I made a couple of changes to my combination last week, but haven't had a chance to take it out and run it yet, so I thought I would ask the "experts" how much of a difference it should make.
The combo is 350 Chevy, standard bore and crank, stock 882 Chevy heads 1.94 intake and 1.60 exhaust valves, nominal 72 cc chambers (if I remember correctly), dished pistons with 4 valve reliefs, Edelbrock preformer RPM, with 750 Edelbrock carb (stock jetting), Osco cast iron riser style manifolds with thru drive exhaust. Boat is Tahiti 18ST, with OMC 800 out drive running 14 1/2 X 21+ SS tri blade prop.
Previous best run was near zero fuel, no wind, almost glass water, and just me in the boat. Turned up to just over 5000 rpm with considerable nose up trim to get there then minor trim down to stay stable. Had to run thru some moderate Chine walk, then it settled in flat.
Here are the changes
1. replaced Felpro .035 crush comp gaskets with the thin steel shim gaskets.
2. replaced thru drive exhaust with 3" exhaust off of the Osco's risers. At least now it sounds like a performance boat instead of a bayliner.....
3. replaced the incorrect Autolite 685 plugs (360 Chrysler plugs) with the correct Autolite 26 Chevy plugs. Yes I put the wrong plugs in, broke a plug and just grabbed a set from the parts bin. Never realized Chrylser and Chevy used the same thread and depth. Much colder plugs though.
If I remember right the shim gaskets should give me about a quarter to half point of compression over the comp gaskets.
Thoughts??