Yea... I'm close on compression... I think pistons are in the hole .020 but not sure ... Heads were new.. Never milled

If your going to pull the engines to fix oil leaks and paint and make a cam change then you may as well pull one head off while your at it to confirm exactly what you do have.

If I decide to do cams I will be doing that, but I may just fix the leaks, not sure depends how $$ looks, have interior work to do too...

Will do...

Just my opinion I don't think I would waste my time and money to make a small cam change like that as the results would probably be disappointing. You MIGHT see 1-2mph if lucky. I would wait till I had the cash to do it right, up the compression and go roller.
Something else you may want to check out is those Holley Strip Dominator single planes aren't the best single plane around. They have a recommended operating range of 4500-8500 rpm's. You said you wanted to keep it under 5400 rpm's so you would be better off with a dual plane. It would give you more power in the operating range you'll be running in. I've seen test where the RPM Air Gaps made better power than the Victor single planes up to 5800rpm's. Just a FYI.

I hear ya, one thing is I want to do what most guys cant, that is maximize what they have already, when I built these engines years ago I was not BBC smart at all, got the heads and intakes in a huge pile of parts I boiught, personally I think the boat runs well even with what I have since a 400 cyclone mistress usually runs 60-62...so to me I think the parts I have are not bad and I am making around 500 hp, if I switch to different heads and dual planes (whick I considered before) I think that cost is WAY more and even then breaking 550 hp is not likely unless I spin em high, add lots of compression and all that, simple things is what I like to do, pulling engines and all that stuff is no big deal to me, keeps bilge clean anyway... hate it looking dingy...lol

I want the boat to run 67-68 tops, since it is gonna take lots more hp to hit 70 in a Mistress, I am ok with that, I am not looking to go super fast, I have friends boats to do that in... but I want the most of what I do have...

I know you are on a tight budget, and I can relate to that for sure. But if theres a way you can do it, Id seriously consider a package like this. Realistically, by the time you bought the flat tappet you were looking at, new lifters, etc, maybe you're out an additional 500 bucks or so, but you'll have a roller setup. IMO, your estimates of 10-20HP by going to a roller grind, are a bit conservative. I'd think its more along the lines of 20-30HP with all else being equal. BUT, you cant compare a flat tappet to roller based on its spec on paper. What Im saying is, a roller spec for spec will pull more vacuum, idle better, and pull better in its range compared to the same spec'd flat tappet. It has nothing to do with friction, its all about the lobe intensity or lobe profile so to speak. A roller can open and close the valves so much quicker than what a flat tappet is limited to. I remember a while back, ''GRIFF'' on here switched from the stock 420 cam, to the crane 731 cam. He picked up about 100-150RPM. Which translates to 1-2mph or so, prob 25hp'ish. BUT, that cam is very close spec wise to the 420 cam. Im sure going slightly hotter than the 731, woulda netted a little more power, maybe even 150-250rpm. If you can pick up 250RPM by just changing to a different flat tappet in the rpm range your limited to, with no other changes, I'd be really surprised.

http://www.competitionracingsupply.c...cl_120405.html

What I'd shoot for, esp since I've owned a few of these heavy slug hulls, is to make enough power not to go fast on top end, but enough to turn a Better wheel that will give me a better cruise speed. The biggest problem when I had my 60-70mph wave crushers, was when everyone else was cruising at 55-60, I was taxing my engines trying to keep up. Hence why I got away from the 3 blade props, even though I knew I might be giving up a mph or two on top.

Not sure if you had a chance to try a set yet, but on my old TRS boats, they loved the Mercury Revolution 4 blades. They planed better, much better rough water control via trim, better cruising, and gave nothing up to the 3 blade mirage plus' up top.

It really depends on what I do to boat otherwise, my engines run fine in reality, but I cracked a pan on one and didnt see till after boat was together, so I have to pull it, and may as well repaint them both since pulling them takes juts a few hours... I have interior work and some odds and ends to do, if I do cams it will be last minute decision..

I may go roller still if money is there, I will be talking to Dean to see thoughts, if a flat really is waste of time, I will either do roller or wait...

propwise, the boat LOVES the 24P quicksilvers I have, cruises 48-50 mph @3700 and WOT 65 @5000

like I said, I think the boat runs good for the power it has, its a tank... so its not a huge deal if I wait another season...trying to get input and ideas...

When I purchased my Baja, the p.o. Had installed a marine crate engine. It came with a Dyno sheet that indicated 466 hp. Mark 4 block just like yours. Merlin heads, grumpy Jenkins edition. Dart int.,800 Holley. 468 ci. Best I ever got was 61 on gps. Bravo 1 very deep. I think about 8". Shortly after purchase, went to knocking. Long story short, I got Speed and Custom Marine to do the rebuild (Scott Mander). We left everything basically the way it was except converted over to Hydraulic roller. After the build, the boat now runs 70.8. Point I am trying to make is Mild Thunder is correct about the amount of gain just by going to a roller set up. If I were you, that would for sure be in my plans.

I know to push the Mistress to 65 they have to be at least 480-500 hp now....I dont expect to gain nearly as much as you did just by going roller, to gain 9 mph that old cam must have been very weak compared to roller cam...