Its at least 25 HP per 1 increase in ratio - SO 8.0 to 1 to 10.0 to 1 is 50+ HP.

Higher compression lets you take advantage of bigger cams thus more HP.

Part thrott;e in the lower rpm ranges (vs full throttle) reduces cylinder pressure (real time compression) in those critical rpms.

So yes, this part is driver controlled.

So like in a gas tow rig engine, when in high vacuum you have lots of ignition lead, but at low vacuum, timing is pulled out. Remember back in the old days, we had something called "vacuum advance".

MT the old 598 i check at the end of each season was low 180's. There was not a sign of detonation. The new engine the builder is very comfortable with the compression as long as the engine temp and timing stay where he suggested.

Did your engine builder determine why the exhaust valve broke? In post 23 it looks like the sister chamber had some fun in the past as well. Dry to the tip exhaust so reversion shouldn't be a problem .

After a lot of discussion. It was just a part failure ss valve. We believe the the other cylinder was debris from the valve. Hard to tell but we think there was no piston contact before the failure. No bent push rods or lifter damage or rod damage.

When it broke we were cruising. About 3400 I let off the throttle to turn and go back to talk to a friend we had just passed. I new something was wrong sounded like a bad miss. I was thinking something happened the the ignition box or distributor.

Were the valves Inconel or just normal SS valves? I tried running normal valves once.... I regretted it...... Inconel only now

Old were stainless per the numbers I can find on them.

Just thinking about my earlier post it sounded like a miss. One of the first things on the dyno he was having trouble setting the timing and all of a sudden the engine just shut off. Long story short answer he had to change the pickup in the distributor it would short out and fire without movement. Of the shaft. The dyno operator and owner had never seen this before.

One way to check to see if its Inconel start at the valve head with magnet half way up the stem the magnet will stick.

I am definitely not an expert at failure analysis. But, looking at the pictures you posted, I noticed the area between the cylinders on the head. With the head bolted on, gasket in place, I cannot see how physically, the broken material from the valve, causing the area between the cylinder, to get damaged like it is. To me, it almost looks like that area got torched between the cylinders, probably led to the misfire you felt, introduced some water from the head gasket being melted, and thermal shocked the valve causing it to let go? Some of the fire ring/aluminum sent to the adjacent cylinder, causing the hammering marks to the quench pad?

Just throwing that out there. Its always easy to say a part failed, but I try to look deeper, so it doesnt happen again. Maybe some of the more experianced builders will weigh in on that.

That sounds very logical to me......

exactly..... I have gotten Inconel very hot and it didn't break, no idea how it didn't, Gellner told me he has yet to see one fail, not that it can't happen, just never seen it in all the years of building, mine had to be INSANE hot to do this.... but didn't break..

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I saw that material missing between the chambers which is confusing as ever.....

The heads that I've seen get torched normally have smoothed rounded edges (generic pic posted from google search), whereas this looks like it chunked out with the square/sharp corners.

Was the head stuck on the head studs and used a pry bar to remove? Pry bar marks? Looks like a lot of corrosion in the bolt holes.

Could very well be what happened

A couple of local engine builders thought it lifted the head. The gasket had the exact same impression but was not burnt out.
The head came off easily.

It looks to me in the pictures that there is carbon in the markings in the quench pad. I don't think that's from the valve in the other cylinder. Does anyone notice all the speckling to the quench pads on the other cylinders? Mayor do you have any pictures of the old piston tops or spark plugs? Did anyone happen to measure the ring lands on the old Pistons to see if the rings were shaking?

I have all of the old parts.

If you get a chance post a pic of the piston that was next to bad cylinder.

Picture of that head gasket?

Not sure they labeled them. There in a box I have not really looked at them. The builder even returned the bearings.

Think this engine has more than one blow up by looking at other pistons. Glad your back up and running though.

Not sure how you came to that conclusion. I have ran the boat for three seasons which is mid May to early October here depending on weather. With out any problems. I would do a leak down test and compression test at the end of every season always had similar numbers as when I bought it.
It's new now hope it last at least 3 seasons or more.

me three my friend .. its a boat they just break .. often . best of luck

Finally took it out for test run today. Runs great didn't really push it. I think a high torque starter may be required now.

Video link initial start on a hose.

http://i927.photobucket.com/albums/a...D_00000127.mp4
.

Very Nice !!!

sounded great .. very crisp . best of luck

hows she running my fiend

Rob as you know it died a violent death September 2015 after the first rebuild. Took it back to the builder he found a stuck lifter it only had 12 hours he stood behind his work and rebuilt it again.
It is running fine was actually out today I think its getting close to 30 hours for the year. New rebuilt outdrive this year also so hopefully good for awhile.

great news .. 12 hrs . dam these boats . sometimes I wonder if there worth the headacke !!

I thought this was an interesting thread from almost 10 years ago concerning 598cid engines and combos--- especially with Haxby's AFR 305cc as cast heads on a 598cid engine experiment.