Modern Motorsports Ltd Posted November 5, 2000 Share Posted November 5, 2000 Thinking (had no time to do...with school) about gaining my hood clearance etc.... I read up on roll centres a while back and been thinking on the JTR recc'd Xmember to frame spacer of 1/2" or so (don't recall and book is in garage, if I go get it I know I'll be distracted for a while). I understand I need to (should) correct control arm geometry (near or above horiz. desired) to compensate for lowering car and crossmember in the end and the steering rack/control arm geometry should be corrected as well (lower or raise tie rod ends to make them parallel). Basically wondering if a 1" frame spacer would be unreal or 3/4" etc as I could really use this 'hood' space and thinking thru the influences (ie. can't exceed steering shaft length;^). thanks...oh yeah, I know I don't want to decrease my ground clearance and lower my pan tooo much either Quote Link to comment Share on other sites More sharing options...
Mikelly Posted November 5, 2000 Share Posted November 5, 2000 Ross, I took lots of measurements on my car before I did the spacer conversion, and I could find no reason NOT to use them. I didn't keep the info after the fact, but I can tell you that in 1 full summer of driving that car I never hit anything with my oilpan, and Chris Cloude can attest to my roll center... Car handles like it is on rails! Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted November 5, 2000 Author Share Posted November 5, 2000 Thanks Mike, did you add strut spacers or were your control arms still horiz. or otherwise? have you played with tie rod/control arm geometry at all? I don't doubt yours handles v. well. I've kept mine just a hair below stock height and surprised many at the track including my passengers. I've also ridden in a kickass 510 that could (it seemed) turn figure 8's at 115mph and see no unbalancing at all..(he took me thru 3 or 4 corners in a row flat out steady at T-hill) .I know it's a huge range to get that last true comfort. Good to know it's working fine for you Mike, if I know your other susp. mods that'd be great, if they're on a URL just point me to it. (you're running similar size treads as me right? or larger? I"m running 245s) I want to make sure I'm not ignoring some other factor and JTR was 1/2" AIR so wondering if 1" poses any problems....can't see outer knuckle doing to low with my high ID/clearance 16x8's, just thinking out loud on line here. ------------------ Ross Corrigan '80 280zx '98 roller 350 with rpm heads/vic. jr. intake/ZZ4 cam (mixed rockers) 13" front brakes, 16x8's all around 50/50 f/r with 7/8's fuel and me in the seat at 3110lbs Quote Link to comment Share on other sites More sharing options...
pparaska Posted November 6, 2000 Share Posted November 6, 2000 Ross, I had the 1/2" spacer in at first, but in trying to get the driveshaft u-joint angles below 4 degrees and equal, I found I had to raise the front of the engine, so I yanked the spacers. BTW, my buddy with a JTR'd 240Z with the spacers installed and a stock pan and the car lowered about an inch hit a 3-1/2" high man hole cover (road was ground down being readied to be repaved) and took out part of his pan just last month. Yikes! ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@home.com">pparaska@home.com - Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 6, 2000 Share Posted November 6, 2000 Everyone, It seems to me that the hieght of the oil pan remains the same because the engine is mounted on the crossmember & it's height doesn't change. I think the spacers just raise the body up a half inch for more hood clearance. But because the struts bolt up to the body I guess it may change the height of the pan but I don't think so. I think the spacers change the angle the engine is sitting at, due to the body/tranny crossmember being raised, but it shouldn't change the height of the oil pan. Just my .02 Glenn Quote Link to comment Share on other sites More sharing options...
pparaska Posted November 6, 2000 Share Posted November 6, 2000 The struts (actually the springs) hold up the car, and the frame rails at a set height (with the car not moving). If you put in the crosmember spacers, it lowers the crossmember and the engine. There's a thread or two on this. I know others have had a hard time seeing this (I thought it worked the way you said at first glance also), but this is how it works. Draw a free body diagram of the car and you'll see what I mean. The tires, wheels, strut tubes, springs, and strut towers hold the car above the ground. For a set tire size, wheel size, strut tube length (whether it's been cut to shorten it), spring perch height, spring stiffness and free length, top perch/isolator height, the height of the strut tower sheet metal off the ground is fixed (if the car is not moving). Therefore, the frame rail is also at a fixed height. Having or not having the JTR crossmember spacer block between the frame rail and the crossmember dictates teh crossmember and engine mount height for a fixed tire/wheel/strut/spring/etc. assembly. ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@home.com">pparaska@home.com - Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted November 6, 2000 Author Share Posted November 6, 2000 quote: Originally posted by pparaska: If you put in the crosmember spacers, it lowers the crossmember and the engine. There's a thread or two on this. I know others have had a hard time seeing this (I thought it worked the way you said at first glance also), but this is how it works. Glen, we last had this thread because I saw it as you did. Then thru discussion realized the crossmember HANGS from the frame and is only connected to the struts via a double pinned connection (the control arm) so no way can it affect height. Same with strut spacers as they install below the spindle/strut interface so only lower the outer control arm end. One thing I've seen and liked was on a local v. full race/prepared 383 Z (he won some award at the NZCC in Vegas this summer, or a few awards). He installed triangular 'wedges' (like an upside down shark fin) on his Xmember in line with his headers (which are his low point) so if he nails a bump it physically (in theory and practise I'd guess) jolts his car up but misses his collectors (or hits the object sending it elsewhere if it's smaller, ie. not a manhole cover:-)d He used 1/4" 2x4 HSS with the one side mitred so two 'fins' were left hanging down from each one. Pete, 70-78 JTR installs w/o this xmember spacer are already lower than my ZX install so can't compare directly although all feedback is welcome. If I dropped an inch I'd likely almost come to where a normal JTR install might be. My engine is far from being level with a dip from front to back so dropping it will allow the rear to stay somewhat fixed and can only improve my angles. Anyone have experience with the true GM motor mounts at a lot higher $? Their was a specific one Ron Tyler used that he fealt (along with his al. driveshaft) really contributed to making it a v. smooth car. Ron and the otehr V8Z'rs that rode in his car also fealt it was the smoothest (no/minimal vibes) V8z setup. Been wondering if anyone else has any similar experiences or knows GM uses a better dampener than others....one of my mounts has been cracked for a while so time for replacement ------------------ Of all the things I've lost, I miss my mind the most. Quote Link to comment Share on other sites More sharing options...
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