Twins with Twins, Anyone?

2004LB7

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Dec 15, 2010
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I've wondered about how well that would work for a while now. It's a shame they didn't take more time to do a good job. Bit that would have probably required removing the engine and stripping it down

I wonder if you could cast a block with integrated heads. Pistons and valves would have to go in through the bottom. Would never have a leaking head gasket and no head bolts required. But a pain to assemble and service
 

1FastBrick

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Liners and finish machining would be interesting on a set up with the heads cast in.... With a big enough Machine you could 3D print one also.
 
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kidturbo

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Picked up the head that let go, and inspected the ones I dropped off. My replacements, are both out by 0.015 or so. Those heads been laying under a workbench for 4yrs, and came off a running engine Yet are out that far.

The other head off this boat engine cleaned up good at 0.020 and valves are now even with the face. The finish is smooth as any examples, and bolt hokes are still round. But the first head, needs another 0.010+ to maybe get rid of the divit.. So calling it scrap because it's so warped, the outer lying valves will be over 0.015 outa the head when all done. Centers will just be even...

If piston clearances aren't a problem, are there any issues having them above deck? The milling machine seems happy to cut them flush..

Ouside Valves
03f6b89444b58e2727f41cb3a8ff4a4b.jpg


Center Valves
38788ac83466a4c0e56eeef9bfc61e51.jpg


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kidturbo

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Oh yeah, my machine buddy taught me something new today.

Seems someone invented these neat little temperature sensing freeze plugs, that have a pop out dot in the middle to alert the machine shop if engine parts were overheated. And last shop stuck some in these heads..

Winner Winner

But they don't tell ya the set value.. What fun is that...
8822626c1f98dcee7f53b28d4f3c07c9.jpg


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Cougar281

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Oh yeah, my machine buddy taught me something new today.

Seems someone invented these neat little temperature sensing freeze plugs, that have a pop out dot in the middle to alert the machine shop if engine parts were overheated. And last shop stuck some in these heads..

Winner Winner

But they don't tell ya the set value.. What fun is that...
8822626c1f98dcee7f53b28d4f3c07c9.jpg


Sent from my SM-S901U using Tapatalk
Well, it's not actually a temperature sensing freeze plug,, but a temperature sensitive tab that is pretty common in the used or reman engine market. They melt when the temp gets above a certain value, so if you go back to where you got the engine and say it failed, if the tab is melted, warranty void. Was that one actually melted? Doesn't really look like it ..
 

kidturbo

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According to some example pics I found, these are melted.

Guessing these were 225F tabs, as I did see hit 235+ when I shut it down for the last time. Also ran that engine at in gear idle for 30 minutes in 220's when that turbo exploded on the other engine a month before. We bumped a sand bar while looking at the turbo carnage, and plugged the seastrainer on this one. A major storm blew up, and didn't have much choice but to keep one running, or get blown out to sea.. And then she started acting up shortly after..
 

kidturbo

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Found this not to old thread on head milling.


Since not interested in reseating all the valves and shimming springs, thinking I'll search around for a better pair. Also not sure how much milling each will effect the Banks charge cooler intake, or the very rigid jacketed crossover exhaust pipes. Seeing in thread above how cutting 22thou impacts the factory Y bridge fit, that could be the deal breaker. Everything is so tight on specs right now, don't know if I want to risk stressing some big $$$ bolt on parts to save a couple bucks on the heads. Gonna have to go digging in the old scraps box again..
 

kidturbo

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Well, it's not actually a temperature sensing freeze plug,, but a temperature sensitive tab that is pretty common in the used or reman engine market. They melt when the temp gets above a certain value, so if you go back to where you got the engine and say it failed, if the tab is melted, warranty void. Was that one actually melted? Doesn't really look like it ..
Ok, I traced the history of these overtemp dotted heads. And as you suspected, they came from a major engine reman. My GM tech buddy reminded me, I bought an engine from local guys shed who was moving same day. He purchased an LMM reman long block, installed it, but claimed it had a bottom end noise. They sent him a replacement, and he tossed this one under a tarp behind the garage. It had like zero hours, but had gotten rained in. We pulled those heads, and had them clean and trued again when it acted up first time in the boat. So it's likely the've had around 0.015+ milled off before this last cutting. So am going to guestimate that's about the max ya wanta take before cutting valve seats. Makeing my spare castings within specs to cut, if truely stock.
 

kidturbo

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New heads not in the budget this time around. Fuel getting turned down to sub 800hp range, where I know it lives happily with 40psi boost. The next player can put some cast iron heads on both engines, and likely resolve all the gasket issue. Or this next head set might be fine for decade, if someone doesn't overheat em like I did.

After considering all head gasket experience gained by my friends at Innovation, who invested thousands of hours working with Curitis H back in the early days trying build a LB7-LBZ Navy version, ya gotta respect the data. Their data all says OEM aluminum heads won't stay torqued when run at over 800 hp in continuous high RPM environments. Simply a difference in expansion rate. They could never get them to hold and pass the 24hr at 80% to WOT test.. Yet at 700hp they stick fine.

Boat runs 80mph plus with em limited to 800hp. Anything above that, milage remains questioable.
 
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1FastBrick

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New heads not in the budget this time around. Fuel getting turned down to sub 800hp range, where I know it lives happily with 40psi boost. The next player can put some cast iron heads on both engines, and likely resolve all the gasket issue. Or this next head set might be fine for decade, if someone doesn't overheat em like I did.

After considering all head gasket experience gained by my friends at Innovation, who invested thousands of hours working with Curitis H back in the early days trying build a LB7-LBZ Navy version, ya gotta respect the data. Their data all says OEM aluminum heads won't stay torqued when run at over 800 hp in continuous high RPM environments. Simply a difference in expansion rate. They could never get them to hold and pass the 24hr at 80% to WOT test.. Yet at 700hp they stick fine.

Boat runs 80mph plus with em limited to 800hp. Anything above that, milage remains questioable.
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