I have a D16Z6 engine that I want to push up over 350 WHP but no more than 400 WHP, but I still have the stock 5 speed transmission. I know it needs help to handle the power, I just don't know what all I need to do.
I want to put in a LSD, upgrade the axles and so forth, but what else do I need to do to the internals to be able to handle the power? Is there a rebuild kit that ups all the gear ratio's through all the gears? Or do I just need to change my final drive?
Any input would be helpful.

 

If you have a Z6 trans the only shorter ratios are the DOHC ZC 3/4/5 and MFactory (but they aren't rated for that much power). MFactory helical LSD, MFactory 3.083 1st gear and MFactory 4.5 final drive is the typical boosted D16 setup I build. I prefer to use the Y8 trans for the steel forks (gearing is the same as the Z6). Stock diff, FD, and 88-95 aluminum forks are the 3 biggest weak areas in the D trans.

 

The internal gears don't exactly have a power limitation...at least not for your HP range. If you have some play and grinding going on and you need to rebuild it, use oem or upgraded carbon synchros.
To lay down the HP once you hit your mark...an LSD, Clutch and axle upgrade will be needed for sure.

 

I missed the mark as to what I was trying to get across, sorry. I want to drop engine RPM at cursing speed, so taller gears for the highway. With the added power and torque I want have a higher top speed. In a way I want to try to add power and keep some economy. Any suggestions for this route?

 

Nope. Unless it's a Del Sol Si trans it's already got the tallest 5th gear available. If you change the final drive to something lower it's going to raise the RPM in 5th. You could swap in higher final drive from a DX or even a VX trans, but it will absolutely kill your acceleration.

 

Can't have your cake and eat it too.

BTW, if you're on typical 205/50/15's with the stock rev limit you can already top out at 166mph...

 

^^didn't know that...

 

So keep the gears I have, just fix all the weaknesses and make other necessary improvements, which have been mentioned above.

Are there any other weak spots I should consider making improvements to? I want to build reliability as well.

 

Keep in mind to get the Steel Y8 forks you actually need a Y8 trans since the case is different as well (along with the 3rd/4th sleeve) Also plan on buying a new 3rd/4th fork as it's almost impossible to find a used one that isn't worn past the service limit.

At 400whp reliability sort of goes out the window. Expect to break stuff. I mean you could remove 5th gear and replace it with a handcuff (if you can find a machine shop that wants to make one, no one makes an off the shelf one that I'm aware of) but even then I think the 3rd/4th gears will break just as easy as without a handcuff. Really IMO you should probably be looking into an '86 - '89 Integra CG trans at the power levels you're going for.

That said some guys can break stuff all day at stock power levels and other guys can be making significantly more power than their transmission is rated for and have it hold together. Driving style can go a long way.

 

If you use a Y8 trans, LSD and FD you likely won't break anything if you are a good driver with a proper chassis setup. The D's are pretty stout when you don't abuse them.

 

The Y8 should bolt to my Z6 with no issue or adapters? Are they hard to find? What's the Part number I should look for if I decide to pick up a Y8?

 

Yes, the external dimensions are exactly the same.

-All '96 - '00 D-series transmissions are stamped S40 on the white barcode tag on the front.
-All '96 - '00 EX (Y8) transmissions are stamped B000 on the transmission case near the axle hole on the passenger's side. So are the HX transmissions, which are not geared the same.

You'll have to either take the sellers word it's an EX transmission, check the green VIN tag if it has one ('96 transmissions legitimately don't have VIN tag, the holes are there, but no tag) and see if the 4th, 5th and 6th digits read EJ8, if they do, it's a Y8 trans. Or finally turn the input shaft with transmission in 3rd gear and count the revolutions compared to one turn of the differential.

 

i just build one with vx 3rd for 4th and mfactory lsd, not waiting for the snow to melt to test it.

 

I did that 2 or 3 years ago, only without the LSD. I never registered the car again so I only took it about half a mile up the road to try it, felt good though from what I can recall. Hopefully this summer I'll have it on the road again.

 

i know the guy is excited. one of the huge problems is how long 4th is, this this should be going through the traps perfect with a 23 inch slick.