Holley Base Gasket 4 hole or 1 LARGE area

[Jims68]

What is the difference between a gasket with 4 holes and one with one LARGE hole (Square bore) on a Holley carb. This is for a 383 with a Holley 4160. The gasket on the engine now is a single LARGE hole, but I see ones for sale with the 4 separate holes.

[Wildergarten]

What is the difference between a gasket with 4 holes and one with one LARGE hole (Square bore) on a Holley carb. This is for a 383 with a Holley 4160. The gasket on the engine now is a single LARGE hole, but I see ones for sale with the 4 separate holes.

The large hole gasket is for manifolds with a common plenum, usually for high performance engines with aluminum manifolds. The four hole gasket is typically for dual plane manifolds that operate at lower maximum RPMs. Use the large hole on the latter manifold and you'll induce turbulence that inhibits even cylinder filling and reduce high end performance. The eddies may also have an effect at idle, but I'd have to test that before making that admonishment.

For that dual plane manifold, I'd get the four hole gasket to match the carb.

[Jims68]

Thanks.... ya know... that gasket has been on the car since 1986 (yes really) and been running GREAT ever since! I replaced the accelerator pump about 5 years ago, but didn't change the base gasket at that time (or ever). I never "noticed" any issues. But, I think I'll take your advice and order the 4 hole job. Who knows, NOW maybe I'll see a difference in performance. I had a VERY LEAKY accelerator pump and when I pulled the carb off, I thought I'd change out the base gasket as well. That was when I started seeing the different types! That got me thinking