you have done the bore or the shave did you see significant results from it

 

[Rick@AP]

I think you're missing the basics of engine building....

Valve to piston clearance, along with compression ratio, is something that you the engine builder set, not a given. There are entirely too many variables to be considered, for someone that really knows what they are talking about, to answer the question you have asked.

Why do I say this? Here's a short list of what will affect what you are asking:

Stock headgasket or metal head gasket?
If metal headgasket what thickness?
What are the valve spring compression values?
Has the block ever been decked or milled?
What is the current deck height?
Has the head ever been decked or milled?
What is the current head height?

See what I mean?

The way to figure out what you are asking is to do the math based on measuring the entire assembly. The other way is to make an educated guess based on experience and then use clay or otherwise to affirm that your guess was correct. If it was not, then you adjust the assembly accordingly.

Good luck...

 

[myblack98gst]

Or just ask some one that has done the same thing to the same motor and see what they did... Yes I know checking all the clearance and everything would be the wiser and make me look smarter but I am trying to build the block

 

[Groomz]

I would say stick w/ the 2G head and go for a Magnus intake manifold. Definitely get it ported while you have it out. This combo w/ some HKS cams would make some pretty good power. Thats what I plan to do.

 

[Rick@AP]

Dude, your missing the whole point. EVERY engine is different. What I do to my engine will probably not have the same affect as what you do to yours. Even if they were manufactured the same right down to the eighteenth decimal place, you have to look at other factors such as what kind of maintance was done on both, what kind of oil was used, how was it prepared, what kind of machining was done, what shape are the parts in, what parts are being used, etc. What works for me may or may not work for you.

We could walk into a machine shop together, both with 4g63 6 bolt blocks, and ask the machinist to mill the block by .10. I could assemble my engine and have it run perfectly fine. You could assemble yours and bend up all the valves in the head. Why? They are all different, from slight deck height differences to slight head height differences to valve seating differences to valve spring compression differences.

Your letting yourself fall into a trap....a potentially expensive. If you don't have the know how or the equipment to do it correctly, spend the money to have the machine shop do it or a ask someone around you that knows what they are doing to help you. I'd hate to see you posting a month from now about how you destroyed your engine. If you choose to ignore what I'm trying to tell you, so be it.

 

[evil_eagle]

From factory you are allowed to shave the head to only .020 thousands max. I have mine milled to .015 thousands and works great, I have had no valve clearance problems, but I allso run a mitsu metal head gasket.

My pistons are Ross 9.0~1
The only problem you run into is pump gas and high boost levels, it will be more prone to knock due to the closer valve clearance and higher compression, so it will be harder to tune with high boost levels on pump, but you should not have to run much boost since the motor will make the power due to the higher compression. Make sense? I like to be able to run low boost levels and still run harder then hell, with my FWD I was able to run 12.2@117mph on only 15lbs of boost, but I also have alot done to my setup.

Hope this helps you some, Just make damn sure who ever mills the head that they do not wack the hell out of the intake valve seats as they are reeeeeeaaaaallly close to the head surface.
-Jake

 

[GrocMax]

Originally posted by evil_eagle
From factory you are allowed to shave the head to only .020 thousands max. I have mine milled to .015 thousands and works great, I have had no valve clearance problems, but I allso run a mitsu metal head gasket.

My pistons are Ross 9.0~1
The only problem you run into is pump gas and high boost levels, it will be more prone to knock due to the closer valve clearance and higher compression, so it will be harder to tune with high boost levels on pump, but you should not have to run much boost since the motor will make the power due to the higher compression. Make sense? I like to be able to run low boost levels and still run harder then hell, with my FWD I was able to run 12.2@117mph on only 15lbs of boost, but I also have alot done to my setup.

Hope this helps you some, Just make damn sure who ever mills the head that they do not wack the hell out of the intake valve seats as they are reeeeeeaaaaallly close to the head surface.
-Jake

Factory maximum head or block total mill spec is .008". RTFM

Doesn't mean you can't get away with more though.

 

[evil_eagle]

Originally posted by GrocMax


Factory maximum head or block total mill spec is .008". RTFM

Doesn't mean you can't get away with more though.

Hmmm, interesting, .008 is not much at all, but yeah the manual does say that, you are right, whats the most you ever seen Groc? My understanding is that you can go .020 max on the head. But like you stated "Doesn't mean you can't get away with more though" I can see why I was told .020 is as much as you can go.

I wonder Groc, in the manual it states .008, now is that to keep it in factory head gasket thickness? (for cam timing and what not) I can't find anywhere in the manual that states the head gasket thickness as far as the head surface and or block surface.
-Jake

 

[jdm93dsm]

Originally posted by evil_eagle
From factory you are allowed to shave the head to only .020 thousands max. I have mine milled to .015 thousands and works great, I have had no valve clearance problems, but I allso run a mitsu metal head gasket.

My pistons are Ross 9.0~1
The only problem you run into is pump gas and high boost levels, it will be more prone to knock due to the closer valve clearance and higher compression, so it will be harder to tune with high boost levels on pump, but you should not have to run much boost since the motor will make the power due to the higher compression. Make sense? I like to be able to run low boost levels and still run harder then hell, with my FWD I was able to run 12.2@117mph on only 15lbs of boost, but I also have alot done to my setup.

Hope this helps you some, Just make damn sure who ever mills the head that they do not wack the hell out of the intake valve seats as they are reeeeeeaaaaallly close to the head surface.
-Jake

do you think I could get away w/ .015 w/ a factory head gasket on my NT... or is there no different between the head in a Turbo and nt?

 

[Groomz]

There should not be a difference between heads on the N/T 4G63. The cams are the only different thing I believe, and the block does not have oil squirters.

 

[jdm93dsm]

does anyone know if i could get away w/ atleast a .010 thousands mill atleast?