Dingo 1 Report post Posted March 5, 2017 (edited) So I'm pretty heavily invested in my m20 stroker engine build. I have 85mm Mahle forged pistons M52B28 crank Schrick 272 cam and valve springs and IE heavy duty rockers. I had kinda overlooked the fact my donor engine does not have the original 885 head but instead has the aftermarket AMC head. There is plenty on the interwebs bagging the head due to the port design and finishing. The ports are pretty rough from the factory casting & machining. On the other hand companies selling the AMC head state they are a solid base for race applications. Has anyone had experience with these heads good or bad? Should I clean up the ports and carry on or find a genuine 885 head for my build? I should say I'm building the engine as a solid engine for my daily driver that might see the odd open day at the track once a year. Edited March 5, 2017 by Dingo Quote Share this post Link to post Share on other sites
No name user 379 Report post Posted March 5, 2017 I would first put it on a flow bench, then see how the cam specs relate as not every drop in cam will give a result you expect or even go backwards. Doing porting is fine art however basic things can be done, polishing to mirror finish is a waste of time i rough the ports with 60/80 grit to create turbulence entering the chamber. Never touch the lower short radius on the floor of the port its the fastest way to kill flow, the exhaust power is the one that controls overall power and big isnt best. Port throat behind the valve head to valve dia i would aim for around .88 ratio, measure the valve head dia x that by .88 will give the throat size. Then try to get as much upper roof area to point directly onto the back of the intake valve and reverse for the exh port. Also taking the head to a pro works too 1 Quote Share this post Link to post Share on other sites
