The heads are polished and ported heads for a early 1980s 305 with the larger intake (1.94) and exhaust valves (1.70 - I believe). I purchased them for a steal at $180/pair. I am using stock pistons 8.5:1 compression and with the small chamber heads (60.5 cc), I will get between about 9.8:1 compression which is a little more than what I was hoping for. For a street engine, 9.3 to 1 would be ideal.

Just an update: I've been running the higher compression 9.8:1 for a couple of years now using 94 Octane gas and haven't had any issues with predetonation or pinging. Seems I lucked out!


Here's a picture of the porting job done on the heads. The intake runners are smooth as silk.


I cc'd the heads to see the actual compression chamber size - it was 60.5 cc

The heads were cc'd using a piece of clear plastic, white grease as a sealant around the edge and some oil to put it simply. The clear piece of plastic has two holes drilled into it: a fill hole and a small air hole. White grease is used to seal the plastic against the head. I went to a pharmancy and picked up two syringes (a 60 cc and a 5 cc) for a total of $5. I put in 55 cc of 10W30 weight oil then filled the rest using the smaller 5 cc syringe. Thinner oil would work better as I had trouble getting the last bubbles out of the 10W30. The syringes are resting on the clear plastic.

The stock chamber has been increased from 58 cc to 60.5 cc and radiused around the larger valves for better flow. To use the heads on a 400 block, additional waterjacket holes have to be drilled in the head to prevent steam buildup in the block. The following picture shows the location of the holes determined by the 400 head gasket and the angle that the hole has to be drilled to miss the bolt hole shaft. I measured the holes in the block and if I remember right, the holes are 1/4" and 3/16" in size.

drill angle

Additional holes required for non 400 block heads and drill angle to miss headbolt shaft.

If this page has helped you, please consider donating $1.00 to support the cost of hosting this site, thanks.

Return to

Copyright May 2011 Eugene Blanchard