Well my engines are almost together. And heading to the dyno Monday. But Still cant find all my answers on the search.

Boat is older 33 Fountain Executioner
Engines are fully rebuilt approx 9.4 : 1 CR
AFR 305's with bowl blend
Victor Jnr Inlet and Holley 800's
Msd Ignition
Imco Powerflow Exhaust Manifolds and Tail pipes
And Roller Cam by Bob Madera
Will prop it rev to 5500-5800 WOT

A few Questions

Which Spark plugs in NGK ?, AFR recomend Champion #C59YC but I cant get them where I am.

What total Timing is 32 Total too much?

Carb jetting ? I have read other similar set ups and use 4 different jets, but my dyno guy has never jetted this way. Am I mad to differ from this. What is the reason for this?

Would be great to hear from thunderstruck and Wags 382 on your set ups now? plugs, timing or any jet changes.

Ive learnt the hard way before and want to get this right first time !!!

Thanks heaps Dan.

Good to hear you're working with Bob. The dyno will answer a bunch of your questions but my setup:

Plugs: I run NGK for the non-tapered heads heat range 8. I will look at a plug for the number. Don't have it with me.

Timing: 36 all in at 2500 rpm with premium gas. No issues in 4 years. I run Crane HI6M boxes with stock 500HP distributors, no problems for the 4 years I've used them.

My jets are 82 square on a holley 950 race carb (I am pretty sure). We tuned for best HP and upped the jets 2 sizes for reliability. No issues in 4 years.
I heard that if you take the same jet stagger as the carb 500HP and keep the stagger difference the same as you play with jetting you will make a little more power. Try it on the dyno, your paying for the time regardless of your engine builders preference.

I run 30" labbed Bravo 1's at 5450 rpm which is close to my max HP rpm.

I installed closed loop cooling after corrosion issues with the heads, long story do a search, due to boating in brackish/salt water. Works well.

PM me if you want to discuss live. I usually check the board every couple of days.

Sound like sweet engines. You can run the timing up like that since the comp is not that high. I am assuming you built the enignes that way so that you could run regular fuel. start at 32- 33 (total timing) on your first couple pulls. work from there. You will have your timing real close. When you get your carbs close, go back to timing, and then carbs and you will be done. Some guys do it a little different, but that is basically how you do it.

Remeber that your MSD distributors are designed to curve. You want the soft springs and the big bushings I think. Been a while since I have messed with one. You want the least amount of advance and you want it to advance bery fast so that you can get on plane easier. Adjuste your timing first then move to the cabs. Rev the engine until the dist, stops advancing. THat is how you know when you are at total timing.

Tune your engines on the dyno using 87 octane first, then see what happens if you use premium, don't do it the other way around.

In a boat, I generally pair the jets. You are not running a drag car, so you don't need them tuned that perfect. You have to many different changing conditions under the hood. Temp, humidity, heat, beer/ water in the bildge to go for that kind of spread on your jets. The reason they do it is because of the distance to each of the cylinders. If you really want to try it, you need to do it in the boat and use a temp gun. Check your EGT's after a hard run at WOT and this will tell you where the jets are fat or lean.

Tune them perfect on the dyno and then go 2-3 higher when you put them in the boat.

While I don't disagree with the first guy who posted, I have always been told by guys in the business a long time, to tune an engine like yours, (milder engine) for 87. You may say that you always fill up with 93, but unless you are draining every drop out of the tank every time you put it up for the weekend, it isn't going to be 93 for long.

Sounds like you have some nice mills there. Good luck with them.

While I don't disagree with the first guy who posted, I have always been told by guys in the business a long time, to tune an engine like yours, (milder engine) for 87. You may say that you always fill up with 93, but unless you are draining every drop out of the tank every time you put it up for the weekend, it isn't going to be 93 for long.

Interesting point regarding gas. My experience with blower motors and my current setup is that if there octane is a significant octane change over time; it is not enough to harm the motor. I have had gas sit in my tank for months over the winter and then run the boat hard with my current setup with no problems. I certainly don't agree with draining the gas to ensure that the gas stays 93 over a week or so. Maybe someone with some data or direct knowlege will chime in.

BTW I made pulls on the dyno with 89 octane at 38 timing with my motors and did OK. Since 38 is too much timing for a marine motor, I put the timing back to 36 in the boat and like I said run premium for a little insurance with no problems with9.6:1 compression. I did email a buddy who is the engineering mgr for a big refinery to ask if he had any octane vs. time data for gasoline so I will try to post some data instead of hearsay.

It's not just the octane, but the condensation in the tank, (rap accumulation etc.

And I was not suggesting at all that you drain the gas. I was saying that over the years you are going to have stuff in that tank that is not all ways going to get pulled backinto emulsion with the new gas and thus not as pure as the 93 that you just pulled out of the pump and stuffed into the stainless clean fuel tank at the dyno room.

The dyno room is a pure environment, even if you open the windows and hook your sea watr pumps up to a garden hose.

What do you mean that you made pulls at 38 and did OK?

What happened? how much did you loose, gain HP/ Torque? If you changed the timing that much and went down to 87 from 93 and NOTHING happened, then that should have told you something also.

The other factors you guys are leaving out, is what kind of engines are these?

Anyway, this guy asked for opinions, not arguments.

Every custom engine is a little different. If they were all the same, we wouldn't need the dyno to tune them, we could just read the instruction manual from Merc.

Good luck.

Are you using power valves ? 1..2 ? I would run a 6.5 primary, none in the secondary jet about 6-8 richer in the sec. just the diff for the lack of a power valve, I would try the timing at 34 total advance, I don't really like the curve in msd dist, not sure how your cam will idle, I run a mallory and keep the advance short so I have more intiall, helps the idle a lot...just start there and change things on the dyno and tune for 87, a lot of the times thats all that can be found on the water...Rob

Thanks Guys, The Engines are now 509 ci chevs gen 6's. Never had a condensation problem and drain the tank and put it in the car before each season for insurance and refill. The Boat will only be run on premium 95 not sure what our regular here is. Still confused what to run on the dyno but will definately fatten it up for insurance. The exhaust for the dyno run will be an old custom unit from an old boat alittle more restrictive than mine. Has anyone done a single pull at the end with marine manifolds with the jacketing filled with water not flowing through them (dyno cant have any water coming out exhaust). last thing I want to do is crack an alluminium manifold or ruin the new paint ha ha. Also initial timing ? Thanks for all your info.

DYNO DAY, Ran the engines in on the Dyno and only had time to a Basic tune on them.
Ran them Fully assembled as in the boat with sea water pump and heat exchangers. Couldn't use my Exhaust so I used an old set (a little more restrictive). Peak Hp was right where I asked for it 5800 and 577hp. Dyno is the lastest model and apparently is the most savage around town (giving the lowest numbers). Cant remember the torque but from memory was much higher in rev range where we wanted it about 4700rpm. I wish I had a bigger carb than the 800's to try on the dyno but the budgets gotta stop somewhere, for the time been anyway.

Back in the boat engines idle great at 700rpm no reversion. Plan was to keep the same props and rev them more for the speed. Boat used to run WOT at 5000-5200, now swings out to 5700-5800rpm. Picked up a solid 10mph on the speedo !!!Will do some runs with a gps soon.

Thanks Rm Builder !!!!!