Answers for 3 posters, thank you.
Dave, 362cid & Bushracing67 (THANK YOU!!!)
Cam part number 35-000-5, AC Nutter chose this cam for me as he did the clay smith cam, and that Smith cam was a total rocket out of the corners and all down the straight, on the Dyno the Comp cam was about 20 more HP and TQ, I’ll post clay smith dyno data soon. I gave his name because he really knows this subject with respect to Hydroplanes, but now both cams are not doing it. Cam timing? We have checked over and over on that.
I only ran one engine all last year, 9 races totaling about 15 minutes wide open each weekend, that’s about it (4 heats each). The bearings were “like new” according to builder and that engine is in the boat now with an lower end having 2 seasons on it and a valve job after last year pounding on the seats terribly. Yes it sounds like its too tight somewhere, but it’s the same builder as when it went fast. Can it be tight and no wear showing? Boats need a bit more bearing clearances, he knows that but I don’t know what mine are. Should I call my builder and ask him? I thought that about the cam myself last year, we put back in the old Clay Smith cam (That cam had awesome acceleration) last year for 2 races, it had a total of .555 lift after lash, it was also dead, no acceleration at all. My apologies for not having that on the list, I thought it was. I even hogged out the shaft and mid strut bushings to a point where the inspectors told me to replace my bearings or I’ll pound them out. I said no, they are fine and if they pound out I’ll replace them as its not a safety issue at all, boats don’t go fast with a tight bushing around the shaft even though I had it that way first.
Cid I’ll think very hard about your note, really.
Bush, I have backed the timing all the way to 25, including 26 and 28. Looking at your plugs Bush you have the older heads that use the shorter spark plug reach? the heads I have need .908 reach, I’ve been using AR474, 473 a few times and B8EFS stock 1049 for a few times. NGK doesn’t have a race plug for this size, that’s why the B8EFS. Water is forced through the engine from the Lake/river, through a tube at the bottom of the rudder, cold. Not like a car at all. Most go IN at the water pump location and out at the heads, I just changed mine to go in at the Thermostat area and out the WP location. Both work fine for me, prefer the heads cooler and block warmer really. Water goes out between 180 and 185, I measure if just outside the block in a manifold I had made. water pressure is 30. I restrict it going in, (.185 hole) and out is at .200 or .215 .
I should probably only focus on what is wrong at this time, Valves are Pounding Hard on the seats, and signs of heat are in the intake ports , from valve bounce? Probably. Have a little detonation so I”ll go back to 27-28 timing or lower.
Question, can Valve bounce occur all the way down to 3000 RPM even with good springs?? I have ferrea hollow valves, and the cast iron seats in the head. (is this not a good combo?) When the boat was fast I only had Titanium valves, it never has accelerated at all with these Ferrea valves, not picking on them but I have to look at whats wrong. My head guy gave me an extra set of springs, said they are different because that’s all that comp cams had at that time, WTF??? I still can’t believe that.
Valve bounce is obviously a problem, Maybe if I fix that I’m fast again?
Comp cam
5000 rpm 493 tq 469 hp
5500 rpm 495 tq 519 hp
6000 rpm 474 tq 542 hp
6500 rpm 465 tq 575 hp
7000 rpm 437 tq 582 hp
7500 rpm 400 tq 571 hp
Older clay smith cam
5000 rpm 487 tq 463 hp
5500 rpm 485 tq 508 hp
6000 rpm 468 tq 534 hp
6500 rpm 447 tq 553 hp
7000 rpm 423 tq 564 hp
7500 rpm 386 tq 538 hp