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BMW 3.5 Z finally begins in earnest


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Well, last night I slid the engine and 5 spd trans (from my 85 635) into the Z. It almosts fits without alterations. The hood lies on the distributor and the intake plenum, so I need to figure out how to get the front down a couple of inches as it sits or move it all back 2 or 3 inches so it will drop down an inch or so. I see options right now of trying to lower the Z steering rack, exploring cutting into the oil pan to remove a few inches across the lower front, or cutting into the firewall. There may be other solutions such as changing the hood, but those are the most obvious. Lowering the rack poses a small problem with the steering shaft universal joint and the cross member, and who knows what else would be compromised in the steering, so I'm not liking that one. Cutting into the oil pan would only be possible if the crank allows it, and even then it is not sounding like a great idea, so it looks like cutting into the firewall or doing some creative massaging with a body hammer may be the best and least invasive solution. I like that the engine would sit even slightly deeper into the body for better weight distribution. I like the placement of the shifter, I think; although I haven't reattached the linkage, it looks like it will come out exactly where it used to or a little farther back where I would prefer. I want it to fit as high as possible, so I can use a short shift kit and cut down the stick to move more like a toggle than a lever.

There is plenty of extra space between the front of the engine and the front framing where the radiator would be mounted. There is still the question of fitting power steering, but I think I will leave that as a later contingency . The Z rack and pinion was very responsive and wasn't very heavy at slow speeds, as I recall, but I have gotten spoiled by power. I wouldn't mind not having that entire system however; it is just more weight, more clutter, more work, and more things to leak, and I am not sure what power rack would fit. AC should be no problem, I may have to move the compressor upwards very slightly, but that shouldn't be too difficult. Again, one of the later stages of the project. I could live without AC if necessary, the Z has a great ventilation system, but I want the comforts of a really nice car. Since there is so much room in front of the engine, I'll probably dispense with the stock viscous clutch cooling fan and use an electric pulling fan on the engine side of the radiator.

Looks like plenty of room for working on everything, and plenty of room for a supercharger...

I'm anxious to get the entire car with engine up off the ground, so I can get under and see how everything else will fit, design mounts, etc. Pretty exciting. I think it will work. I can feel it accelerating out of a corner already. Later, Jim

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Wow, creative idea jim. I love hearing about new things people are doing with the Z cars, inovative minds at work. I'm sure the 635 engine will be nice, producing plenty of torque. Good luck with your build, continue to update, im anxious to hear about it, as I am a Z and a BMW guy like you.

P.S. I am sure a few people will telly ou this so I'll just get it done in the first post. Over at hybridZ they will be more interested then some here will be, because they focus purely on swaps and other modifications. I would like to continue hearing about your journey though

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Lowering the rack poses a small problem with the steering shaft universal joint and the cross member, and who knows what else would be compromised in the steering, so I'm not liking that one. Cutting into the oil pan would only be possible if the crank allows it, and even then it is not sounding like a great idea, so it looks like cutting into the firewall or doing some creative massaging with a body hammer may be the best and least invasive solution.

Lowering the rack also changes bumpsteer. Could be used to fix bumpsteer in a Z if lowered the right amount since the rack is too high relative to the control arm pivots in the stock location, but could also really screw it up, and you'd really need to measure to get it right.

I agree with you that moving the engine back is the way to go if you can. I wouldn't be too worried about cutting into the oilpan if that ends up being the easiest solution. Look at how shallow it is at it's most shallow point. You can go that depth all the way across if you have a dry sump. The only reason for the sump is that it is a sump and it stores the extra oil. If you had to really modify it and lost a whole lot of capacity you could add "wings" to it like a Nissan Comp oil pan to get back the capacity.

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Hey thanks for the thoughts, guys. Yeah, I posted at HybridZ also. I've been around there for some time, too, mostly just cruising. These and Roadfly E24 and 2002 are favorite forums. I appreciate the mention of bumpsteer, as I am planning to lower the Z a bit, and wondered of the combined effects of lowering chassis and then lowering the steering rack. Still, it does seem a last resort to screw with steering. I've sat on this Z for over 15 years through many other past and current projects, and it's just now things may be falling together to do it, but time and $$$ are scarce commodities.

