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I currently have a 240z with a chevy small block installed but am planning on upgrading to an ls3. The car has upgraded suspension but when going on the freeway the car drifts side to side with no steering input and I think this may be do to the weak chassis. Would it be worth it To sell the car and upgrade to a 280z which I have heard has a stiffer chassis and do the engine swap into that car instead of the 240z?

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Check the steering rack bushings. They are inside the clamps that  bolt the rack to the cross member. The originals are rubber and wear/rot out which allows the rack to move.  If the bushings look worn,  or there is any movement of the rack while moving the  steering wheel,  replace the bushings with polyurethane bushings.

Also, failed  rubber tension/compression (T/C) rod bushings can cause the car to dart under braking and to drift left - right. Do not replace the T/C bushing with polyurethane as it is too stiff and can cause failure of the T/C rod. Replace with stock rubber bushings only.

 

The polyurethane and T/C rod  bushings are available from Motor Sports Auto (MSA).

Edited by Miles

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"Drifting from side to side" at highway speeds is often imputed to bad aerodynamics.  In my view, this is partially correct.  If the consumables in the suspension are worn, but only slightly worn, then with sedate driving on surface-streets, there may be no sensation of there being anything amiss.  But at highway speeds, the steering might grow light, or otherwise twitchy.  In steady straight-line driving on smooth pavement, there are presumably no strong transient forces - or than those having to do with wind.  So, it's not the case that the aerodynamics are inherently bad (and least, not entirely), but rather, than wind-effects at higher speeds expose problems with the (front) suspension, that would not otherwise have been noticed.  That at least was my own experience, driving a worn  but serviceable 240z on the highway, now so many years ago.

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Old Z's are notorious for getting light in the front end at speed. Too much air gets up under the hood at speed. The grill opening is way to big with no where for the wind to go. If frame rail strength worries you about the differences between the 240 and the 280 just add big dog fame rails. That is the biggest difference that I have noticed between all my Z's. As to the wind under the hood I have seen it mentioned a number of times in the forums. Do you have a front spoiler on your car now?

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16 minutes ago, Marks260z said:

Old Z's are notorious for getting light in the front end at speed. Too much air gets up under the hood at speed. The grill opening is way to big with no where for the wind to go. If frame rail strength worries you about the differences between the 240 and the 280 just add big dog fame rails. That is the biggest difference that I have noticed between all my Z's. As to the wind under the hood I have seen it mentioned a number of times in the forums. Do you have a front spoiler on your car now?

Great call!  I forgot the very first mod I put on my car was a BRE front spoiler.  Definitely stabilized the car at highway speeds.

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47 minutes ago, Marks260z said:

Old Z's are notorious for getting light in the front end at speed. Too much air gets up under the hood at speed. The grill opening is way to big with no where for the wind to go. If frame rail strength worries you about the differences between the 240 and the 280 just add big dog fame rails. That is the biggest difference that I have noticed between all my Z's. As to the wind under the hood I have seen it mentioned a number of times in the forums. Do you have a front spoiler on your car now?

I currently have urethane air dam and it doesn't seem to help much with the aerodynamics. I plan on painting the car soon so before that happens in a BRE style front spoiler worth it?

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I've used both on the front end of my car on race tracks in So Cal.  The BRE spoiler is great because it's rigid.  I think the urethane spoiler bends at 90+mph without a splitter underneath.  The other problem with the urethane spoiler is that you have to remove that thin piece of stock bodywork below the grill to mount it which makes the grill opening with the urethane spoiler even bigger which isn't good for the ride either.  That being said, I have a custom lowered suspension (RIP John Coffey) so my ride height is 4+"" lower than stock.

*One other thing -- I think the BRE spoiler works better than the urethane air dam because the air dam only blocks the air while the BRE spoiler set at a 45 degree angle from the body work creates downforce.  Bottom line is that the BRE spoiler was on the early Z cars that won EVERYTHING.  That's good enough for me. :)

Edited by Sandy455

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