Cant find it make it: the unicorn engine

[Festiver]

So I know this is a bit silly but I wanna hear what people have to say the GTX bj engine is a unicorn to say the least and what if we made one out of a b6t and some custom internals hell itd already be turbo charged lol
Both engines are 78mm bore but we would have to cut 16.1 mm out of the stroke could do this with the crank and add longer much stronger rods or maybe deck the hell out of the block does anyone know how far a b6t block can be decked before it's too thin to handle heat? Idk let's talk about it

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[FestYboy]

Have a crank forged... Or hunt down an NOS Mazda crank.
I had already discussed this with Charlie and mused soon a billet crank but he advised against it, so a forged casting is the way to go.

[Advancedynamix]

What's a guy gotta do around here to get a BJ?
The B6D/T/ZE crank is cast, so any reputable crank shop won't weld them. A custom crank is going to cost the same amount as going to Japan for a little holiday to search for a nice BJ crank. I say book a flight to Hiroshima and start looking for the crank you can't live without.

[shorestiva]

Has anyone actually asked a engine importer if they could find one?

[skeeters_keeper]

I had already discussed this with Charlie and mused soon a billet crank but he advised against it, so a forged casting is the way to go.

I'm curious, why not a billet crank? Sure a forged one is probably going to be a bit stronger, but if you want a 1-off billet would probably be cheaper (though still $$$$!)

[Festiver]

I'm thinking custom because if we're going this far into the bank account for a crank let's make a engine of serious stoutness probably gonna need custom conrods too so what if we used very large journals like Chevy 350 journals though that's alot of crank weight it should dampen harmonics if well balanced

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[Advancedynamix]

I'm curious, why not a billet crank? Sure a forged one is probably going to be a bit stronger, but if you want a 1-off billet would probably be cheaper (though still $$$$!)

Forged and billet are usually the same thing when it's a custom, low volume crank. They machine the crank from a forged billet. Those cranks tend to ring more than a crank that's been forged to shape. In high revving, inline 4 engines, that ring can cause bearing failures. A good portion of engine builders blame these bearing failures on oil starvation or cavitation, when the problem is a harmonic issue that displaces the oil film. The truth is told through harmonic analysis of the engine while it's failing. This will often expose a tertiary harmonic that reaches maximum intensity within seconds of bearing failure.
I saw this issue first hand while running the dyno for a ecotec project that Katech was working on.

[Advancedynamix]

If I were to personally invest in a custom crank, or even if I could get my grimy hands on a BJ crank, it wouldn't go into the B6D block. I'd stuff that little guy in a ZMDE block and make use of the improved port shapes, solid lifter design, more aggressive cam profiles and added oil return ports. The Z series engine will support much higher RPM than its predecessor.

[Festiver]

If I were to personally invest in a custom crank, or even if I could get my grimy hands on a BJ crank, it wouldn't go into the B6D block. I'd stuff that little guy in a ZMDE block and make use of the improved port shapes, solid lifter design, more aggressive cam profiles and added oil return ports. The Z series engine will support much higher RPM than its predecessor.

Hmmmmmm this is an extremely interesting I think this would be a very fun project in the future when I'm more financially stable lol

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[blake4591]

If I were to personally invest in a custom crank, or even if I could get my grimy hands on a BJ crank, it wouldn't go into the B6D block. I'd stuff that little guy in a ZMDE block and make use of the improved port shapes, solid lifter design, more aggressive cam profiles and added oil return ports. The Z series engine will support much higher RPM than its predecessor.

Are the cams really that much more aggressive? I remember them being somewhere between the manual capri and manual miata B6D cams.

[Advancedynamix]

I'm not sure of the ZM, as I only have a ZL, but the ZL cams appear to have a good bit more lift. They are a noticeably sharper profile as well (this is possible with solid lifter). The thinner cam lobes also allow for a steeper ramp without as much side load on the follower buckets.
When I pull the head off the car I'll put an indicator on the valves and compare the two. I know for a fact that the cams in a b6ze are a HP limiting factor long before the head or intake manifold. The ZL/ZM head is a significant improvement over the B6ze/d/t head. That's easy to see just by looking at it.

[blake4591]

I looked a little over lunch and the numbers I found for the ZM where more lift (w/ same duration) on the intake and less duration (w/ same lift) on the exhuast when compared to B6ze cams. So that means the profiles are opening faster and more aggressive in that sense. But as you said this is achievable due to the mechanical lifters. I've never seen numbers for the ZL-DE or ZL-VE camsbut I would guess that they are probably both better than the USDM ZMs since they both make more HP out of less displacement. If this assumption is true then there could be some good benefits to the Z series cams in JDM engines. Sort of sucks that the only the ZD-ME in full emissions and economy tune up is readily available in the US.

One interesting thing I noticed was very little over lap on the ZM specs so it's going to fight being reved without some mods. Would be good for turbos though.

[Advancedynamix]

Overlap is easy to achieve though. The cam sprockets aren't a crossover from the B series, but I can make them adjustable. They also may be comparable to some other engine with available adjustable sprockets. TODA shim under buckets are a direct drop in, so that's nice for a little more weight reduction and more durability at high revs. I don't think ATI has a damper for the Z series, and the B series damper won't work because the timing sprocket is integrated, and it's a different size. I've had my ATI damper apart though, and I'm pretty confident that I can replicate the important part of it.
This is turning into a great discussion. Thanks for jumping in and doing the research. I just started tearing into this ZL, so my info is only from what my eyeballs tell me. I've held enough B6ZE cams to visually see a difference, but exact numbers will require a degree wheel and an indicator. The ZL is particularly interesting due to its near perfect square dimensions (78x78.4iirc) and drastically better rod ratio (1:74). If this engine had come with a forged, double throw crank with bigger rod journals, it would be a true thoroughbred that was hidden in the donkey barn.

[shorestiva]

What's stamped on your zl cams?

[Advancedynamix]

Both cams are ground from the same blanks that are cast with ZL01 in them.