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Thanks, It's working out pretty well so far. Actually by removing the steering rack I was able to shoehorn the engine et al into a proper position without surgery. I as amazed. I will massage the front top of the tunnel for s slightly better angle and more clearance, but that is no big deal. Shifter is in the original hole. Now just have to deal with the rack. I'm a patient person, and the answers will come, often so simple and convenient, if you go at it from a Zen perspective. I think I can cut the engine mounting points off the 6er crossmember weld them directly to the Z crossmember and also devise a way to bolt them to the frame rails and the stock 6er mount bushings will work. This would add strength to the structure as they would work as a gusset or brace without adding much weight. I hope to hear more from jmortenson about the bumpsteer and moving the rack, btw, that was a great FYI article! You out there? If I lower the car about an inch, will moving the rack about an inch downward have a positive or negative effect on the steering geometry? I could possibly alter the front of the oil pan, but again, it's a wait and see situation, before I do anything drastic. Gotta set the diff in and get things lined up first. Bought a small welder at a garage sale this morning, just to be able to tack things up for a real welder. Thanks again guys. This is so cool. Jim

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If I'm visualizing this correctly, lowering the rack will make the bumpsteer worse, not better. When you lower the car, you are already lowering the rack (as well as the rest of the car) in relation to the wheels. Lowering the rack will make that worse.

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If I'm visualizing this correctly, lowering the rack will make the bumpsteer worse, not better. When you lower the car, you are already lowering the rack (as well as the rest of the car) in relation to the wheels. Lowering the rack will make that worse.

I don't think so. Bumpsteer isn't about the rack getting lower or higher in relation to the ground as the suspension moves through the travel. It's about getting the angle of the control arm equal to the angle of the tie rod. Lowering the rack the right amount will make the bumpsteer better. Think about it this way: if you raise the control arm pivot you can make the bumpsteer better. So that means that the control arm pivot is too low in comparison to the inner tie rod. So options are to lower the rack or raise the pivot. This graphic from Rob might make it clearer. I know it helped me when I managed to confuse myself... http://forums.hybridz.org/attachment.php?attachmentid=155

The downside to lowering the rack is that you can't later raise the control arm pivot. A closely related issue to bumpsteer (on a Z anyway) is roll center. The roll center is such that when you lower the car more than a couple inches it gets too low and actually goes below ground. A roll center below ground increases body roll. You can mitigate that issue with "bumpsteer spacers" which are really "roll center raisers". One issue with bumpsteer spacers is clearance for the wheel. You can't just keep adding bigger spacers because of tie rod to wheel clearance issues, which is why you can buy different heights of bumpsteer spacers for 14 and 15 inch wheels.

So everything will be fine in your BMWZ if you leave it near stock ride height. You can choose to lower the rack and actually improve the bumpsteer in doing so if you lower it the correct amount. You'd need to measure the bumpsteer while you lowered the rack to get it exactly right. Or you could conceivably use the JTR method and just lower it 3/4" and it should be in the ballpark. If you decide you want to lower the car a lot you may run into issues with the roll center, which means stiffer springs to control the body roll and the $$$ struts to handle the spring rates if you're feeling racey. If you haven't already looked, it's not going to be real easy to move the rack.

If your plan is to lower the car 1" and drive it on the street, I'd say don't mess with the bumpsteer at all, and cut the oil pan to gain clearance at the crossmember, especially if you're not going to race the car.

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Hmm, very good stuff. Thanks guys. These thoughts have been running around loose in my head, so to read this discussion helps to clear things up. I did appreciate Rob's graphic, and lying under the car last night put some more of this into perspective. Of course I really don't want to mess with the steering, and true, the rack relocation isn't the easiest thing to do, but I was just wondering from the perspective of combining the ride height and relocating to acheive a positive effect.

