v8 280zx w/t-tops -- chassis twisting??

[Guest zmaize]

This is approx. what my setup will be when I finish my 280zx v8 swap.

 

83 zx

350+ hp 327

t56

posi rear from q45 (r230)

 

I'm planning some minor chassis mods such as front and rear strut braces and maybe sway bars, probably stiffer springs, at least in the rear (to reduce squat, which was pretty bad even with the 6 cyl.)

 

Well my question is has anyone done a v8 swap in a car with t tops? Logic would tell me that having t tops weakens the entire car somewhat, but how much, i don't know.

 

I've searched the chassis forum and found no mention of t tops. Does this mean I'm a pioneer?

 

That would be pretty cool, but twisting my car in half wouldnt...

 

If anyone has any experience with this please let me know if The "minor" changes I've mentioned would be enough, or if a roll bar/cage is necessary. (possibly add underbody supports?)

 

Any help would be greatly appreciated.

[danc]

Zmaize:

I have an 83 with T-Tops running a SBC. I was concerned about twisting the body piece/parts and installed a strut bar across the front strut towers. Plan on doing the same across the back ones too. I'd be interested to know from a structural engineering perspective if a "T" top car is substantially weaker than a non "T" top car. I would suspect not.

Dan

[Guest greimann]

Well, I'm not a vehicle dynamics engineer - but I play one on TV....... JK!

 

I wouldn't worry about destroying your vehicle with the added torque of a V8. If you were able to instrument the car with strain gauges and such, you could probably measure a difference between a T-top and a hardtop for flex and resonance, but seat of the pants, it might be hard to tell. If you look at the front end of a car from a structural standpoint, the firewall / cowel area supports two inner fenders / strut towers that come out of the front. That whole system works pretty well except for side to side flex of the towers. Adding a bar between the tower tops is OK, but you create a parallelogram effect between the towers. One flexi part is attached to another flexi part. A better solution structurally, is to triangulate the system by connecting the flexible parts to the non flexi parts. Running a bar from the top of the tower to the center of the firewall accomplishes triangualtion in two planes - the inner / outward and the up and down. I have this setup and have noticed a seat of the pants difference in the front rigidity of the car. Ther are pix at my website below.

[Danno74Z]

David,

 

Very nice car!!!

 

Danno74Z

[danc]

David:

I agree, nice car, and detail! Thanks for the additional info. I've noticed a few guys having the strut tower to firewall brace, and it does make sense. Is your custom made, or do you have a part#. I have an 83 with a Fastburn 385/700R4 that's been running since late November that I'm trying to find time to work the bugs out of! What kind of suspension do you have, and what size are your tires? Thanx

Dan

[Guest greimann]

Thanks for the compliments guys (I assume you are all guys!)

 

The bars are made from panhard bars from Summit - #CCE-2037. One end comes welded and then you cut the bar to length and TIG weld the other end. The brackets are made from 1x2" square tubing. Just cut away everything that doesn't look like a bracket.

 

I have Eibach springs, KYB struts and shocks, and the tires are 225-60R15 Yokohama AVS Intermediates from Tire Rack. Really nice tires BTW. They fit with no spacers or mods.

 

(BTW DanC, I am originally from Kettering! I bought this car in '84 from a dealer in Centerville, and I am still batteling the rust!)

[danc]

Greimann:

It is a small world. You've done a good job keeping up with the rust! I bought mine here locally from Dick Osman's in Centerville early 1985 with 3K miles on it. Almost stopped driving it the last several years since it was such a performance pig, but the conversion has definitely changed that! It's never been in the snow, garaged and covered most of the time. Fortunately very little rust, and a good bud as a body shop owner for the touch-ups I've needed. I'll pick up a couple of the panhard bars for sure. I'm still on the fence on suspension; waffling between coil-overs and Eibach or TRW progressive rate springs. I like the height you cars sits. How do you like the Eibachs? Do you have the "Pro-Kit" springs? The opinions on coil-overs versus OEM type springs are all over the board depending on application I'm sure. I still have the factory 14" 6 spokes on mine, but have a set of the turbo wheels like yours. Don't plan on going over 225's, and my driving is primarily straight line. Are you satisfied with them? Does your ride height changing depending on load? Did they help the rear end squat? I'm leaning towards the Eibachs, but any opinions you might offer would be very helpful. I did purchase a pair of Tokico Illuminas from British Victoria for the rear since they are no longer made. If you ever get back this way, let me know..

Dan

[Guest greimann]

I replied to your e-mail too Dan.

 

I like the Eibachs' really well. They are progressive and ride sporty, not choppy. Between the springs and KYB gas struts, the rear squat is under control. No more bottoming on acceleration.