cracked head!!!!!!!!

[cameljockey]

so Ihave a cracked head on the 200 ci engine in my '66 'stang but the good news is I have a spare motor in the back yard a 250 ci from a 71 maveric and it has a head from a 78 I 6 I wanna use the head but I know I'll loose some compression so while I have it off I wanna mill it down so as to restore compression but I don't konw haw much is safe to mill off? any body have a clue thanks guys

keep sixn'

Dan Hanna

 

[CZLN6]

Howdy Dan:

All heads can stand a mill of .090" safely. Beyond that it is best to do some sonic testing to insure no thin spots.

You will need to mill /050" to compensate for the larger chamber volume.

And another amount for the difference in head gasket thickness. That will vary depending on which head gasket you use. The stock factory steel shim gaskets are .025".

It will be cheap insurance to do a valve job and put new valve stem seals on while it is apart for machining.

Adios, David

 

[cameljockey]

is that assumming the head has been milled before? how can you tell?

incedentally this is a reman head so it must have been milled before right?

 

[addo]

http://www.inlinepages.com/~inlinefever ... tions.html is Mustang Geezer's web page with brief instructions on how to measure the cc of your head. Measuring first is the only way to be sure of ending up where you want to go.

 

[CZLN6]

Howdy Bck

A remanufactured head will, most likely, have been milled to true the mating surface. How Much? At least .010", maybe more.

Measuring the volume of each chamber, in cubic centmeters is the only way to know, and then use that dimension to figure the ture compression ratio. Adam posted the "How to" link from Doug's home page.

On a late model, 62 cc chamber head, a formula for estimating chamber volume reduction is 2 ccs = .010". Estimating and measuring are not the same. It is best to measure.

If you measure the volume of each chamber you will likely find considerable variances. FoMoCo quality control was less than ideal on these casting. It is a good idea to know the smallest for figuring CR. It is best to even the chamber volumes up to within one cc.

What head gasket will you be using?

Once you have the dimensions you might want to go to our web site. It is in my signature. Click on the compression calculator, plug in your numbers to get your new CR.

Adios, David

 

[cameljockey]

thanks guys very good info the head is goin to the shop either today or wed

thanks again and keep sixn'

DanHanna