The sump of the pan isn't a problem actually;it fits pretty well right behind the crossmember; it's just the area directly in front of the sump, below piston #1. The pan isn't at its least depth there, but I can't remember what exactly is in that area of the pan, and I'm thinking lopping off a bit of the pan could be problematic because the pump may be right there, but it's been a while since I've had the pan off one of these. Gotta get out the books. Now you've gotten me thinking again, less pan depth, lower engine, more room for play, hmm...it's nice to have intelligent people to ponder ideas with. Thanks, Jim

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  • 3 months later...

Jim,

Try this out, how about placing a spacer between the x-member & the chassis rails where it bolts up to... then to rectify bumpsteer, buy the spacers that go between the strut & steering link... this will do the trick.

Nick.

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Damn! Somebody had this idea first! My dad has and extra e32 735i parts car but the engine is still in good condition! But I'll stick to the original engine system. Good Luck on the conversion and let us know how the car reacts! Safe swapping!

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alternativez:

Good luck with this project! As a past owner of BMW's (they've gotten too expensive for me - maybe I'll be a bimwad again when/if the new 1 or 2 come to our shores), I've thought that putting a BMW 6 in a 240 would be a killer way to have a truly unique "hybrid Z" without altering its character too much. I've mentioned this to other Z owners over the last 4 years since I got my 240, and nobody else seemed to think it was a worthy idea. Seems like anybody looking to swap something into a 240 wants a small block or some variety of Nissan JDM turbo-charged supermotor.

Heck with a late 90's or early 2000's 2.5 liter, one would end up with roughly the same displacement and still have a straight six, but with a very reliable and free-revving ~200 HP. I image the weight wouldn't be far off either what with BMW's use of cool alloys and all.

Again, good luck with your project. I hope it all works out well. You're a true pioneer :-)

History: '97 318ti, 00 323i Sport, 01 Z3 2.3, 00 323ci, 01 323iT

-Ken P.

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Hey, hope everyone has been having a great Christmas. I got just what I've been needing...a digital camera..., so I'll try my fingers at posting some photos in the near future. I have so many projects going, this will seem like one of the slowest swaps ever, but then I've been sitting on this Z for 15 years already, so another year won't make such a difference. It's a complete restoration with body and paint also, so imagine doing everything you want to do to your favorite car before you ever let it on the street. Anyway, thanks for the encouragement. I'll try to give some visuals later. Jim. Anybody need an 86 735i in cosmos blue, by any chance? Very low price ($500) for a very reasonable car? Call me at home, 765-947-5248.

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  • 1 month later...

Ok, so I have a digital camera, took some shots, but haven't had time to sit and post them yet. So, now the project is taking a slight turn...for the better. In order to gain some room, I'm just going to have to supercharge the big six and eliminate the distributor. I found (I think) I can invert the body of the intake by judiciously cutting the end ports off just after the injector ports, invert the intake, and reweld. There is a point along the vertical cross-section of all six runners where they are all straight and parallel. I think this may be a job for a professional shop. This allows the use of the original intake shape and volume even if I don't SC, and it lowers the engine clearance below the hood by at least 6.5 inches. Just move the throttle body basically and AFM to the driver's side as I had desired. Yet, it looks perfectly likely a Magnuson/Eaton twin screw SC would sit very nicely right on top of the intake. Later, Jim

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Hey BadDog, I also have an 87 325e with a bum AT going real cheap. I hate AT's and I'm sure this one is shot. Otherwise the car itself is still reasonable for 240k. I'm thinking about $200. It will drive, but slips badly under acceleration. I thought I would havefixed the heat in the 7, but new heater valve, reconnecting a loose vacuum, and checking the fuses hasn't fixed it yet. It is a very decent car though, just cold.

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also dosnt take much to make those "e"s quick. U can convert it to a super eta by bolting on the "I" which is a direct bolt on. Then you could use a 524td to turbo that m20 engine. kinda the equivlant of a z with a 280zx manifold and turbo with a p90 or some turbo head. Those cars run forever aswell. My super eta has 290,xxx miles and still runs beauitfully.

