i'm looking at having my head milled .020. i know that with doing that setting my timing using the timing marks will be off therefore adj. cam gears are needed. how can you tell what true timing is and where to set the cam gears?

 

From what I understand, a good ballpark is 1 degree (at the cam, which is 2 degrees at the crank) of retard for every 0.012" taken off the head or block. So if you have your head milled 0.024" you would advance the cam gear(s) 2 degrees (at the cam) to get back to straight up timing.

 

So in your case-0.020",advance the gears roughly 2 degrees or a tiny bit less.

 

cool.

i'm still not certain if i want to go about milling the head

 

Milling the head is a great way to gain compression and power. Many people are weary and say it's not worth it , but I know many people with high HP motors that mill their heads. On the setup we have, we milled our head .040 with CTR pistons and we have no problems lining up the timing marks. It all depends on how crazy you want to get and how much power you want. However, It all depends on how tall and what compression your pistons will be too. At that point you have to get involved in "claying" the motor to test for piston to valve clearence. So don't always believe what you hear. Go out and find out for yourself. See what's working for smoe people and try to adapt it to you own thing. Good Luck.

 

Milling the head is the easy way to gain compression. It all depends really on what you are trying to accomplish and your budget. For small budget setups, milling the head is cheap and can get you the power.
But what I always tell customers when we build their custom engines is to keep the head UNMILLED and if they are trying to get the max compression out of the motor they want to build. we do a custom piston to match the combustion chamber, valve relief size to match the cam specs and make the adjustments on the piston design to get the compression they desire.

and what d16dcoe said, dont forget about that when putting the motor back together.

 

But wouldn't milling be better than running a very large dome--say run a mid-dome with some milling to get the compression you are after? Which for most street builds (11-12.5 compression) is achieveable with a small to medium dome and a moderate mill. I had a Gude head some years ago that was milled to where the open quench d16a6 head became flush with the head surface. I went from stock a6 compression (with stock pistons) to 11:1 with the milling and 3 layer HG. Worked good.

 

ya nt saying milling is all that bad, but it should be done with knwoledge of what is going to happen with valve clearance and possible piston clearance later on.
I guess what I'm saying is if you know what you are getting into, then tahts fine.

Alot of people come through our shop and send us badly milled heads, over milled heads, etc and at the same time they want off the shelf high compression pistons to work with what they have. In many of the cases, there will be clearance issues, etc. We just dont want it to be the first resort when building a motor, in general.

 

Your right,milling the head should not be a first resort unless you have someone who knows what they're doing. I've seen badly milled heads myself and was weary of it for a long time. Bill(Gude) showed us the right way and wrong way heads are milled and we decided to give it a shot. So far so good. We've been banging on this motor for 6 months or so and it works for us. That's the great thing about these motors,there are so many different ways to build 'em and everyone has their nitch. But overall, exospeedAMcrx is right,if you have the money,get some custom pistons and check all your clearences that way your safe.Either way you should be pleased.

 

i decided on getting the head milled after talking to my machine shop. when i'm ready to swap on B20 bottom end my machinest is going to help my pick a properly matched set of pistons for the work thats been done

 

Yeah Bill was famous for compression through EXTREME milling--I remember I talked to him once after I bought a cam from him, I had a ported a6 head and stock a6 pistons, he said the cam really wouldn't run very well if at all on stock compression so he told me how much to get milled locally--I did it--the machine shop was like "are you sure you want this much?--we are not responsible for any damages or problems down the line"--but it worked and it worked well at 11:1 with an Hccs10 Gorilla cam--still have the cam, awesome cam.

 

Now I use a combination of shelf SRP 4.3cc dome pistons and some mill off the head and deck to get the compression I want--around 12:1 in an a6 block and head. You are absolutely right though Exospeed, it does require more care and I can see how a shop doing a cam install would be weary with an exremely milled head.

 

from our point of view. telling the customer to mill the head alot puts us in a position where the customer can end up blaming us. There are alot of knowledgeable people out there, but think of the others that dont know as much. You can't guide everyone to just go mill your head and expect it to run perfect.

I do have to gauge every person that calls us and see if they know something about what they are doing. I'll give advice and choices. its up to them to do what they want to do. but I dont feel comfortable with just telling everyone to mill their heads. all our head packages are NEVER milled to get power. It's only done by request of the customer themselves or if we've talked about the whole plan of the engine build and milling suits the needs.

I've seen other head specialists just mill the head and never tell the customer about it. They use Milling as a way to get power out of the head. We rely on the porting to do the talking. In the long run, you dont want someone to call you up later and say, why did you mill the head, now I cant put off the shelf pistons anymore.

