7A-FE Compression Ratio, Looking at changing the CR of my 7afe when I rebuild. Options

[PaukST]

Hey all, I'm trying to decide what to do with my 7AFE (have to take it apart due to a rod knock anyway). I've kicked around a few ideas (or maybe a lot ), and I'm currently researching what an increase in compression ratio might do. Does anyone have any info on this? I'm unsure of the potential difference in performance, and I can't seem to find any hard data on what pistons (4age, smallport 4age, 4agze) result in what CR. I've been trying to make sense of these tools and formulas - http://www.csgnetwork.com/compcalc.html http://s-86.com/s-cr.html and http://s-86.com/s-cr-chart.html - but I'm having a hard time digging out the relevant numbers. Doing the math myself or using the calculator I come up with significantly different numbers than their little handy chart, so I don't know what to think. Is this a futile exercise? Will I even be able to notice a performance difference over the stock 9.5:1 without having to use higher octane?

[mandrek]

CAN you? yes. its is worth it? NO... sure you can get 4age/fe ARP rod bolts/studs.. but to get it to work on the stock 7a rods you would have to have the rods machined and then re tapped/cut to be able to take the new ARP hardware.. the problem is that the 7a rod is a configuration were the bolt goes through the cap, and into the rod.. the 4age (not sure about the 4afe but pretty sure ARP had no support for that motor) rods use a pass through type configuration. IIRC the 4age rods have bolts that come from the top (wrist pin side) through the bottom of the rod twords the cap. and then secured with the nuts. the top of the "bolt" is square and locked into place with the shape of the rod.. so by the time you do what you need to make the ARP hardware work, you are better off just getting the belfab rods.

link to nice write up on difrences, and lots of pix on page.

This post has been edited by mandrek: May 4, 2012 - 12:38 PM