A: You've got a very common problem with the TPI injection. The TPI system is comprised of a plenum, runners, and a manifold base. These components have gaskets to seal them to each other. The four tube runners have an additional small tube that on one side transfers the idle air to the manifold base to equally distribute the idle air to each cylinder, and on the other bank the small tube is used to transfer exhaust gas from the manifold base up to the plenum to feed the EGR distribution holes directly behind the throttle body. If you accidentally put the left gasket on the right side, there will be a large vacuum leak, which creates all kinds of problems like those you're experiencing. The only way to fix the problem is to dissemble the intake and replace the gaskets. You can try to swap the gaskets, but they are rather fragile. Also, you don't want to have to take the thing apart again.

Get the gaskets on the correct side and enjoy your convertible. Sorry your mechanic did the switch-a-roo. We're sure he won't want to hear this answer. Don't beat on him too hard-we've all done it!

Hard Line
Q: I loved the article on brake line replacement by Sean Haggai in the Dec. '09 issue. I have a '70 Chevelle and am getting ready to change from drum to disc on the front. I'm also rebuilding the frontend and am glad to see they have a new set of lines and rotors that will work with my 14-inch wheels. I really like to buy American-built products and plan to get my kit from Inline Tube. What can you tell me about silicone brake fluid? I don't know anyone who has used it. Can it be used in the new system or should I stick with the original? Also, what is the advantage of the 2-inch drop spindles? I like my Chevelle's stance the way it is, but I also know things change with new products. What do you think? Love to read your articles; they are informative and entertaining!
John C. Moore
Trenton, SC

A: Glad to be of service. New brake lines from Inline Tube really clean up any restoration. Over the years, the original lines can rust out and have the fittings rounded off by abuse or, in your case, by adding front disc brakes.

Silicone brake fluid (DOT 5) is some really nasty stuff. This came on the scene about 30 years ago. It was going to revolutionize brake fluid with its very high boiling point and resistance in attracting moisture. Well, the first thing that happened is people added silicon fluid to standard DOT 3 fluid and, well, the two fluids really don't like each other and the combination turns the fluid to a congealed mess. If someone does this, they basically have to replace the entire hydraulic system. There are a few motorcycles and other specific applications that use silicone fluid. Please read any owner's manuals and make sure what type of fluid is used in any application.

The best bet is to stick with a quality DOT 3 brake fluid and flush the system approximately every 30,000-50,000 miles. You can tell when the fluid is getting contaminated with moisture when it changes color and goes from near clear to a brown tint, then to black. Moisture-contaminated fluid is when you'll get rust in your calipers, wheel cylinders, and master cylinder. It's much cheaper to swap out the fluid occasionally than to replace these expensive components.

Drop spindles do just what the name states. They raise the spindle in relation to the ball-joint mounting, whatever the dimensions of the design. A 2-inch drop spindle will lower the ride height with no other changes by 2 inches. The benefit of lowering a car with drop spindles is that you do not reduce the suspension travel. When you lower a car by lowering springs you lose that amount of suspension travel on the compression side-and alter the suspension geometry. The added benefit of using drop spindles is that you lower the center of gravity of your car, which gives you improved handling by reducing body roll. However, if you like the stance of your Chevelle with The General's spindles, then leave it alone!