Didn't feel like working on my regular project yesterday so I dug out one of my 318 poly project heads and went at roughing in a raising the intake port. Like I did with my spare slant six head I went after ideal shape without concern for breaking through. Believing of course that if I did I can now weld it or in the worst case grab another since these engines are still around although not popular here. I raised the port roof over 1/4 inch , eliminated the huge obstructive valve guide boss and reworked the bowl as much as I dared to get a straighter approach to the back of the valve. I photoed the port after initial roughing and the stock one beside it. This approach was spurred on by the absolute success of my Slant six head experiments a couple years ago.
Thanks Did all the intakes on one head at the flange and finished that one port. No water. Looks very good. Only need 210.25CFm for full power at 8000RPM because the cubes is small. Should have that more then covered. A stroker though would be challenged while with a low cubed, close to stock size engine, a modified head can feed it easily. Sometimes a big crank is like shooting yourself in the foot. This engine is one of those cases. don
Can't buy a set of aluminium heads for a 318 Poly can you Don but then that is against your nature. Will be following this one closely.
Very interesting experiment. 318 Poly heads have valves sized in between LA 318 and 340. And, the Poly head design has some advantages over the conventional wedge head. So it will be interesting to see how the poly compares to the wedge. I believe the LA actually gave up some performance potential by going to the wedge head.
neat work Don, great to see you're still chipping away and experimenting, although I imagine you'd be sick and tired of the grinding dust after buzzing it down so much. Cheers, Drewfus
Don, That's some nice work,and I like the thinking behind it.I can't believe those guide bosses though!They almost choked off the entire cross-section of the port! I'm out of the loop here....Are you building a "class-legal" motor for racing,or just a guy who doesn't want to build the same thing that 900,000 other guys have been building for the last 50 yrs,so you went and found a cheap,readily available alternative that will make power if it gets some of the right kind of attention? On the Slant Six topic: I saw one at Grand Bend a dozen years ago that was running 13.60's I believe in a Dodge Dart.MAN did it sound cool during the burnout.....! Scott Posted using two Dixie cups and a medium length piece of string.
Me I am retired and just exploring what interests me. I race the dragster to the left but had started the poly for another rail but that chassis was bought by someone so all I have left is the motor and a lot of time. Block is bored to 4 inch and 360/340 rods were subbed for the old poly ones as the newer rods are much stronger. I found a off the shelf piston that would work and a cam as already been ground. I started with a poly when I was 16 so I figured I should have one at the other end as well. don
The Jalopy Journal
