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Head cooling on cylinder #5 - solutions?


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  I assume you did try to source the LD pump in Australia, I saw a thread and you mentioned you got it from Japan (?)

My thoughts on the Summary:   - The path of coolant through the L engines results in the rear of the head receiving the hottest coolant having stagnated water flow, insufficient for the he

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Before I start making swiss cheese out of my P90, I'd like to know where the water passages are above 3&4, and whether one fitting is needed above each, or one fitting for both (centered between 3&4)???

 

 

I've noticed this as well: looks like -8 minimum, maybe even -10 was used on the Electromotive car.

 

Originally, my plan was to use 1/4 NPT to -6 fittings, but I am considering going with 3/8 NPT to -8. I just need to resolve the issue with 3&4.

 

Thanks..

 

I tapped 1/4 npt above #4.

 

post-3218-021398400 1305567314_thumb.jpg

post-3218-023252500 1305567392_thumb.jpg

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Very nice...

 

Are you satisfied with the location? Is there room to go larger than 1/4 NPT?

 

Are you planning to do #3?

 

Great pics,

Thanks.

 

It clears both intake and exhaust manifolds so I guess I'm satisfied. I forgot to mention that the top of that hole is at the very top of the internal ceiling of the water jacket. You go any higher and you will cut into the ceiling wall.

 

I also plugged the internal bypass hole and drilled out almost every coolant hole in the block and head that was present in the N42 MLS gasket. There was one hole in the head (P90A) that wasn't present in the gasket or head. I didn't mess with the gasket for fear of tearing it up.

 

I figured that the hole above #4 is close enough to 3 to count for both :).

 

I think you would have to scarf out the manifolds to get a larger fitting in there. At least a fitting like the one I have that is removable with the manifolds attached. There is only .06" between the tips of the fitting nut and the intake manifold. You could move the hole a little aft to gain more clearance to the exhaust.

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It clears both intake and exhaust manifolds so I guess I'm satisfied. I forgot to mention that the top of that hole is at the very top of the internal ceiling of the water jacket. You go any higher and you will cut into the ceiling wall.

 

I also plugged the internal bypass hole and drilled out almost every coolant hole in the block and head that was present in the N42 MLS gasket. There was one hole in the head (P90A) that wasn't present in the gasket or head. I didn't mess with the gasket for fear of tearing it up.

 

I figured that the hole above #4 is close enough to 3 to count for both :).

 

I think you would have to scarf out the manifolds to get a larger fitting in there. At least a fitting like the one I have that is removable with the manifolds attached. There is only .06" between the tips of the fitting nut and the intake manifold. You could move the hole a little aft to gain more clearance to the exhaust.

 

 

Great info.

 

Did you check if the water jacket above 3&4 is continuous?

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I'd say make a separate abridged version if you must, but don't ruin this thread by cutting it down Barney style. There's so much good information here... :(

I second this. +1 All we need is 1post with the "dummies" version of these 23 pages. Great thread, and next time I blow the head gasket...

 

 

 

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I'll take a stab at summarizing this thread in terms of what can be done to reduce detonation by improving how the head is cooled.

 

Disclaimer #1: I've been following it from the beginning and have not gone back to reread from the start, so I've probably missed a few things.

 

Disclaimer #2: There is a lot of really valuable discussion that anyone serious about pushing above-average power out of their L2X should read. The summary below completely ignores all of it, but that doesn't mean it isn't important. Think of this as the Cliff Notes of the Cliff Notes :)

 

Summary:

 

- The path of coolant through the L engines results in the rear of the head receiving the hottest coolant and hence having the highest operating temps.

 

- This can result in nucleate boiling at the rear of the head which can create a vapor barrier that slows the absorption of heat from the head to the coolant, making the #5 and 6 cylinders most likely to detonate.

 

There are several things that can be done to improve this:

 

1) Drill and tap above the #5 and 6 exhaust ports and route coolant to the thermostat housing to improve the flow of coolant at the rear of the head. Some have gone further and include #3 and 4, and some have even tapped all 6.

 

2) A higher pressure radiator cap can help reduce nucleate boiling.

 

3) The L28 diesel water pump can be made to fit and improves coolant flow.

 

4) Tapping and plugging the block to stop coolant flow from bypassing the thermostat (and hence radiator) helps, but make sure that the #1 mod above is done to avoid water pump cavitation before the thermostat opens.

 

5) Non-aqueous coolant helps prevent nucleate boiling.

 

6) Water wetter seems to help in some cases, not so much in others.

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My thoughts on the Summary:

 

- The path of coolant through the L engines results in the rear of the head receiving the hottest coolant having stagnated water flow, insufficient for the heat produced in the rear two cylinders and hence having the highest operating temps.

 

- This can result in nucleate boiling at the rear of the head which can create a vapor barrier that slows the absorption of heat from the head to the coolant, making the #5 and 6 cylinders most likely to detonate. This modification allows flow in an area with insufficient flow to take the heat out of this area.

 

There are several things that can be done to improve this:

 

1) Drill and tap above the #5 and 6 exhaust ports and route coolant to the thermostat housing generally below the thermostat to retain it's control on proper warmupto improve the flow of coolant at the rear of the head. Some have gone further and include #3 and 4, and some have even tapped all 6.

 

2) A higher pressure radiator cap can help reduce nucleate boiling.

 

3) The L28 diesel water pump can be made to fit and improves coolant flow.

 

4) Tapping and plugging the block to stop coolant flow from bypassing the thermostat (and hence radiator) helps devote more flow THRU THE ENGINE, but make sure that some path exists during warmup the #1 mod above is done to avoid water pump cavitation before the thermostat opens.

 

5) Non-aqueous coolant helps preventchanges when nucleate boiling occurs, and generally results in much higher operating temperatures across the board which may have other detrimental under-hood effects.

 

6) Water wetter seems to help in somemost cases,through decreasing surface tension of the coolant, very similar to a higher pressure radiator cap not so much in others.

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