My RB25DET--> Z31 project

[Racinjitter]

May 1, 2006

Here is where I am at as of today. I should have hte engine out by this weekend. I would have never guess that there are so many bolts in the front end of our Z31's. All I have to say is DAYUMMM!

As you can see I have everything ready to pull the engine out. Just need the cherrypicker.Yea, I already have the engine and trans. I had an exhaust mani made, but dont plan on using it this year. The turbo will be my winter project. I hope that the column clears. I havent heard if it does or doesnt yet fit. Here is a pic of my RB25DET.

May 3, 2006

I found some more things to disconnect, like heater core hoses and a few connectors hidden below the battery tray. The connectors below the tray lead to the trans, whew i am glad those are off. I also removed the drive shaft, transmission mounts, hood and passenger fender. I removed the fender because the passenger door isnt gapped properly to the rear quarter. When I removed the lower plastics (ground effects) I noticed a little bit of rust starting. I might as well fix that while I am in here.

Here are a few pics.

Can you tell there was an engine fire? (it was really bad when I bought it in Georgia for $375)

June 2, 2006

Here is the latest on the swap, I have the engine & transmission out. Right now I am removing everything in the engine bay to re-paint it. I am aslo waiting for the 200ZR engine mounts and the isloators. Hopefully they will be here in a week or so. I had no idea that the transmission mount is the same as the 300ZX's transmission mount. But great to find these thing out. With any luck I will have the RB in the car in a few weeks.



July 19, 2006

OK so I actually started to work on the car again... Right now I am flipping the engine mounts on the crossmember, Putting a new clutch and all new timing parts. While I am at it I am going through the turbo because I found a MAF screen and plactic in the intake piping. I am first cleaning out the garage though. Here are a few pics of the ride and engine(s)....

July 20, 2006

A couple more pics...The timing belt appears to be unworn/unstretched. Thus confirming the 20k miles that the importer showed on the video.



July 23, 2006

I don't know what got into me lately, but I now have the engine on a stand, the car is being stripped of all the engine bay rust and I am getting all the measurements done for setting it in there. This engine will be a very tight squeeze as the engine alone is about 30 inches and the measurement from the firewall to the core support is 31.5 inches. This should be fun. I plan on cutting the core support out and making some brackets to make it a bolt in core support like the dodge intrepids are.

Well here are some pics....I am not done removing all of the rust in the primered areas, it started to rain.

July 26, 2006

OK, so I took some more measurements today... What I need to do to get the RB to sit in the engine bay... I need to swap the two engine mount brackets on the crossmember so that it moves them in 2" each. 18"22"

The factory engine isloators form the VG bolt on to the RB, so I can use the poly mounts. The only difference between the isloators is the diameter and the length of the stud going through to the engine mount bracket. Well I guess that the two studs is a difference too, but That is only on one side.

RB isolatorVG isolator

I forgot to mention that the distance from transmission mount to the engine mounts are identical between the VG and the RB at 39.5".

Now I am waiting for the 200ZR rear sump oil pan and pickup. By the time they get here I should have the mounts swapped. So it will also be test fit time!!!!

July 28, 2006

I did some more mearsuring again. The trans from the VG30 is the same length as the RB transmission. Both are 32" from bell housing to tailshaft seal. As for transmission size the RB transmission is the same length and larger in diameter at the bellhousing and the mid-section(where the gears are).Pics...

As for the physical dimensions of the RB25DET it is 30.5" long about 28" tall and 26" wide. That is with the factory intake plenum and the turbo with heat shields. The measurement from the front of the engine to the mounts is....14". That is the centerline of the engine mounts or to the top mount bolt(which is in the center).

I'll get around to the engine bay measurements later. Right now I have a bunch of sand stuck to me form sandblasting 90% of the rust out of hte engine bay.

Pic...

July 29, 2006

Measurements of the engine bay and the RB engine itself.



I think I will not be moving the existing mounts on the crossmember... Instead I am thinking of making this out of 1/4" steel plate...(for mockup) then reinforcing it. Any suggestions? (besides being in actual scale)

[nsrZ32]

Moved this over here for you as it was posted in the Z32 section.

Looks like quite the fun project you've got though. Keep us updated!

[jEzTeR]

Great Thread!

Keep up the good work and post lots more.

[Florida240sx]

Going to be awesome when it's finished...

[evildky]

awesome job, I soo want an RBZ31

[79`280ZX]

Great looking Z31 you got there

[Flicktitty]

looks good! your on HybridZ showing your progress too right?

[Racinjitter]

Yea, I have been on Hybridz for quite a few years now. All of my progress is on there. I will have the engine mounts in this weekend and the 200ZR oil pan on thursday next week. So with any luck I will have the engine test fit by sunday next week.

