7a-ge

[Kwanza]

Originally Posted by Flashmn

Have you tested it? Because the 4A-GE pistons have cuts in them for the valves, as the valves are at a larger angle, thats the problem and thats why they would hit.

Yes I have. The 7AFE pistons on a stock 4AGE head do not touch because the 7AFE pistons are slightly dished all the way around. They do have minor flycuts for valve clearences for the 7AFE, but that is because the 7AFE runs a smaller combustion chamber at a tighter angle. The 4AG valves, even though at different angles, still do not hit the pistons because of the differences in the combustion chambers and the dished design of the pistons. It's not a matter of flycuts or angles... it's just the design of the pistons. FYI, the 7AFE bottom-end and pistons only yeild around 8:0 compression when mated to a 4AGE head.

On another note, 4AGZE pistons have been proven to clear the 7AFE's valves in a different build (4AGZE pistons in a 7AFE). That set-up made compression in the 10 range. 4AGZE pistons have been shown to clear 4AG 20V heads without flycuts, and my personal testing showed the 7AFE pistons can even clear a 4AG 20V head. I personally am still considering building a 7AGE 20V for track... I've done all of the tests... it's a matter of whether or not I want to build up the 7A bottom-end. Regardless... anytime someone choose to build a 7AGE... you GOTTA use matching 4AGE pistons. It's reccomended that smallport high-comp pistons are the prime choice in a 16V build up, making compression in the 11 range with the 7A stroke, but any 20mm 4AG piston will work (5 valve pistons for 20V of course). You cannot use the 7AFE pistons because they simply do not make enough compression...