So ive made a huge mistake and bought heads for my car that are too big.

They are World Sportsman 2, 70cc 200cc going on a stock internal 350 that will get a mild cam pretty soon.

Ive decided on getting the heads milled or angle milled. Which is better to do and why.

This car is my daily driver and i cant really take my intake manifold off to match it with the heads for milling so i was leaning towards getting them angle milled from 70 to 64 so my compression wont be way off.

Im going to have the machinest check all clearences as well which is also something i was worried about.

Lastly, ive been reading that alot of people have had there sportsmans smoke alot and use oil, has anyone else had this issue?

Thanks for all comments

 

Angle milling means, milling off the deck surface of the head at an angle to where it is now. It's usually done such that more material is removed from the exh side. It SPECIFICALLY REQUIRES that the intake be milled if more than about .010" - .015" is removed, because if you try to bolt on the intake, the gasket will be compressed to the limit across the bottom of the ports, but FAR LESS across the top.

Think about it: if you are looking at the engine from, say, the front, and you mill the head at an angle, it rotates, right? meaning, the intake face is now rotated as well, right? THat's why.

Also, angle milling any significant amount usually requires re-drilling the head bolt holes through the heads.

Not a good idea.

You could mill them straight, which takes off roughly 1cc for every .006" you mill; based on, the "area" of the chamber, times .001". As you mill farther and farther, it makes less and less change to the volume, because the cross-sectional area of the chamber at that point becomes smaller. That means you'd need to take off AT LEAST .036" to get from 70 to 64cc, and more likely, closer to .040".

Milling them that far will move the intake bolt holes about that far down from where they are in the intake. It will be VERY DIFFICULT, if not impossible, to get them to go in. The intake will VIRTUALLY CERTAINLY require milling as well.

Better idea: return the heads to the vendor and trade for the ones you really need.