How short can a downpipe be?

[gustavm]

Im getting a 3 inch dp done tommorow and Im wondering what the minimum length can be and still be effective . I was thinking only to the junction just behind the of the engine then back to standard exhaust which in my case is a resinator and 2 1/4 inch pipe through to a glasspack standard rear muffler with twin megaphone type tail pipes. Obviously later with funds availiable more 3 inch pipe could be added .BTW Battery is under the air intake pipe so a nice initial curve is not a problem

[dmgb5]

Umm...? Whats your objective here...i.e. what do you hope to gain from a 3" downpipe? What are your plans for the rest of the exhaust?

[gustavm]

To safely support about 12-14 lbs boost and increase spool up time . No big turbo or high horse power stuff . Id like to leave the rest fairly standard to keep that old fishing boat sound ! The guys are working on it at the moment and have decided to only go to the end of the engine block just after the hanger in 3 inch .Will give you all a report once Ive driven it.

[dmgb5]

Even just getting rid of the cast iron elbow would help with spool. So building it to the CAT/heat shield is plenty for what your after. Is the battery staying put or are you moving it for your downpipe?

[gustavm]

Battery is on the air intake side so no problem there.

[gustavm]

New DP . Seems to have done the trick . Pulls well from 1500 revs in 5th now.