[Racinjitter]

So I did a test fit today... So far the issues are that I would like to have te engine sit down in the cradle about 2 inches further lowering the CG. I think I will cut the existing crossmember down. I also need to change the angle of the engine mounting pates that I made by about 10-15 degrees, this can be done when I cut the crossmember brackets. I will need to make a powersteering hose to run to the rack, and mount the resivior on the US drivers side. There is pretty good clearance all around the engine other than that, I think that A/C could easily be used if I wanted. Well if you have any questions or suggestions please leave me a message. Here are the pics.

[Racinjitter]

I did a test fit today, and it looks pretty good so far. I need to bolt up the transmission for final fitment. Aslo there is going to be a revision in the mounting plates that I made. They are going to be an inch longer and the bolts are no longer going to be staggered.

like this...

So here are some pics of what I got done today...













There are just a couple of interference issues so far, most notably the power steering lines to the rack. The other is the steering shaft it clears but not by enough yet...

Another issue is the ride height, right now with just the rb in there it seems way too high, seeing as to how mush the transmission weighs it will still sit a little higher than factory. No biggie, I plan on getting coilovers anyhow.

[theboz]

Awesome thread. I can't wait to see the completed project. Keep us posted.

[Racinjitter]

As Dramier suggested I cut the core support/ hood latch out to get the engine/trans assembly into the car. I plan on making some brackets to weld onto the removable hood latch portion, so that the timing belt will be easy to access instead of removing the whole engine.



I finally dropped the whole assembly into the car, and wouldnt you know, I dont need to modify the transmission tunnel at all.













But on the downside, I do have to make a bracket to mount the transmission to the trans crossmember, this should be butter to do.

Z31 transmission mount on left, RB transmission mount on the right



Z31 transmission mount on top, RB transmission mount on the bottom



The shifter lines up perfectly in the old automatic hole in the tunnel.



There is about 1/4 inch clearance between the steering shaft and the turbo elbow/downpipe.



And there is plenty of clearance under the hood.

[DustinZ]

Let me know what it will take for you to send me some of those mounts....

Great Work.........

DustinZ

[Racinjitter]

Let me know what it will take for you to send me some of those mounts....

Great Work.........

DustinZ

It would probably be easier to go to a local shop with my illustrations, and have them make you up a few. Also, I will make a draft of the transmission brackets as soon as I make them. I wish I could be of more help, but right now I am hardly at home. Work has been sending everywhere, I just dont have much time anymore.

[DustinZ]

I will probably cut some out with the plasma after you get the trany done too. This is a great write up and going to be a killer car. Good Luck!!!

[Racinjitter]

I made up some brackets for the transmission today. I havent gotten around to putting it in yet, but I am 85% sure it will work with no problems.

[DJButton]

Wow awesome project, the updates kept me ethralled, can't wait to see some more. My 280 seems to be begging for an RB these days. Too bad the 240's getting one first.

[nizmo_dryfta]

wow seems like a serious project. how much time have u spent on it? and how much has it costed so far? and how much more $$ do u think ull need to finish it?

cant wait til its done keep up the good work..

[Racinjitter]

wow seems like a serious project. how much time have u spent on it? and how much has it costed so far? and how much more $$ do u think ull need to finish it?

cant wait til its done keep up the good work..

So far I have probably spent about 50 hours on the whole car and where I am at in the swap. I have spent about $4,500-$5,000 total on the purchase of the car, all maintenance and the swap. I have owned this car for over 5 years now. I have set a budget of $7,000 for the initial build and 400whp. I have a GT35R but want to get it running and driveable before I put it on.

[nizmo_dryfta]

wow doesnt sound half bad. but im assuming you are pretty mecahnially inclined lol. so how much do you think this swap would cost at a shop? also hows the room inside your z31? because im a taller driver whos intrested in picking one up cheap as a project car but it wont be worth it if i can drive it lol

thanx

[Racinjitter]

wow doesnt sound half bad. but im assuming you are pretty mecahnially inclined lol. so how much do you think this swap would cost at a shop? also hows the room inside your z31? because im a taller driver whos intrested in picking one up cheap as a project car but it wont be worth it if i can drive it lol

thanx

You may want to ask Dramier about costs of of a shop putting one in. He had Agusta customs put his RB in his Z31. I am 6'5" tall and I dont have a problem driving the car comfortably. EVery now and again I hit my head on the back lip where the t-top sits.

[nizmo_dryfta]

sweet yea im 6-4 myself and ive been lookin for an older import to restore and the ones ive checkd out ive hit my head now and then too lol...is Draimer on here?and im actually on my way to Speedquest a shop here in the midwest to pick up my buddies s2000, too bad i can drive that car lol its the seeeecksss. i can barely ride in the passenger lol...but ill see how much they're talkin bout. keep us updated on the project and hopefully i'll be able to join the ranks of rb powered z31s out there..

