Its been my experience that when u Use SOR.COM's Stainless Steel HeaT Riser Block off
plate , that u do loose 2-3 critical threads / Turns of Solid Bite on the 3 Center Manifold to
Manifold
" Sandwich " bolts 2 from underneath , 3 on top .
This , combined with the Female Threads in the Intake are Not Usually in the Best condition
the first few turns for some
Age & Time reason ?
This is where i have found Longer Bolts are usually needed or necessary
But , Not using there Heat Riser Block off plate is
Not really a option in the Real world any more Due to the Age & time factor of the Bi-metalic
spring breaking , & the Heat Riser Shaft Seizing in the Open or Cold Position where it Contacts the Chromium pressed in Bushings in the
exhaust manifold , Hence this Super heats the Bottom of the Intake and causes a Crack and Subsequent Vacuum Leak
This is also a
Focus Point where i Do Believe in and Always Use the Rem-Flex Graphite Gasket , Because its NOT a Machinable , or at least the
Top / Vertical Gasket Mating Surface on the Exhaust Manifold , the surface is Typically Pitted form age & Time
I take it to the Extreme Level a bit maybe , ...................
By removing the Heat Riser & Shaft All Together , Weld in 2 stubby bolts , and eliminate the potential problematic problem altogether
Im a Purist when it comes to the Exhaust Manifold VS Headers Topic , i Roll with that Crowd 
