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I just finished putting new poly bushings and a 3.90 diff in my 1977 280Z.

Now, when I run down the highway, the engine seems to be running hot. The temp gauge normally runs just left of dead center. The temp is now showing to the right of dead center (enough where you can see the whole symbol there in the middle).

As far as driving, I do realize that I will be running higher RPM with a 77 5-speed and this 3.90 rear end. I have been running it at 3,000 RPM down the highway when seeing this "overheating" issue.

Any other 77/3.90's out there have the same problem? What can be done to help alleviate this besides:

1. Stay off the highway
2. Put in an 81-83 5-speed
3. Put the original 3.54 diff back in.

Could I get a 160 degree thermostat to help out instead of the stock 180 degree thermostat?

Any other suggestions?


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