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Like I said, its too bad we're not closer, sounds like it'd be worthwhile to look at :-\ I always loved my bimmers but unless they bring the 1-series here I can't afford them anymore :(

bemmerguy714, you're so signature is so spot-on. I can't tell you how many times I was minding my own business, cruising along the freeway at 75 mph, when someone who was previously going a few mph slower than me until I happened to pass by them, suddenly felt the need to not be passed by a bimmer and was compelled to floor it, only to slow down again a few moments later, and repeat the cycle. Hardly eve happens with my Subaru LOL

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Like I said, its too bad we're not closer, sounds like it'd be worthwhile to look at :-\ I always loved my bimmers but unless they bring the 1-series here I can't afford them anymore :(
The answer to that is to not buy them new. My current family car is a '96 328i that I bought in 2002 with 37,000 miles on it, for about 40% of what it cost new. It will last me for many years.
bemmerguy714, you're so signature is so spot-on. I can't tell you how many times I was minding my own business, cruising along the freeway at 75 mph, when someone who was previously going a few mph slower than me until I happened to pass by them, suddenly felt the need to not be passed by a bimmer and was compelled to floor it, only to slow down again a few moments later, and repeat the cycle. Hardly eve happens with my Subaru LOL
The 328i is my second BMW (not counting bikes), the previous one was an '81 European 323i. (For those in the US, imagine a 320i with small 240Z-like bumpers, four wheel disk brakes and a 2.3 liter six.) I don't catch too much of that behaviour on the road from other cars, but even driving a 20 year old BMW prompts comments like, "Ooh, you drive a BMW!" Jeeze people, the 323i had 250,000 miles on it and cost me $5000. And my 328i cost less than a new Civic would have! And these people are probably driving around in a $35k Tahoe or Explorer! :stupid:

Sorry, that punched one of my buttons.

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Yeah, cars have and present certain aspects of character, dependent upon the viewer's perception. I started owning older bimmers many years back, working on them myself to save my economy. In my area there aren't many others, particularly older ones, so mine are obvious, 735, 635 (now destroyed to build the Z) 325e, and 76 2002, along with a 2004 MINI CS. There is only one other MINI nearby, and that's my brother. People around the area know me and are constantly commenting on how many cars I own, because I may drive a different one any day. And then one day I'll have the only Z around. Thing is though, I have less invested in 6 cars than many people have in one, and the lifespan of a well built car is amazing, easily getting 250k on the old straight sixes. I hope to liquidate the 7 and 3 so I can better concentrate on more important priorities...mostly the Z and the 02...

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*sigh* it all brings back so many fond memories... I'd like to find my old 318ti some day or pick up an old Z3 (even the 4-banger was a blast to drive)... but then again I *have* an old sports car to play with, and a very reliable and all-weather-capable affordable new car for all other driving duties (the new Legacy's are VERY nice... about the closest thing to BMW-ness out there... probably why lotys of people say "Subaru wants to be the Japanese BMW"). Still, if I had the $$ and the space, I'd have some BMW's in my stable:

318ti Sport

any Z3

any 7

a 1st-gen 5-er

and a 2002tii for good measure ;-)

Oh, and Yes, at the time, my 318ti cost less than (and 323i cost ~ the same as) a loaded-up V6 Accord or Camry!

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Try an old 2002 with the drivetrain from a 90 or so 318i. Nice fit, smooth starting and more power, 5 speed...I may do that with mine some day, but first the Z. I just keep my eyes open in case a cheap 318 might come my way, strip it and wait until the old 02 dies. It runs so well I can't see starting that kind of project on a good, running car, especially when I have the Z project, and I'm building my home on my own...a major project.

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That sounds like a blast! I've always wanted to get behind the wheel of an '02. And you're right, no use in messing with a good runner. That's why I waited 2 years to strip and paint my 240 :)

Keep up the good work and keep us posted! :)

-Ken

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