76SeaRay
Lieutenant Junior Grade
- Joined
- Aug 24, 2017
- Messages
- 1,071
I haven't found a discussion on the correct gaskets to use when running a dual plane intake with a 4 barrel. So, here goes a thread on the issue:
Both Holley and Rochester (QJet) have gaskets that use individual holes for the 2 primaries and 2 secondaries (4 total). There are also gaskets that are "open" across all the primaries and secondaries. The open gaskets means that there is a gap between the base of the carb and the center of the dual plane intake allowing cross over to occur. Using a 4 hole gasket prevents this so it would seem that is the route to go. However, that means there will be unsupported portions of the gasket in the opening of the dual plane intake (potential to age and fall into the intake?).
Admittedly, the cross over flow is probably pretty small due to the thin gasket material but what happens if you run a thicker (say 1/4 inch) insulating gasket. Cross over would likely increase and I have heard that some engines don't perform as well. However, it has also been mentioned that the thicker gasket, which helps keep heat out of the carburetor, would also increase the plenum size and raise the secondaries out of the designed plenum area avoiding secondary disruption of air flow in the plenum.
Finally, there are metal shims that are used to prevent heat transfer as well (but those seem to be all 4 hole plates) to add into the mix.
Any thoughts and opinions or real life examples on which way to go with it?
Both Holley and Rochester (QJet) have gaskets that use individual holes for the 2 primaries and 2 secondaries (4 total). There are also gaskets that are "open" across all the primaries and secondaries. The open gaskets means that there is a gap between the base of the carb and the center of the dual plane intake allowing cross over to occur. Using a 4 hole gasket prevents this so it would seem that is the route to go. However, that means there will be unsupported portions of the gasket in the opening of the dual plane intake (potential to age and fall into the intake?).
Admittedly, the cross over flow is probably pretty small due to the thin gasket material but what happens if you run a thicker (say 1/4 inch) insulating gasket. Cross over would likely increase and I have heard that some engines don't perform as well. However, it has also been mentioned that the thicker gasket, which helps keep heat out of the carburetor, would also increase the plenum size and raise the secondaries out of the designed plenum area avoiding secondary disruption of air flow in the plenum.
Finally, there are metal shims that are used to prevent heat transfer as well (but those seem to be all 4 hole plates) to add into the mix.
Any thoughts and opinions or real life examples on which way to go with it?
