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1996 Ek coupe
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Discussion Starter #1 (Edited)
I want to build up a D15 block with d16 sized rods and have some revability. I've done my homework on the setup. I can pick up a JDM D15B Single-stage vtec crank, use my D16 Eagle rods and my D16Z6 8.5:1 C/R Wiseco pistons in a D15 block and have the pistons stick out 2mm above the deck. Is 2mm too high? I'll be using a built D15B7 head with the 38mm combustion chamber. I thought about shaving 1mm off the pistons to bring down the compression height but I hear shaving pistons throws off their balance and weakens them. So to keep the pistons from hitting the head I can use a Cometic 2mm head gasket right? And with my head shaved like it is my C/R will be about 8.6:1 with a 2mm hg and the pistons will stick out from the hg only .05mm. Does this sound like a good idea?What is the max they can stick out on a stock a6/b7 hg without hitting the head? Does anyone have experience with using a thicker headgasket (don't tell me to stack OEM hg, I'm not doing that ghetto mess). If anyone has some input or experience please share but keep the negative comments to yourself. Thanks

Edit: the specs on the pistons are -15.4cc dish and a 29.82 compression height.
 

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boom!
you need to rethink your idea a bit because there is way to much piston above deck and
milling pistons isnt advised since it weakens them

A really thick hg isnt the best idea either...it being so thick causes sealing issues and if the block and head arent perfectly flat and have fresh surfaces it will cause the head to lift/warp. ARP studs probably help but idk how much. The pistons being up in the combustion chamber can also cause p2h and p2v clearance issues and the flame will also take its toll on the headgasket itself.
 

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Honda City
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People work with deck plates, and 2 head gaskets (one between the block and plate and another between plate and head).

If you want to rev high, just get a D15 block, D15 3-stage vtec crank, 3 stage vtec rods (137mm) and single-stage JDM D15 vtec pistons which have a shorter compression height. No need to shave pistons and assuming you're stick to NA, the parts will be able to take quite a bit of abuse.
 

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1996 Ek coupe
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Discussion Starter #5
I'll look into a deckplate. Anyone sell them? If I go the thick hg way I will have the head and block trued and mirror finished. I'd like to run boost on this setup and a lot of it. D15 crank has too small main bearings to fit into d16 block.
 

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If you have the cash you can get custom pistons made that relocate the piston pin higher in the piston it may end up in the oil scraper ring grove. Will d16 rods fit on a d15 crank? I was under the impression the rod and crank journals sized are small on the d15 crank but I could be wrong its happened before.

Running a piston out of the hole is crazy to me but people have done it just make sure to clay the motor to find out how much space you have. Rod stretch and heat expansion may shit on your parade. Running a deck plate is ok as long as your top ring is not pooping out of the block bore lol. You will have to find a timing belt that will fit and you will probably end up altering cam timing. That will have to be corrected with a gear.

Anything is possible its just is it cost effective? I know forged d15 rods and pistons may hit the market some day. Patients may prevail.

I know your probably just trying to think out side the box a bit and that's a good thing. I always like seeing something different but if it was me I would just find a d16 block and crank keep things simple and boost the crap out of it but that's just me.
 

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1996 Ek coupe
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Discussion Starter #8
The JDM D15B single stage vtec has d16 rod journals. I want to know if a thick (2mm) headgasket will hold up to boost or nitrous?
 

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Its a toss up really...im sure you can do it but idk if its the best idea.
The head lifting under high boost could be a real issue because the head and block are now so much further apart than they are meant to be.

With combustion happening so close around the edges of the gasket it can also burn it up, weaken it and cause head gasket failures.

Those are the main issues in my opinion. The piston sticking out of the hole may also cause lots of clearance issues and the ringlands to be exposed to more heat than normal which can lead to ring failure or a piston cracking etc...

but in the end its totally up to you
 

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FJ Distributors have D15 rods now. I'm working on getting myself some. The rods
are the only downfall to the B7/D15 blocks in my opinion.
 

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1996 Ek coupe
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Discussion Starter #11
Isn't there like a 3 month wait on those fj rods? They would make so much more money by producing them in large quantities and listing them on ebay.
 

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ej1
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So you'll be out of the hole .081". You may not have to run as thick of a head gasket as you might think. With the non vtec head an O.G. guys pistons stuck out .041" with z1 rods N/A build. He had his chambers fly cut so the piston edges didn't hit. With claying his piston to valve clearance turned out ok. The pm3/pm9 heads have deep chambers.

You might look into a commetic thicker head gasket if you want to go there.
I've also seen other brands of thick turbo head gaskets up for sale.

This deal might not be as bad as you think. After fly cutting the chamber edges you might have enough piston to head and valve clearance to get by with an .06xx" thickness head gasket for example. I don't know how well the top ring land can take it, but it sounds like a plan.
 

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Discussion Starter #13
I never thought about fly cutting the head. The only problem is that my head is already milled. Hmmm I'll do a little more searching on the subject and see if I can get a price from the machine shop. Thanks!
 

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Discussion Starter #14
How much material can be taken off from fly cutting before I start to weaken the head and run into cooling problems?
 

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Discussion Starter #16
^^ any experience with it?
 
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