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putting MN47 head on a W24 block that has dished pistons?


boundish

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Hi i have an 810 wagon with a broken block( badly corroded cyl.wall on no.3) . I have gotten hold of an L24 from a 81 Laurel(euro) and the block says W24 and the head says e88  this is a stock engine . The pistons are dished on this engine and on my 810 they have two indents in them. Would this be a problem compression wise?

 

IMG_20160123_141135.jpg

 This is the laurel block . Note: have not cleaned the surface for the new gastet yet so its dirty.

 

IMG_20151208_151742.jpg

 

And this is the 810 .

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I bet it would be very similiar. I would think that combo would work well. The small chambers on the Mn47 would bump compression slightly, but maybe not much at all.

I don't know anything about the W24 block, but as long as it's Nissan, it should work:)

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No one here can really answer the question without knowing the displacement of the W24 blocked engine, (you can get this from the stamped pad near cylinder 5 on the oil filter side of the engine, up near the headgasket face) And knowing the dish volume of the piston.

 

The maxima N47 casting is a 38-39cc casting if it has never been machined to repair damage.

 

Assuming an L24 engine, with flat-top pistons the compression ration is 10.2:1 when using a Fel-Pro brand headgasket.

 

Assuming an L24 engine with a 4CC dished piston (I've seen them a few times) then compression will result at 9.4:1. again with the Fel-Pro headgasket.

 

If the volume of the dish is different, then the compression ratio will be different. So far though, either piston will yield a nice base for a hot street engine.

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No one here can really answer the question without knowing the displacement of the W24 blocked engine, (you can get this from the stamped pad near cylinder 5 on the oil filter side of the engine, up near the headgasket face) And knowing the dish volume of the piston.

 

The maxima N47 casting is a 38-39cc casting if it has never been machined to repair damage.

 

Assuming an L24 engine, with flat-top pistons the compression ration is 10.2:1 when using a Fel-Pro brand headgasket.

 

Assuming an L24 engine with a 4CC dished piston (I've seen them a few times) then compression will result at 9.4:1. again with the Fel-Pro headgasket.

 

If the volume of the dish is different, then the compression ratio will be different. So far though, either piston will yield a nice base for a hot street engine.

Im going to doublecheck when i get back to the garage near the weekend, but i think the displacement is 2393 and as for the pistons all i can say is that they have 27L stamped on them

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Clay the top of a piston, pack the top with modeling clay when it's at top dead center, and take a thin wire to cut the top of the clay off flush with the top of the piston. Roll the clay out of the hole and wad it up into a ball, drop it into a graduated cylinder with milliliter markings that has 10-50 ml of water already in it. Read the marking and the increase in volume will tell you the dish volume of the piston.

 

Do the same with your cylinder head, and you can compute compression ratio, but from what I see in your photos, if the engine code stamped on the engine says L24XXXXXXXX then you will have the 9.4:1 compression ratio. It's a good place to be for a street engine with a stock cam or a mild to moderate cam!

 

If it says L26XXXXXX or L20XXXXXX then you'll have a very high compression engine (too high for street duty) or a lower compression, turbo ready engine.

 

The only difference from engines built on other blocks and engines built on W24 blocks is the rod bearing diameter. That only matters if you're changing the crankshaft or rotating assembly.

Edited by Xnke
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Clay the top of a piston, pack the top with modeling clay when it's at top dead center, and take a thin wire to cut the top of the clay off flush with the top of the piston. Roll the clay out of the hole and wad it up into a ball, drop it into a graduated cylinder with milliliter markings that has 10-50 ml of water already in it. Read the marking and the increase in volume will tell you the dish volume of the piston.

 

Do the same with your cylinder head, and you can compute compression ratio, but from what I see in your photos, if the engine code stamped on the engine says L24XXXXXXXX then you will have the 9.4:1 compression ratio. It's a good place to be for a street engine with a stock cam or a mild to moderate cam!

 

If it says L26XXXXXX or L20XXXXXX then you'll have a very high compression engine (too high for street duty) or a lower compression, turbo ready engine.

 

The only difference from engines built on other blocks and engines built on W24 blocks is the rod bearing diameter. That only matters if you're changing the crankshaft or rotating assembly.

From what i can find the laurel L24 engine has 8.5.1 compression and the 810 has 8.6.1 the head on the laurel engine has E88 stamped on it.

 

The dish is very slight , but to me it looked like the "dents" in the 810 pistions were even smaller . Thats why i feared the compression might become even lower .

 

Im pretty sure it says L24xxxxx , but im gonna confirm it in the weekend.

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If the cylinder head you have has the small, heart-shaped chamber and is marked N47, it's a 38cc chamber. Combined with the L24 displacement and the approximately 4cc dish, I get 9.4:1 compression ratio-which is just fine. Gives a lot more flexibility, and is perfectly drivable.

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If the cylinder head you have has the small, heart-shaped chamber and is marked N47, it's a 38cc chamber. Combined with the L24 displacement and the approximately 4cc dish, I get 9.4:1 compression ratio-which is just fine. Gives a lot more flexibility, and is perfectly drivable.

Sounds good!, but i found a better picture of the piston thats in my oroginal 810 block and i just cant wrsp my head around how a slight dish can give higher compression than the small valve reliefs , might the 810 pistons be slightly lower? Anyway thanks for helping out :-)

post-51515-0-95233400-1454103198_thumb.jpg

Edited by boundish
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It's unlikely that your 810 has compression that low. In fact, if it came equipped with a flat-topped piston and the maxima N47, it could not have had compression that low.

 

If it came with the E88 head, then it would have the 8.6:1 compression ratio that you find listed.

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It's unlikely that your 810 has compression that low. In fact, if it came equipped with a flat-topped piston and the maxima N47, it could not have had compression that low.

 

If it came with the E88 head, then it would have the 8.6:1 compression ratio that you find listed.

Here are some data from the 810 workshop manual post-51515-0-41014300-1454136575_thumb.jpg

 

It says 8.6.1 for the 810 and my pistons are stock. And the dished pistons in the engine im going to put the 810 mn47 head on are also stock.

 

Btw Ive confirmed that the block from the c31 has L24xxxxxx on it :-)

Edited by boundish
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