Power wise the difference from 33 to 35 was like 7HP. But, the EGT's came down with the extra 2 degrees.

I can care less about the 7hp, obviously that means nothing in a boat. I guess my main concern is the overall tune, and keeping it together.

So, too little timing and possibly tuliping valves if the EGT's are too hot, and too much timing you're putting holes in pistons if it detonates.

I remember a few years back, a well known marine builder had told me "Nobody can tell you what timing your engine needs over the internet or the phone. Every engine is different, thousand variables, and the engine will tell you what it likes, thats where the dyno can be helpful".

I'm still learning some of this stuff, but from what i've seen, some of these are variables

Static compression
Boost psi
Cam profile
Quench area
Octane of fuel
piston design
Stroke/bore size
Intercooled or not

So, lets say you have two engines, both have blowers, no chillers, and lets say both run 6psi of boost.

Engine #1
11.5afr
8.5:1 Static
140* water temps
Iron Heads, unpolished chambers
.070 quench
Overdriven small blower (hotter Charge)

Engine #2
11.5AFR
8.5:1
100* water temps
Alum heads with polished chambers
.040 quench
Underdriven Large Blower(cooler charge)

My guess would be engine #1, would not be tolerate as much timing advance as Engine #2. So, while the guy who owns engine #1, would tell people he only runs 30* total timing, and everyone agrees thats a safe setup, based on that "31" number. Where the guy running engine #2, tells people he runs 34* or 35* total, and everyone agress that it is not safe, and will detonate. However, the 32* engine with the higher water temps, iron heads, wide quench, and overdriven blower would probably go into detonation mode before engine #2. This is just my thoughts, so please correct me if Im wrong on any of this.

I agree with you guys on the AFR numbers. The added fuel under boost slows down the burn. Plus I would imagine the added fuel helps cool the intake temps a bit?

My engines used to have 177 blowers, 217% overdriven at 5psi, 35* timing, ran for a long time like that, same heads, same comp ratio, same cam. Not one tuliped valve, pistons all looked brand new after a couple hundred hours. Now im running 1 more psi of boost, but turning the blower waaaaayyy slower, much better fuel distribution (dual carbs instead of a single).

BTW, not trying to debate you guys on timing, just like to hear some more thoughts. I don't like holes in pistons nor do i like tuliped exhaust valves!

I never tuliped a valve at 30* timing. I did melt a piston at 34-35* timing. The timing was set at 30* all in but the balancer had slipped 4-5* and I didn't catch it. This was a forged piston engine. The one running next to it taking the same thrashing but had the correct timing was perfect and btw had hyper pistons. I really think the bottom line is how close to the edge you are getting with your dynamic comp and cranking pressures. I run real close to the edge and need more margin. What is you dynamic compession, cranking pressure and boosted effective compression with the new mills? Also in my way of thinking .040" quench is a given in any hp marine app. I dropped exhaust valves in both my engines when I first got this boat due in large part to .065-.070 quench areas. That's NFG in a boat engine.

joe,very good explanation,in my experiances,i have found that a 4 in stroke bbc,with aluminum heads,a tight quench area,and a camshaft with 240 to 260 @.050 always likes 33 to 35 deg of timing,30 deg will make really hot egt,s,.i agree ,a car with a radiater that runs at 160 deg or more water temp,might have problems with 35 deg of timing,but a marine engine,running 125 deg water temp,lives much longer at 35 than the same eng at 30 deg,but what do i know,i have only been doing this for 35 years.btw,i run my blown 540s imn my cat at 35,and the 588s for the fountain liked 34 on the dyno,we tried lower timing,and the engine let us know it needed timing.i,like you won,t get into a pizzin contest about how much timing to run,but i do know what works,just saying,to each their own.

ofcourse i am talking about a properly built supercharged engine with inbetween 8 and 9 to1compression and a blower that is properly sized for the engine.i cant tell you about timing requirement on a 454 with 10 to 1,iorn heads,a blower to small for the application,and a cam that allow,s high cyl pressure,above 160 cranking compression,and a single carb setup,i just wont get involved with a setup like that,it is destin to fail,and probibally soon.

Don't worry about getting in a pizzing match with me. I just like to hear what others are doing and to share what I have experienced. I find that typically the best advice is a compilation of many views, then tailored to individual situations.

Joe-
Nice work on the engines!

Thanks mike !

Figured I'd update some of you. Engines have been running great. Been playing with props, got 88mph so far. Turning a 17x28 4 blade prop at 5600. Boost is 6lbs wot. AFR is like 10.5 at wot, so may pull a couple jet sizes. But overall a fun project. Not blistering speeds, but the hull is a 1990, non stepped, running thru SSM drives. If I had bravo's i'd probably be in the 90's. But I love the SSM drives.

again,,thanx for the phone call..