Cylinder Head Milling

Hello everyone and Happy New Year. I have a question regarding milling of cylinder heads. I have a 95 Mustang Cobra and I currently rebuilding the engine. It will be a 306. I am about to purchase AFR 165 heads but need some additional info. on head milling. I did not have the block 0 decked so I will have to have the heads milled in order to get 10:1 compression ratio. The pistons are .017" in the hole. From the formula I found online, I need to mill the heads to 54cc in order to get 10:1 compression ratio. Keep in mind, the bottom end is completed. I spoke with AFR and the person stated that they would have to mill the heads .004" per cc or .024" to get 54cc. The questions are below.

1. What is the maximum amount of material that can come off of the heads without having to mill the lower intake? I've been told .020" is the max. that can come off without having to mill the intake.

2. Is it a good idea to mill the heads to get a higher compression ratio.

3. How does milling of the heads affect how the valves come down on the pistons? Note: I have Probe Racing pistons that can accept upto 2.08 valves

I need to know before I spend my money and end up having tons of other problems.

Thanks for any help.

Are you getting the heads directly from AFR? If so, it is best to have them mill the heads. They will mill the intake side of the heads the corresponding amount so your intake manifold is still aligned properly.

If you are only milling 0.024" however, it is not likely that your intake will have any problems. So again, if you can..have AFR take care of the milling. If not, then have your machine shop take 0.024" off and be done with it. Do a mockup and visual/feeler check with the intake and gasket dry mounted. Again, usually that is not enought to severly misalign the intake.

Your valves will naturally be closer to the heads by the distance you mill. 0.024" is not highly significant considering you should have at least 0.150" clearance on the exh valve and 0.100" on the intake. All of this will depend on your cam. So do a piston to valve check (article in the Tech Department/Fundamentals section.)
Your probably safe with the Probe pistons...the wide and deep eyebrow is good for pretty high lifts/durations. The 1.94" valve on the AFR 165 is also not going to pose any diameter clearance problems with the piston eye brow.

All in all I don't think you will have any problems, but get in the habit of checking twice if you plan to be in this hobby!

Hello 67Stang and thanks for the reply. I am happy to know that I should not have any problems. Yes, I am getting the heads directly from AFR and they are going to do the mill work and they are going to upgrade the spring package for me. By the way, the cam I've installed is the Lunati P/N 54014 which is .500/.510 (intake/exhaust) with 218/226 duration (intake/exhaust) with 1.6 roller rockers. However, I plan to install 1.7 roller rockers and increase the lift to .531/.541. Would the 1.7s work ok with this cam? From my readings this is a pretty mild cam but I was concerned about emissions. They are pretty tight here in Maryland. Again thanks for the reply:

you wont have problems with clearance, but emmissions I dont know... the higher compression ratio tends to increase NOx, which is one of the five gasses in a 5 gas analyzer. Now not all states have limits for NOx, so who knows. The best thing is to ensure you have good working catalytic converters that are nice and hot when you go to the smog test. Get a pre-test as well to see if the numbers are passable. Our '88 LX project car used a similar Lunati cam, and it passed.

This article has more info...
http://www.fordmuscle.com/archives/2...pe/index.shtml

Thanks again 67Stang. Yes, I do have good working catalyic converters. As a matter of fact, they are the stock ones that came with the car when I purchase the car in 7/95 and they were only on the car for roughly 3 months (still brand new). So whenever I have to go thru emissions I just get out the wrenches and change to the stock pipe and after the test reinstall the O/R H pipe. Also, I don't know if MD has the NOX limits but I will look at my last report. However for cars 1996 and newer in MD with OBD II the emission center only plugs into the OBD II to see if there are any emission codes. No codes you pass. But they still do the visual test. So that's good for the newer car owners with lots of aftermarket upgrades and no check engine light on. And thanks for the article I enjoy learning new things especially since I'm building the Mustang myself. Thanks again and have a good weekend. Peace.

Oh I forgot to mention. The emission center does no look under the hood for after market parts. They only stick the mirror under the car to see if you have the cats on. They also test the gas cap pressure. Also, the 1995 and older cars are tested on the dynameter. Prior to the change they only stuck the sniffer in your tail pipes. Peace.

67Stang I have another question. I've seen yours and other tech article on the 3G alternator(130 amps). One article suggested to obtain an alternator from a 1994-1995 Mustang. I have a 1995 Mustang Cobra so am I to assume that I already have the 3G 130 amp alternator. Also, how can I verify whether or not I have the 3G alternator. Thanks again.

95's should have a 3G from the factory. You can call PAPerformance and they will know for sure. As for Rick.

Very good advise;I have a similar setup and it works for me. The only thing I would add, when you bolt on the Intake manifold, do not use the rubber or cork end pieces that come with the intake gaskets, use a healthy bead of silicion sealant instead. This should keep the oil in the engine as well assuring a tight water seal. Good luck.

<font size=-1>[ This Message was edited by: 19mustang93 on 1/21/04 8:18am ]</font>