An intresting thaught re Compression - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

Walkinshaw · 11-11-2003, 18:44

Well, thinking about this today made me thaught. The AU series of 6cyls used diffrent rods and pistons to try and improve the stroke/rod ratio to get the engine to rev cleaner and higher. To do this the rods were slightly longer and the piston height was changed or the pin was moved further up the skirt. Well this brings to mind two sujestions.

Use AU rods and EF pistions to achive super high CR. This would be dictated by the increased length of the rods and if the extra height pushed the piston above deck height. If not this would make for a nice high CR N/A race motor. Say 12.5:1 compression

The other school of thaught may also hold. Use EA/L rods and Au pistions. This should see the piston sitting further down the bore at TDC, thus reducing the CR. Perfect for big boost turbo applications.

If the demensions work out, (read: the pistond dont hit the head/valves or the CR gets way to low), it would make a good alternative to using custom forgies in wild applications.

just a thaught........

Daniel

gm dstroya · 11-11-2003, 20:48

yes all very true,

but in boost aplications you dont want to run the standard piston in any application past 15 psi.

as far as i know, acl dont make a race series piston yet for the au (could be wrong now, as i checked 8 months ago).

you actually dont really need to drop compression on a ea motor to run 20-25 psi. 8.8 is already low enuf. the later model cars (ed newer) to drop compression grab a set of acl race series ea pistons, 20 thou over size and have ur bottom end honed out 3 thou to accept the pistons, the acl race ea piston has a 11.8cc dish, the acl race ed and newer has a 5.8cc dish.

the au rod is 6.05 inches long the pre au is 5.88 inches long, check the pin heights and dech heights if ur thinking of running au rods in an older car.

cheers.joe.