So I purchased a 1986 Firebird. I had a 89 9 bolt and ls1 setup ready and bolted up to my 92 Rs. I have heard or read that pre 89 used diff fittings/threads than 89+. Is this true? What would be needed to adapt it?

 

Check out some of the information on this link:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

 

I assume the LS1's were the fronts. The 9-bolt is a drop-in. The tube nut threads are different at the combination valve, early 89 and late 89. If you wish to swap in larger rear brakes, Ed Miller sells the correct 1LE valve (so you'd need the second design for your 92).

JamesC

 

This is for the 86. The brakes were in my 92. So the difference is only on the prop valve? So everything else would be the same?

 

Where the braking systems are concerned, there is no difference between 9- and 10-bolts. The PBR system into your 86 will require some changes. Check the following link, toward the end, for more info:

https://www.thirdgen.org/forums/tran...-10-bolts.html

In short, you'll need the first design 1LE combination valve, parking brake cables, and if you've changed rear end gearing, appropriate speedo gears.

JamesC