Engine Clearance Question.
 

In doing research here on OSO lots of threads. No mention of any consideration for closed cooling system or open.
Question is do you take open/closed cooling into account when rebuilding? Are the clearances the same for both?

There are a lot of variables that go into it. Piston to wall and ring gap will change especially on the front cylinders. But there are a lot of things that need to be considered. Piston and ring manufacturers can be a big help when it comes to these kinds of questions.

Call mercury marine, volvo penta, indmar, General motors marine powertrain, etc . Ask them if they size their rings, or spec piston to wall clearances according to the cylinders location in the block, or if they change the spec's depending on whether raw water, or closed cooling is going to be the setup.

Why would clearance needs change? Raw water cooler and closed cooling operating temps will be close if not the same if setup properly. What are we missing?

closed cooling generally runs hotter, the thought that salt cystalizes @ 150 deg or so is why most raw water cooled boats had 140 stats, closed 160-180 depending on brand, year etc. But I do not see a need for anything different in a 20-30 deg swing...

When buying my pistons from Carillo, they wanted to know about how we planned on cooling the engine before recommending a piston to wall clearance.

I agree. We aren't talking about an automobile engine, that must operate from -40 degrees, to 220+ degree coolant temps, having a 250+ swing in metal temperatures. The average marine engine, especially our kind of boats, ever see that kind of temp change.

1997 and up all raw water cooled OEM marine engines have 160 degree t-stat installed. One or 2 blue engine packages did not use 160 degree t stat.. All black production mercruisers since 1997 use 160 degree t-stat for raw water cooled engines and so does Volvo penta and Indmar and PCM. Some closed cooling marine apps use 170 degree t-stats.

For what its worth. My piston to wall, and ring gap, were set to what JE recommends for a marine supercharged engine. I am running JE blower, pistons, and speed pro file fit rings. I did not clearance cylinders differently. These engines do not have thermostats, or circulating pumps. My engine water temp gauges, never go above 100 degrees. I change my oil around 15 hours of use. in those 15 hours, I do not add ANY oil to them. Last year, I ran over 400 miles by water, most of it beating on them pretty hard, and did not have to add a drop of oil. These engines make right at 800HP, and currently have 4 seasons on them since last rebuild.

Nothing fancy here. No magic. However, the machine shop we use, has top of the line equipment, like a Rottler cnc full machining center, etc. I think the best bet, is always to follow the piston/ring manufacters advice, and use a machine shop, that delivers a quality product. Nothing is gonna cure a poor RA finish, poor boring/honing procedure, old worn out equipment, etc.

1996 and 1997 raw water / standard cooling - example - 2 bbl CARB V-6 Mercruiser the number one selling I/O app in the USA at that timeframe. click on link and scroll down to part number # 5 and Yes carb apps using 160 degree t stat for almost 20 years now nothing new you can check all carb apps for 1997 and they will have 160 degree t stat. only one or 2 blue motors did not

http://www.marineengine.com/parts/me...cooling-system