I am taking my 454 to be dynoed tomorrow. It is getting hooked up but will not be run til monday. Its a 454 with a 525sc induction setup. My questions are how much should my setup be changed from the dyno to the boat for jetting? What should my all in timing be limited to? What should be my target air to fuel ratio.

468CI
2399 pistons
HP 500 heads completely rebuilt
17046 Fel Pro head gaskets
Crane 134561 cam
177 Blower 2:1 drive
1050 Dominator carb

It will be run on the dyno with no accessories and longtube headers. I will also be running 91 non ethanol all the time.

Make sure you do a peak TQ pull and keep it there for like 20 seconds or better and shut dyno off and pull plugs that is where you will make sure a meltdown is safe, mine showed mid 12 A/F and at 4400 shut off the plugs looked like new, we jetted up from 87/93 to 93/95 in carbs, picked up 9ftlbs tq and only lost .2 hp, plugs looked WAY better then... my final A/f average 12.2 across the board...

From what I always been told is boats like fuel, safe tune will make sure it lives... got for TUNE not a NUMBER!!

good luck bud!!

On a setup like that, I wouldn't focus on a particular air fuel ratio number.

I would do some pulls, make note of the power for each pull. The engine will tell you if it likes the fuel, or doesnt. Some guys go chasing a textbook air fuel ratio, and don't bother to see what the engine likes. I've seen engines make their best power with air fuel ratio's in the low to mid 11's. Leaning it out from there gained nothing as far as HP, and lost torque. Same goes for timing. Give the engine what it likes, no more, no less . Spark plugs will tell you something as well. The entire purpose to dyno an engine, is to tune the engine to what it needs and responds to, not what the internet or someones opinion says it needs. If that was the case, why bother dyno'ing, we have air fuel meters and timing lights these days.

Good luck, keep us posted on the results.

I'm assuming your probably using dyno headers. I had very similar on the dyno years ago with dyno headers and no accessories and coincindently onky ended up changing very little. Ended up jetting down slightly but not much. Like a size or two on 3 jets. If I recall that ended up with Holley hp 1000.

What time will you be there? I plan on heading out there myself. Probably get there around 930 I guess. Steve does a decent amount of marine engines so I'd hope he can provide you some info. Pretty sure he's got one of Alex's engines on the dyno now.

You can get your timing very close by doing a full pull and plug chop. Look at the ground electrode for burn back. You want it about 3/4 of the way back before the 90 degree bend. This is your true timing burn. For jetting the main.. Look at the porcelain , top by the electrode is you bottom end. 1/2 down is your midrange and all the way down is your top end.. I would bring a magnifying glass and a few sets of plugs..

Good call on bringing a few sets of plugs.

Any updates

I've been hogging all the dyno time. I finally wrapped things up. You might be up next.