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Throttle body rebuild


Well-known member
Nov 5, 2002
El puerto de Santa Maria Spain
before 60,63&82 now 90 383 Stroker & 91 ZR1-Sold

This turned out to be too easy. I planed on several days of good training for the kids in the shop. If my business ran this smooth I would have even more time to play.:duh

One of the US Navy boys here has an F body LT-1 with high mileage. The shaft of the throttle body was worn and his idle was heading for the 2K mark. The kid is strapped for cash so I offered to give him my stock L98 TB if it would work. I think it would have worked ok but he was advised otherwise, so we rebuilt his.

To dissemble the TB the shaft has to be ground off on both ends to remove the cable and TPS fittings. The screws holding the throttle plated on were welded on the back side and these welds had to be ground off as well. One of those hobby tools that they advertise as, ¨ the perfect gift for dad¨ is perfect for the job.

When we got it apart there was about 1/32¨ of play on the cable side and maybe half that much on the TPS side.

Even though all the fasteners are metric, the throttle shaft is 3/8¨ we could not find a needle bearing with 3/8¨ id that was small enough to mount in the TB so we went with a metric 8-12-10 double sealed bearing and turned both ends of the shaft down to fit.

The machine work to the TB could have been done on a precision drill press, but the kids need experience on the mill so we clamped the TB down, centered it with a 3/8¨ shaft and reamed her out on both sides to accept the bearings. The center passage for the throttle shaft was not modified.

While we were turning the shaft to fit the bearings we drilled and tapped both ends to 2.5mm. The cable and TPS fittings will be secured with screws now. It looks better to me.

The throttle plates were secured with new screws which were put in with locktight and then the back side of each screw was splayed to be sure none would end up in the engine.

When everything was back together the throttle action was as smooth as a baby’s backside and the throttle shaft had no play so we bolted it back in the FireBird.

The owner started the car while I was looking for my cheat sheet to adjust min. idle speed but there was no need, she settled down to 650RPM.

We are so happy with the results that we are going to rework my old TB and bore it out to 52mm.

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