[Racinjitter]

Yea, He is on here. But he spends most of his time in the RB section. I too love the s2000 My good friend has one that put down almost 500whp a few years ago. He always told me to take it to the store knowing that I cant even fit in it! LOL. Here is a link to his thread. zerothread/119390.

[Racinjitter]

So I got everything bolted up on the Z, The crossmember bolts directly in now. It went pretty smoothly only a little bit of prybar action. The turbo elbow has more than a half inch clearance between the heat shield and the steering shaft. I did encounter a clearance issue with the speedo sensor on the passenger side, I will bring home the air hammer soon to fix this issue. I also had an issue with the transmission mount bolts, they were too wide so I ground the head down to the bolt itself. Now I am wondering if the driveline angle is correct. I guess I will have to bring home a magentic angle gauge. Here are the pics...

[nizmo_dryfta]

that engine looks awfully cozy in there cant wait til u fire er up and get some vids lol. do you have any other plans for the z exteriro??interior?? keep up the good work...oh and about my friends s2k yea hes putting roughly 300 i beleive.was your friend na? lol two problems i cant really drive stick and i dont stand a chance fittin in that car lol me and his girlfried went to pick it up and she drove....

[Racinjitter]

It looks like I have a lot of room, But I am sure after the remote oil filter and oil cooler plus all of the accesories and piping it will fill up pretty quickly.

My friends s2k was supercharged, intercooled and aftercooled, and had nos(never sprayed). He basically had two intercoolers. We all recommended that he not spray until he wants to rebuild. With the factory 12:1 compression I am sure it wouldnt have lasted long. O Yea he was on the cover of Speed Style and Sound a few years back. There is plenty of info on the car in that mag.

[nizmo_dryfta]

cool so wat is the update....and wat kind numbers are you looking to put down? oh and when i aske the guys at speedquest about the swap they said since its a bit of an "off-the-wall" swap they said it probably cost a couple thousand..does that sound about right?

[Racinjitter]

Well I have everything in and bolted up, Measuring for drive shaft and welding in the new engine mount brackets. On this build I plan on about 450-500whp. Then on the rb30det build about 700+ whp. Once I am ready to put the rb30 in I will be repainting the whole car a black cherry pearl. I will probably completely gut the interior and remake everything and put a cage in it.

If you can find a 200zr crossmember it would be a straight forward bolt in affair. However I could see a shop wanting that much money for all of the fabrication and getting it running properly. I am sure that there will be more costs and problems that they will run into along the way anw will end up being closer to 2000-4000.

[rbsileighty]

Nice ride bud! Very good writeup!

Just a few tips though:

Next time you have to take the engine in and out/put it back in... drop the engine/crossmember on the ground with the trans bolted and then lift the car off of the motor with the engine hoist. Takes no time (min time I've ever dropped mine out of my 240 is 2hrs going from fully wired install to sitting beside the car).

Don't gut it and put a full cage in unless this is going to be a full time track car with occational street use. My RB 240 has an 8 pt cage and no interior... she's a bear to drive daily (you'll make a lot less trips to stores... getting in and out's the hard part... but once you're in it's great!).

Very interesting find though... came to this forum looking for info on Z31's as I just picked up a NA 85 5spd hardtop for my daily driver... nice surprise to find this thread!

So you're going to need a new driveshaft? I thought I understood from your thread that everything between the VG and RB were the same? I'd be surprised if it wasn't the same condition as my RB20 working with my 240's driveshaft. Yours was an auto right? I wonder if a MT driveshaft would work...

Keep up the good work and welcome to the world of RB fabrication

What do you have planned for wiring?

So on to looking for Z31 info for me...

[Racinjitter]

I would drop the crossmember, however the city ordinances do not permit me to do so. I have already been contacted by the city blight official, and as long as I adhere to his rules I can keep my car where it is.

Right I know exactly how much of a pain it is to get into a fully caged car, I plan on a custom 6 point with a few add ons for comfort. I am by no means short either at 6'5" tall.

Congrats on the slicktop they are Very hard to find anymore. I kinda wish I had a slicktop.

I am measuring for the driveshaft this weekend. I will have a custom one made to fit. The Z31 output yoke is much smaller than the RB25det's. But the rb25det output yoke is the same as a Z32's. I believe that the rb20det outupt yoke is the same spline as the VG's. Mine was an auto, but the sizes of the auto and manual are nearly the same, I think just the spline count is 1 tooth off. There are only a few similarities between the vg and the rb, but not many.

Thank you for the props, Wiring is almost done I am modding my current harness to fit and try to get all of the guages to work. Shouldnt be much longer before it is done.