Anyways, Im not against milled heads, it should just be done with precaution and planning. "

 

sorry if this question may seem dumb, but by milling the head you decrease the volume of the combustion chamber right? does that in return lower the displacment of the cylinder?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by d16dcoe45 &raquo;</TD></TR><TR><TD CLASS="quote">Yeah Bill was famous for compression through EXTREME milling--I remember I talked to him once after I bought a cam from him, I had a ported a6 head and stock a6 pistons, he said the cam really wouldn't run very well if at all on stock compression so he told me how much to get milled locally--I did it--the machine shop was like "are you sure you want this much?--we are not responsible for any damages or problems down the line"--but it worked and it worked well at 11:1 with an Hccs10 Gorilla cam--still have the cam, awesome cam.</TD></TR></TABLE>

Nice!

 

Sounds like you are very involved with your customers and the setups they want. to you for that. Many shops don't really care anymore and just sell work and don't really get into detail with the customer about what exactly they are getting. We always give our customers the pros and cons of a setup whether an all motor setup or boosted one. That way it covers our butt if they want it a certain way. All you can do is explain it and if they still want to do it a certain way, that's on them. But your right , it isn't always good to do so. Every setup is different.

 

i dont really see the big deal about extreme milling if the clearances are set and you dont plan on doing anything else internally to the motor...if your going to reuse the head on a different setup you will have to build around its limitations...it might be a little more difficult for the average consumer but for someone who has access to a machine shop there are options for dealing with PTV clearance as well as high compression such as flycutting valve reliefs as well as running a thicker head gasket...
IMO milling is a great way to raise compression as part of a total build...but forsomeone looking for a quick way to make more power i wouldnt recommend it since it does limit some options in the future...HG's are only made so thick.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fat vulture &raquo;</TD></TR><TR><TD CLASS="quote">i dont really see the big deal about extreme milling if the clearances are set and you dont plan on doing anything else internally to the motor...if your going to reuse the head on a different setup you will have to build around its limitations...it might be a little more difficult for the average consumer but for someone who has access to a machine shop there are options for dealing with PTV clearance as well as high compression such as flycutting valve reliefs as well as running a thicker head gasket...
IMO milling is a great way to raise compression as part of a total build...but forsomeone looking for a quick way to make more power i wouldnt recommend it since it does limit some options in the future...HG's are only made so thick.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suck my DX &raquo;</TD></TR><TR><TD CLASS="quote">sorry if this question may seem dumb, but by milling the head you decrease the volume of the combustion chamber right? does that in return lower the displacment of the cylinder? </TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suck my DX &raquo;</TD></TR><TR><TD CLASS="quote">sorry if this question may seem dumb, but by milling the head you decrease the volume of the combustion chamber right? does that in return lower the displacment of the cylinder? </TD></TR></TABLE>

Combustion chamber volume doesnt calculate into the displacement of the "cylinder". The chamber is what provides the air/fuel mixture and what it is compressed into when the piston is at TDC on the compression stroke, however, it is only "feeding" the cylinder below it on the intake stroke.

 

so what factors determine displacment of a cylinder?

 

bore and stroke.

 

D'oh! kinda overthinking the obvious huh?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fat vulture &raquo;</TD></TR><TR><TD CLASS="quote">D'oh! kinda overthinking the obvious huh?</TD></TR></TABLE>
lol yeah sometimes i get too ahead of myself and bonehead the basics

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by exospeedAMcrx &raquo;</TD></TR><TR><TD CLASS="quote">from our point of view. telling the customer to mill the head alot puts us in a position where the customer can end up blaming us. There are alot of knowledgeable people out there, but think of the others that dont know as much. You can't guide everyone to just go mill your head and expect it to run perfect.

I do have to gauge every person that calls us and see if they know something about what they are doing. I'll give advice and choices. its up to them to do what they want to do. but I dont feel comfortable with just telling everyone to mill their heads. all our head packages are NEVER milled to get power. It's only done by request of the customer themselves or if we've talked about the whole plan of the engine build and milling suits the needs.

I've seen other head specialists just mill the head and never tell the customer about it. They use Milling as a way to get power out of the head. We rely on the porting to do the talking. In the long run, you dont want someone to call you up later and say, why did you mill the head, now I cant put off the shelf pistons anymore.

Anyways, Im not against milled heads, it should just be done with precaution and planning. "</TD></TR></TABLE>

the machine shop i deal with, the owner is a family friend. i talked with him about my current setup as well as future plans. After the discussion we had i felt that it was the proper course of action.