170 to 250

Hello Everyone,

Quick question: I currently have a 170 in my mustang, and have a '69 250 sitting on my garage floor. I am planning on doing the head swap, but was also planning on maybe dropping the 250 in at some point once I rebuild it.

Will milling the head to put it on my 170 prevent me from putting it back on the 250 if I decide to rebuild it and plop it in the mustang?

Thanks!

Shaving the head shouldn't be a problem to eventually go back to your 250. it will increase your compression ratio, depending how much you have shaved off.

Howdy Back Stang:

2X on rabbits reply. I would add that as long as the head is stripped for milling you should add a performance valve job and have the intake valves back-cut to improve flow.

Putting this head back on the 250 will be no problem, but know that the 250 engine, with a tall deck height is prone to pre-ignition. So, you will want to plan on a cam upgrade with more duration to reduce the cylinder pressure, that adds to ping.

A mill cut of .025" to compensate for the thicker aftermarket head gasket, and another .025" for a slight increase in compression ratio, for a total cut of .050" should be about right for now.

Good luck and keep it coming.

Adios, David

Thanks for the info!