1. where can i find the data for to tell me how much to cut heads to change combustion chamber how much? 2. what is the deal on small water holes in the heads. i forget. i am putting 351w heads on a 302. do i need to drill small water holes in each cylinder on the head, or is this needed if putting 302 heads on a 351w? thanx in advance
how much to cut heads to change combustion chamber how much? I have always been told 10 thousands gives you a half of point in compression increase. example 8.5 would be 9.0 what is the deal on small water holes in the heads. Never heard of this unless your putting 351c heads on a 302 or 351w i am putting 351w heads on a 302. do i need to drill small water holes in each cylinder on the head, or is this needed if putting 302 heads on a 351w? There is no need to cut the 302 or 351w water holes for them to work on 302 or 351w but if you use 302 heads on a 351w you must have the bolt holes on the 302 head cut bigger for the 7/16 bolts and the block taped for 7/16 bolts if putting a 351w heads on a 302 block.
I ran 351w heads on my 289 for years. When I installed the heads I was instructed to drill the holes for steam relief.
If your block has a small water hole directly above each cylinder at the 12 o'clock position you need to drill a matching hole in the 351W heads. Use the head gasket as a template. The early 302 blocks had a pocket in the water jacket there. If the hole isn't drilled your motor can overheat. I've heard that some people with high pressure aftermarket water pumps sometimes get away without drilling the hole. Personally I would, and did, drill the holes. Late 302 and 5.0 blocks had redesigned water jackets and don't have those holes in the block or heads.
Water Jackets I agree with BMC Daniel. They are very important to your engine...the water jackets that is. They do exactly what he says: Prevent the heads from over heating.
