Thanks Charlie.  eBay listing photo shows no slot on new Y-Block models, though I notice their FE manifolds still have it.

P.S. re: the high/$700 (delivered) price.  Nobody else selling them on eBay.  ‘Google shopping’ neither.
BTW:  I like the seller’s blurb re: prep & handling.  If you have been buying things from China like I have recently, you would appreciate, & happily pay a premium to avoid grief down the road.

6 VOLTS/POS. GRD. NW INDIANA

Here’s some more info on both the Blue Thunder intakes and the slots.

The latest version Blue Intake (Version V) has the firing order and no plenum slot.  Version IV intakes also came without the plenum slot but has no firing order.  Version I, II, & III intakes have the plenum slots.  Version III intakes were modified at the back to accommodate the larger diameter MSD distributors.  Version 1V & V intakes continue to have that modification for the larger diameter distributors.  Version II has a slightly higher carburetor base than version I.

Here is the article that was in a previous issue of ‘The Y-Block Magazine’ that went into detail as to the different performance attributes of plenum slots versus no plenum slots.
Intake Manifold Plenum Slots – Eaton Balancing

Keep in mind that the ECZ-B 4V iron intakes came from the factory with and without the firing order on the intakes.  As a general rule, ECZ-B intake manifolds cast until mid-February 1957 did not have the firing order on them and intakes cast after that had the firing order.

As Joe points out, the performance between the Blue Thunder and the Mummert intakes are similar when comparing both as un-ported and ported.  Despite the higher cost of the Blue Thunder intake manifolds, I still have those people that want the Blue Thunder due to them being heat riser capable and/or having an appearance that looks closer to being stock.  When the Blue Thunder intake is painted, it takes a sharp eye to discern that manifold from a stock intake.

Lorena, Texas (South of Waco)

RE: Version lll -V larger diameter Distributor mount… Can a stock diameter distributor be used

The one in my picture is Version II or earlier and it works with stock distributors so III and later will definitely work for a stock distributor..


Lawrenceville, GA

Ted,
I see the seller also offers (alum.?) BT hold-down clamps.  Is there reason (aside from weight) to use instead of the OEM steel clamps?  
Also, the eBay seller lists you as a customer.  Have you experience with their powder-coat/Duplicate-Color work, and likely recommend?  



6 VOLTS/POS. GRD. NW INDIANA