Gentlemen, Can someone explain why the 68-69 Toro's have a heat spring in the left exhaust manifold? I noticed that the 70's do not have any spring at all. Would I be able to use a 70 mainifold on a 68-69?
Thanks

 

Yes, but you won't have a heat riser. That may cause some warmup and cold drivability issues but nothing you won't learn to live with.

Most 1970 Olds do not have heat riser flaps. Can't explain why, but Engineering must have thought they could get away without using it.

 

Thanks for the reply, I believe I have a cracked left exhaust manifiold (sure sound like it but cannot see for certain because of the shround covering it). The car already does have some warm-up issues. It takes forever for the fast idle and or choke to come off. I have a 68 parts car but the manifold is not going to be easy to take off without some heat from a torch. I found two from a 70 that are already off and ready to bolt on.
Did GM change or improve the casting on the 70 vs 68? It has an updated part number. I know Ford did this with their exhaust manifolds. The early ones on 429-460 motors all cracked. The improved the design with a beefier castingthat was ribbed.
thanks, J

 

Both of my manifolds had symmetric cracks (between the 3rd and 4th runner.) Fixed with silver brazing rod. Casting defect for sure (they poured the iron in both ends of the mold; where the two fronts of molten iron met it trapped air bubbles that would form the fault line for later cracks.) While I had it out I found that the heat riser was frozen up, so I burned it out with a cutting torch and plugged the holes with shrink-fitted dowel pins.