What is your CR and boost if u dont mind sharing. Seems like u mentioned it before but don't remember off hand. I'm facing this same ordeal but will probably run a year NA. I'd really like to stay under 8.5 so I can throw some boost at them to make it worthy.

I figured it to 8.5:1
7.5psi @wot
Dart 345 Iron heads.

EGTs drop 100* with more fuel.
Knock 'noise' goes from 75 to 30 which is low. (at wot)

Do we know the cc of the 1075 head?

Are you intercooled, and what blowers?

Here you go The piston has CH 1.381 witch puts it in the hole .096 on a 10.2 deck block. VP is .064 deep with a caliper. I never measured a 1075 to see if the deck is exactly 10.2 and I don't know the CC of the head. You owe me some beers :drink:

Thank you so much!!! What does VP stand for....?

Valve pocket depth is 1/16 of a inch almost nothing.

Pull some boost out and try mid 11s again might save you some fuel and ware and tare and still make the same power. Low 10s the 900s I did would start to misfire on dyno.

10-71 ...non intercooled.

Interesting, the boat did go a little slower at the lower AFR .
How did you know it was misfiring?

I remember in the early days of engine masters they commented about how all the engines were run quite lean and knocking pretty badly. They didn't like it and I don't know if they made rules different.

Rob I hope you don't mind me inquiring opinions etc with my particular builds but thought since it was similar to what I was doing that I'd get some info for myself and others facing the same. So in a nutshell given proper size Blower per CI engine that 8.5 + or - is a good target to run 6 to 8 pds of boost. On a 548-565 without intercooler what would size blower would be recommended. 10-71, 12-71. 14-71 on a 598.

Back to the intercooler from what I understand it takes another 1 to 1 1/2 pds of boost to achieve same hp vs non intercooled engine due the restriction however resulting in a more dense charge being more efficient and help preventing detonation. But in a way would it be safe to say you have the work the blower harder to maintain same amount of boost when comparing apples to apples. Two identacle builds/blowers. One without intercooler and one with. If properly sized blower is fitted to said CI how important is an intercooler if your cruising under 3,000 rpm 80 percent of the time and WOT throttle runs for only a few minutes or so. If used for this type of driving characteristics how important is the intercooler unless you were looking to optimize your hp and running WOT from port to port. Just trying to get it clear what would be recommended for this type of application. I've been out of the blower seen for a while now and when I was intercoolers were just coming into the picture.

I basically looked at them as a way to spin a somewhat undersized blower for more boost without all the accessive harmful heat. Like the 525 SC days.

Rob, you read this yet? Good information,
http://www.offshoreonly.com/forums/g...ch-thread.html

They certainly aren't mandatory in this application, intercoolers that is. You can make great power, and still be reliable without them. 10-71 works good on a 548-565ci. I simply think they give you a small increase in power from the cooler air charge, a little more consistant power on those hot days, and a little safety factor from detonation. The downside, is the cost to purchase them, extra plumbing to install them, the added height to the engines making a possible clearance issue, and the risk of them leaking and filling the engine with water.

Icdedppl's setup, runs pretty cool imo for not having intercoolers. as i stated, the intake temps stay around 135* at wot. Thats a 1071 setup, on a 548. He also has a well ventilated engine hatch, with a good fresh air supply. I'm sure his setup is running cooler than say, a guy who has a 250 blower on a 502, thats at 80% overdrive, no intercooler , with a factory sunpad. What that setup runs for intake temps, I couldn't say. I would think the intercooler would show more of a reduction in temperature on a setup like that. The cores are only so efficient. When your are moving say , 80* water thru them, and 135* air, maybe it will get the air down to 120*. With a setup that has 80* water thru it, but 200* air, maybe it will get it down to 120, maybe not. I don't know..

I don't mind at all, great conversation!!!

Found this last night!! I definitely think i am leaning towards running a thicker mls head gasket to drop my cr. Especially since it would appear that Merc is routinely doing this with there boosted motors.

When I first bought my Apache and tore down the engines, it had JE plat-top pistons and it was zero-decked with a .060 copper head gasket and Grumpy Heads. They also set up the carbs very rich. The dyno sheets I had with 5PSI boost was 800hp.

You are correct. The higher the delta between the IAT and the water temp, the larger the temp drop across the IC will be. although the outlet temp will always still be higher in a higher inlet temp application.

The biggest improvement will be seen on combos where you are really spinning the blower hard.