I've been away from tearing into motors for awhile....289 which i'm updating to AFR 165's....Cam is unknown but with a dial indicator i'm coming up with about .475-480 on cam lift...Are these pistons killing compression?....What's a stock 289 {'66} chamber size compared to the AFR'S?
Are you going to take them out? The notches on the side make it a little tougher to CC, but it is easy enough to do yourself. If I had to guess, they look like a Keith Black 281 - which has a 6.5 cc reduction in compression which is not a really bad killer. In a stock engine that would give about a 9:1 ratio with a 60cc head But this is just my guess - the only real way to tell is to CC it yourself ........ Picture of KB281 Do you have the stock heads? What are the casting numbers and we can look up the chamber volume. .
No i wasn't gonna take them out....Motor is fresh...The heads are '65 non hi-po's...The AFR's have a 58 cc chamber
Don't know....I guess what i was wondering is did 289's have flat tops and if so do these notches lower compression.....In other words for example if a stock 289 had 10:1 compression with flat tops and if someone rebuilt this engine with these notched pistons did that lower the cr and will putting the AFR's on lower it more
According to my chart, all 65 289 heads, hipo and regular, had a 54.5cc chamber. While you will lose a bit of compression with the 58cc AFR - the flow will be so much better than the stock heads. I'd go with the AFR. Here is a great read (with pictures ) on the 65 pistons and heads. http://www.fordsmallblock.com/PDF/Pistons.pdf
Oh, and I need to add - don't forget the stock cam has been changed. Depending on what that cam is doing those bigger valve reliefs might have beeen needed to avoid a piston - valve collision. The science of engine building is cool ..........
